EVALUATION OF THE EFFECT OF SCATTER CORRECTION ON LESION DETECTION INHEPATIC SPECT IMAGING

The effect of scatter correction on the accuracy of lesion detection i n single-photon emission computed tomography (SPECT) imaging requires analysis of observer performance. Experiments were designed to evaluat e the class of correction methods that subtract counts. Simulations we re used to approximate liver imaging with labeled antibodies. The lesi on was a 2.5-cm-diameter, spherical, ''cold'' tumor. Ramp-filtered bac kprojection and noniterative Chang attenuation compensation were used to approximate clinical practice. Perfect scatter rejection, defined a s images containing only primary (nonscattered) photons, was selected as the ideal case. These images were compared with uncorrected images for conditions of both low-and high-scatter fractions (SF). The dual p hotopeak window (DPW) method was also tested to evaluate a practical s ubtraction correction. Receiver operating characteristic (ROC) experim ents were conducted under signal-known-exactly (SKE) conditions, using the area under the curve as the index of accuracy. A statistically si gnificant difference in detection was found only in a few experiments when scatter rejection was compared with no correction. The results su ggest that scatter correction does not necessarily assure improved det ection accuracy at a statistically significant level. However, correct ions that produce conditions similar to ideal scatter rejection may of fer such improvement in detection, particularly for cases of high SF's .