Evaluation of a technique for the quantification of radioactivity and volume of an object using SPECT

The technique of threshold determination using maximization of interclass variance (MIV) has been evaluated for the assessment of radioactivity and volume in single photon emission computed tomography (SPECT). The SPECT reconstruction incorporated scatter and attenuation correction using an attenuation map from computed tomographic (CT) images. The technique has been examined on a large number of phantom objects with both 99Tcm and 131I. Volume measurement of objects was performed using a variety of methods of applying the MIV technique. The standard error of volume estimation for the optimum method was 7.3 ml for 99Tcm and 15.3 ml for 131I. Activity was measured by expansion of the volume of interest representing the space occupied by the object to make allowance for limited SPECT resolution. The standard errors of the activity measurements were 0.22 MBq for 99Tcm and 0.24 MBq for 131I.