Noninvasive detection ofHelicobacter pylori colonization in stomach using [11C]urea

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Abstract
Helicobacter pylori is associated with chronic type B gastritis. Diagnosis can be made on gastric biopsy specimens and noninvasively using [13C]-or [14C]urea breath tests. Both breath tests require meticulous breath collection, and false positive results are possible from urease producing oral-pharyngeal flora. We used [11C]urea, a positronemitting radionuclide allowing dynamic imaging, to measure metabolism of urea in the stomach of biopsy documentedH. pylori-positive patients. [11C]urea was synthesized from11CO2 produced using a Van de Graaff accelerator and administered with [99mTc]DTPA to control for loss of radioactivity via gastric emptying. Images were obtained externally by gamma camera every minute and11CO2 was monitored in the breath continuously for 30 min. AnH. pylori-positive patient exhibited a99mTc/11C activity ratio of 2.1 in the stomach 10–20 min following administration, compared to a 1∶1 ratio in a negative control, indicating metabolism of urea to11CO2 with subsequent diffusion of11C activity out of the stomach. The11C activity in the breath peaked at 10–20 min in theH. pylori-positive patients. The short half-life of carbon-11 (20.4 min) alleviates radiation safety concerns and results in low absorbed radiation doses to patients.