SPECT/CT with a hybrid imaging system in the study of lower gastrointestinal bleeding with technetium-99m red blood cells

AIM: Lower gastrointestinal (GI) hemorrhage is an important clinical problem. We performed a study to investigate the applicability of single photon emission computed tomography/computed tomography (SPECT/CT) in patients with acute lower gastrointestinal bleeding undergoing scintigraphy with 99mTc-labelled red blood cells (RBC) and to evaluate the additional clinical value of fused images when compared to the standard radionuclide scan. METHODS: Twenty-seven patients with acute lower GI tract hemorrhage were studied with conventional dynamic and planar 99mTc-RBC imaging. In 19 patients with positive findings on scans recorded within 6 hours, a SPECT/CT study was immediately carried out using a hybrid system consisting of a dual-head, variable angle gamma camera and an X-ray tube. The number of patients in whom SPECT/CT imaging modified the scintigraphic interpretation with regard to the presence or site of GI blood loss as confirmed by other diagnostic or therapeutical procedures was evaluated. RESULTS: Image fusion showed perfect correspondence between SPECT and CT data in all patients and allowed precise anatomical localization of the sites of 99mTc-RBC extravasation. SPECT/CT presented significant impact on the scintigraphic results in 7/19 patients (36.8%): in 6 patients hybrid imaging precisely localized the bleeding foci whose location could not be identified in standard scans and in one it excluded the presence of an active GI hemorrhage. CONCLUSIONS: SPECT/CT with a hybrid system is able to improve imaging interpretation and increase the accuracy of 99mTc-RBC scintigraphy in patients with acute lower GI bleeding.