Noninvasive measurement of human ascending colon volume

The capacitance and motor functions of the colon are important determinants of its overall function. A simple, noninvasive method to quantify regional colonic volume is required for further physiologic and pharmacologic studies. Our aim was to determine whether measurements of human ascending colon (AC) volume using two-dimensional (2-D) images are as accurate as estimates using three-dimensional (3-D) images. Five healthy male volunteers each ingested a methacrylate-coated capsule containing⁹⁹Tc^m-labelled Amberlite pellets. Two- and 3-D images were obtained using a gamma camera with single photon emission computed tomography (SPECT) capability. Ascending colon volume was estimated by a variable region of interest (VROI) program and by full-width half-maximum (FWHM) analysis, and results were compared to the volume estimates by SPECT. Full-width half-maximum analysis yielded volume estimates that were not significantly different from SPECT (slope = 1.093; t = 0.51; P>0.5), whereas VROI estimates were significantly different from volume measurements by SPECT and, hence, considered less accurate (slope = 0.438; t = 4.93; P<0.02). Thus, the less expensive and more easily available planar imaging technique with analysis by FWHM estimates AC volume as accurately as SPECT.