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Reconstruction Parameters for ¹¹¹In-Pentetreotide SPECT: Variability with Respect to Body Weight and Body Region

¹ PET Unit, Nuclear Medicine Service, S. Maria della Misericordia Hospital, Rovigo, Italy; ² Technician and Nursing Service, S. Maria della Misericordia Hospital, Rovigo, Italy; and ³ Medical Physic Service, S. Maria della Misericordia Hospital, Rovigo, Italy

Correspondence: For correspondence or reprints contact: Arianna Massaro, CNMT, Nuclear Medicine Service, PET Unit, "S. Maria della Misericordia Rovigo" Hospital, Istituto Oncologico Veneto (IOV)-IRCCS, Viale Tre Martiri, 140, 45100, Rovigo, Italy. E-mail: rubello.domenico{at}azisanrovigo.it

This study, which was based on a large series of consecutive patients imaged by ¹¹¹In-pentetreotide SPECT for a neuroendocrine tumor, evaluated variability in reconstruction parameters in relation to patient body weight and the body region imaged, looking for the possibility of standardizing such parameters. Methods: One hundred twenty-four patients underwent ¹¹¹In-pentetreotide scintigraphy: 4- and 24-h whole-body and planar scans and a 24-h SPECT examination. All patients were injected with 140–150 MBq of ¹¹¹In-pentetreotide at least 1 wk after somatostatin analogs had been discontinued. SPECT images were systematically acquired at the levels of the head, chest, and abdomen. SPECT was performed using a dual-head -camera with medium-energy collimators, step-and-shoot method, no circular orbit, a 64 x 64 matrix, and 30 s per view for a total of 64 views. Two reconstruction procedures were compared: the iterative method using 10 iterations and the filtered backprojection method using a Butterworth filter with different cutoffs and orders. Results: Optimal SPECT images were obtained by applying the Butterworth filter. The reconstruction parameters could be standardized for the head and chest but were more variable for the abdomen, mainly because ¹¹¹In-pentetreotide is physiologically trapped in different intestinal areas and varies over time, especially in the liver, spleen, bowel, and urinary tract. Conclusion: Filtered backprojection using a Butterworth filter appears adequate for standardizing the reconstruction parameters for ¹¹¹In-pentetreotide SPECT of the head and chest. Processing of abdominal images is more operator-dependent. A 150-MBq dose of ¹¹¹In-pentetreotide is recommended when planning multiple SPECT acquisitions in the same patient.

Key Words: ¹¹¹In-pentetreotide; SPECT; reconstruction parameters; standardization; neuroendocrine tumors