Imaging Modalities: Nuclear Medicine

Abstract

Nuclear medicine is a medical discipline which uses molecular imaging by labeling a pharmaceutical molecule with a radioactive compound in order to visualize the metabolism of the labeled molecule in the human body. It provides noninvasive quantification of metabolism, receptor binding, and assessment of regional blood flow. Nuclear medicine techniques are used for diagnosis, treatment planning, outcome prediction, and control of the effectiveness of therapy. The nuclear medical techniques include SPECT (Single Photon Emission Computed Tomography) in which tracers emit gamma rays, and PET (Positron Emission Tomography) in which tracers emit positrons (positively charged electrons—antimatter) which collide with electrons and thereby emit annihilation radiation. Technical aspects include distribution of the radiotracer during the time of image collection, half-life, energy of emission, type of radiation, tracer kinetics, production of radionuclides, data analysis, appropriate patient preparation, and standardized acquisition protocols. The following techniques are discussed: FDG [fluorine-18 fluoro-2-deoxyglucose]-PET, amino acid PET (tracer: [Methyl-11C]-l-methionine (MET), 18F-FET (F-18-ethyltyrosin), 123I-FP-CIT for the assessment of the DAT (dopamine transporter) system in the presynaptic neurons, D2 receptor ligands (available radiotracers: 123I-IBZM and 123I-epidepride for SPECT and 11C-raclopride, 18F-fallypride, and 18F-desmethoxyfallypride (DMFP for PET), brain perfusion SPECT (radiopharmaceuticals used: ECD (ethyl cysteine dimer) and HMPAO (hexamethyl propylene amine oxime)), and amyloid imaging PET with the 11C-Pittsburgh-Compound-B (11C-PIB). Indications for Nuclear Medicine Examinations and the respective tracers are provided.