CAT and PET Scan
CAT (Computerized Axial Tomography) and PET (Positron Emission Tomography) scans are imaging techniques used in psychology to study brain structure and function. CAT scans provide detailed images of the brain's structure, while PET scans show brain activity by measuring blood flow and glucose metabolism. These scans help psychologists understand the relationship between brain structure, function, and psychological processes.
8 Key excerpts on "CAT and PET Scan"
eBook - ePub- G Neil Martin(Author)
- 2015(Publication Date)
- Routledge(Publisher)
...The CT technique is relatively non-invasive – that is, no object or process invades the body – but its spatial resolution is a little poor. This means that some of the structures cannot be seen with cut-glass clarity. CT is a measure of brain structure, not activity. 2.3 Positron Emission Tomography (PET) Positron Emission Tomography (PET), unlike CT, is a measure of the living brain's activity, rather than its structure. A PET scanner measures blood flow/oxygen consumption in the brain – the more active cells are, the more blood will flow to them and the more oxygen they will need (provided by the blood). The procedure and rationale for a PET scan is roughly as follows: harmless radioactively labelled water or glucose is injected into the participant as he or she lies on a bed with their head just inside a doughnut-shaped hole in the scanner (this is the part of the equipment that will detect the brain activity). Once injected, it takes about a minute for the water to reach the brain via blood flow. This tracer substance, as it is called, decays, but when it does particles called positrons are emitted (hence, Positron Emission Tomography). When positrons are emitted and collide with electrons, they form gamma rays, which are detected by the scanner. Thus, as water containing oxygen moves to active cells that need oxygen, the labelled water emits positrons that are detected by the scanner. The scanner can then construct a 2D or 3D, colour-coded image of 'active' brain areas based on the emission of these positrons. The water takes about 10-15 minutes to decay fully and become non-radioactive. A similar pattern is seen when radioactive glucose (2-DG) is injected. Radioactive glucose is taken up by metabolically active cells; the glucose emits positrons – like the water – which are detected by the scanner...
eBook - ePubPsychophysiology
Human Behavior and Physiological Response
- John L. Andreassi(Author)
- 2010(Publication Date)
- Psychology Press(Publisher)
...The two circles indicate the left and right amygdalae From Abercrombie et al. (1998). Copyright 1998 by Lippincott, Williams, and Wilkins. Adapted by permission. techniques that involve optical imaging. The magnetoencephalogram, involving measures of the brain’s magnetic fields, is also discussed. Several approaches that utilize optical imaging for studying the brain have been described by Gratton, Fabiani, Elbert, and Rockstroh (2003). An optical imaging technique that has psychophysiological applications is a process called photon migration. Another relatively new neuroimaging technique is referred to as SPECT (single photon emission computed tomography). Both SPECT and PET use radioactive tracers that are injected into the bloodstream. The bloodstream carries the tracer to the brain where local concentration is higher in areas with an increased blood flow or metabolism. The neuroimaging techniques mentioned here have enabled psychophysiologists and other neuroscientists to determine which brain areas become active during sensation, attention, perception, memory, language, emotion, and language processing. They have also enabled the examination of brain areas affected by stroke and various neurological diseases. POSITRON EMISSION TOMOGRAPHY (PET) The PET imaging technique has allowed clinicians and scientists to study normal and abnormal brain function. The so-called PET scan permits the viewing of various brain regions through a technique that combines computed tomography and a tracer assay method (Aine, 1995). The PET technique can provide information about glucose and oxygen metabolism in brain structures, blood flow in brain tissue (cerebral blood flow), and blood volume in brain areas (cerebral blood volume). The method allows researchers to view cross sections of different brain areas that are color coded to indicate differing amounts of activity...
eBook - ePubPicturing Personhood
Brain Scans and Biomedical Identity
- Joseph Dumit(Author)
- 2021(Publication Date)
- Princeton University Press(Publisher)
...These histories are thus ethnohistories, perspective-dependent accounts told within a contested field. PET Scanner: A History in One Thousand Words* PET is an acronym for positron emission tomography, a set of techniques and technologies for obtaining tomographic images (slices) of molecular biological activity in living beings. In contrast to CT scanning, which provides structural information about bodies (e.g., bone density), PET provides functional, time-dependent images of the rate of flow of specific molecules through a particular area of the body. PET thus provides a solution to the problem of how to obtain useful information about biochemical processes taking place in relatively inaccessible sections of living organisms (e.g., the heart and brain). The information that PET presents is both quantitative and visual, demanding careful measurement and complex physiological modeling in order to be interpreted. PET is currently used in a variety of clinical studies, including heart tissue viability, epilepsy focal localization, bone and breast cancer detection, and head trauma diagnosis. It has also been used in psychophysiological studies—correlating oxygen blood flow in specific regions of the brain with motor movement, visual attention, and cognitive tasks, as well as more complex cognitive skills. In psychiatry, Seymour Kety, David Ingvar, Monte Buchsbaum, and Jonathan Brodie each led teams that conducted extensive studies of schizophrenia. Other mental disorders have also been imaged. These have stimulated speculation on possible biological or molecular explanations of these disorders, but diagnostic ability still eludes investigators. PET is located at the intersection of a number of disciplines and technical paradigms. Though they are numerous, it is perhaps better to gesture toward the complexity than exclude, outright, vital participants...
eBook - ePubComing into Mind
The Mind-Brain Relationship: A Jungian Clinical Perspective
- Margaret Wilkinson(Author)
- 2014(Publication Date)
- Routledge(Publisher)
...This type of scan is able to scan rapidly and offers the finest resolution of all the scans but is very expensive. The PET scan records and translates into computer images the effects of an injection of a radioactive substance that gives off gamma rays: active areas of the brain appear red. The resolution is less defined and they necessitate a radioactive injection, which limits their use. It is the development of these ‘new non-invasive imaging techniques that allow three-dimensional spatial mapping of metabolic activity (which reflects the level of neuronal activity) in real time’ (Sherwood 2005), and in particular the use of fMRI and PET scans, that has enabled much of the advance in neuroscience. In the words of Solms and Turnbull, they are ‘yielding previously undreamed of knowledge about the physiological underpinnings of the inner world’ (Solms and Turnbull 2002: 5). But some caveats are required when assessing the contribution they can make to our knowledge at present. Imaging techniques cannot yet examine the complexity of interaction between brain regions. The time frames under consideration are those of milliseconds rather than the observational time frame of years in traditional analysis. Equipment remains clumsy, expensive and difficult to access. Much of the research data so far has been based on animal studies although human research data is now beginning to be available. Those who seek to map the brain have become increasingly aware of the complexity of that which they seek to map and, because of this, they are also increasingly aware of the danger of false positives in research results. With these words of caution in mind, I suggest we are experiencing the birth of a new and exciting era in our understanding of the brain-mind. Cells and their connections Cells and their connections produce the functioning mind that has for so long been the subject of our detailed observation in the consulting-room...
eBook - ePubNeuropsychology
From Theory to Practice
- David Andrewes(Author)
- 2015(Publication Date)
- Psychology Press(Publisher)
...Appendix 2 Brain Scans and Other Measures of Cognitive Neuroscience Commonly Used Research Measures Introduction In recent years there has been a huge expansion of imaging techniques that has not been easy to keep up with. The following are some reflections on the various techniques. Hopefully, some of these comments may increase some critical appraisal in this area and give an indication of just some of the approaches to neuroimaging. Computer Tomography (CT) Computer tomography provides an X-ray of the brain. This is often used clinically as a cheaper method of brain scanning. However, there are limitations to its use. It is best at measuring more salient measures of high density such as areas of haemorrhage causing pockets of blood in the brain that are referred to as haematoma. CT scans are good measures of bone mass in such conditions as fractures of the cranium (skull). While CT scans are often used as part of routine clinical testing, CT exposes the research participant to a large dose of ionizing radiation which limits the ethics permission for research use. Structural Magnetic Resonance Imaging (sMRI) Structural magnetic resonance imaging provides a contrast between the grey (brain cells) and white matter (axons) and cerebrospinal fluid that surrounds the brain and dwells in the ventricles (spaces in the brain). This delineation is superior to CT scan and allows volumes of structures (volumetrics) to be measured, e.g. the volume of the hippocampi. The physics is based on the fact that tissues absorb energy from radio waves and then give off these waves proportionally to the concentration of fluid in the tissue, as measured by hydrogen ions in water. Using a burst of a powerful magnetic field, the protons are realigned at time one (T1). After a period of relaxation (after the burst) a second scan may be taken at time two (T2)...
eBook - ePub- Aaron Newman(Author)
- 2019(Publication Date)
- SAGE Publications Ltd(Publisher)
...While conventional X-ray images produce only a single two-dimensional image taken from a single perspective, CT scanners incorporate an X-ray device that rotates around the person being scanned, acquiring many images from different angles and then using computer algorithms to create higher-resolution, 2D or 3D images from these. Clinical CT was developed beginning in the 1960s and first became available in the 1970s, and has since become a mainstay of diagnostic imaging for the head as well as other organs. Contrast in CT images is based on the ability of different types of tissue to block X-rays. It is sensitive to contrast between bone, fat, and water; however, its soft tissue contrast (for example, between grey and white matter and CSF) and spatial resolution are inferior to that of MRI. Therefore, a CT scan of the head does not allow visualization of gyral and sulcal anatomy with the same precision as structural MRI. It is, however, very useful in diagnosing different types of stroke (for example, haemorrhagic – bleeding – vs. ischaemic – caused by clotting), tumours, and other pathologies in the brain, and provides much more anatomical precision than PET alone. Combining CT with PET was a natural and logical technical development, as both rely on radiation detection (albeit different types of radiation), and there are clinical advantages to doing both scans at the same time. For one, accurate PET scanning requires attenuation correction, which compensates for the fact that different tissues absorb PERs differently (especially bone). CT scans provide ideal information for PET attenuation correction, especially if the scans are obtained without the patient moving (that is, in the same scanner)...
eBook - ePub- Bryon Adinoff, Elliot A. Stein, Bryon Adinoff, Elliot A. Stein(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
...The potential for these factors to vary from subject to subject necessitates that they be accounted for to provide interpretable results. The principles for detecting the emerging radiation and forming images are similar for single photon and positron emitters, but the underlying physics and the instruments employed are different [4,201]. Although both SPECT and PET detect radiotracer distribution, it is the chemical versatility of the positron emitters, the ability to measure their concentration quantitatively with relatively little attenuation by tissue, the greater sensitivity and the superior resolution of PET, which differentiates these two methods. Many positron-labeled compounds have been synthesized, enabling a wide range of biological processes to be measured quantitatively, non-invasively, and repeatedly. These include cerebral metabolism [202], blood flow [203]), neurotransmitter release [204], and enzyme activity [205--208]. Examples of those processes studied as they have been applied to drug abuse are given below. 3.3.2 Brain Activation PET and SPECT allow the mapping of neuronal activity using an index of changes in energy demand in specific brain areas as a surrogate of neuronal activity. Most often, the measure has been the regional cerebral metabolic rate for glucose (rCMRglc) using the PET tracer [ 18 F]fluorodeoxyglucose (FDG). Assays of regional cerebral blood flow (rCBF) have also been conducted with PET using [ 15 O]H 2 0 and with SPECT using [ 99m Tc] d,l- hexamethylpropyleneamine oxime (HMPAO). Measurements of CBF and metabolism are intimately related to local neuronal activity [90] and use the same principle discussed earlier for BOLD fMRI imaging. The measurement of rCMRglc utilizes FDG and is based on the technique previously developed to measure rCMRglc in laboratory animals with [ 14 C]-deoxyglucose and tissue autoradiography [209] and adapted for PET by using 18 F as the label [210,211]...
eBook - ePub- Simon R. Cherry, James A. Sorenson, Michael E. Phelps(Authors)
- 2012(Publication Date)
- Saunders(Publisher)
...Virtually all PET scanners, and a rapidly growing number of SPECT systems, are now integrated with a CT scanner in combined PET/CT and SPECT/CT configurations. These systems enable the facile correlation of structure (CT) and function (PET or SPECT), yielding better diagnostic insight in many clinical situations. The combination of nuclear medicine scanners with MRI systems also is under investigation, and as of 2011, first commercial PET/MRI systems were being delivered. In addition to its clinical role, PET (and to a certain extent, SPECT) continues to play a major role in the biomedical research community. PET has become an established and powerful research tool for quantitatively and noninvasively measuring the rates of biologic processes, both in the healthy and diseased state. In this research environment, the radiolabeled compounds and clinical nuclear medicine assays of the future are being developed. In preclinical, translational and clinical research, nuclear medicine has been at the forefront in developing new diagnostic opportunities in the field of molecular medicine, created by the merger of biology and medicine. A rapid growth is now occurring in the number and diversity of PET and SPECT molecular imaging tracers targeted to specific proteins and molecular pathways implicated in disease. These nuclear medicine technologies also have been embraced by the pharmaceutical and biotechnology industries to aid in drug development and validation. e The Role of Physics in Nuclear Medicine Although the physics underlying nuclear medicine is not changing, the technology for producing radioactive tracers and for obtaining images of those tracer distributions most certainly is. We can expect to continue seeing major improvements in nuclear medicine technology, which will come from combining advances in detector and accelerator physics, electronics, signal processing, and computer technology with the underlying physics of nuclear medicine...
