Optimal Timing Of Imaging In Gastric Emptying Scintigraphy For The Detection Of Delayed Emptying

424 Objectives: To evaluate various imaging time points in a standard protocol for Gastric Emptying Scintigraphy (GES) for detection of Gastric Emptying Delay (GED). This could potentially lead to protocol optimization by shortening the total study interval while maintaining its diagnostic potential.\n Methods: Gamma camera conjugate imaging was performed in the anterior and posterior views at time points 0, 0.5, 1, 1.5, 2, 2.5 and 4-hours as per established Miami Method (MIA) and National Standard Protocol (NSP), in accordance with the consensus guidelines of the ANMS/SNMMI Societies. Patients (N=1002) received a standardized low-fat egg-white meal, of a specific caloric content, radiolabeled with 1 mCi of Tc-99m Sulfur Colloid. Quantitative analysis was performed based on the geometric mean calculation of the decay-corrected counts at each imaging time point, expressed as percent emptying or percent retention. GES data was then collected and analyzed for GED with emphasis on the 2, 2.5 and 4-hour time points.\n Results: In our large GES patient cohort, 51/167 (30%) and 97/255 (38%) of patients who had GED at 2 and 2.5 hours respectively, per combined MIA and NSP, normalized at 4 hours as defined by less than 10% retention. In, 80/835 (9.6%) and 37/414 (8.9%) patients with normal Gastric Emptying (GE) at 2 and 2.5 hours respectively, per combined NSP and MIA, the GES became abnormal with \u003e 10% retention at 4 hours. Greater than 90% (normal) GE was found in 93/1002 (9.3%) at 2 hours and 249/1002 (24.8%) at 2.5 hours of patients respectively. A threshold value of 80% GE at 2 hours, found in 216/1002 (22%) of patients, was predictive of GE \u003e 90% at 4 hours with 100% certainty.\n Conclusions: Based on our patient population, the 4-hour scintigraphy is very important in detecting GED studies at 2 and 2.5 hours that become normal with 10% retention at 4 hours; these findings further support the ANMS/SNMMI recommendations. Furthermore, GE value of 80% at 2 hours can be used as threshold in determining predictively normal GE (