Diagnostic evaluation of separately acquired PET and CT images by nuclear medicine physicians and radiologists in cancer patients.

The aim of our study was to analyze how many oncology patients might benefit from a) integrated positron emission tomography - multidetector computed tomography (PET/MDCT) and additionally b) clinically relevant information provided by either the CT scan or PET scan. A total of 285 consecutive patients 164 male and 121 female, age range 17-84 years, 153 lung cancer, 112 lymphoma, 20 miscellaneous, referred for PET and separate CT scan, were included. The CT scan was performed after the intravenous injection of a soluble contrast media. Patients were retrospectively classified into six Groups: Group I: No pathological uptake on the PET scan, Group II: Suspected lesions were correctly identified by the PET scan alone, Group III: Side-by-side evaluation of PET and CT appeared sufficient to assess the localization of lesions, Group IV: Side-by-side reading was not sufficient and integrated PET/CT was considered beneficial. Additionally all patients with a CT scan with additional clinical relevant information (not visualized by the PET scan) were classified in Group V. Group VI was set for lesions detected by PET alone (not visualized by the CT scan). The CT scan was used as the gold standard to confirm or disprove PET lesion localization. Our results showed: A number of 77 patients, (Group I: 77/285, 27%) had no pathologic fluorine-18-fluorodeoxyglucose (18F-FDG)-uptake. Lesions were correctly localized by either conventional PET alone (Group II: 76/285, 27%) or side-by-side evaluation of PET and CT scans (Group III: 44/285, 15%). Integrated PET/CT or software fusion, was considered beneficial in 31% (88/285) of the patients with pathological 18F-FDG-uptake (Group IV). Additionally to the above, in 15% of all patients clinically relevant information, referring to disseminated small pulmonary lesions, abdominal aortic aneurysms >5 cm, thrombi or pulmonary emboli, was also provided by the CT scan (Group V). Also, in 7% of all patients, unsuspected pathological lesions, mainly bone metastases, were correctly detected by PET alone (Group VI). In conclusion, in 54% of all oncologic patients, PET alone was diagnostic. In 46% of all patients side-by-side reading (15%) or integrated PET/CT images (31%) were considered beneficial for more accurate anatomical localization of the lesions. Additionally, the CT scan added clinically relevant information in 15% of all patients and the PET scan showed unsuspected metastases in 7% of all studied patients. Therefore, integrated reading of PET and MDCT images by nuclear physicians and radiologists may gain quality in the staging of oncology patients.