Immunoscintigraphy of an inflammatory process in Crohn's disease with a technetium-99m-labeled fragment (MN3 Fab') and with an intact monoclonal anti-granulocyte antibody (Mab BW 250/183)

Molecular Imaging in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are chronic immune-mediated inflammatory diseases affecting the gastrointestinal tract. Classically, two subtypes of IBD are recognized: Ulcerative colitis and Crohn's disease. There is not a single and reliable test for IBD diagnosis but the nuclear medicine techniques like ^99mTc-HMPAO autologous labelled leukocytes scintigraphy (WBCS) and PET/CT plays a role in the management of IBD. Leukocytes can be labelled "in vitro" (using ^99mTc-HMPAO in Europe or ¹¹¹In-oxine in America) or "in vivo" using antigranulocyte monoclonal antibodies. Nuclear medicine techniques are not the first choice to investigate IBD. Ultrasonography and magnetic resonance (radiation free) are probably the first option, and the diagnosis is commonly established by endoscopic biopsies. Nevertheless, WBCS is highly sensitive and accurate and represent a real option when other methods cannot used for whatever reason. In fact, a normal scan discards the presence of active IBD. The test is also useful to measure the extension and severity of the diseases and to evaluate the response to treatment. PET/CT imaging using ¹⁸F-FDG has recently been introduced and studied in both children and adults showing an excellent sensitivity for detecting active intestinal inflammation, but poor specificity in some studies. PET alone appears to be sufficient for the evaluation of ulcerative colitis, but PET/CT provides considerably more information than PET alone in the evaluation of Crohn's disease. Current clinical applications of PET in IBD include its use in the early evaluation of IBD, especially in children who may not tolerate an invasive test such as colonoscopy. Many questions remain to be answered, but PET appears to be a promising tool in the non-invasive evaluation of IBD. On the other hand, PET/MR could become in the near future a powerful tool in the evaluation of IBD patients. In addition, immuno-PET with antibodies targeting innate immune markers is also being investigated to detect colonic inflammation. The development of these technologies in humans could offer a less invasive method than endoscopy for the diagnosis and monitoring of IBD.

Noninvasive assessment of Crohn's disease activity: a comparison of 18F-fluorodeoxyglucose positron emission tomography, hydromagnetic resonance imaging, and granulocyte scintigraphy with labeled antibodies

OBJECTIVES

Detection of disease activity in Crohn's disease (CD) is of crucial importance for diagnosis and management of the disease. Noninvasive methods for monitoring are desirable and comprise hydromagnetic resonance imaging (hydro-MRI) and leukocyte scintigraphy. In addition, a recent case report indicated the potential of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to assess CD activity. However, comparative prospective studies are lacking.

METHODS

Between February, 1999 and August, 2000, 59 patients with CD were enrolled in a prospective study to assess disease activity by FDG-PET, hydro-MRI, and immunoscintigraphy with anti-nonspecific cross-reacting antigen 95 antigranulocyte antibodies. In 28 of these patients, colonoscopy could be performed. Twelve patients with irritable bowel syndrome and 20 tumor patients without gut inflammation served as controls. Results were compared by statistical analysis.

RESULTS

FDG-PET detected 127 pathological findings (average maximum standardized uptake value = 4.4 +/- 1.1) in the terminal/neoterminal ileum (37), small bowel (24), and colon (66) of 54 patients with CD, whereas no pathological findings were seen in five patients with CD, the control patients with irritable bowel syndrome, and the tumor patients without gut inflammation. In contrast, examination with hydro-MRI or granulocyte antibodies detected less pathological findings in CD patients. Forty-five of the detected foci were accessible to endoscopic verification. The correlation of the foci with endoscopic findings showed a high specificity (>89%) of all three methods to detect inflamed areas in the terminal ileum and colon of patients with CD, although analyses by hydro-MRI and granulocyte antibody scan had strikingly lower sensitivities (40.9% and 66.7%) than FDG-PET analysis (85.4%).

CONCLUSIONS

FDG-PET appears to be a reliable noninvasive tool for simultaneous detection of inflamed areas in the small and large bowel of patients with CD. FDG-PET can be used to detect disease activity in the terminal ileum and colon of CD patients with high sensitivity and specificity.