Tests and procedures
Sarah Bekaert in Women's Health, 2018
In a bone scan, a radionuclide is used which accumulates in areas where there is a lot of bone activity (i.e. where bone cells are breaking down or parts of the bone are being repaired). This type of scan can therefore be used to detect areas of bone where there is cancer, infection or damage. These areas of activity are seen as ‘hot spots’ on the scan image. A radionuclide (sometimes called a radioisotope or isotope) is a chemical that emits a type of radioactivity known as gamma rays. A tiny amount of radionuclide is introduced into the body, usually by injection into a vein (sometimes it is breathed in or swallowed, depending on the test). Gamma rays are similar to X-rays and are detected by means of a device called a gamma camera. The gamma rays that are emitted from inside the body are detected by the gamma camera and converted into an electrical signal which is then sent to a computer. The computer builds a picture by converting the different intensities of radioactivity emitted into different colours or shades of grey. For example, areas of the target organ or tissue which emit high levels of gamma rays may be shown as red spots on the picture on the computer monitor, areas that emit low levels of gamma rays may be shown as blue spots, and various other colours may be used to show intermediate levels of gamma rays emitted.
Introduction
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha in Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A typical gamma camera system will have the following collimators: Low-energy, general purpose (LEGP) or low-energy all purpose (LEAP) collimator, designed for the energy emitted by 99mTc (140 keV) and ideal for dynamic studies (Figs 1.53a,b).Low-energy high-resolution collimator, ideal for applications such as bone imaging where image detail is necessary. The collimator will have lower sensitivity than a LEAP collimator and thus images take longer to acquire (Fig. 1.53b).Medium-energy collimators are designed to work with higher-energy nuclides such as indium-111 (111In), gallium-67 (67Ga) and iodine-131 (131I).Pinhole collimators are useful in imaging small organs such as the thyroid or for imaging joints. They are designed for low-energy isotopes and are of value as they magnify the area of interest. The pinhole collimator is a hollow cone of lead with a small hole at its apex, which produces a high-resolution magnified image.
Imaging Science, Imaging Equipment (Pretreatment and On-treatment)
Mike Kirby, Kerrie-Anne Calder in On-treatment Verification Imaging, 2019
Positron emission tomography (PET) is another form of functional imaging used to inform, in particular, of the potential of malignant cells in the body. It relies on the use of radioisotopes, which are positron emitters (rather than mainly gamma emitters as used for standard radioisotope imaging), and uses subtly different technology inside the PET scanner as compared with a gamma camera. When a positron emitting isotope (such as Fluorine 18) is chemically bound to a glucose analogue (e.g. as in fluorodeoxyglucose, FDG), it becomes a means for targeting cells and tissues that have a high metabolic function and process glucose and other sugars to get the energy for proliferation. This is the case for all cells, but malignant cells do so at a much more rapid rate than normal tissues and differentially use up more glucose than normal cells. By detecting the increased radiolabeled glucose metabolism with a high degree of sensitivity, PET potentially can identify cancerous cells, even at an early stage, when other imaging modalities may miss them. PET imaging, therefore, can be used to inform better the size and positioning of the planning target volume for radiotherapy.
Progress in large field-of-view interventional planar scintigraphy and SPECT imaging
Published in Expert Review of Medical Devices, 2022
Martijn M.A. Dietze, Hugo W.A.M de Jong
Several companies have introduced mobile gamma cameras to translate large field-of-view imaging to the operation room. Three examples, that are based on a conventional NaI(Tl) scintillation crystal that is coupled with photomultiplier-tubes, are the Nucline TH by Mediso Medical Imaging Systems [35], the SoloMobile by DDD Diagnostic [36], and the Cardiotom by Adolesco AB (see Figure 1b) [37–39]. These devices have the benefit that they are based on the conventional gamma camera design for which a lot of experience is already available. A disadvantage is that this conventional gamma camera is relatively bulky: this makes it somewhat less appropriate for use in the dynamic environment of the intervention room (because there is a bigger chance for collisions) and this places more demands on the supporting gantry.
Alpha-ketoglutarate mediated hepatoprotection against alcohol induced toxicity: in vivo functional observation studies in Sprague Dawley rats using gamma scintigraphy
Published in Drug and Chemical Toxicology, 2020
Lalita Mehra, Harish Rawat, Abhinav Jaimini, Amit Tyagi, Gaurav Mittal
Present study elucidates the hepatoprotective potential of alpha-ketoglutarate against alcohol-induced toxicity by estimating its effect on the levels of transaminases, enzymatic antioxidants (catalase, superoxide dismutase, and total reduced glutathione) and lipid peroxidation. Histological assessment between different treatment groups was also done. Besides these conventional markers, another important highlight of the study is the use of hepatobiliary scintigraphy (HBS) in establishing the hypothesis in vivo. This real time functional imaging study was done under a gamma camera using 99mTc-mebrofenin as radiotracer. We determined (a) Hepatic extraction fraction (HEF), for quantification of radiotracer uptake, thereby signifying viable parenchymal liver cell mass, (b) Time to reach maximum hepatic uptake (Tpeak), and (c) Time for hepatic uptake to reduce by 50% (T1/2 peak), for quantification of radiotracer excretion from the liver cells.
Prostate-specific membrane antigen-directed imaging and radioguided surgery with single-photon emission computed tomography: state of the art and future outlook
Published in Expert Review of Medical Devices, 2022
Luca Filippi, Barbara Palumbo, Viviana Frantellizzi, Susanna Nuvoli, Giuseppe De Vincentis, Angela Spanu, Orazio Schillaci
PET/CT presents a plethora of advantages with respect to conventional gamma-camera, such as high resolution, precise anatomical localization and possibility of performing accurate quantitative calculations [11]. However, in spite of PET/CT’s aforementioned advantages, imaging with single-photon emitting nuclides represents a widespread diagnostic modality, since it can provide clinically useful information in front of more affordable costs. Notably, the advent of hybrid single photon emission computed tomography/X-ray computed tomography (SPECT/CT) device has represented a cornerstone in the field, since it has allowed both precise correlation of anatomical and functional data and accurate attenuation correction. Notably, further improvements of SPECT/CT technology have been made in recent years, such as the implementation of novel detectors and the introduction of whole-body SPECT/CT scan through multiple bed positions with the consequent possibility of tracers’ uptake quantification in absolute units [12–15].
Related Knowledge Centers
- Cardiac Stress Test
- Drug Development
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- Radionuclide
- Scintigraphy
- Scintillation
- Nuclear Medicine
- Single-Photon Emission Computed Tomography
- Radiopharmaceutical