LAG PHASE QUANTIFICATION FOR SOLID GASTRIC-EMPTYING STUDIES

This study compared the different calculation methods of the solid gas tric emptying lag phase and evaluated the effect of the temporal sampl ing interval on the calculated value using the modified power exponent ial (WIPE) method. Methods: Twenty normal control subjects and 42 pati ents had anterior and posterior image acquisition on a multihead gamma camera, one frame per minute x 90. ROls were selected for the stomach , gastric antrum and small bowel. Time-activity curves (TACs) were gen erated for anterior, posterior and geometric mean data. The lag phase was calculated using various methods such as transition point, startin g index, first appearance of bower activity (FABA), WIPE and antral pe ak filling time. To determine the importance of the temporal sampling rate on the calculation of the lag phase by the WIPE, intervals betwee n 1 and 20 min were analyzed. Results: The transition point, starting index and FABA correlated extremely high (r = greater than or equal to 0.92) in normal control subjects and patients. Normal lag phase value s were mean 22-24 +/- 10 min for transition point, starting index and FABA compared with 47 +/- 18 min for the WIPE method (p < 0.0001). The WIPE correlated poorly with the other methods (r = 0.74). Antral peak filling time correlated poorly (r = 0.47) with transition point, star ting index and FABA, but somewhat better with the MPE (r = 0.70). Comp aring 15-min versus I-min sampling intervals using the WIPE, 35% of su bjects had values that differed by greater than or equal to 7.5 min an d 10% had values differing by greater than or equal to 15 min. Conclus ion: The lag phase calculated by the WIPE correlated poorly with other methods, and its accuracy was limited by the rate of the temporal sam pling. The transition point, starting index and FABA all highly correl ated with each other; the latter is a particularly reliable physiologi cal indicator and is easily quantified using a small-bowel TAC.