Nuclear medicine imaging techniques

Nuclear medicine is a rapidly developing field which focuses on the imaging of physiological processes and the evaluation of treatment of specific diseases. It involves the use of radiopharmaceuticals for both purposes. Different radiopharmaceuticals have different kinetics and can therefore be used to image processes in the body, the function of an organ or the presence of a specific cellular target. In sports medicine, bone scintigraphy and leukocyte scintigraphy play important roles. Radiopharmaceuticals in bone scintigraphy are diphosphonate complexes which are absorbed onto the hydroxyapatite crystal of newly formed bone and therefore represent osteoblast activity. When combined with the radionuclide technetium-99 m (99m Tc), it is very suitable for imaging. Bone scintigraphy, especially combined with additional single-photon emission computed tomography and conventional computed tomography (SPECT/CT), can, e.g. discriminate a (stress) fracture from osteoarthritis. In leukocyte scintigraphy, autologous white blood cells are labelled with 99m Tc and reinjected in the patient. In case of an active infection, the leukocytes accumulate at the location within 24 h after administration. The combination of three-phase bone scintigraphy with leukocyte scintigraphy has the best test characteristics for identifying infectious processes in the peripheral skeleton. The positron emission tomography (PET) radiopharmaceutical fluor-18-labelled fluorodeoxyglucose (18 F-FDG) is indicated for infectious processes of the axial skeleton (osteomyelitis and spondylodiscitis). Its uptake mechanism is distinct from that of diphosphonate complexes; it represents the glycolytic activity of cells. 18 F sodium fluoride is another PET tracer to image the skeleton. However, at the moment it has no role in sports medicine.