A comparison of methods of assessment of scintigraphic colon transit

There is no standard method of analysis of scintigraphic colonic transit investigation. This study was designed to compare 4 techniques.

Sixteen subjects (median age, 37.5 y; range, 21-61 y), who had sustained a spinal cord injury more than a year before the study, were given a pancake labeled with 10-18 MBq of (111)In bound to resin beads to eat. Anterior and posterior images were acquired with a gamma-camera 3 h after the meal and then 3 times a day for the next 4 d. Seven regions of interest, outlining the ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, rectosigmoid, and total abdominal activity at each time point, were drawn on the anterior and posterior images. The counts were decay corrected and the geometric mean (GM), for each region, at each time point calculated. The GM was used to calculate the percentage of the initial total abdominal activity in each region, at each time point. Colonic transit was assessed in 4 ways: (a) Three independent nuclear medicine physicians visually assessed transit on the analog images and classified subjects into 5 categories of colonic transit (rapid, intermediate, generalized delay, right-sided delay, or left-sided delay). (b) Parametric images were constructed from the percentage activity in each region at each time point. (c) The arrival and clearance times of the activity in the right and left colon were plotted as time-activity curves. (d) The geometric center of the distribution of the activity was calculated and plotted on a graph versus time. The results of these 4 methods were compared using an agreement matrix.

Though simple to perform, the visual assessment was unreliable. The best agreement occurred between the parametric images and the arrival and clearance times of the activity in the right and left colon.

The different methods of assessment do not produce uniform results. The best option for evaluating colonic transit appears to be a combination of the analog images, which provide a general overview of colonic transit and a quantitative method that demonstrates segmental transit.