Techniques and errors in scintigraphic measurements of gastric emptying. [/sup 99m/Tc and /sup 113m/In tracer techniques]

For the monitoring of gastric emptying, a gamma camera or scanner operating from one side of the patient is subject to variations of counting efficiency due to the changing depth of radioactivity. A double-headed scanner was used to investigate the effects of such changes. Tc-99m and In-113m were used as labels for the solid and liquid components of a meal. It was found that the depth of Tc-99m within the stomach decreased by a mean of 13 mm during the first half hour of emptying. Anterior detection alone underestimated emptying rates by an average of 26 percent. Depth changes also introduced errors into ''early emptying'' measurements made unilaterally. Such artifacts of measurement may compromise mathematical analyses of emptying patterns.