ABSTRACT
Radionucleide brain scan has undergone recent advances mainly related to improved imaging technology and radiopharmaceutical developments. The introduction of technetium-labeled compounds, such as HMPAO (hexamethylpropyl amine oxime) and ECD (ethyl cysteinate dimer) as perfusion tracers has provided gains in the availability, safety and sensitivity of the method. Indeed, the radioactive compound is readily marked on site. With its short radioactive half-life (6 h), the dosimetry of technetium is quite favorable. The energy of the radioactive emission (140 keV) is well adapted to the detectors of the gamma-cameras. The implementation of the tomographic principle, by making the gamma-camera rotating, enables the acquisition of volumetric data sets in which any reconstruction plane can be obtained with a spatial resolution of 1-1.5 cm. The lipophilic perfusion tracers cross the intact blood-brain barrier and are subsequently retained in the brain because of local hydrophilic transformation. The remanence of the tracers eases the data acquisition which may be delayed from an acute episode, the picture of which is representative of the perfusion at the time of the injection.
