ABSTRACT
The detection of an abnormal concentration of a radiopharmaceutical in a localized region depends on the interplay of a number of parameters. These include the ratio of target-to-background activity, the size of the target, the absolute amount of activity, and the sensitivity of the detection system to the emitted radiations. All of these factors influence the detectability of a lesion. Quantitative measures of the size and shape, as well as relative or absolute activity in the target region, will depend upon the spatial resolution of the imaging system in addition to the factors mentioned above, particularly when several target regions are near each other. This chapter deals with the question of how well or whether an abnormal accumulation can be detected at a certain depth, and certain target-to-background ratio using a gamma camera and a single projected image. The same subject as it relates to emission computerized tomography is discussed in chapters by Hoffman and by Ell et al.
