Prescintigraphic morphine application for abdominal adenocarcinoma imaging, with technetium-99m methoxy isobutyl...

Imaging of tumors with cationic tracers, especially with technetium-99 methoxy isobutyl isonitrile ((99m)Tc-MIBI), revealed high specificity for the diagnosis and follow up of various malignancies. However, these radiopharmaceuticals are of limited value for the diagnosis of malignancies of the abdominal region due to the immediate biliary secretion of the tracer and the associated high background activity. In a prospective, single-blinded protocol, patients with endoscopically diagnosed gastrointestinal malignancies were assigned to undergo (99m)Tc-MIBI imaging of the abdomen. To overcome biliary secretion of cationic tracer we administered 0.04 mg/kg morphine hydrochloride intravenously before the administration of 600 MBq (99m)Tc-MIBI. Planar images were performed in the anterior and posterior views with a double-headed gamma camera and with 3 min acquisition time, followed by single photon emission tomography images (3 degrees, 20 sec/frame). Results were compared to findings of endoscopy, computed tomography scan and surgery. Twenty four patients 17 male and 7 female , mean age 69 years, range 52-83, years were enrolled. All patients suffered from adenocarcinoma, (19 from colorectum, 3 from gastric, 1 from pancreatic and one patient had both gastric and colorectal adenocarcinoma, for a total of 25 tumor lesions). The primary objective- inhibition of biliary secretion- was achieved in 23 of the 24 patients. (99m)Tc-MIBI-imaging was accumulated intra-abdominally in 19 patients. In 2 patients the tumor was endoscopically completely removed before the scan. In these two patients (99m)Tc-MIBI imaging showed no intra-abdominal tracer accumulation. When compared to the endoscopic findings, (99m)Tc-MIBI imaging showed time positive results in 13 of the 23 remaining individual tumor lesions, false positive in 6 and false negative in 4. This study showed a sensitivity of 57% and a specificity of 20% of the above technique for the identification of intra-abnominal adenocarcinomas. Correct diagnosis did not correlate with tumor size. In conclusion, prescintigraphic morphine administration inhibits background activity coming from biliary secretion, and enables better intra-abdominal (99m)Tc-MIBI imaging but with limited sensitivity and poor specificity.