No abstract

No abstract

621.384.63The characteristics of 7.5-80 MeV proton cyclotrons for the production of short-lived and generator radionuclides for positron-emission tomography are presented. A classifi cation of cyclotrons by proton energy is given. Recommendations are made for choosing compact 7.5-12 MeV cyclotrons for producing short-lived 18 F, 15 O, 13 N, and 11 C and cyclotrons with proton energy tens of MeV for producing the generators 68 Ge/ 68 Ga and 82 Sr/ 82 Rb.Nuclear medicine is an effective means for diagnostics and treatment of different diseases. Radionuclides with a short half-life are used for diagnostics so that their post-examination activity decreases rapidly to a safe level. The radionuclides are produced in nuclear reactors and charged-particle accelerators as a result of reactions occurring under the action of neutrons, protons, and deuterium ions.Cyclotrons are located directly in the centers of nuclear medicine [1, 2]. Short-lived radionuclides are used immediately after production to synthesize radiopharmaceuticals containing labeled atoms emitting γ-rays or positrons. Fluorodesoxyglucose -glucose labeled with fl uorine 18 F -is widely used in positron-emission tomography to detect oncological diseases. It accumulates in organs where tumor growth actively occurs. Positrons, emitted at the fl uoroglucose accumulation site, annihilate with electrons. As a result two γ-rays are formed and fl y apart in opposite directions. A tomograph detects the location from which paired γ-rays are emitted and displays it on a monitor. Different radiopharmaceuticals are used in oncology and cardiology as carriers of labeled atoms. Radiopharmaceuticals are used to determine the site where radionuclides accumulate or to monitor their movement in the organism. Ordinarily, a positron-emission tomograph is combined with an x-ray computer tomograph for careful localization of the disease focus.In the generator method, a proton accelerator is used to obtain a long-lived parent radionuclide with a long half-life from which a different short-lived radionuclide is formed continually as a result of decay. The parent radionuclide is retained by a sorbent inside a column placed in a protective container. The accumulated short-lived radionuclide, but now weakly bound with the sorbent, is periodically washed out (eluated) of the generator by pumping a special solution for subsequent injection into the patient's circulatory system. The primary advantages of radionuclide generators are their long service life and deliverability to clinics located at a large distance from their production site. Three generators are widely used in diagnostics: 99 Mo/ 99m Tc, 82 Sr/ 82 Rb, and 68 Ge/ 68 Ga. The γ-emitting generator 99m Tc is used in single-photon emission computerized tomography. A tomograph records single γ-rays. About 80% of all examinations in oncology and cardiology are conducted using radiopharmaceuticals based on this radionuclide. The generators 82 Sr/ 82 Rb and 68 Ge/ 68 Ga are used for positron-emission diagnostics [3]. 82 Ru is used...

No abstract

No abstract