Determination of the gastric emptying of solid dosage forms using gamma-scintigraphy: a problem of image timing and mathematical analysis

This work was designed to identify the maximum time interval of image acquisition by gamma-scintigraphy for monitoring the emptying of a dosage form such as a tablet. Appropriate statistical parameters to describe this process were sought, including a statistical procedure for group comparisons of such data. Gamma-scintigraphy was employed in seven healthy male volunteers, who swallowed a light and a dense tablet, each 12 mm in diameter, formulated to contain different isotopes to allow identification. Images were taken sequentially at 30-s intervals to provide images of each tablet in 1-min spacing until emptying of both tablets was reported. In selecting images, it was also possible to simulate image acquisition intervals of 2, 3, 5, 10, 15, 20 and 30 min. The values derived are discrete random variables. The maximum time interval between image acquisitions that permitted reliable results to be obtained was found to be 3 min for light and 2 min for dense tablets. Consideration of the emptying of a tablet as a Bernoulli random event provided a suitable statistical approach to the analysis of such data, giving a median and an interquartile range. While the commonly applied method, which is based on parametric procedures deriving arithmetic means and standard deviations, failed to detect a difference in the emptying times of the two types of tablets, the use of non-parametric statistics (Wilcoxon test) provided a clear distinction between them in this respect. The assessment of gastric emptying by gamma-scintigraphy studies can be improved by using short image intervals and application of appropriate statistical analysis.