Advantages of percutaneous abdominal biopsy under PET-CT/ultrasound fusion imaging guidance: a pictorial essay

Positron emission tomography (PET) is a functional imaging technique that can investigate the metabolic characteristics of tissues. Currently, PET images are acquired and co-registered with a computed tomography (CT) scan (PET-CT), which is employed for correction of attenuation and anatomical localization. In spite of the high negative predictive value of PET, false-positive results may occur; indeed, Fluorine 18 (18F)-fluorodeoxyglucose (18F-FDG) uptake is not specific to cancer. As 18F-FDG uptake may also be seen in non-malignant infectious or inflammatory processes, FDG-avid lesions may necessitate biopsy to confirm or rule out malignancy. However, some PET-positive lesions may have little or no correlative ultrasound (US) and/or CT findings (i.e., low conspicuity on morphological imaging). Since it is not possible to perform biopsy under PET guidance alone, owing to intrinsic technical limitations, PET information has to be integrated into a CT- or US-guided biopsy procedure (multimodal US/PET-CT fusion imaging). The purpose of this pictorial essay is to describe the technique of multimodal imaging fusion between real-time US and PET/CT, and to provide an overview of the clinical settings in which this multimodal integration may be useful in guiding biopsy procedures in PET-positive abdominal lesions.