A simplified method for processing dynamic images of gastric antrum

By means of a dynamic acquisition protocol and a Fourier transform algorith m the scintigraphic technique can be used to assess gastric antral motility . In previous approaches, however, the definition of a region of interest ( ROI) that gives rise to an unequivocal result of the analysis of the corres ponding time-activity curve might be crucial. To overcome this problem we e valuated a new technique based on a fixed box-ROI and a simple weighting pr inciple. Eight healthy volunteers ingested a meal that contained a Tc-99(m) -stannous colloid labelled omelette. Gastric emptying was assessed from sta tic images taken at 30-mm intervals for 2 h. Anterior dynamic frames of 1 s each, which were acquired for 5 mm after each static acquisition, were use d to determine the frequency of antral contractions. In order to allow for precise outlining of the antrum, each set of dynamic images was at first re framed into a single 5-mm image. The same ROI (20 pixels vertical, 15 pixel s horizontal) was then positioned over the distal portion of the antrum on each reframed image. On each 1-s frame the obtained counts in each of the 1 5 columns of 20 pixels were summed. Then the localization of the geometric centre of radioactivity in the 15 columns was determined. On the assumption that the horizontal oscillations of the geometric centre of radioactivity in the ROI reflected the contractile activity of the antrum, the frequency of these contractions was calculated by fast Fourier transform analysis of the obtained time versus geometric centre curve. In all subjects, our techn ique gave unequivocal frequencies of antral contractions at each time point . Statistical analysis did not reveal any intraindividual variation in this frequency during gastric emptying. We believe that the simplified scintigr aphic method is an advantageous alternative for assessing the frequency of antral contractions. ((C) 2000 Lippincott Williams & Wilkins).