A Review of Modern Imaging Technologies Used in Nuclear Medicine
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A Review of Modern Imaging Technologies Used in Nuclear Medicine M. M. Khanukaev and S. A. Kulaga*
Medical equipment used for scintigraphic diagnosis of cancer (including early stages of cancer) is reviewed; its principles of operation and the advantages of its use are described. Both conventional and innovative diagnostic methods used in nuclear medicine are considered. In particular, innovative methods based on intraoperative navigation and determination of the resection completeness are described.
Introduction One of the most pressing problems of modern medi cine is the problem of cancer. According to the BBC News statistics [1], about 8.2 million people die from can cer every year. An effective way to combat this disease is to diagnose and treat it at the early stages. This leads to the need for the development of new diagnostic devices for nuclear medicine. Nuclear medical testing is an imaging technique based on the use of injectable or inhaled radioactive trac ers. The tracers emit gamma radiation that is then detected and converted into images using gamma detec tors. The principle of operation of all devices described in this article is based on the scintillation effect. The scintil lation method for detecting ionizing radiation is based on the interaction of radiation with a scintillating material resulting in flashes of visible light 10–910–4 s in duration. Sodium or cesium iodides activated by thallium (NaI(Tl), CsI(Tl)) can be used as a scintillating material. A photo multiplier tube (PMT) is used to register flashes of visible light in the scintillator crystal. Each such flash generates a current pulse at the PMT anode. Thus, the intensity of ionizing radiation can be determined from the photomul tiplier anode current. In radiology, radioactive isotopes with a relatively short halflife are used as sources of ionizing radiation; Don State Technical University, RostovonDon, Russia; Email: [email protected] * To whom correspondence should be addressed.
for example, 99mTc (6 h), 125I (59 days), 18F (110 min), etc. Special pharmaceuticals are used as isotope carriers, forming thereby a radiopharmaceutical that ensures the accumulation of the isotope in cancer cells.
Conventional Devices for Nuclear Medicine Since the late 1960s, singlephoton emission com puted tomography (SPECT) and positron emission tomography (PET) devices have been widely used in nuclear medicine. SPECT is based on the detection and visualization of single gamma quanta (photons) emitted by the isotope nuclei of a radiopharmaceutical. The main functional unit of a SPECT device (such as GE Optima, Siemens Symbia, etc.) is a pair of gamma detectors rotating around the table where the patient injected with a radio pharmaceutical lies. PET is a diagnostic method based on the detection of a pair of gamma quanta generated in the process of electron–positron annihilation and moving in opposite directions. The positron is previously generated by the beta decay of a radiopharmaceutical administered to the patient. The main
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