Validation of a Single-Time-Point Measurement of Total Abdominal Counts to Simplify Small Bowel and Colon Transit Analyses

The Society of Nuclear Medicine and Molecular Imaging and European Association of Nuclear Medicine procedure guide on gastrointestinal transit currently indicates that the mean of total abdominal counts of 7 time points (0–360 min) is used to define the total abdominal counts for bowel transit studies. The purpose of this study was to investigate the variability of total abdominal counts during the initial 6 h of bowel transit and to determine whether a simplified, single-time-point measurement can be used. Methods: Thirty consecutive bowel transit studies were retrospectively analyzed. Patients received an oral dose of 4.6 MBq (125 μCi) of 111In-DTPA in 300 cc of water together with a standard egg white solid-phase, gastric-emptying meal to measure small bowel and colon transit. 111In-DTPA geometric mean and decay-corrected total abdominal counts obtained at 0, 30, 60, 120, 180, 240, 300, and 360 min after meal ingestion were analyzed. The coefficient of variation was used to determine the variability of the mean total abdominal counts. Slope of the regression line, Student t test, and a Pearson product-moment correlation coefficient (PCC) were also calculated to determine the correlation of total abdominal counts at each time point compared with the mean of all time points. Results: The mean coefficient of variation of total abdominal counts of each patient was 3.3%, with a range of 1.1%–6.3%. The mean of the slope of the regression line of the total abdominal counts of the patients was −0.001 ± 0.003. There was no significant difference between the measured slope of the regression line compared with a line with a slope of 0 (P > 0.05). When the counts at each time were compared with the mean counts, there was no significant difference (P > 0.05). The PCC of each of the counts showed a significant and strong correlation between each interval and the mean total abdominal counts (P < 0.01). Conclusion: There is no significant variability in geometric mean 111In-DTPA total abdominal counts during the initial 6 h of bowel transit studies. This can permit a more simplified analysis using the total abdominal counts from only a single time point.