A Point Source Device to Determine Small and Large Bowel Transit Time - Proof of concept and initial results

Objectives Gastric emptying scintigraphy is a well-established technique for the determination of gastroparesis or dumping syndrome. The technique however does not lend well to determination of the small bowel or large bowel transit times. Techniques to evaluate bowel transit time include barium small bowel follow through, radio-opaque markers, non-digestible foods, food dyes, a capsule filled with radiolabelled resin or charcoal, and the video capsule. We have developed an easy to use device that is inexpensive, can be visualized throughout the entire GI tract, and can be used in conjuntion with a standard gastric emptying study. Our objective was to study the device in-vivo stability and suitability for imaging small and large bowel transit times.

Methods The device consists of a standard gelatin capsule filled with melted paraffin. A grain of rice labelled with 50-100 microcuries (1.85 - 3.7 megabecquerels) of Ga-67 was placed into the paraffin and the capsule sealed. Four volunteers and four patients with constipation or diarrhea were asked to swallow the capsule and allow imaging for up to six hours on the first day and were given the option to return for additional imaging on the following days until excretion. The volunteers and patients swallowed the capsule and imaging was performed at various times to identify the location in the bowel. Initial protcols included transmission imaging with a sheet source, comparison to a barium small bowel follow through study, and used in combination with a gastric emptying study. Our initial evaluations included suitability of dose, device stability, ease of imaging, and attempted to quantify small bowel and large bowel transit times. The Loyola University Health System IRB approved the use of this device in volunteers and patients.

Results We found a dose of 50-100 microcuries of Ga-67 to be sufficient for imaging alone or in conjunction with a gastric emptying study. The device remained intact throughout the GI tract. Imaging using a transmission source or performed in conjunction with a small bowel follow through was suboptimal to anatomically localize the ileocecal junction. Dual isotope imaging (Tc99m and Ga-67) combining the device with a gastric emptying study and fusion of images allowed for the most accurate localization. The device did not reach the ileocecal junction by six hours in all subjects.

Conclusions In this initial trial, the device demonstrated stability throughout the GI tract, low additional radiation exposure, and that optimum imaging can be performed in conjunction with a standard gastric emptying study. Though easily used and imaged, optimization of the imaging protocol to more accurately identify small and large bowel transit times remains. Further evaluation of this device in larger populations is required.

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