Abstract
1764
Objectives: Although SPECT/CT (HRCT) scanners have the potential for precise fused registration of anatomic structures, physiological motion during the acquisition of both studies may alter the appearance of organ shape, size or location. The aim of this study was to assess the consistency in location and measured size of upper abdominal organs with In111 Octreotide SPECT and CT using a combined SPECT high resolution CT system. Methods: We evaluated ten consecutive patients who underwent clinical SPECT/CT scans for suspected/follow-up of somatostatin avid tumors using a 16 slice CT/SPECT system (Philips, Precedence). Both SPECT and CT images were acquired with patients in tidal breathing. CT scans were performed without iv. contrast. We separately determined the location of the cranial and caudal margins for liver, spleen, and bilateral kidneys, on SPECT and CT. Differences between the two modalities in terms of location and measured organ size were investigated. Results: The results of the analysis are presented in the attached table. The upper pole of the left kidney could not be reliably identified on the SPECT images due to proximity of spleen. Due to the mild uptake of radiotracer in the liver, and the narrow, elongated shape of the inferior liver tip, the full inferior extent of liver radiotracer activity was also not reliably assessed. Conclusions: The upper abdominal normal organs appear slightly larger on SPECT compared with CT with the windows selected for clinical interpretation. Intraperitoneal organs (spleen) had a larger cranio-caudal displacement between SPECT and CT than the retroperitoneal organs (kidneys). Overall, registration quality with the high quality CT/SPECT system was excellent.
- Society of Nuclear Medicine, Inc.