Oral Administration of ^99mTechnetium-Labeled Heparin in Eosinophilic Esophagitis

To determine if heparin labeled with ^99mTechnetium (^99mTc) could be an imaging probe to detect eosinophil-related inflammation in eosinophilic esophagitis and to determine the biodistribution and radiation dosimetry of ^99mTc-heparin oral administration using image-based dosimetry models with esophageal modeling.

Freshly prepared ^99mTc-heparin was administered orally to 5 research subjects. Radioactivity was measured by whole-body scintigraphy and single-photon emission computed tomography during the 24 hours postadministration. Following imaging, endoscopic examination was performed. The biodistribution of esophageal radioactivity was compared with endoscopic findings, eosinophil counts in biopsy tissues, and immunostaining for eosinophil granule major basic protein-1 (eMBP1). These studies were conducted from July 1, 2013, until April 22, 2017.

Oral administration of ^99mTc-heparin was well tolerated in all 5 subjects. The entire esophagus could be visualized dynamically during oral administration. Bound esophageal radioactivity marked areas of inflammation as judged by endoscopy scores, by eosinophils per high power field and by localization of eMBP1 using immunostaining. Ninety percent of the radioactivity did not bind to the esophagus and passed through the gastrointestinal tract.

The biodistribution of ingested ^99mTc-heparin is almost exclusively localized to the gastrointestinal tract. Radiation exposure was highest in the lower gastrointestinal tract and was comparable with other orally administered diagnostic radiopharmaceuticals. The use of swallowed ^99mTc-heparin may aid in assessing eosinophil-related inflammation in the esophagus.