20. The Case for PET/CT

Purpose: Whole-body positron emission tomography (PET) with [F-18]fluorodeoxyglucose (FDG) is an important tool in the management of patients with cancer. While the sensitivity of FDG PET for tumor localization is most often reported to be ≥ 85%, the specificity is frequently found to be lower. One limitation of whole-body PET imaging is the confounding effect of normal physiologic FDG accumulation in kidneys, ureters, bladder, stomach and bowel. Also, highly metabolically active tissues such as brain and muscle can mask detection of adjacent abnormalities. Interpretation of functional PET images can be improved by correlation with anatomic imaging, e.g. CT or MRI. The utility of both visual comparison and retrospective fusion of PET with previously acquired morphologic studies may be, however, limited by the time interval between image acquisition and patient positioning differences.

Results: In our experience with over 150 examinations using a unique combined PET/CT scanner, we have frequently found that the direct registered images were critical to correct study interpretation. In this work, we review the beneficial results of a combined PET/CT tomograph for diagnosis/staging and localization of malignancy. We will further present specific examples of clinical questions uniquely addressed by PET/CT, and their impact on patient management.

Conclusion: Acquisition of co-registered PET and CT images in the same scanning session may enable physicians to more precisely discriminate physiologic uptake and tumor. Our initial experience suggests that this combined PET/CT device may improve the accuracy of PET, and in so doing, enhance the value of diagnostic PET in oncologic applications.