Comparison between Transversal SPECT,3-dimensional Rendering and 3-dimensional Rendering plus Clipping in the Diagnosis of Somatostatin Receptor Distribution in Malignancies using 111 In-DTPA-D-Phe 1 -octreotide Scintigraphy

Two hundred and seven patients were investigated with [¹¹¹In-DTPA-D-Phe¹]-octreotide Single Photon Emission Computerized Tomography (SPECT) scintigraphy. A comparison was carried out of the diagnostic accuracy of the three display modalities, viz. transversal SPECT (trvSPECT), three dimensional volume rendering (3Dvr) and three dimensional volume rendering plus clipping (3Dvr+c) in the rendered volume. TrvSPECT could visualize a greater number of lesions in 85 (41 %) cases when compared with 3Dvr. In 48 (23%) cases, trvSPECT could visualize a greater number of lesions when compared with 3Dvr+c. The differences were caused by radioactivity in intestines and the gallbladder and in lesions shaped like an hour-glass. In conclusion, 3Dvr+c imaging was regarded as the reference since it combines both transversal and volume information. An overall sensitivity of 0.998 was found for trvSPECT and the corresponding value for 3Dvr was 0.75. The specificity was 0.45 for trvSPECT and 0.80 for 3Dvr. The accuracy was 0.87 for trvSPECT and 0.76 for 3Dvr, when compared with 3Dvr+c.

The value of3Dvr is in high-contrast images, where it provides additional anatomical information, whereas in low-contrast images, 3Dvr was found to have low accuracy. In low-contrast images, trvSPECT was found to be almost equal in accuracy to 3Dvr+c imaging. However, in high-contrast images, trvSPECT was found to give more false positives than 3Dvr+c in the assessment of SPECT studies using [¹¹¹In-DTPA-D-Phel]-octreotide. The interpretation was that trvSPECT has to be used in conjunction with 3Dvr+c and, in high-contrast images, 3Dvr provides additional value.