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How to make diagnosis of these symptoms using Pet scan, fMRI, and EEG?

How to make diagnosis of these symptoms using Pet scan, fMRI, and EEG?

The symptoms are muscle weakness, slow reaction time, visual perception issues, seizures, hearing loss, weight gain, general sense of pain and delusions. Using the above scanning techniques, a doctor concluded that there are problems in emission of neurotransmitters and secretion of hormones as well as myelin sheath of some neurons, occipital lobe, and temporal lobe. Could you tell me how the doctor used the scanning tools to reach to his conclusion? I totally have no idea how the doctor learned that there's problem in emission of neurotransmitter by using scanning techniques.


You would have to ask your doctor to be certain but it seems to me that the PET could have identified the myelin sheath problems by the MeDAS binding and certainly could identify the neurotransmitters which were out of balance. The neurotransmitters are found by using a radiotracer which makes them measurable on the PET. The fMRI would have confirmed or identified the myelin sheath problems in a more localized way. The EEG was also given to rule out certain kinds of seizures and possibly identify the correct type.

PET

PET scanning is also used for diagnosis of brain disease, most notably because brain tumors, strokes, and neuron-damaging diseases which cause dementia (such as Alzheimer's disease) all cause great changes in brain metabolism, which in turn causes easily detectable changes in PET scans. PET is probably most useful in early cases of certain dementias (with classic examples being Alzheimer's disease and Pick's disease) where the early damage is too diffuse and makes too little difference in brain volume and gross structure to change CT and standard MRI images enough to be able to reliably differentiate it from the "normal" range of cortical atrophy which occurs with aging (in many but not all) persons, and which does not cause clinical dementia.

-wikipedia

fMRI

The primary form of fMRI uses the Blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo shots, surgery, or to ingest substances, or be exposed to radiation. Other methods of obtaining contrast are arterial spin labeling and diffusion MRI.

The procedure is similar to MRI but uses the change in magnetization between oxygen-rich and oxygen-poor blood as its basic measure. This measure is frequently corrupted by noise from various sources and hence statistical procedures are used to extract the underlying signal. The resulting brain activation can be presented graphically by color-coding the strength of activation across the brain or the specific region studied. The technique can localize activity to within millimeters but, using standard techniques, no better than within a window of a few seconds.

-wikipedia

EEG

In neurology, the main diagnostic application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study.

-wikipedia


T2 weighted MRI scans can reveal white matter lesions, so that may explain the detection of demyelination.

Of course, that's not fMRI…


Alzheimer's diagnosis, management improved by brain scans

Amyloid-positive (left) and amyloid-negative (right) PET scans can respectively be used to diagnose or rule out Alzheimer's disease in individuals with memory loss or cognitive decline. Credit: UCSF Memory and Aging Center

A first-of-its-kind national study has found that a form of brain imaging that detects Alzheimer's-related "plaques" significantly influenced clinical management of patients with mild cognitive impairment and dementia.

The study revealed that providing clinicians with the results of positron emission tomography (PET) scans that identify amyloid plaques in the brain changed medical management—including the use of medications and counseling—in nearly two-thirds of cases, more than double what researchers predicted in advance of the study. The technique, known as "amyloid PET imaging," also altered the diagnosis of the cause of cognitive impairment in more than one in three study participants.

The multicenter study of more than 11,000 Medicare beneficiaries, published April 2, 2019 in the Journal of the American Medical Association (JAMA), was managed by the American College of Radiology and led by scientists at the Alzheimer's Association, UC San Francisco, Brown University School of Public Health, Virginia Commonwealth University School of Public Health, Washington University School of Medicine in St. Louis, UC Davis School of Medicine, and the Kaiser Permanente Division of Research.

"We are impressed by the magnitude of these results, which make it clear that amyloid PET imaging can have a major impact on how we diagnose and care for patients with Alzheimer's disease and other forms of cognitive decline," said study lead author and principal investigator Gil Rabinovici, MD, Distinguished Professor of Neurology at the UCSF Memory and Aging Center and member of the UCSF Weill Institute for Neurosciences.

"These results present highly credible, large-scale evidence that amyloid PET imaging can be a powerful tool to improve the accuracy of Alzheimer's diagnosis and lead to better medical management, especially in difficult-to-diagnose cases," added Maria C. Carrillo, Ph.D., Alzheimer's Association chief science officer and a co-author of the study. "It is important that amyloid PET imaging be more broadly accessible to those who need it."

Alzheimer's disease is characterized by the accumulation of both amyloid protein plaques and tau protein "tangles" in the brain, the presence of which are required for a definitive diagnosis. Until recently, amyloid plaques could only be detected by postmortem analysis of autopsied brain tissue. With the advent of amyloid PET—which involves injecting patients with "tracer" molecules that stick to amyloid plaques and can be used to visualize their location in the brain—it became possible to detect plaques with a brain scan and therefore more accurately diagnose people living with the disease.

Though there is no cure for Alzheimer's disease, early diagnoses enable physicians to prescribe appropriate symptom-management therapies, counsel families on important safety and care-planning issues and direct people to clinical trials for promising new drugs. It also allows people with the disease and their families to plan for the future, including legal and financial issues, and accessing resources and support programs. PET imaging results that reveal no signs of amyloid buildup in the brain rule out Alzheimer's disease as the cause of memory loss, which can prompt an evaluation for alternative and sometimes reversible causes, such as medication side effects, sleep or mood disorders and other medical conditions.

However, despite FDA approval of amyloid PET tracers, use of amyloid PET imaging to assist with the accurate diagnosis of the cause of someone's dementia is currently not covered by Medicare or health insurance plans, making it unavailable to most people.

Launched in 2016, the four-year Imaging Dementia—Evidence for Amyloid Scanning (IDEAS) study was developed by a team of scientists convened by the Alzheimer's Association to determine whether learning the results amyloid PET imaging would change medical management and health outcomes of people with memory loss and cognitive decline. IDEAS recruited nearly 1,000 dementia specialists at 595 sites in the U.S. and enrolled more than 16,000 Medicare beneficiaries with mild cognitive impairment or dementia of uncertain cause. Under their Coverage with Evidence Development policy, the Centers for Medicare & Medicaid Services (CMS) reimbursed amyloid PET scans conducted at 343 facilities and interpreted by more than 700 imaging specialists as part of this clinical study.

"This was a uniquely real-world study that looked at the impact of amyloid PET imaging in community clinics and other non-academic settings, and demonstrates for the first time how much impact this technology has in real-world dementia care," Rabinovici said.

The newly published results from the first phase of the IDEAS study focused on how amyloid PET scans altered physician diagnosis and treatment plans for the 11,409 participants who completed the study. As the study's primary endpoint, the scientists collected data on how physicians altered participants' medication prescriptions and counseling about safety and future planning. As a secondary endpoint, the researchers evaluated whether PET imaging results caused physicians to alter participants' diagnoses. Finally, several exploratory endpoints included physician decisions about referrals to Alzheimer's clinical trials.

The newly published data reveal that physicians changed their clinical management of more than 60 percent of patients in the study, more than double the number the authors had predicted in advance.

In participants who joined the study with mild cognitive impairment and whose brain scans revealed the presence of significant amyloid deposits, clinicians were twice as likely to prescribe Alzheimer's drugs following PET imaging (

40 percent prior to imaging vs.

82 percent following imaging). In those with dementia and significant amyloid buildup on PET scans, prescriptions of these drugs rose from

91 percent after the study. Doctors discontinued the use of these drugs in some patients whose scans revealed little amyloid deposition. In addition, for approximately one quarter of study participants, physicians changed non-Alzheimer's drug prescriptions and counseling recommendations based on PET imaging results.

PET scans that revealed no significant amyloid buildup led physicians to rule out Alzheimer's disease for approximately one in three patients who had previously been given an Alzheimer's diagnosis. On the other hand, PET scans that showed significant amyloid plaque buildup led to a new diagnosis of Alzheimer's disease in nearly half of patients who had not previously been diagnosed with the disease.

The researchers also discovered that one-third of participants who had previously been referred to Alzheimer's clinical trials showed no sign of amyloid buildup based on PET imaging, which generally rules out Alzheimer's disease as the cause of their cognitive symptoms. Based on the imaging results, physicians were able to ensure that nearly all patients referred to Alzheimer's trials were amyloid-positive (93 percent), which is critical to these trials' success.

"Accurate diagnoses are critical to ensure patients are receiving the most appropriate treatments. In particular, Alzheimer's medications can worsen cognitive decline in people with other brain diseases," said Rabinovici. "But perhaps more fundamentally, people who come into the clinic with concerns about memory problems want answers. An early, definitive diagnosis may allow individuals to be part of planning for the next phase of their lives and to make decisions that otherwise would eventually need to be made by others."

The IDEAS team is currently analyzing data on the study's second phase, which will examine how amyloid PET scans affect health outcomes following the scan. The researchers are using CMS claims data to document hospitalization rates and Emergency Department visits for IDEAS participants, and comparing them to participants with similar neurologic problems but who did not undergo amyloid PET. They plan to publish their findings in 2020. In addition, the researchers are developing a second study (known as New IDEAS) to include more people with both typical and atypical clinical presentations of Alzheimer's and recruit a study group that better reflects the racial and socioeconomic diversity of the national population.


Purpose of Test

Positron emission tomography has a broad range of diagnostic applications but is typically ordered if your doctor either suspects cancer or that a cancer may have spread. It is routinely used to assess the status of your heart prior to bypass surgery, especially if other imaging tests are inconclusive. It is also commonly ordered if early Alzheimer's disease is suspected or to evaluate the brain prior to surgery to treat refractory seizures.

Beyond these indications, a PET scan is also commonly used to stage cancer, to evaluate the extent of damage following a heart attack or stroke, and to monitor your response to cardiovascular, neurological, or cancer treatments.

PET differs from CT and MRI in that it examines the function, rather than the structure, of living cells. By contrast, CT and MRI are used to detect damage caused by a disease. In essence, PET looks at how your body responds to a disease, while computed tomography (CT) and magnetic resonance imaging (MRI) look at the damage caused by one.

Among its many functions, PET can measure blood flow, oxygen intake, how your body uses glucose (sugar), and the speed by which a cell replicates. By identifying abnormalities in cellular metabolism, a PET scan can detect the early onset of a disease well before other imaging tests.  

PET can be used to diagnose different conditions depending on the type of radiotracer used. The most common tracer, known as fluorodeoxyglucose (FDG), is used in 90 percent of PET scans, the procedure of which is commonly referred to as FDG-PET.

When injected into the bloodstream, FDG is taken up by glucose transporter molecules in cells. Because cancer cells multiply rapidly and do not undergo programmed cell death like normal cells, they will absorb far more FDG in the course of metabolizing sugar.

FDG can also be used to highlight areas of low metabolic activity caused by the obstruction of blood flow. Similarly, FDG-PET can spot changes in oxygen and glucose levels in the brain consistent with disease, impairment, and psychiatric illness.  

Other types of radiotracers highlight cellular abnormalities not detected by FDG. These include:

  • 11C-metomidate used to detect adrenocortical tumors (those occurring in hormone-producing cells of the adrenal cortex)
  • Fluorodeoxysorbital (FDS) used to diagnose bacterial infections
  • Fluorodopa used to detect neuroendocrine tumors (those occurring in hormone-producing cells of the nervous system)
  • Gallium-68 dotatate, also used to detect neuroendocrine tumors
  • Nitrogen-13 and oxygen-15 used to detect impaired blood flow

There are well over 40 different radiotracers used for PET scanning purposes with more being developed every day.

Conditions Diagnosed

PET is primarily used to diagnose cancer, cardiovascular disease, and neurologic disorders.

For cancer, PET is especially useful as it can scan the entire body and pinpoint both a primary tumor and areas of metastasis (where the cancer has spread). With that being said, not all cancers can be detected by PET.

For cardiovascular disease, a PET scan can reveal areas of decreased blood flow to the heart, brain, or lungs. By viewing the effects of circulatory impairment, your doctor can make the most appropriate treatment choice, including angioplasty or cardiac bypass surgery.

PET can also help predict the likelihood of a heart attack or stroke by detecting and measuring the hardening of arteries (atherosclerosis).

Among the cardiovascular conditions the test can diagnose:

For neurologic disorders, a PET scan can be used to measure brain activity in relation to areas of high and low radioactivity. Since the brain requires large amounts of glucose and oxygen to function, any shortages can easily be detected on a scan.

Among the neurologic disorders a PET can help diagnose:

  • Alzheimer disease
  • Brain hematomas (blood clots)
  • Dementia
  • Multiple sclerosis
  • Parkinson's disease

In addition, PET can be used to detect bacterial infections, most specifically enterobacterial types associated with endocarditis, septic arthritis, osteomyelitis, and central nervous system infections.  

Combination Scanning

When constructing a diagnosis, there is an advantage to looking at both the cause and consequence of a disease. It is for this reason that PET is frequently combined with CT or MRI, an approach referred to as either special views or co-registration. Doing so provides the doctor with both anatomic (physical) and metabolic (biochemical) information.

Modern PET scanners are now available with integrated CT scanners (PET-CT) which can create two sets of precisely matched images. Modern PET scanners are now available with integrated CT scanners (PET-CT) or MRI scanners (PET-MRI) which can create two sets of precisely matched images.  


Neuropsychological Testing

Neuropsychological testing adds to the clinical assessment of a person. These tests evaluate behavior, language, visuospatial abilities, memory, abstraction, planning and mental control, motor skills and intelligence. The patterns of strengths and weaknesses in a person help identify which areas of the brain are functioning well and which ones are doing poorly.

  • Tests of a person with frontotemporal dementia (FTD) may show visual and memory abilities intact. However, abstract thinking, word generation, motivation and ability to follow rules may be disrupted.

What Are the Benefits of an Early Alzheimer's Diagnosis?

Early, accurate diagnosis is beneficial for several reasons. Beginning treatment early in the disease process may help preserve daily functioning for some time, even though the underlying Alzheimer’s process cannot be stopped or reversed.

Having an early diagnosis helps people with Alzheimer’s and their families:

In addition, an early diagnosis gives people greater opportunities to participate in clinical trials that are testing possible new treatments for Alzheimer’s disease or in other research studies.

Learn more about Alzheimer's disease from MedlinePlus.


An fMRI is safe, painless, and noninvasive. There are no known health risks of the procedure, as long as the patient has no metal or electronic implants (because the MRI machine has a very powerful magnet).

The benefits, on the other hand, are significant. Before the invention of fMRI, the only way to locate a person’s language or motor-skills center was to stimulate parts of the brain during an operation or perform invasive angiographic examinations—both of which required the patient to be awake to respond to questions. Knowing this information ahead of time makes surgery safer and faster and the patient can stay under sedation during surgery.


Difference Between MRI and fMRI

Currently, in the advent of technological advancements, a number of different types of innovations are invented and modified to make the diagnosis of common and even rare diseases a lot easier. These diagnostic tools make use of either machines or biologic studies, and in some cases both. One of the most common ways to diagnose internal diseases not seen by the naked eye is through imaging. In the laboratory, different types of sources are used to make the imaging possible. Radiation, electricity, and magnetic fields are only some to name a few. One type of imaging device that utilizes the magnetic and electrical sources of energy is what we call the MRI. Through some modifications in technological aspects, a sister machine was created out of the MRI and was called an fMRI. The differences between the two machines are hereby noted.

Magnetic resonance imaging, or MRI, is a machine used for brain structure imaging. When in some cases a CT scan cannot detect the existing problem, an MRI is helpful for discovering unnoticed anatomical anomalies caused by a disease process or traumatic event. It is a utility used for grand research in determining structural differences and a behavior correlation. On the other hand, functional magnetic resonance imaging, or fMRI, is a one of the highlights of the MRI technology wherein it functions through blood flow or blood oxygen level measurements to achieve the brain’s functional image. It is primarily used to gather relevant data as to the consumption of oxygen by the tissues. Through its modernization, fMRI sequences will view a picture of the brain’s active region by picking up the excess blood supply called Blood Oxygen Level Dependence (BOLD). In general, an MRI and fMRI differ from each other in a way that an MRI views the anatomical structure while an fMRI views the metabolic function.

In addition, the measurement of signals is different for an MRI and an fMRI individually. An MRI studies the water molecule’s hydrogen nuclei whereas an fMRI calculates the levels of oxygen. In atomic physics, the MRI’s structural imaging views at a high resolution the difference between tissue types with respect to space. On the other hand, an fMRI’s functional imaging views the tissue differences with respect to time. In addition to this, an MRI has a high, spatial resolution while an fMRI has a long-distance, superior, temporal resolution.

When talking about its technological advancement, an fMRI is still starting to build up its name unlike the MRI wherein it is already at its peak as one of the widely used equipment technologies in the medical world. Moreover, the fMRI is yet to be introduced for diagnostic purposes and is only used in experiments unlike the revolutionary MRI.

In terms of the cost in buying the machine, the fMRI is considered to be more expensive than an MRI because of the additional software and hardware required for it. The price may reach up to hundreds of thousands to millions, and that is quite a lot of money. For a cheaper choice, the MRI is preferred.

To make things clear, neither an MRI nor an fMRI has an advantage over the other because both machines serve for different functions.

1.The MRI and fMRI differ from each other in a way that the MRI views the anatomical structure while the fMRI views the metabolic function.

2.An MRI studies the water molecule’s hydrogen nuclei whereas an fMRI calculates the levels of oxygen.

3.An MRI’s structural imaging views at a high resolution the differences between tissue types with respect to space. On the other hand, an fMRI’s functional imaging views the tissue differences with respect to time.

4.The MRI has a high, spatial resolution while an fMRI has a long-distance, superior, temporal resolution.

5.When talking about its technological advancements, the fMRI is still starting to build up its name unlike the MRI wherein it is already at its peak as one of the widely used equipment technologies in the medical world.

6.The fMRI is yet to be introduced for diagnostic purposes and is only used in experiments unlike the revolutionary MRI.

7.The fMRI is considered to be more expensive than the MRI because of the additional software and hardware required for it.


Can I get an fMRI scan to show that my daughter has dyslexia?

Answer:

Unfortunately, brain scans can’t be used yet to “prove” that a child has dyslexia. The same is true for other learning and thinking differences, like ADHD .

Scientists use functional magnetic resonance imaging (fMRI) and other technologies like EEG to study how the brain works when it does complex tasks like reading. They’re using these tools to create better maps of the brain.

But everyone’s brains look different. If you pick two random people off the street, their brain anatomy and brain function will not be identical, just as their faces aren’t identical. We need to better understand this kind of variation before it becomes clear how the dyslexic brain is truly different.

Another challenge with fMRI research is that the differences between the brain scans of people with and without dyslexia are small. That’s why research studies need to look at groups of people to see which differences reliably occur in people with dyslexia. Typically in a research study, 15 or more people who have reading issues are compared to roughly the same size group of people who don’t have reading issues. Then the study looks for statistically significant differences between the two groups.

In other words, it takes a lot of brains (literally!) to reliably identify which features look different in people with dyslexia. A single brain is not enough.

Some researchers are starting to look into using a brain scan to identify people with dyslexia. But this is still just a concept. For this to become a reality, researchers need to develop techniques that allow them to pinpoint differences in an individual that can be identified reliably in most people with dyslexia.

Your child’s doctor may have heard of something called a “clinical fMRI.” For example, fMRI can help map out critical language areas of the brain so they can be avoided when a surgeon removes a tumor that is causing seizures. But before this became acceptable practice, researchers had to provide sufficient evidence to show that fMRI was helpful and reliable in this process.

We haven’t reached the point where fMRI can be used in clinical settings to identify dyslexia. When children participate in one of our research studies, we always let their parents know that we can share with them the results of the behavioral testing in the study. For example, some parents want to know their child’s scores on the reading tests that are given as part of the study. These tests take place separately from the fMRI session.

But we never provide families with an interpretation based on the scans. And we can’t comment on any individual differences (unless we make an incidental observation, such as a tumor). We give the kids a picture of their brain, which they think is very cool. But the brain of a child with dyslexia doesn’t look different to the naked eye.

Perhaps one day imaging will play a role in identifying individuals with dyslexia. Until then, parents need to continue to use traditional options, such as a neuropsychological evaluation . This process can provide useful insights into your daughter’s strengths and weaknesses. It can also inform decisions about what kinds of services and support she needs in school.


Neuroimaging (Brain Imaging)

Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the nervous system. It is a relatively new discipline within medicine, neuroscience, and psychology.[1] Physicians who specialize in the performance and interpretation of neuroimaging in the clinical setting are neuroradiologists.

Neuroimaging falls into two broad categories:

  • Structural imaging, which deals with the structure of the nervous system and the diagnosis of gross (large scale) intracranial disease (such as a tumor) and injury.
  • Functional imaging, which is used to diagnose metabolic diseases and lesions on a finer scale (such as Alzheimer's disease) and also for neurological and cognitive psychology research and building brain-computer interfaces.

Functional imaging enables, for example, the processing of information by centers in the brain to be visualized directly. Such processing causes the involved area of the brain to increase metabolism and "light up" on the scan. One of the more controversial uses of neuroimaging has been researching "thought identification" or mind-reading.

The first chapter of the history of neuroimaging traces back to the Italian neuroscientist Angelo Mosso who invented the 'human circulation balance', which could non-invasively measure the redistribution of blood during emotional and intellectual activity.[2] However, although briefly mentioned by William James in 1890, the details and precise workings of this balance and the experiments Mosso performed with it have remained largely unknown until the recent discovery of the original instrument as well as Mosso&rsquos reports by Stefano Sandrone and colleagues.[3]

In 1918 the American neurosurgeon Walter Dandy introduced the technique of ventriculography. X-ray images of the ventricular system within the brain were obtained by injection of filtered air directly into one or both lateral ventricles of the brain. Dandy also observed that air introduced into the subarachnoid space via lumbar spinal puncture could enter the cerebral ventricles and also demonstrate the cerebrospinal fluid compartments around the base of the brain and over its surface. This technique was called pneumoencephalography.

In 1927 Egas Moniz introduced cerebral angiography, whereby both normal and abnormal blood vessels in and around the brain could be visualized with great precision.

In the early 1970s, Allan McLeod Cormack and Godfrey Newbold Hounsfield introduced computerized axial tomography (CAT or CT scanning), and ever more detailed anatomic images of the brain became available for diagnostic and research purposes. Cormack and Hounsfield won the 1979 Nobel Prize for Physiology or Medicine for their work. Soon after the introduction of CAT in the early 1980s, the development of radioligands allowed single photon emission computed tomography (SPECT) and positron emission tomography (PET) of the brain.

More or less concurrently, magnetic resonance imaging (MRI or MR scanning) was developed by researchers including Peter Mansfield and Paul Lauterbur, who were awarded the Nobel Prize for Physiology or Medicine in 2003. In the early 1980s MRI was introduced clinically, and during the 1980s a veritable explosion of technical refinements and diagnostic MR applications took place. Scientists soon learned that the large blood flow changes measured by PET could also be imaged by the correct type of MRI. Functional magnetic resonance imaging (fMRI) was born, and since the 1990s, fMRI has come to dominate the brain mapping field due to its low invasiveness, lack of radiation exposure, and relatively wide availability.

In the early 2000s, the field of neuroimaging reached the stage where limited practical applications of functional brain imaging have become feasible. The main application area is crude forms of brain-computer interface.

Indications

Neuroimaging follows a neurological examination in which a physician has found cause to more deeply investigate a patient who has or may have a neurological disorder.

One of the more common neurological problems which a person may experience is simple syncope.[4][5] In cases of simple syncope in which the patient's history does not suggest other neurological symptoms, the diagnosis includes a neurological examination but routine neurological imaging is not indicated because the likelihood of finding a cause in the central nervous system is extremely low and the patient is unlikely to benefit from the procedure.[5]

Neuroimaging is not indicated for patients with stable headaches which are diagnosed as migraine.[6] Studies indicate that presence of migraine does not increase a patient's risk for intracranial disease.[6] A diagnosis of migraine which notes the absence of other problems, such as papilledema, would not indicate a need for neuroimaging.[6] In the course of conducting a careful diagnosis, the physician should consider whether the headache has a cause other than the migraine and might require neuroimaging.[6]

Another indication for neuroimaging is CT-, MRI- and PET-guided stereotactic surgery or radiosurgery for treatment of intracranial tumors, arteriovenous malformations and other surgically treatable conditions.[7][8][9][10]

Brain imaging techniques

Computed axial tomography

Computed tomography (CT) or Computed Axial Tomography (CAT) scanning uses a series of x-rays of the head taken from many different directions. Typically used for quickly viewing brain injuries, CT scanning uses a computer program that performs a numerical integral calculation (the inverse Radon transform) on the measured x-ray series to estimate how much of an x-ray beam is absorbed in a small volume of the brain. Typically the information is presented as cross-sections of the brain.[11]

Diffuse optical imaging

Diffuse optical imaging (DOI) or diffuse optical tomography (DOT) is a medical imaging modality which uses near infrared light to generate images of the body. The technique measures the optical absorption of haemoglobin, and relies on the absorption spectrum of haemoglobin varying with its oxygenation status. High-density diffuse optical tomography (HD-DOT) has been compared directly to fMRI using response to visual stimulation in subjects studied with both techniques, with reassuringly similar results.[12] HD-DOT has also been compared to fMRI in terms of language tasks and resting state functional connectivity.[13]

Event-related optical signal

Event-related optical signal (EROS) is a brain-scanning technique which uses infrared light through optical fibers to measure changes in optical properties of active areas of the cerebral cortex. Whereas techniques such as diffuse optical imaging (DOT) and near-infrared spectroscopy (NIRS) measure optical absorption of haemoglobin, and thus are based on blood flow, EROS takes advantage of the scattering properties of the neurons themselves and thus provides a much more direct measure of cellular activity. EROS can pinpoint activity in the brain within millimeters (spatially) and within milliseconds (temporally). Its biggest downside is the inability to detect activity more than a few centimeters deep. EROS is a new, relatively inexpensive technique that is non-invasive to the test subject. It was developed at the University of Illinois at Urbana-Champaign where it is now used in the Cognitive Neuroimaging Laboratory of Dr. Gabriele Gratton and Dr. Monica Fabiani.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without the use of ionizing radiation (X-rays) or radioactive tracers.

Functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) and arterial spin labeling (ASL) relies on the paramagnetic properties of oxygenated and deoxygenated hemoglobin to see images of changing blood flow in the brain associated with neural activity. This allows images to be generated that reflect which brain structures are activated (and how) during the performance of different tasks or at resting state. According to the oxygenation hypothesis, changes in oxygen usage in regional cerebral blood flow during cognitive or behavioral activity can be associated with the regional neurons as being directly related to the cognitive or behavioral tasks being attended.

Most fMRI scanners allow subjects to be presented with different visual images, sounds and touch stimuli, and to make different actions such as pressing a button or moving a joystick. Consequently, fMRI can be used to reveal brain structures and processes associated with perception, thought and action. The resolution of fMRI is about 2-3 millimeters at present, limited by the spatial spread of the hemodynamic response to neural activity. It has largely superseded PET for the study of brain activation patterns. PET, however, retains the significant advantage of being able to identify specific brain receptors (or transporters) associated with particular neurotransmitters through its ability to image radiolabelled receptor "ligands" (receptor ligands are any chemicals that stick to receptors).

As well as research on healthy subjects, fMRI is increasingly used for the medical diagnosis of disease. Because fMRI is exquisitely sensitive to oxygen usage in blood flow, it is extremely sensitive to early changes in the brain resulting from ischemia (abnormally low blood flow), such as the changes which follow stroke. Early diagnosis of certain types of stroke is increasingly important in neurology, since substances which dissolve blood clots may be used in the first few hours after certain types of stroke occur, but are dangerous to use afterward. Brain changes seen on fMRI may help to make the decision to treat with these agents. With between 72% and 90% accuracy where chance would achieve 0.8%,[14] fMRI techniques can decide which of a set of known images the subject is viewing.[15]

Magnetoencephalography

Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices such as superconducting quantum interference devices (SQUIDs) or spin exchange relaxation-free[16] (SERF) magnetometers. MEG offers a very direct measurement of neural electrical activity (compared to fMRI for example) with very high temporal resolution but relatively low spatial resolution. The advantage of measuring the magnetic fields produced by neural activity is that they are likely to be less distorted by surrounding tissue (particularly the skull and scalp) compared to the electric fields measured by electroencephalography (EEG). Specifically, it can be shown that magnetic fields produced by electrical activity are not affected by the surrounding head tissue, when the head is modeled as a set of concentric spherical shells, each being an isotropic homogeneous conductor. Real heads are non-spherical and have largely anisotropic conductivities (particularly white matter and skull). While skull anisotropy has a negligible effect on MEG (unlike EEG), white matter anisotropy strongly affects MEG measurements for radial and deep sources.[17] Note, however, that the skull was assumed to be uniformly anisotropic in this study, which is not true for a real head: the absolute and relative thicknesses of diploë and tables layers vary among and within the skull bones. This makes it likely that MEG is also affected by the skull anisotropy,[18] although probably not to the same degree as EEG.

There are many uses for MEG, including assisting surgeons in localizing a pathology, assisting researchers in determining the function of various parts of the brain, neurofeedback, and others.

Positron emission tomography

Positron emission tomography (PET) and brain positron emission tomography, measure emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream. The emission data are computer-processed to produce 2- or 3-dimensional images of the distribution of the chemicals throughout the brain.[19]:57 The positron emitting radioisotopes used are produced by a cyclotron, and chemicals are labeled with these radioactive atoms. The labeled compound, called a radiotracer, is injected into the bloodstream and eventually makes its way to the brain. Sensors in the PET scanner detect the radioactivity as the compound accumulates in various regions of the brain. A computer uses the data gathered by the sensors to create multicolored 2- or 3-dimensional images that show where the compound acts in the brain. Especially useful are a wide array of ligands used to map different aspects of neurotransmitter activity, with by far the most commonly used PET tracer being a labeled form of glucose (see Fludeoxyglucose (18F) (FDG)).

The greatest benefit of PET scanning is that different compounds can show blood flow and oxygen and glucose metabolism in the tissues of the working brain. These measurements reflect the amount of brain activity in the various regions of the brain and allow to learn more about how the brain works. PET scans were superior to all other metabolic imaging methods in terms of resolution and speed of completion (as little as 30 seconds) when they first became available. The improved resolution permitted better study to be made as to the area of the brain activated by a particular task. The biggest drawback of PET scanning is that because the radioactivity decays rapidly, it is limited to monitoring short tasks.[19]:60 Before fMRI technology came online, PET scanning was the preferred method of functional (as opposed to structural) brain imaging, and it continues to make large contributions to neuroscience.

PET scanning is also used for diagnosis of brain disease, most notably because brain tumors, strokes, and neuron-damaging diseases which cause dementia (such as Alzheimer's disease) all cause great changes in brain metabolism, which in turn causes easily detectable changes in PET scans. PET is probably most useful in early cases of certain dementias (with classic examples being Alzheimer's disease and Pick's disease) where the early damage is too diffuse and makes too little difference in brain volume and gross structure to change CT and standard MRI images enough to be able to reliably differentiate it from the "normal" range of cortical atrophy which occurs with aging (in many but not all) persons, and which does not cause clinical dementia.

Single-photon emission computed tomography

Single-photon emission computed tomography (SPECT) is similar to PET and uses gamma ray-emitting radioisotopes and a gamma camera to record data that a computer uses to construct two- or three-dimensional images of active brain regions.[20] SPECT relies on an injection of radioactive tracer, or "SPECT agent," which is rapidly taken up by the brain but does not redistribute. Uptake of SPECT agent is nearly 100% complete within 30 to 60 seconds, reflecting cerebral blood flow (CBF) at the time of injection. These properties of SPECT make it particularly well-suited for epilepsy imaging, which is usually made difficult by problems with patient movement and variable seizure types. SPECT provides a "snapshot" of cerebral blood flow since scans can be acquired after seizure termination (so long as the radioactive tracer was injected at the time of the seizure). A significant limitation of SPECT is its poor resolution (about 1 cm) compared to that of MRI. Today, SPECT machines with Dual Detector Heads are commonly used, although Triple Detector Head machines are available in the marketplace. Tomographic reconstruction, (mainly used for functional "snapshots" of the brain) requires multiple projections from Detector Heads which rotate around the human skull, so some researchers have developed 6 and 11 Detector Head SPECT machines to cut imaging time and give higher resolution.[21][22]

Like PET, SPECT also can be used to differentiate different kinds of disease processes which produce dementia, and it is increasingly used for this purpose. Neuro-PET has a disadvantage of requiring the use of tracers with half-lives of at most 110 minutes, such as FDG. These must be made in a cyclotron, and are expensive or even unavailable if necessary transport times are prolonged more than a few half-lives. SPECT, however, is able to make use of tracers with much longer half-lives, such as technetium-99m, and as a result, is far more widely available.

Cranial ultrasound

Cranial ultrasound is usually only used in babies, whose open fontanelles provide acoustic windows allowing ultrasound imaging of the brain. Advantages include the absence of ionising radiation and the possibility of bedside scanning, but the lack of soft-tissue detail means MRI is preferred for some conditions.

Advantages and Concerns of Neuroimaging Techniques

Functional Magnetic Resonance Imaging (fMRI)

fMRI is commonly classified as a minimally-to-moderate risk due to its non-invasiveness compared to other imaging methods. fMRI uses blood oxygenation level dependent (BOLD)-contrast in order to produce its form of imaging. BOLD-contrast is a naturally occurring process in the body so fMRI is often preferred over imaging methods that require radioactive markers to produce similar imaging.[23] A concern in the use of fMRI is its use in individuals with medical implants or devices and metallic items in the body. The magnetic resonance (MR) emitted from the equipment can cause failure of medical devices and attract metallic objects in the body if not properly screened for. Currently, the FDA classifies medical implants and devices into three categories, depending on MR-compatibility: MR-safe (safe in all MR environments), MR-unsafe (unsafe in any MR environment), and MR-conditional (MR-compatible in certain environments, requiring further information).[24]

Computed Tomography (CT) Scan

The CT scan was introduced in the 1970s and quickly became one of the most widely used methods of imaging. A CT scan can be performed in under a second and produce rapid results for clinicians, with its ease of use leading to an increase in CT scans performed in the United States from 3 million in 1980 to 62 million in 2007. Clinicians oftentimes take multiple scans, with 30% of individuals undergoing at least 3 scans in one study of CT scan usage[26]. CT scans can expose patients to levels of radiation 100-500 times higher than traditional x-rays, with higher radiation doses producing better resolution imaging.[27] While easy to use, increases in CT scan use, especially in asymptomatic patients, is a topic of concern since patients are exposed to significantly high levels of radiation[26].

Positron Emission Tomography (PET)

In PET scans, imaging does not rely on intrinsic biological processes, but relies on a foreign substance injected into the bloodstream traveling to the brain. Patients are injected with radioisotopes that are metabolized in the brain and emit positrons to produce a visualization of brain activity.[23] The amount of radiation a patient is exposed to in a PET scan is relatively small, comparable to the amount of environmental radiation an individual is exposed to across a year. PET radioisotopes have limited exposure time in the body as they commonly have very short half-lives (

2 hours) and decay rapidly.[28] Currently, fMRI is a preferred method of imaging brain activity compared to PET, since it does not involve radiation, has a higher temporal resolution than PET, and is more readily available in most medical settings.[23]

Magnetoencephalography (MEG) & Electroencephalography (EEG)

The high temporal resolution of MEG and EEG allow these methods to measure brain activity down to the millisecond. Both MEG and EEG do not require exposure of the patient to radiation to function. EEG electrodes detect electrical signals produced by neurons to measure brain activity and MEG uses oscillations in the magnetic field produced by these electrical currents to measure activity. A barrier in the widespread usage of MEG is due to pricing, as MEG systems can cost millions of dollars. EEG is a much more widely used method to achieve such temporal resolution as EEG systems cost much less than MEG systems. A disadvantage of EEG and MEG is that both methods have poor spatial resolution when compared to fMRI.[23]

Criticism and cautions

Some scientists have criticized the brain image-based claims made in scientific journals and the popular press, like the discovery of "the part of the brain responsible" for functions like talents, specific memories, or generating emotions such as love. Many mapping techniques have a relatively low resolution, including hundreds of thousands of neurons in a single voxel. Many functions also involve multiple parts of the brain, meaning that this type of claim is probably both unverifiable with the equipment used, and generally based on an incorrect assumption about how brain functions are divided. It may be that most brain functions will only be described correctly after being measured with much more fine-grained measurements that look not at large regions but instead at a very large number of tiny individual brain circuits. Many of these studies also have technical problems like small sample size or poor equipment calibration which means they cannot be reproduced - considerations which are sometimes ignored to produce a sensational journal article or news headline. In some cases the brain mapping techniques are used for commercial purposes, lie detection, or medical diagnosis in ways which have not been scientifically validated.[29]

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Neuroimaging."


Using MRI to diagnose mental illness

Diagnosing mental health issues accurately and in a timely way has historically been a challenge for the health care industry. Unlike many physical ailments, which can be diagnosed with the aid of objective tests and tools, mental illness has long required a more subjective approach to evaluating symptoms. In recent years, magnetic resonance imaging (MRI) has allowed practitioners to make steady progress in improving their diagnostic approach.


An fMRI is safe, painless, and noninvasive. There are no known health risks of the procedure, as long as the patient has no metal or electronic implants (because the MRI machine has a very powerful magnet).

The benefits, on the other hand, are significant. Before the invention of fMRI, the only way to locate a person’s language or motor-skills center was to stimulate parts of the brain during an operation or perform invasive angiographic examinations—both of which required the patient to be awake to respond to questions. Knowing this information ahead of time makes surgery safer and faster and the patient can stay under sedation during surgery.


Difference Between MRI and fMRI

Currently, in the advent of technological advancements, a number of different types of innovations are invented and modified to make the diagnosis of common and even rare diseases a lot easier. These diagnostic tools make use of either machines or biologic studies, and in some cases both. One of the most common ways to diagnose internal diseases not seen by the naked eye is through imaging. In the laboratory, different types of sources are used to make the imaging possible. Radiation, electricity, and magnetic fields are only some to name a few. One type of imaging device that utilizes the magnetic and electrical sources of energy is what we call the MRI. Through some modifications in technological aspects, a sister machine was created out of the MRI and was called an fMRI. The differences between the two machines are hereby noted.

Magnetic resonance imaging, or MRI, is a machine used for brain structure imaging. When in some cases a CT scan cannot detect the existing problem, an MRI is helpful for discovering unnoticed anatomical anomalies caused by a disease process or traumatic event. It is a utility used for grand research in determining structural differences and a behavior correlation. On the other hand, functional magnetic resonance imaging, or fMRI, is a one of the highlights of the MRI technology wherein it functions through blood flow or blood oxygen level measurements to achieve the brain’s functional image. It is primarily used to gather relevant data as to the consumption of oxygen by the tissues. Through its modernization, fMRI sequences will view a picture of the brain’s active region by picking up the excess blood supply called Blood Oxygen Level Dependence (BOLD). In general, an MRI and fMRI differ from each other in a way that an MRI views the anatomical structure while an fMRI views the metabolic function.

In addition, the measurement of signals is different for an MRI and an fMRI individually. An MRI studies the water molecule’s hydrogen nuclei whereas an fMRI calculates the levels of oxygen. In atomic physics, the MRI’s structural imaging views at a high resolution the difference between tissue types with respect to space. On the other hand, an fMRI’s functional imaging views the tissue differences with respect to time. In addition to this, an MRI has a high, spatial resolution while an fMRI has a long-distance, superior, temporal resolution.

When talking about its technological advancement, an fMRI is still starting to build up its name unlike the MRI wherein it is already at its peak as one of the widely used equipment technologies in the medical world. Moreover, the fMRI is yet to be introduced for diagnostic purposes and is only used in experiments unlike the revolutionary MRI.

In terms of the cost in buying the machine, the fMRI is considered to be more expensive than an MRI because of the additional software and hardware required for it. The price may reach up to hundreds of thousands to millions, and that is quite a lot of money. For a cheaper choice, the MRI is preferred.

To make things clear, neither an MRI nor an fMRI has an advantage over the other because both machines serve for different functions.

1.The MRI and fMRI differ from each other in a way that the MRI views the anatomical structure while the fMRI views the metabolic function.

2.An MRI studies the water molecule’s hydrogen nuclei whereas an fMRI calculates the levels of oxygen.

3.An MRI’s structural imaging views at a high resolution the differences between tissue types with respect to space. On the other hand, an fMRI’s functional imaging views the tissue differences with respect to time.

4.The MRI has a high, spatial resolution while an fMRI has a long-distance, superior, temporal resolution.

5.When talking about its technological advancements, the fMRI is still starting to build up its name unlike the MRI wherein it is already at its peak as one of the widely used equipment technologies in the medical world.

6.The fMRI is yet to be introduced for diagnostic purposes and is only used in experiments unlike the revolutionary MRI.

7.The fMRI is considered to be more expensive than the MRI because of the additional software and hardware required for it.


What Are the Benefits of an Early Alzheimer's Diagnosis?

Early, accurate diagnosis is beneficial for several reasons. Beginning treatment early in the disease process may help preserve daily functioning for some time, even though the underlying Alzheimer’s process cannot be stopped or reversed.

Having an early diagnosis helps people with Alzheimer’s and their families:

In addition, an early diagnosis gives people greater opportunities to participate in clinical trials that are testing possible new treatments for Alzheimer’s disease or in other research studies.

Learn more about Alzheimer's disease from MedlinePlus.


Purpose of Test

Positron emission tomography has a broad range of diagnostic applications but is typically ordered if your doctor either suspects cancer or that a cancer may have spread. It is routinely used to assess the status of your heart prior to bypass surgery, especially if other imaging tests are inconclusive. It is also commonly ordered if early Alzheimer's disease is suspected or to evaluate the brain prior to surgery to treat refractory seizures.

Beyond these indications, a PET scan is also commonly used to stage cancer, to evaluate the extent of damage following a heart attack or stroke, and to monitor your response to cardiovascular, neurological, or cancer treatments.

PET differs from CT and MRI in that it examines the function, rather than the structure, of living cells. By contrast, CT and MRI are used to detect damage caused by a disease. In essence, PET looks at how your body responds to a disease, while computed tomography (CT) and magnetic resonance imaging (MRI) look at the damage caused by one.

Among its many functions, PET can measure blood flow, oxygen intake, how your body uses glucose (sugar), and the speed by which a cell replicates. By identifying abnormalities in cellular metabolism, a PET scan can detect the early onset of a disease well before other imaging tests.  

PET can be used to diagnose different conditions depending on the type of radiotracer used. The most common tracer, known as fluorodeoxyglucose (FDG), is used in 90 percent of PET scans, the procedure of which is commonly referred to as FDG-PET.

When injected into the bloodstream, FDG is taken up by glucose transporter molecules in cells. Because cancer cells multiply rapidly and do not undergo programmed cell death like normal cells, they will absorb far more FDG in the course of metabolizing sugar.

FDG can also be used to highlight areas of low metabolic activity caused by the obstruction of blood flow. Similarly, FDG-PET can spot changes in oxygen and glucose levels in the brain consistent with disease, impairment, and psychiatric illness.  

Other types of radiotracers highlight cellular abnormalities not detected by FDG. These include:

  • 11C-metomidate used to detect adrenocortical tumors (those occurring in hormone-producing cells of the adrenal cortex)
  • Fluorodeoxysorbital (FDS) used to diagnose bacterial infections
  • Fluorodopa used to detect neuroendocrine tumors (those occurring in hormone-producing cells of the nervous system)
  • Gallium-68 dotatate, also used to detect neuroendocrine tumors
  • Nitrogen-13 and oxygen-15 used to detect impaired blood flow

There are well over 40 different radiotracers used for PET scanning purposes with more being developed every day.

Conditions Diagnosed

PET is primarily used to diagnose cancer, cardiovascular disease, and neurologic disorders.

For cancer, PET is especially useful as it can scan the entire body and pinpoint both a primary tumor and areas of metastasis (where the cancer has spread). With that being said, not all cancers can be detected by PET.

For cardiovascular disease, a PET scan can reveal areas of decreased blood flow to the heart, brain, or lungs. By viewing the effects of circulatory impairment, your doctor can make the most appropriate treatment choice, including angioplasty or cardiac bypass surgery.

PET can also help predict the likelihood of a heart attack or stroke by detecting and measuring the hardening of arteries (atherosclerosis).

Among the cardiovascular conditions the test can diagnose:

For neurologic disorders, a PET scan can be used to measure brain activity in relation to areas of high and low radioactivity. Since the brain requires large amounts of glucose and oxygen to function, any shortages can easily be detected on a scan.

Among the neurologic disorders a PET can help diagnose:

  • Alzheimer disease
  • Brain hematomas (blood clots)
  • Dementia
  • Multiple sclerosis
  • Parkinson's disease

In addition, PET can be used to detect bacterial infections, most specifically enterobacterial types associated with endocarditis, septic arthritis, osteomyelitis, and central nervous system infections.  

Combination Scanning

When constructing a diagnosis, there is an advantage to looking at both the cause and consequence of a disease. It is for this reason that PET is frequently combined with CT or MRI, an approach referred to as either special views or co-registration. Doing so provides the doctor with both anatomic (physical) and metabolic (biochemical) information.

Modern PET scanners are now available with integrated CT scanners (PET-CT) which can create two sets of precisely matched images. Modern PET scanners are now available with integrated CT scanners (PET-CT) or MRI scanners (PET-MRI) which can create two sets of precisely matched images.  


Neuroimaging (Brain Imaging)

Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the nervous system. It is a relatively new discipline within medicine, neuroscience, and psychology.[1] Physicians who specialize in the performance and interpretation of neuroimaging in the clinical setting are neuroradiologists.

Neuroimaging falls into two broad categories:

  • Structural imaging, which deals with the structure of the nervous system and the diagnosis of gross (large scale) intracranial disease (such as a tumor) and injury.
  • Functional imaging, which is used to diagnose metabolic diseases and lesions on a finer scale (such as Alzheimer's disease) and also for neurological and cognitive psychology research and building brain-computer interfaces.

Functional imaging enables, for example, the processing of information by centers in the brain to be visualized directly. Such processing causes the involved area of the brain to increase metabolism and "light up" on the scan. One of the more controversial uses of neuroimaging has been researching "thought identification" or mind-reading.

The first chapter of the history of neuroimaging traces back to the Italian neuroscientist Angelo Mosso who invented the 'human circulation balance', which could non-invasively measure the redistribution of blood during emotional and intellectual activity.[2] However, although briefly mentioned by William James in 1890, the details and precise workings of this balance and the experiments Mosso performed with it have remained largely unknown until the recent discovery of the original instrument as well as Mosso&rsquos reports by Stefano Sandrone and colleagues.[3]

In 1918 the American neurosurgeon Walter Dandy introduced the technique of ventriculography. X-ray images of the ventricular system within the brain were obtained by injection of filtered air directly into one or both lateral ventricles of the brain. Dandy also observed that air introduced into the subarachnoid space via lumbar spinal puncture could enter the cerebral ventricles and also demonstrate the cerebrospinal fluid compartments around the base of the brain and over its surface. This technique was called pneumoencephalography.

In 1927 Egas Moniz introduced cerebral angiography, whereby both normal and abnormal blood vessels in and around the brain could be visualized with great precision.

In the early 1970s, Allan McLeod Cormack and Godfrey Newbold Hounsfield introduced computerized axial tomography (CAT or CT scanning), and ever more detailed anatomic images of the brain became available for diagnostic and research purposes. Cormack and Hounsfield won the 1979 Nobel Prize for Physiology or Medicine for their work. Soon after the introduction of CAT in the early 1980s, the development of radioligands allowed single photon emission computed tomography (SPECT) and positron emission tomography (PET) of the brain.

More or less concurrently, magnetic resonance imaging (MRI or MR scanning) was developed by researchers including Peter Mansfield and Paul Lauterbur, who were awarded the Nobel Prize for Physiology or Medicine in 2003. In the early 1980s MRI was introduced clinically, and during the 1980s a veritable explosion of technical refinements and diagnostic MR applications took place. Scientists soon learned that the large blood flow changes measured by PET could also be imaged by the correct type of MRI. Functional magnetic resonance imaging (fMRI) was born, and since the 1990s, fMRI has come to dominate the brain mapping field due to its low invasiveness, lack of radiation exposure, and relatively wide availability.

In the early 2000s, the field of neuroimaging reached the stage where limited practical applications of functional brain imaging have become feasible. The main application area is crude forms of brain-computer interface.

Indications

Neuroimaging follows a neurological examination in which a physician has found cause to more deeply investigate a patient who has or may have a neurological disorder.

One of the more common neurological problems which a person may experience is simple syncope.[4][5] In cases of simple syncope in which the patient's history does not suggest other neurological symptoms, the diagnosis includes a neurological examination but routine neurological imaging is not indicated because the likelihood of finding a cause in the central nervous system is extremely low and the patient is unlikely to benefit from the procedure.[5]

Neuroimaging is not indicated for patients with stable headaches which are diagnosed as migraine.[6] Studies indicate that presence of migraine does not increase a patient's risk for intracranial disease.[6] A diagnosis of migraine which notes the absence of other problems, such as papilledema, would not indicate a need for neuroimaging.[6] In the course of conducting a careful diagnosis, the physician should consider whether the headache has a cause other than the migraine and might require neuroimaging.[6]

Another indication for neuroimaging is CT-, MRI- and PET-guided stereotactic surgery or radiosurgery for treatment of intracranial tumors, arteriovenous malformations and other surgically treatable conditions.[7][8][9][10]

Brain imaging techniques

Computed axial tomography

Computed tomography (CT) or Computed Axial Tomography (CAT) scanning uses a series of x-rays of the head taken from many different directions. Typically used for quickly viewing brain injuries, CT scanning uses a computer program that performs a numerical integral calculation (the inverse Radon transform) on the measured x-ray series to estimate how much of an x-ray beam is absorbed in a small volume of the brain. Typically the information is presented as cross-sections of the brain.[11]

Diffuse optical imaging

Diffuse optical imaging (DOI) or diffuse optical tomography (DOT) is a medical imaging modality which uses near infrared light to generate images of the body. The technique measures the optical absorption of haemoglobin, and relies on the absorption spectrum of haemoglobin varying with its oxygenation status. High-density diffuse optical tomography (HD-DOT) has been compared directly to fMRI using response to visual stimulation in subjects studied with both techniques, with reassuringly similar results.[12] HD-DOT has also been compared to fMRI in terms of language tasks and resting state functional connectivity.[13]

Event-related optical signal

Event-related optical signal (EROS) is a brain-scanning technique which uses infrared light through optical fibers to measure changes in optical properties of active areas of the cerebral cortex. Whereas techniques such as diffuse optical imaging (DOT) and near-infrared spectroscopy (NIRS) measure optical absorption of haemoglobin, and thus are based on blood flow, EROS takes advantage of the scattering properties of the neurons themselves and thus provides a much more direct measure of cellular activity. EROS can pinpoint activity in the brain within millimeters (spatially) and within milliseconds (temporally). Its biggest downside is the inability to detect activity more than a few centimeters deep. EROS is a new, relatively inexpensive technique that is non-invasive to the test subject. It was developed at the University of Illinois at Urbana-Champaign where it is now used in the Cognitive Neuroimaging Laboratory of Dr. Gabriele Gratton and Dr. Monica Fabiani.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without the use of ionizing radiation (X-rays) or radioactive tracers.

Functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) and arterial spin labeling (ASL) relies on the paramagnetic properties of oxygenated and deoxygenated hemoglobin to see images of changing blood flow in the brain associated with neural activity. This allows images to be generated that reflect which brain structures are activated (and how) during the performance of different tasks or at resting state. According to the oxygenation hypothesis, changes in oxygen usage in regional cerebral blood flow during cognitive or behavioral activity can be associated with the regional neurons as being directly related to the cognitive or behavioral tasks being attended.

Most fMRI scanners allow subjects to be presented with different visual images, sounds and touch stimuli, and to make different actions such as pressing a button or moving a joystick. Consequently, fMRI can be used to reveal brain structures and processes associated with perception, thought and action. The resolution of fMRI is about 2-3 millimeters at present, limited by the spatial spread of the hemodynamic response to neural activity. It has largely superseded PET for the study of brain activation patterns. PET, however, retains the significant advantage of being able to identify specific brain receptors (or transporters) associated with particular neurotransmitters through its ability to image radiolabelled receptor "ligands" (receptor ligands are any chemicals that stick to receptors).

As well as research on healthy subjects, fMRI is increasingly used for the medical diagnosis of disease. Because fMRI is exquisitely sensitive to oxygen usage in blood flow, it is extremely sensitive to early changes in the brain resulting from ischemia (abnormally low blood flow), such as the changes which follow stroke. Early diagnosis of certain types of stroke is increasingly important in neurology, since substances which dissolve blood clots may be used in the first few hours after certain types of stroke occur, but are dangerous to use afterward. Brain changes seen on fMRI may help to make the decision to treat with these agents. With between 72% and 90% accuracy where chance would achieve 0.8%,[14] fMRI techniques can decide which of a set of known images the subject is viewing.[15]

Magnetoencephalography

Magnetoencephalography (MEG) is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices such as superconducting quantum interference devices (SQUIDs) or spin exchange relaxation-free[16] (SERF) magnetometers. MEG offers a very direct measurement of neural electrical activity (compared to fMRI for example) with very high temporal resolution but relatively low spatial resolution. The advantage of measuring the magnetic fields produced by neural activity is that they are likely to be less distorted by surrounding tissue (particularly the skull and scalp) compared to the electric fields measured by electroencephalography (EEG). Specifically, it can be shown that magnetic fields produced by electrical activity are not affected by the surrounding head tissue, when the head is modeled as a set of concentric spherical shells, each being an isotropic homogeneous conductor. Real heads are non-spherical and have largely anisotropic conductivities (particularly white matter and skull). While skull anisotropy has a negligible effect on MEG (unlike EEG), white matter anisotropy strongly affects MEG measurements for radial and deep sources.[17] Note, however, that the skull was assumed to be uniformly anisotropic in this study, which is not true for a real head: the absolute and relative thicknesses of diploë and tables layers vary among and within the skull bones. This makes it likely that MEG is also affected by the skull anisotropy,[18] although probably not to the same degree as EEG.

There are many uses for MEG, including assisting surgeons in localizing a pathology, assisting researchers in determining the function of various parts of the brain, neurofeedback, and others.

Positron emission tomography

Positron emission tomography (PET) and brain positron emission tomography, measure emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream. The emission data are computer-processed to produce 2- or 3-dimensional images of the distribution of the chemicals throughout the brain.[19]:57 The positron emitting radioisotopes used are produced by a cyclotron, and chemicals are labeled with these radioactive atoms. The labeled compound, called a radiotracer, is injected into the bloodstream and eventually makes its way to the brain. Sensors in the PET scanner detect the radioactivity as the compound accumulates in various regions of the brain. A computer uses the data gathered by the sensors to create multicolored 2- or 3-dimensional images that show where the compound acts in the brain. Especially useful are a wide array of ligands used to map different aspects of neurotransmitter activity, with by far the most commonly used PET tracer being a labeled form of glucose (see Fludeoxyglucose (18F) (FDG)).

The greatest benefit of PET scanning is that different compounds can show blood flow and oxygen and glucose metabolism in the tissues of the working brain. These measurements reflect the amount of brain activity in the various regions of the brain and allow to learn more about how the brain works. PET scans were superior to all other metabolic imaging methods in terms of resolution and speed of completion (as little as 30 seconds) when they first became available. The improved resolution permitted better study to be made as to the area of the brain activated by a particular task. The biggest drawback of PET scanning is that because the radioactivity decays rapidly, it is limited to monitoring short tasks.[19]:60 Before fMRI technology came online, PET scanning was the preferred method of functional (as opposed to structural) brain imaging, and it continues to make large contributions to neuroscience.

PET scanning is also used for diagnosis of brain disease, most notably because brain tumors, strokes, and neuron-damaging diseases which cause dementia (such as Alzheimer's disease) all cause great changes in brain metabolism, which in turn causes easily detectable changes in PET scans. PET is probably most useful in early cases of certain dementias (with classic examples being Alzheimer's disease and Pick's disease) where the early damage is too diffuse and makes too little difference in brain volume and gross structure to change CT and standard MRI images enough to be able to reliably differentiate it from the "normal" range of cortical atrophy which occurs with aging (in many but not all) persons, and which does not cause clinical dementia.

Single-photon emission computed tomography

Single-photon emission computed tomography (SPECT) is similar to PET and uses gamma ray-emitting radioisotopes and a gamma camera to record data that a computer uses to construct two- or three-dimensional images of active brain regions.[20] SPECT relies on an injection of radioactive tracer, or "SPECT agent," which is rapidly taken up by the brain but does not redistribute. Uptake of SPECT agent is nearly 100% complete within 30 to 60 seconds, reflecting cerebral blood flow (CBF) at the time of injection. These properties of SPECT make it particularly well-suited for epilepsy imaging, which is usually made difficult by problems with patient movement and variable seizure types. SPECT provides a "snapshot" of cerebral blood flow since scans can be acquired after seizure termination (so long as the radioactive tracer was injected at the time of the seizure). A significant limitation of SPECT is its poor resolution (about 1 cm) compared to that of MRI. Today, SPECT machines with Dual Detector Heads are commonly used, although Triple Detector Head machines are available in the marketplace. Tomographic reconstruction, (mainly used for functional "snapshots" of the brain) requires multiple projections from Detector Heads which rotate around the human skull, so some researchers have developed 6 and 11 Detector Head SPECT machines to cut imaging time and give higher resolution.[21][22]

Like PET, SPECT also can be used to differentiate different kinds of disease processes which produce dementia, and it is increasingly used for this purpose. Neuro-PET has a disadvantage of requiring the use of tracers with half-lives of at most 110 minutes, such as FDG. These must be made in a cyclotron, and are expensive or even unavailable if necessary transport times are prolonged more than a few half-lives. SPECT, however, is able to make use of tracers with much longer half-lives, such as technetium-99m, and as a result, is far more widely available.

Cranial ultrasound

Cranial ultrasound is usually only used in babies, whose open fontanelles provide acoustic windows allowing ultrasound imaging of the brain. Advantages include the absence of ionising radiation and the possibility of bedside scanning, but the lack of soft-tissue detail means MRI is preferred for some conditions.

Advantages and Concerns of Neuroimaging Techniques

Functional Magnetic Resonance Imaging (fMRI)

fMRI is commonly classified as a minimally-to-moderate risk due to its non-invasiveness compared to other imaging methods. fMRI uses blood oxygenation level dependent (BOLD)-contrast in order to produce its form of imaging. BOLD-contrast is a naturally occurring process in the body so fMRI is often preferred over imaging methods that require radioactive markers to produce similar imaging.[23] A concern in the use of fMRI is its use in individuals with medical implants or devices and metallic items in the body. The magnetic resonance (MR) emitted from the equipment can cause failure of medical devices and attract metallic objects in the body if not properly screened for. Currently, the FDA classifies medical implants and devices into three categories, depending on MR-compatibility: MR-safe (safe in all MR environments), MR-unsafe (unsafe in any MR environment), and MR-conditional (MR-compatible in certain environments, requiring further information).[24]

Computed Tomography (CT) Scan

The CT scan was introduced in the 1970s and quickly became one of the most widely used methods of imaging. A CT scan can be performed in under a second and produce rapid results for clinicians, with its ease of use leading to an increase in CT scans performed in the United States from 3 million in 1980 to 62 million in 2007. Clinicians oftentimes take multiple scans, with 30% of individuals undergoing at least 3 scans in one study of CT scan usage[26]. CT scans can expose patients to levels of radiation 100-500 times higher than traditional x-rays, with higher radiation doses producing better resolution imaging.[27] While easy to use, increases in CT scan use, especially in asymptomatic patients, is a topic of concern since patients are exposed to significantly high levels of radiation[26].

Positron Emission Tomography (PET)

In PET scans, imaging does not rely on intrinsic biological processes, but relies on a foreign substance injected into the bloodstream traveling to the brain. Patients are injected with radioisotopes that are metabolized in the brain and emit positrons to produce a visualization of brain activity.[23] The amount of radiation a patient is exposed to in a PET scan is relatively small, comparable to the amount of environmental radiation an individual is exposed to across a year. PET radioisotopes have limited exposure time in the body as they commonly have very short half-lives (

2 hours) and decay rapidly.[28] Currently, fMRI is a preferred method of imaging brain activity compared to PET, since it does not involve radiation, has a higher temporal resolution than PET, and is more readily available in most medical settings.[23]

Magnetoencephalography (MEG) & Electroencephalography (EEG)

The high temporal resolution of MEG and EEG allow these methods to measure brain activity down to the millisecond. Both MEG and EEG do not require exposure of the patient to radiation to function. EEG electrodes detect electrical signals produced by neurons to measure brain activity and MEG uses oscillations in the magnetic field produced by these electrical currents to measure activity. A barrier in the widespread usage of MEG is due to pricing, as MEG systems can cost millions of dollars. EEG is a much more widely used method to achieve such temporal resolution as EEG systems cost much less than MEG systems. A disadvantage of EEG and MEG is that both methods have poor spatial resolution when compared to fMRI.[23]

Criticism and cautions

Some scientists have criticized the brain image-based claims made in scientific journals and the popular press, like the discovery of "the part of the brain responsible" for functions like talents, specific memories, or generating emotions such as love. Many mapping techniques have a relatively low resolution, including hundreds of thousands of neurons in a single voxel. Many functions also involve multiple parts of the brain, meaning that this type of claim is probably both unverifiable with the equipment used, and generally based on an incorrect assumption about how brain functions are divided. It may be that most brain functions will only be described correctly after being measured with much more fine-grained measurements that look not at large regions but instead at a very large number of tiny individual brain circuits. Many of these studies also have technical problems like small sample size or poor equipment calibration which means they cannot be reproduced - considerations which are sometimes ignored to produce a sensational journal article or news headline. In some cases the brain mapping techniques are used for commercial purposes, lie detection, or medical diagnosis in ways which have not been scientifically validated.[29]

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Neuroimaging."


Can I get an fMRI scan to show that my daughter has dyslexia?

Answer:

Unfortunately, brain scans can’t be used yet to “prove” that a child has dyslexia. The same is true for other learning and thinking differences, like ADHD .

Scientists use functional magnetic resonance imaging (fMRI) and other technologies like EEG to study how the brain works when it does complex tasks like reading. They’re using these tools to create better maps of the brain.

But everyone’s brains look different. If you pick two random people off the street, their brain anatomy and brain function will not be identical, just as their faces aren’t identical. We need to better understand this kind of variation before it becomes clear how the dyslexic brain is truly different.

Another challenge with fMRI research is that the differences between the brain scans of people with and without dyslexia are small. That’s why research studies need to look at groups of people to see which differences reliably occur in people with dyslexia. Typically in a research study, 15 or more people who have reading issues are compared to roughly the same size group of people who don’t have reading issues. Then the study looks for statistically significant differences between the two groups.

In other words, it takes a lot of brains (literally!) to reliably identify which features look different in people with dyslexia. A single brain is not enough.

Some researchers are starting to look into using a brain scan to identify people with dyslexia. But this is still just a concept. For this to become a reality, researchers need to develop techniques that allow them to pinpoint differences in an individual that can be identified reliably in most people with dyslexia.

Your child’s doctor may have heard of something called a “clinical fMRI.” For example, fMRI can help map out critical language areas of the brain so they can be avoided when a surgeon removes a tumor that is causing seizures. But before this became acceptable practice, researchers had to provide sufficient evidence to show that fMRI was helpful and reliable in this process.

We haven’t reached the point where fMRI can be used in clinical settings to identify dyslexia. When children participate in one of our research studies, we always let their parents know that we can share with them the results of the behavioral testing in the study. For example, some parents want to know their child’s scores on the reading tests that are given as part of the study. These tests take place separately from the fMRI session.

But we never provide families with an interpretation based on the scans. And we can’t comment on any individual differences (unless we make an incidental observation, such as a tumor). We give the kids a picture of their brain, which they think is very cool. But the brain of a child with dyslexia doesn’t look different to the naked eye.

Perhaps one day imaging will play a role in identifying individuals with dyslexia. Until then, parents need to continue to use traditional options, such as a neuropsychological evaluation . This process can provide useful insights into your daughter’s strengths and weaknesses. It can also inform decisions about what kinds of services and support she needs in school.


Using MRI to diagnose mental illness

Diagnosing mental health issues accurately and in a timely way has historically been a challenge for the health care industry. Unlike many physical ailments, which can be diagnosed with the aid of objective tests and tools, mental illness has long required a more subjective approach to evaluating symptoms. In recent years, magnetic resonance imaging (MRI) has allowed practitioners to make steady progress in improving their diagnostic approach.


Alzheimer's diagnosis, management improved by brain scans

Amyloid-positive (left) and amyloid-negative (right) PET scans can respectively be used to diagnose or rule out Alzheimer's disease in individuals with memory loss or cognitive decline. Credit: UCSF Memory and Aging Center

A first-of-its-kind national study has found that a form of brain imaging that detects Alzheimer's-related "plaques" significantly influenced clinical management of patients with mild cognitive impairment and dementia.

The study revealed that providing clinicians with the results of positron emission tomography (PET) scans that identify amyloid plaques in the brain changed medical management—including the use of medications and counseling—in nearly two-thirds of cases, more than double what researchers predicted in advance of the study. The technique, known as "amyloid PET imaging," also altered the diagnosis of the cause of cognitive impairment in more than one in three study participants.

The multicenter study of more than 11,000 Medicare beneficiaries, published April 2, 2019 in the Journal of the American Medical Association (JAMA), was managed by the American College of Radiology and led by scientists at the Alzheimer's Association, UC San Francisco, Brown University School of Public Health, Virginia Commonwealth University School of Public Health, Washington University School of Medicine in St. Louis, UC Davis School of Medicine, and the Kaiser Permanente Division of Research.

"We are impressed by the magnitude of these results, which make it clear that amyloid PET imaging can have a major impact on how we diagnose and care for patients with Alzheimer's disease and other forms of cognitive decline," said study lead author and principal investigator Gil Rabinovici, MD, Distinguished Professor of Neurology at the UCSF Memory and Aging Center and member of the UCSF Weill Institute for Neurosciences.

"These results present highly credible, large-scale evidence that amyloid PET imaging can be a powerful tool to improve the accuracy of Alzheimer's diagnosis and lead to better medical management, especially in difficult-to-diagnose cases," added Maria C. Carrillo, Ph.D., Alzheimer's Association chief science officer and a co-author of the study. "It is important that amyloid PET imaging be more broadly accessible to those who need it."

Alzheimer's disease is characterized by the accumulation of both amyloid protein plaques and tau protein "tangles" in the brain, the presence of which are required for a definitive diagnosis. Until recently, amyloid plaques could only be detected by postmortem analysis of autopsied brain tissue. With the advent of amyloid PET—which involves injecting patients with "tracer" molecules that stick to amyloid plaques and can be used to visualize their location in the brain—it became possible to detect plaques with a brain scan and therefore more accurately diagnose people living with the disease.

Though there is no cure for Alzheimer's disease, early diagnoses enable physicians to prescribe appropriate symptom-management therapies, counsel families on important safety and care-planning issues and direct people to clinical trials for promising new drugs. It also allows people with the disease and their families to plan for the future, including legal and financial issues, and accessing resources and support programs. PET imaging results that reveal no signs of amyloid buildup in the brain rule out Alzheimer's disease as the cause of memory loss, which can prompt an evaluation for alternative and sometimes reversible causes, such as medication side effects, sleep or mood disorders and other medical conditions.

However, despite FDA approval of amyloid PET tracers, use of amyloid PET imaging to assist with the accurate diagnosis of the cause of someone's dementia is currently not covered by Medicare or health insurance plans, making it unavailable to most people.

Launched in 2016, the four-year Imaging Dementia—Evidence for Amyloid Scanning (IDEAS) study was developed by a team of scientists convened by the Alzheimer's Association to determine whether learning the results amyloid PET imaging would change medical management and health outcomes of people with memory loss and cognitive decline. IDEAS recruited nearly 1,000 dementia specialists at 595 sites in the U.S. and enrolled more than 16,000 Medicare beneficiaries with mild cognitive impairment or dementia of uncertain cause. Under their Coverage with Evidence Development policy, the Centers for Medicare & Medicaid Services (CMS) reimbursed amyloid PET scans conducted at 343 facilities and interpreted by more than 700 imaging specialists as part of this clinical study.

"This was a uniquely real-world study that looked at the impact of amyloid PET imaging in community clinics and other non-academic settings, and demonstrates for the first time how much impact this technology has in real-world dementia care," Rabinovici said.

The newly published results from the first phase of the IDEAS study focused on how amyloid PET scans altered physician diagnosis and treatment plans for the 11,409 participants who completed the study. As the study's primary endpoint, the scientists collected data on how physicians altered participants' medication prescriptions and counseling about safety and future planning. As a secondary endpoint, the researchers evaluated whether PET imaging results caused physicians to alter participants' diagnoses. Finally, several exploratory endpoints included physician decisions about referrals to Alzheimer's clinical trials.

The newly published data reveal that physicians changed their clinical management of more than 60 percent of patients in the study, more than double the number the authors had predicted in advance.

In participants who joined the study with mild cognitive impairment and whose brain scans revealed the presence of significant amyloid deposits, clinicians were twice as likely to prescribe Alzheimer's drugs following PET imaging (

40 percent prior to imaging vs.

82 percent following imaging). In those with dementia and significant amyloid buildup on PET scans, prescriptions of these drugs rose from

91 percent after the study. Doctors discontinued the use of these drugs in some patients whose scans revealed little amyloid deposition. In addition, for approximately one quarter of study participants, physicians changed non-Alzheimer's drug prescriptions and counseling recommendations based on PET imaging results.

PET scans that revealed no significant amyloid buildup led physicians to rule out Alzheimer's disease for approximately one in three patients who had previously been given an Alzheimer's diagnosis. On the other hand, PET scans that showed significant amyloid plaque buildup led to a new diagnosis of Alzheimer's disease in nearly half of patients who had not previously been diagnosed with the disease.

The researchers also discovered that one-third of participants who had previously been referred to Alzheimer's clinical trials showed no sign of amyloid buildup based on PET imaging, which generally rules out Alzheimer's disease as the cause of their cognitive symptoms. Based on the imaging results, physicians were able to ensure that nearly all patients referred to Alzheimer's trials were amyloid-positive (93 percent), which is critical to these trials' success.

"Accurate diagnoses are critical to ensure patients are receiving the most appropriate treatments. In particular, Alzheimer's medications can worsen cognitive decline in people with other brain diseases," said Rabinovici. "But perhaps more fundamentally, people who come into the clinic with concerns about memory problems want answers. An early, definitive diagnosis may allow individuals to be part of planning for the next phase of their lives and to make decisions that otherwise would eventually need to be made by others."

The IDEAS team is currently analyzing data on the study's second phase, which will examine how amyloid PET scans affect health outcomes following the scan. The researchers are using CMS claims data to document hospitalization rates and Emergency Department visits for IDEAS participants, and comparing them to participants with similar neurologic problems but who did not undergo amyloid PET. They plan to publish their findings in 2020. In addition, the researchers are developing a second study (known as New IDEAS) to include more people with both typical and atypical clinical presentations of Alzheimer's and recruit a study group that better reflects the racial and socioeconomic diversity of the national population.


Neuropsychological Testing

Neuropsychological testing adds to the clinical assessment of a person. These tests evaluate behavior, language, visuospatial abilities, memory, abstraction, planning and mental control, motor skills and intelligence. The patterns of strengths and weaknesses in a person help identify which areas of the brain are functioning well and which ones are doing poorly.

  • Tests of a person with frontotemporal dementia (FTD) may show visual and memory abilities intact. However, abstract thinking, word generation, motivation and ability to follow rules may be disrupted.