Scintigraphic evaluation of experimental colitis in rabbits

Area of Science:

• Nuclear medicine
• Gastroenterology
• Inflammatory bowel disease research

Background:

• Scintigraphy is crucial for evaluating inflammatory bowel disease (IBD).
• Labeled leukocytes are the standard radiopharmaceutical for IBD scintigraphy.
• Novel agents are needed to improve diagnostic accuracy.

Purpose of the Study:

• To compare the efficacy of indium-111-labeled polyethylene glycol-coated liposomes and indium-111-labeled human nonspecific gamma globulin (IgG) against indium-111-leukocytes.
• To assess these agents in a rabbit model of colitis.
• To determine the correlation between radiopharmaceutical uptake and colitis severity.

Main Methods:

• Acute colitis was induced in rabbits using trinitrobenzene sulfonic acid.
• Radiopharmaceuticals (111In-liposomes, 111In-IgG, 111In-leukocytes) were intravenously injected.
• Macroscopic abnormalities were scored, and ex vivo uptake was measured in colonic segments.
• The colitis index (CI) was calculated as the ratio of affected-to-normal colon uptake.

Main Results:

• All agents showed increased uptake in inflamed colonic tissue.
• Indium-111-liposomes exhibited the highest CI, correlating best with morphological abnormalities (r2 = 0.68).
• Indium-111-leukocytes (r2 = 0.31) and 111In-IgG (r2 = 0.29) also showed correlation but were less effective.

Conclusions:

• Indium-111-labeled liposomes, IgG, and leukocytes all detect inflamed colonic tissue.
• Indium-111-liposomes offer superior performance for colitis imaging due to higher and more correlated uptake.
• Indium-111-leukocytes and 111In-liposomes are more effective than 111In-IgG for evaluating colitis.