Retrospective digital image fusion of multidetector CT and 18F-FDG PET: clinical value in pancreatic lesions--a prospective study with 104 patients.

Differential diagnosis of pancreatic lesions still remains a problem. Whereas CT provides high spatial resolution, PET detects malignant lesions with high sensitivity. The objective of this study was to evaluate the clinical benefit of PET/CT image fusion in the diagnostic workup of pancreatic cancer. METHODS: One hundred four patients with suspected pancreatic lesion underwent triple-phase multidetector CT and (18)F-FDG PET scanning. Voxel-based retrospective registration and fusion of CT and PET were performed with recently developed software. CT, PET, and fused images were assessed by 2 radiologists with regard to the detection of malignancies, possible infiltration of adjacent tissue or lymph nodes, or distant metastases. RESULTS: Fusion of CT and PET images was technically successful in 96.2%. In 2 cases, paraaortic lymph node infiltration was detected only by image fusion; in a further 8 cases, lymph node metastases were confirmed with improved localization. In 5 patients, additional pancreatic tumors or distant metastases only suspected during PET scanning were confirmed. Image fusion improved the sensitivity of malignancy detection from 76.6% (CT) and 84.4% (PET) to 89.1% (image fusion). Compared with CT alone, image fusion increased the sensitivity of detecting tissue infiltration to 68.2%, but at the cost of decreased specificity. CONCLUSION: The most important supplementary finding supplied by image fusion is a more precise correlation with focal tracer hot spots in PET. Image fusion improved the sensitivity of differentiating between benign and malignant pancreatic lesions with no significant change in specificity. All image modalities failed to stage lymph node involvement.