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Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain. Neuroanatomy is the science for localizing function in the Human brain. Pharmacology (from Greek grc φάρμακον pharmakon, "drug" and grc -λογία -logia) is the study of how Drugs The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain It is a relatively new discipline within medicine and neuroscience/psychology. Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the Neuroscience is a field devoted to the scientific study of the nervous system Psychology (from Greek grc ψῡχή psȳkhē, "breath life soul" and grc -λογία -logia) is an Academic and

Neuroimaging falls into two broad categories: structural imaging and functional imaging. Functional neuroimaging is the use of Neuroimaging technology to measure an aspect of brain function often with a view to understanding the relationship between activity in Structural imaging deals with the structure of the brain and the diagnosis of gross (large scale) intracranial disease (such as tumor), and injury. Functional imaging 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. Cognitive psychology is a branch of Psychology that investigates internal mental processes such as problem solving memory and language A brain-computer interface (BCI sometimes called a direct neural interface or a brain-machine interface, is a direct communication pathway between a human or animal 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.

Contents

Brain imaging techniques

CAT

Main article: Computed tomography

Computed Tomography (CT) or Computed Axial Tomography (CAT) scanning uses a series of x-rays of the head taken from many different directions. Computed tomography (CT is a Medical imaging method employing Tomography. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. 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. In Mathematics, the Radon transform in two dimensions named after the Austrian mathmematician Johann Radon, is the Integral transform consisting of the Typically the information is presented as cross sections of the brain. [1] In approximation, the more dense a material is, the whiter a volume of it will appear on the scan (just as in the more familiar "flat" X-rays). Rhodes Adair (of Harvard Medical School) is working on a new, more efficient version of the traditional CT scan. CT scans are primarily used for evaluating swelling from tissue damage in the brain and in assessment of ventricle size. Modern CT scanning can provide reasonably good images in a matter of minutes.

MRI

Main article: Magnetic resonance imaging
Sagittal MRI slice at the midline.
Sagittal MRI slice at the midline.

Magnetic Resonance Imaging (MRI) uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without use of ionizing radiation (X-rays) or radioactive tracers. During an MRI, a large cylindrical magnet creates a magnetic field around the head of the patient through which radio waves are sent. A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges When the magnetic field is imposed, each point in space has a unique radio frequency at which the signal is received and transmitted (Preuss). Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz Sensors read the frequencies and a computer uses the information to construct an image. The detection mechanisms are so precise that changes in structures over time can be detected. Using MRI, scientists can create images of both surface and subsurface structures with a high degree of anatomical detail. Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration MRI scans can produce cross sectional images in any direction from top to bottom, side to side, or front to back. The problem with original MRI technology was that while it provides a detailed assessment of the physical appearance, water content, and many kinds of subtle derangements of structure of the brain (such as inflammation or bleeding), it fails to provide information about the metabolism of the brain (i. e. how actively it is functioning) at the time of imaging. A distinction is therefore made between "MRI imaging" and "functional MRI imaging" (fMRI), where MRI provides only structural information on the brain while fMRI yields both structural and functional data.

fMRI

Main article: Functional magnetic resonance imaging
Axial MRI slice at the level of the basal ganglia, showing fMRI BOLD signal changes overlayed in red (increase) and blue (decrease) tones.
Axial MRI slice at the level of the basal ganglia, showing fMRI BOLD signal changes overlayed in red (increase) and blue (decrease) tones. Functional MRI or functional Magnetic Resonance Imaging (fMRI is a type of specialized MRI scan The basal ganglia (or basal nuclei) are a group of nuclei in the Brain interconnected with the Cerebral cortex, Thalamus and

Functional Magnetic Resonance Imaging (fMRI) relies on the paramagnetic properties of oxygenated and deoxygenated hemoglobin to see images of changing blood flow in the brain associated with neural activity. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein This allows images to be generated that reflect which brain structures are activated (and how) during performance of different tasks. 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). In Biochemistry, a receptor is a Protein molecule embedded in either the Plasma membrane or Cytoplasm of a cell to which a mobile signaling Monoamine transporters are structures in nerve-cell membranes that function as Neurotransmitter transporters transferring Monoamine neurotransmitters See Chemical synapse for an introduction to concepts and terminology used in this article

As well as research on healthy subjects, fMRI is increasingly used for the medical diagnosis of disease. Because fMRI is exquisitely sensitive to 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. A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain 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 afterwards. 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%,[2] fMRI techniques can decide which of a set of known images the subject is viewing. [3]

PET

Main article: Positron emission tomography
PET scan of a normal 20-year-old brain.
PET scan of a normal 20-year-old brain. Positron emission tomography ( PET) is a Nuclear medicine imaging technique which produces a three-dimensional image or map of functional processes in the

Positron Emission Tomography (PET) measures 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 (Nilsson 57). The positron emitting radioisotopes used are produced by a cyclotron, and chemicals are labelled with these radioactive atoms. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created A cyclotron is a type of Particle accelerator. Cyclotrons accelerate Charged particles using a high- Frequency, alternating Voltage (potential 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 FDG). In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally Fluorodeoxyglucose is a Glucose analog. Its full chemical name is 2-fluoro-2-deoxy-D-glucose, commonly abbreviated to 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. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. These measurements reflect the amount of brain activity in the various regions of the brain and allow us 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 (Nilsson 60). Before fMRI technology came online, PET scanning was the preferred method of functional (as opposed to structural) brain imaging, and it still continues to make large contributions to neuroscience. Neuroscience is a field devoted to the scientific study of the nervous system

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 Azheimer'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. Pick’s disease, also known as Pick disease and PiD, is a rare Neurodegenerative disease.

SPECT

Main article: 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 (Ball). Single photon emission computed tomography (SPECT or less commonly SPET is a Nuclear medicine tomographic imaging technique using Gamma rays. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created A gamma camera is a device used to image gamma radiation emitting radioisotopes a technique known as scintigraphy SPECT relies on an injection of radioactive tracer, which is rapidly taken up by the brain but does not redistribute. Uptake of SPECT agent is nearly 100% complete within 30 – 60s, 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.

Like PET, SPECT also can be used to differentiate different kinds of disease process which produce dementia, and it is increasingly used for this purpose. Neuro-PET has a disadvantage of requiring use of a tracers with half-lives of at most 110 minutes, such as FDG. Fluorodeoxyglucose is a Glucose analog. Its full chemical name is 2-fluoro-2-deoxy-D-glucose, commonly abbreviated to 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.

DOT

Main article: 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. Diffuse optical imaging (DOI or diffuse optical tomography (DOT is a Medical imaging modality which uses near Infrared light to generate images of the Medical imaging refers to the techniques and processes used to create Images of the human body (or parts thereof for clinical purposes ( Medical procedures seeking to Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of The technique measures the optical absorption of haemoglobin, and relies on the absorption spectrum of haemoglobin varying with its oxygenation status. In Physics, absorption of electromagnetic radiation is the process by which the Energy of a Photon is taken up by matter typically the electrons of an Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein A material's absorption spectrum shows the fraction of incident Electromagnetic radiation absorbed by the material over a range of Frequencies.

EROS

Main article: 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. 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 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 provide a much more direct measure of cellular activity. Diffuse optical imaging (DOI or diffuse optical tomography (DOT is a Medical imaging modality which uses near Infrared light to generate images of the 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.

History

Main article: History of neuroimaging

In 1918 the American neurosurgeon Walter Dandy introduced the technique of ventriculography. The history of Neuroimaging, began in the early 1900s with a technique called Pneumoencephalography. 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. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. The ventricular system is a set of structures in the Brain continuous with the Central canal of the Spinal cord. 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. Pneumoencephalography (sometimes abbreviated PEG is a Medical procedure in which Cerebrospinal fluid is drained to a small amount from around the Brain

In 1927 Egas Moniz, professor of neurology in Lisbon, introduced cerebral angiography, whereby both normal and abnormal blood vessels in and around the brain could be visualized with great accuracy. António Caetano de Abreu Freire EGAS MONIZ ('ɛgɐʃ mu'niʃ ( November 29, 1874 &ndash December 13, 1955 Lisbon (Lisboa liʒˈboɐ is the Capital and largest city of Portugal. Angiography or arteriography is a Medical imaging technique in which an X-ray image is taken to visualize the inside or lumen, of blood vessels

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. Allan MacLeod Cormack ( February 23, 1924 &ndash May 7, 1998) was a South African born American Physicist Sir Godfrey Newbold Hounsfield CBE FRS, ( 28 August 1919 &ndash 12 August 2004) was an English Electrical engineer Computed tomography (CT is a Medical imaging method employing Tomography. Cormack and Hounsfield won the 1979 Nobel Prize for Physiology or Medicine for their work. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. 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. A radioligand is a Radioactive biochemical substance (in particular a ligand) that is used for diagnosis or for research-oriented study of the receptor Single photon emission computed tomography (SPECT or less commonly SPET is a Nuclear medicine tomographic imaging technique using Gamma rays. Positron emission tomography ( PET) is a Nuclear medicine imaging technique which produces a three-dimensional image or map of functional processes in the

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. Sir Peter Mansfield, FRS, (born 9 October 1933) is a British Physicist who was awarded the 2003 Nobel Prize in Physiology or Paul Christian Lauterbur ( May 6, 1929 – March 27, 2007) was an American Chemist who shared the Nobel Prize The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. 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. Functional MRI or functional Magnetic Resonance Imaging (fMRI is a type of specialized MRI scan As noted above fMRI is also beginning to dominate the field of stroke treatment.

In 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. A brain-computer interface (BCI sometimes called a direct neural interface or a brain-machine interface, is a direct communication pathway between a human or animal

See also

References

  1. ^ Jeeves, p. Functional neuroimaging is the use of Neuroimaging technology to measure an aspect of brain function often with a view to understanding the relationship between activity in fNIR stands for functional Near-infrared imaging. fNIR is a spectroscopic neuro-imaging method for measuring the level of neuronal activity in the Brain Magnetoencephalography ( MEG) is an imaging technique used to measure the Magnetic fields produced by electrical activity in the Transcranial magnetic stimulation ( TMS) is a noninvasive method to excite neurons in the Brain: weak Electric currents are induced in the tissue by rapidly FreeSurfer is an MRI brain imaging software package developed by the Athinoula A The history of Neuroimaging, began in the early 1900s with a technique called Pneumoencephalography. The Human Cognome Project seeks to reverse engineer the Human brain, paralleling in many ways the Human Genome Project and its success in deciphering the Medical imaging refers to the techniques and processes used to create Images of the human body (or parts thereof for clinical purposes ( Medical procedures seeking to Brain mapping is a set of Neuroscience techniques predicated on the Mapping of (biological quantities or properties onto spatial representations of the (human or Statistical parametric mapping or SPM is a Statistical technique for examining differences in Brain activity recorded during Functional neuroimaging Neuroimaging software is used to study the structure and function of the brain Voxel based morphometry (VBM is a Neuroimaging analysis technique that allows investigation of focal differences in Brain Anatomy, using the statistical 21
  2. ^ Smith, Kerri. "Mind-reading with a brain scan", Nature News, Nature Publishing Group, March 5, 2008. Events 363 - Roman Emperor Julian moves from Antioch with an army of 90000 to attack the Sassanid Empire, in a 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Retrieved on 2008-03-05. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 363 - Roman Emperor Julian moves from Antioch with an army of 90000 to attack the Sassanid Empire, in a  
  3. ^ Keim, Brandon. "Brain Scanner Can Tell What You're Looking At", Wired News, CondéNet, March 5, 2008. Events 363 - Roman Emperor Julian moves from Antioch with an army of 90000 to attack the Sassanid Empire, in a 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Retrieved on 2008-03-05. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 363 - Roman Emperor Julian moves from Antioch with an army of 90000 to attack the Sassanid Empire, in a  

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Works cited

Dictionary

neuroimaging

-verb

  1. Present participle of neuroimage.
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