Radioactive Noble Gases for Medical Applications
Garimella V. S. Rayudu, Lelio G. Colombetti in Radiotracers for Medical Applications, 2019
The use of positron-emitting noble gases such as 123Xe and 77Kr and positron emission tomography to measure regional cerebral blood flow is an approach that should circumvent some of the limitations of the 133Xe washout technique. Positron emission tomography (PET) is an imaging technique that is capable of providing a quantitative measure of the distribution of a previously administered radiotracer in selected transverse sections of the body. The applicability of PET to the determination of regional cerebral blood flow has been reviewed by Raichle.9 The described techniques attempt both to exploit the potential of PET for increased spatial resolution and to utilize the depth independence of response of positron annihilation detection in order to investigate the blood flow in interior regions of the brain.
Malignant Neoplasms of the Colon
Philip H. Gordon, Santhat Nivatvongs, Lee E. Smith, Scott Thorn Barrows, Carla Gunn, Gregory Blew, David Ehlert, Craig Kiefer, Kim Martens in Neoplasms of the Colon, Rectum, and Anus, 2007
Positron emission tomography (PET) is a method of imaging using a positron-emitting isotope-labeled compound that is incorporated into the biochemical process occurring in organs and tissues of the body. The anatomic and morphologic characteristics are not as well delineated as with other imaging modalities such as CT and MRI, but PET images provide useful information about the nature and physiology of the cellular function of the tissue and have been used to evaluate neoplasms, including colorectal carcinoma. The most widely used isotope is 2-deoxy-2(18F) fluoro-D-glucose, or fluorodeoxyglucose (FDG). Imaging relies on the premise that there is an enhanced rate of glucose in malignant tissue. PET scanning is more accurate than CT scanning in identifying malignancy. This is especially true in the postoperative follow-up in differentiating recurrent carcinoma from fibrosis. Tempero et al. (359) reviewed three studies that compared the results of PET to CT, MRI, and radioimmunoguided scintigraphy (RIGS). In each case PET sensitivity and specificity were very high and better than the other modalities. The major problems are to clarify the role of PET in clinical management and determine who will benefit from this additional expensive, time consuming study. PET scans may have a role in both the diagnosis of and response to therapy of hepatic metastases.
Imaging procedures in understanding brain injury
Barbara A. Wilson, Samira Kashinath Dhamapurkar, Anita Rose in Surviving Brain Damage After Assault, 2016
Both CT and MRI scans produce structural images or images of a still brain. Even more sophisticated imaging involves functional imaging in which the brain can be seen in action. These include functional MRI (fMRI), positron emission tomography (PET) and single photon emission tomography (SPECT). When an area of the brain is in use because it is engaged in a particular activity such as speaking or thinking or imagining something, blood flow to that area increases. This is what is measured in an fMRI scan. Because fMRI does not require injections, surgery, the taking of substances or exposure to radiation, it is popular in research studies. For a PET scan, a radioactive tracer is introduced into the body, allowing the scanner to detect rays that are emitted and, from these, it can produce a three-dimensional image. A PET scan can identify many complex aspects of the brain but it is mainly a research tool that is expensive and not widely available (Coleman et al. (2007)). Because PET scans expose people to radiation, they cannot be used as frequently as fMRI, and women of child bearing age are not allowed to be used as research subjects. SPECT scans use radiation to measure cerebral blood flow. Although it is a relatively simple and inexpensive technique, it tends to produce rather poor images.
Application of advanced MRI techniques to monitor pharmacologic and rehabilitative treatment in multiple sclerosis: current status and future perspectives
Published in Expert Review of Neurotherapeutics, 2019
Maria A. Rocca, Paolo Preziosa, Massimo Filippi
PET is an imaging technique that uses radio-labeled molecules to provide information about function and metabolism of different tissues [26]. This technique is based on the detection and quantification of pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule [26]. Three dimensional images of tracer concentration within the body are then constructed by computer analysis [26]. Many radiotracers have been used in PET to image tissue concentration of many types of molecules of interest in MS (Figure 1) [27]. 18F-fluorodeoxyglucose (18F-FDG) showed a decreased cerebral metabolism in MS patients. 11C -Pittsburgh Compound B (11C-PIB) ([methyl-11C]-2-(40-methylaminophenyl)-6-hydroxybenzothiazole) showed a decreased myelin content in MS focal lesions. First (11C-(R)-PK11195) and second (11C-PBR28) generation radio-ligands in translocator protein (TSPO) and a radio-ligand to adenosine A2A receptor (11C-TMSX) can track activated microglia/macrophages and demonstrated a significant neuroinflammation in MS brains [27].
In vivo imaging of Lyme arthritis in mice by [18F]fluorodeoxyglucose positron emission tomography/computed tomography
Published in Scandinavian Journal of Rheumatology, 2018
A Pietikäinen, R Siitonen, H Liljenbäck, O Eskola, M Söderström, A Roivainen, J Hytönen
Positron emission tomography combined with computed tomography (PET/CT) is a quantitative and non-invasive imaging method used to monitor several different types of diseases in humans and in animal models. The decay of radiolabelled PET/CT tracers leads to detectable gamma radiation which can be monitored with PET/CT equipment and three-dimensional (3D) images of the location of the radiation can be recorded. Importantly, the combination of PET with CT enables the determination of the precise anatomical locations of PET signals. Probably the most common tracer used in PET studies is a radiolabelled glucose analogue, [18F]fluorodeoxyglucose ([18F]FDG). It is metabolized as glucose and it accumulates in hypermetabolic tissues such as tumours (4, 5). As a result, [18F]FDG tracer is widely used in cancer research but it can also be used to study infection and inflammation (6–8).
Do you understand English?
Published in Journal of Communication in Healthcare, 2021
Chaoyan Dong
Finally, someone called my son's name and led us to a cramped consultation room. He sat down at the desk and signaled me to sit on an empty chair by the door. I do not remember exactly how the doctor started the conversation, but he introduced himself as Dr … , asking me if I knew why my son was getting the scans. I told him we just learned on Friday that he had cancer. He interrupted me, instructing me that he needed to go through the Consent Form. The Consent Form should be quite standard for any imaging test, the doctor added, but this was my first time reading one at the Radiology Department as a caregiver. The form started with the purpose of a PEC/CT scan, the benefits of the scans, and the risks from getting the scans. One part under the Potential Risks caught my attention. It said, ‘Exposure to radiation during a PET/CT scan can slightly increase your risk of developing cancer in the future.’
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