Combined CT colonography and 18F-FDG PET of colon polyps:: Potential technique for selective detection of cancer and precancerous lesions

OBJECTIVE. The purpose of this study was to determine the feasibility of imaging the colon with fused CT colonography (CTC) and F-18-FDG PET and to correlate the findings with the histologic features of polyps. SUBJECTS AND METHODS. Eighteen patients with suspected colorectal polyps enrolled in this prospective study. Before colonoscopy, 17 of the patients underwent a combination of FDG PET and CTC. CTC consisted of 4-MDCT merged with PET. PET of the abdomen and pelvis was performed after each CTC scan. One radiologist and one nuclear medicine physician in consensus analyzed PET and CTC fusion data. PET standard uptake value was correlated with the findings at histologic examination of polyps. Patient feasibility was defined as the ability to tolerate prolonged scanning with good colonic distention. Technical feasibility was determined by how closely anatomically matched polyps overlapped on fusion images. RESULTS. Seventeen of 18 patients tolerated scanning. Eighty-five percent of colon segments were optimally distended. Twenty-three of 27 FDG-avid polyps measuring 10 mm or more had excellent overlap at fusion imaging. PET depicted 23 of 39 premalignant polyps and even showed increased tracer activity associated with four small tubular adenomas ( 4 - 6 mm). Sixteen benign polyps ( 10 - 25 mm) were not depicted on PET. All nine cases of cancer ( tumors measuring 11 - 60 mm) were detected with both PET and CTC. The standard uptake value of malignant tumors ranged from 4 to 20 ( mean, 9). However, six benign flat polyps did not exhibit FDG avidity. CONCLUSION. The novel combination of CTC and PET was feasible in 17 of 18 patients and allowed excellent image correlation in 23 of 27 proven polyps measuring 10 mm or more on PET - CTC fusion. This technique shows promise in accurate anatomic correlation of both malignant and premalignant lesions evaluated with FDG PET.