Improved detection and localization of lower gastrointestinal tract hemorrhage by subtraction scintigraphy: phantom analysis.

UNLABELLED Acute lower gastrointestinal tract hemorrhage (LGIH) has significant morbidity and mortality outcomes. Although several causes of LGIH can be life threatening, most can be effectively treated; therefore, early detection and accurate localization of bleeding sites are critical for successful patient management. METHODS This study was a phantom experimental study with a repeated-measures design. The minimum detectable bleeding rate, the minimum detectable bleed volume, the sensitivity for detection, and the time required for detection were determined and compared for conventional scintigraphy (CS) and 3 experimental techniques: reference subtraction scintigraphy (RSS), sequential subtraction scintigraphy (SSS), and alternate sequential subtraction scintigraphy (ASSS). RESULTS The minimum detectable bleeding rates within the first hour were 0.05 mL.min-1 for CS and RSS, 0.1 mL.min-1 for ASSS, and 0.5 mL.min-1 for SSS. This study demonstrated minimum detectable bleed volumes of 2.2 mL for CS, 2.3 mL for RSS, 5 mL for ASSS, and 5 mL for SSS stratified to a "definitely present" certainty. No statistically significant difference was noted in the mean time to detection between CS and the subtraction techniques. Receiver-operating-characteristic analysis indicated that combining CS and RSS improved test performance and increased overall sensitivity to 75% from 68.3% for CS and 71.7% for RSS. CONCLUSION Supplementing conventional datasets with RSS and ASSS may provide a useful tool that combines the advantages offered for lesion detectability by a high-contrast 99mTc-sulfur colloid study with the window of opportunity offered by 99mTc-labeled red blood cell scanning.