Image-guided Biopsy: What the Interventional Radiologist Needs to Know about PET/CT

Abstract

Positron emission tomography (PET)/computed tomography (CT) with fluorine 18 fluorodeoxyglucose (FDG) is increasingly used in evaluation of oncology patients. Because PET/CT can demonstrate malignancy before morphologic changes are evident, application of PET/CT information to image-guided biopsy can facilitate early histologic diagnosis and staging. However, because FDG uptake is not specific to cancer, PET/CT findings may raise questions about whether uptake in a lesion is an indication for biopsy. To properly select patients for image-guided biopsy, interventional radiologists should be familiar with the biologic significance of FDG uptake and various causes of false-positive uptake. PET/CT images may also become a source of confusion in the interpretation of biopsy results. Various causes of false-positive and false-negative FDG uptake need to be considered, especially when there is a discrepancy between biopsy results and PET/CT findings. False-negative FDG uptake can result from cancers that are too small to be observed or not FDG avid. False-positive FDG uptake can be due to underlying inflammation from recent treatment. Conversely, complete resolution of FDG uptake in a treated lesion does not necessarily indicate absence of viable cells. When questions about PET/CT findings arise in the context of image-guided biopsy, discussion with experienced nuclear imaging physicians is essential.

PET/CT-guided biopsy of liver lesions

“…In these latter cases, PET/CT allows the physician performing the biopsy to access the region with the highest FDG uptake, i.e., the region more likely to contain representative cancer cells [20,22]; in the same way, the technique is useful in lymph node chains where only some lymph nodes present FDG uptake.…”

“…Furthermore, the growing interest in accessing masses with PET/CT guidance is also due to its ability to determine, within a lesion, the most accessible region showing higher metabolic uptake. Naturally, the physician responsible for the biopsy must have an excellent understanding of the FDG uptake characteristics related to malignant processes to define what, of all the metabolic information provided by FDG PET, is truly reliable [22].…”

Advances in medical imaging for the diagnosis and management of common genitourinary cancers

“…The spatial combination of sensitivity and specificity of the respective modalities can not only aid in diagnosis and staging of multiple tumor types, but can also help to visually and spatially communicate radiologic findings among the subspecialties involved in patient care. For instance, biopsy and surgical planning with a PET/CT combination (Figure 4) can show the spatial coexistence of complex CT structures and elevated activity [58]. Structures with a large component of nonviable cells, necrosis, and fluid can be approached in favor of regions with viable tumor cells with intact cell membranes, as indicated by higher FDG activity.…”

Toward Simultaneous Real-Time Fluoroscopic and Nuclear Imaging in the Intervention Room

“…Tomosynthesis producing intrinsically registered hybrid images. Procedures that can potentially benefit from real-time simultaneous hybrid imaging include selective internal radiation therapy and liver radioembolization (6)(7)(8), biopsies (3,9), tumor resections (10), and radiofrequency ablations (11). Real-time functional imaging in concert with anatomic imaging would provide the physician with valuable information during the procedure, thereby improving therapeutic efficiency.…”