FDG-PET CT for Tumor Imaging

摘要

Positron emission tomography (PET) using 2-[~(18)F]fluoro-2-deoxyglucose (FDG) as a tracer has been shown to affect patient management for a number of oncologic applications [1]. Recognizing this, the Centers for Medicare and Medicaid Services currently covers FDG-PET to include diagnosis, staging, restaging, and monitoring response to treatment for a number of malignancies (Table 1). Coverage for brain, cervical, small-cell lung, ovarian, pancreatic, and testicular cancers is under consideration [2]. Because PET has relatively low image resolution (4 to 6 mm) and anatomic detail, interpretation requires correlation with computed tomography (CT) or magnetic resonance images. The side-by-side review of PET and CT scans has been shown to be more accurate than review of PET images alone [3,4]. Ina study of 921 lesions, CT was necessary in addition to PET for the correct localization and evaluation of tumor extent in 30% to 50% of cases of suspected malignancy [5]. However, even side-by-side viewing of images from separate PET and CT examinations was inadequate for the correct localization or evaluation of tumor extent in 7% to 10% of patients with malignancies, especially those with tumors in regions of complex anatomy in the head, neck, abdomen, and pelvis [5,6]. Although software has been designed for the coregistration of PET and CT or magnetic resonance imaging (MRI) data sets, its application for body imaging is limited because of multiple variables, including differences in patient positioning and bladder filling and motion from bowel and ureteral peristalsis. For example, softwarefusion fails to accurately stage in 24% of colorectal cancers and in 39% of lymphomas [7].