The additional diagnostic value of contemporary evaluation of FDG PET/CT scan and contrast enhanced CT imaging both acquired by a last generation PET/CT system in oncologic patients

Abstract

Last generation PET tomographs are equipped with a state-of-the-art CT scanner. Normally, CT images are acquired with suboptimal parameters and without intravenous contrast media, being used for attenuation correction and localization only. For this reason, no CT report is usually provided. Most of the patients who are referred for an FDG PET/CT scan, however, present with a diagnostic CT indicating that a PET/CT is required to characterize otherwise equivocal findings and, in the end, undergo both the techniques to reach a final diagnosis. The aim of this study was to evaluate the impact of the contemporary execution of both the techniques employing a PET/CT scanner on the conclusiveness of the final report. Secondary aim was to verify the concordance of the two reports.

Patients and methods: Thirty-eight patients affected by hypermetabolic malignant diseases (15F-23M, mean age 58±17 years) were enrolled. Twenty-two were in staging, 16 in restaging. They underwent a standard FDG PET/CT scan immediately followed by a diagnostic contrast enhanced (ce)CT scan acquired on the same tomograph. The PET/CT scan was reported by a nuclear medicine physician while the ceCT by a radiologist, independently. Then, they wrote a conclusive paragraph formulated by consensus. The results were compared in terms of stage (FDG PET/CT vs. ceCT and vs. final stage by consensus) and positivity of T, N and M by the inter-rater agreement K.

Results: In all the patients, a final, conclusive and agreed stage was reached. There was a high concordance in terms of stage between FDG PET/CT and ceCT (K=0.874), ceCT and final stage (K=0.936), FDG PET/CT and final stage (K=0.938). In two cases, ceCT contributed significantly to the final stage, while PET/CT in four patients. More in details, for the detection of T, there was a complete concordance between PET/CT and ceCT, despite PET/CT wasn't able to provide an accurate evaluation of nearby structures infiltration. K was 0.785 for the assessing of N and 0.718 for M. In general, ceCT was more sensitive for the detection of lung and brain metastasis. FDG PET/CT was more accurate for the identification of nodal metastasis and small distant lesions, especially in the abdomen.

Discussion: Our data show that the execution of PET/ceCT in the same session by using the same hybrid tomography increases the quality of the final report by nuclear physician and radiologist and provides clear diagnostic information to the clinician.