Evaluation of the effect of scatter correction on lesion detection in hepatic SPECT imaging

The effect of scatter correction on the accuracy of lesion detection in single-photon emission computed tomography (SPECT) imaging requires analysis of observer performance. Experiments were designed to evaluate the class of correction methods that subtract counts. Simulations were used to approximate liver imaging with labeled antibodies. The lesion was a 2.5-cm-diameter, spherical, "cold" tumor. Ramp-filtered backprojection and noniterative Chang attenuation compensation were used to approximate clinical practice. Perfect scatter rejection, defined as 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 photopeak window (DPW) method was also tested to evaluate a practical subtraction correction. Receiver operating characteristic (ROC) experiments were conducted under signal-known-exactly (SKE) conditions, using the area under the curve as the index of accuracy. A statistically significant difference in detection was found only in a few experiments when scatter rejection was compared with no correction. The results suggest that scatter correction does not necessarily assure improved detection accuracy at a statistically significant level. However, corrections that produce conditions similar to ideal scatter rejection may offer such improvement in detection, particularly for cases of high SF's.