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

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 positron-emitting radionuclide allowing dynamic imaging, to measure metabolism of urea in the stomach of biopsy documented H. pylori-positive patients. [11C]urea was synthesized from 11CO2 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 and 11CO2 was monitored in the breath continuously for 30 min. An H. 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 to 11CO2 with subsequent diffusion of 11C activity out of the stomach. The 11C activity in the breath peaked at 10-20 min in the H. 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.

Radiosynthesis, Preclinical, and Clinical Positron Emission Tomography Studies of Carbon-11 Labeled Endogenous and Natural Exogenous Compounds

“…Simultaneously, in the breath test in the same time frame, increasing 11 C activity was registered in the patient due to [ 11 C]­urea hydrolysis in [ 11 C]­CO 2 by H. pylori, while 11 C activity in control subject breath remains at background level …”

Helicobacter pylori urease for diagnosis of Helicobacter pylori infection: A mini review

“…During the Kornberg era 14 C and 13 C isotope-based methodology was used to identify urease activity non-invasively as quasi-breath tests in experimental animals including the frog [1] , [3] . Methods using stable and radioactive isotopes were subsequently used to develop diagnostic tests in humans utilizing isotopic enrichment of breath, blood, or urine following oral administration of labeled compounds, most often urea, to detect the presence of H. pylori infections [31] , [32] , [33] , [34] , [35] , [36] , [37] . Although urea and ammonia can easily be measured in gastric juice [38] , the first clinically useful rapid tests for diagnosis of H. pylori using gastric contents or biopsies targeted urease and were adaptations of standard laboratory tests for urease activity and named Rapid Urease Tests (RUTs).…”

The application of infrared spectroscopy to breath CO2isotope ratio measurements and the risk of spurious results

“…Other 14 CO 2 breath tests followed, and techniques improved including the development of low-dose 14 C breath, giving an exposure to the gonads and bone marrow equivalent to one quarter of a day's background radiation (Atherton and Spiller 1994). An 11 CO 2 breath test has also been developed for specialist applications (Hartman et al 1992). However, the utility of radioactive tracers has declined as the potential health risks associated with them have made it difficult to justify their use in clinical investigations.…”