Sincalide-stimulated cholescintigraphy: A retrospective study and proposal of a modified workflow.

Introduction: Sincalide-stimulated cholescintigraphy (SSC) is an effective tool to quantify the gallbladder contraction. The current guideline calls for a 60-min sincalide infusion of 0.02 μg/kg body weight, and a gallbladder ejection fraction (GBEF) >38% at 60 min is considered normal. We hypothesize that many subjects with normal GBEF will do so by the 30-min mark; and if true, an enhanced workflow is proposed.

Methods: This retrospective study involved 147 adults who underwent a clinically indicated SSC as per standard 60-min infusion. The auto-generated GBEF was calculated as follows: [(maximum count - minimum count)/ maximum count] x 100, corrected for background and decay; and the time-activity-curve (TAC) displayed the GBEF in min-interval for 60 min. In subjects with GBEF >38% at standard 60-min scan, the GBEF at 20 min and 30 min were obtained manually based on the auto-generated GBEF TAC, using pixel distance measurements on an iSite PACS monitor. GBEF at 30 min was calculated as [(maximum pixel distance - pixel distance at 30 min)/ maximum pixel distance] x 100. The manually generated GBEF at 20 min and 30 min were correlated with the auto-generated ones, whenever available, using student’s t-test and Pearson’s correlation. Subgroup analyses assessed the potential impact of gender, age, and occurrence of patient symptoms on the GBEF, using Fisher’s exact test.

Results: Of the 147 subjects, there were 40 males and 107 females, mean age 48.4±16.3 years. Under the standard 60-minute protocol, a normal GBEF >38% was achieved in 131/147 subjects (89.1%). Of these, normal GBEF was seen in 82/131 subjects (62.6%) at 20 minutes and in 107/131 subjects (81.7%) at 30 minutes. There was no significant difference across subgroups of gender, age (≤40 vs. >40 years old), or presence/absence of symptoms, stratified by GBEF ≤38% vs. >38%, see Table. 55/131 subjects (42.0%) with normal GBEF developed abdominal symptoms during the 60-min sincalide infusion. Manually calculated GBEF correlated well with the auto-generated ones (R>0.9, p>0.05[AV1] ). A modified workflow for SSC is proposed which aims to improve procedure efficiency and reduce patients’ discomfort and symptoms associated with the sincalide infusion, while maintaining diagnostic accuracy. Instead of obtaining the GBEF after completion of the standard 60-min sincalide infusion, the data acquisition should be divided into 2 x 30 min sections so a screening GBEF could be obtained at the 30-min mark, while the acquisition of 2^nd section ensues. If a normal GBEF (>38%) is achieved at 30 min, the study may be stopped, which would result in close to 30 min reduction in scan time and help reduce patient discomfort and abdominal symptoms. Otherwise, the study would continue until the acquisition of the 2^nd section has been completed, and data of both sections are combined to derive the final GBEF. The proposed workflow modification has been validated at our institution based on the GE Xeleris, version 3.0 and 3.1, and has been deemed feasible. Conclusion: Most patients (81.7%) with a normal SSC achieved the GBEF >38% already by 30 min. The proposed workflow of dividing the 60-min data acquisition into 2 x 30 min sections and obtaining a screening GBEF at 30 min would have a positive impact on procedure efficiency and help reduce patients’ discomfort and side effects from sincalide administration.