NUCLEAR MEDICINE


What is nuclear medicine?

Methods based on the use of ionizing radiation and radioactivity have penetrated many areas of science and technology, medicine and industry. In medicine, in addition to the oldest and most widespread X-ray diagnostics , radiotherapy is also used . From the 1950s. Open radioactive substances applied to the body began to be used for medical purposes - nuclear medicine was created .

Nuclear medicine is a field dealing with diagnostics and therapy using radioactive isotopes in open form, applied to the internal environment of the organism.

In vivo diagnostics

In radionuclide diagnostics in vivo in nuclear medicine, the patient is administered (usually intravenously, sometimes orally or by inhalation) a small amount of a suitable g- radioactive substance - the so-called radiondicator or radiopharmaceutical . The radioindicator used is specific to individual organs and types of examinations. The applied radioactive substance enters the metabolism of the organism and is distributed there according to its chemical composition - physiologically or pathologically it accumulates in certain organs and their parts and is subsequently excreted or regrouped. Gamma radiation emanates from the deposition sites of the radio indicator which, due to its penetration, passes through the tissue out of the body. Using sensitive detectors, we measure this radiation g and thus determine the distribution of the radiondicator in individual organs and structures inside the body.

Scintigraphy
The most perfect devices of this type are gamma cameras (scintillation cameras) - with the help of them we display the distribution of a radio indicator in the organism in
g radiation . This method, called scintigraphy or gammagraphy , makes it possible to obtain information not only anatomically, but mainly about organ functions and metabolism. By mathematical evaluation of scintigraphic studies, we can obtain time curves of the radioindicator distribution and calculate dynamic parameters characterizing the function of the relevant organs.

Schematic representation of the entire process of scintigraphic examination - from the application of a radio indicator to the patient, through the process of scintigraphic imaging with a gamma camera, evaluation, mathematical analysis and quantification, to the interpretation and diagnosis.
The SPECT (Single Photon Emission Copied Computerized Tomography) gamma camera slowly rotates around the patient's body, scans scintigraphic images from various angles and then uses computer reconstruction to create cross-sectional images (sections perpendicular to the camera's axis of rotation), from which computer graphics can be used to construct spatial (3-dimensional) images of the distribution of the radio indicator in the organs inside the body.

The PET gamma camera (Positron Computerized Tomography) detects photons of gamma annihilation radiation (511 keV energy) flying in opposite directions during the annihilation of positrons emitted by a b + radio indicator applied to a patient. These photons of annihilation radiation are coincidentally detected by an annular scintillation detector, and by computer reconstruction of the line projections of the coincidence sites, images of cross sections and, if necessary, are generated. 3D images similar to SPECT.

Nuclear medicine provides specific methods for the examination of virtually all organs and thus cooperates with a wide range of clinical disciplines. The most widespread use is mainly in  cardiology , nephrology , neurology , oncology , thyrology, gastroenterology .

Nuclear medicine methods are among the least burdensome non-invasive diagnostic examination methods. Due to the high sensitivity of the detectors, only a very small amount of radiopharmaceutical is applied to the patient, which is needed to obtain quality image information. The radiation exposure in methods in nuclear medicine is comparable (and often smaller) as in X-ray examinations.

Radionuclide scintigraphy is described in detail in Chapter 4 " Radioisotope Scintigraphy " of the book " Nuclear Physics and Ionizing Radiation Physics ".

In vitro diagnostics

In nuclear medicine, in vitro radioisotope diagnostic methods are also performed , where (non-radioactive) samples taken from patients are analyzed using radiochemical as well as biochemical techniques using radioisotopes. Most often it is a radioimmunoassay (RIA) or radiosaturation analysis, which is used to highly sensitive determination of the concentration of complex biological substances in the blood serum - hormones, tumor markers and other biologically important substances (it is briefly described in 3.5 " Radioisotope tracking methods ", section " Diagnostics in vitro. Radioimmunoassay ") .

Radioisotope therapy

Nuclear medicine also includes therapy with beta and alpha radionuclides, eg in the treatment of hyperthyroidism or thyroid cancer, blood diseases, palliative and curative therapy of tumors (and metastases), joint diseases.

A more detailed description of radionuclide therapy is given in the section " Radioisotope therapy " in Chapter 3 " Applications of ionizing radiation " of the book " Nuclear physics and physics of ionizing radiation ".

Nuclear medicine - interdisciplinary field of
nuclear medicine is due to the physical nature of its methods and instrumentation used branch interdisciplinary . In addition to physicians (specialized and certified in the field of nuclear medicine), health. nurses and laboratory technicians, are working in teamwork as well as experts from other professions - physicist , electronics , radiochemik , pharmacist . Along with medical and physical-technical aspects, considerable attention is also paid to the radiation protection of workers and patients in the workplaces of nuclear medicine when working with radioisotopes .

Detailed description of principles, methods and applications of nuclear medicine + nuclear physics:

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RNDr. Vojtech Ullmann