Measurement of gallbladder volume and dynamics by combined SPECT and planar scintigraphy

A new method is described for measurement of gallbladder volume based on three-dimensional single photon emission computed tomography (SPECT). The technique was first validated in a body phantom that used a balloon to represent the gallbladder. The balloon was inflated with a known volume and SPECT volume was calculated by summing the voxels in each transaxial slice above a percentage count threshold. The SPECT and true volume showed a high linear correlation between 15 to 90 ml (r = 0.99). The mean fasting gallbladder volume using a technetium-99m-labelled hepatobiliary agent in nine normal subjects was 26 +/- 2 ml (range 18 to 39 ml). By combining the SPECT measurement with a planar technique, it was also possible to evaluate gallbladder emptying parameters. Following a 3 min infusion of 10 ng kg-1 of cholecystokinin octapeptide (CCK), the mean gallbladder ejection rate was 1.2 +/- 0.2 ml min-1 and the residual volume was 12 +/- 2 ml. SPECT offers a new noninvasive method for accurate measurement of gallbladder volume.