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

Summary

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 a^99mTc/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.