Potential added value of dynamic PET in the detection and characterization of Hepatocellular Carcinoma (HCC): A case study.

3118 Objectives: MRI and CT are the gold standard imaging for the diagnosis of HCC due to their superiority in preforming the dynamic multiphase contrast enhancement protocols which have high specificity (95%-100%) and relatively limited sensitivity 76%. CT and MRI are unable to provide the biological status (degree of differentiation) of HCC which is important for therapy selection (ie. transplant vs resection vs radiation) and assessing treatment response. According to national guidelines, standard analog FDG PET/CT plays a role in prognosis but has limited sensitivity in the detection of HCC with relatively high false negative rate due to the lack of dynamic multiphase enhancement capabilities. Digital PET/CT (dPET/CT) with its high sensitivity has led to shorter scan time and reduction in radiation dose, while improving image quality and small lesion detectability. In addition, dPET/CT has the capability to acquire dynamic scans which may improve FDG PET sensitivity for the detection of HCC lesions. Dynamic dPET/CT may help obtaining FDG arterial enhancement, venous washout and delayed imaging which matches the dynamic information obtained by CT or MRI. We aimed to discuss the potential added value of dynamic dPET/CT imaging and its usefulness in the detection and characterization of HCC. Methods: A literature review of current guidelines regarding HCC detection and characterization as well as dynamic dPET/CT capabilities was conducted to evaluate the potential added value in clinical practice. Additionally, a case study was examined at our PET center to determine the potential role of dynamic dPET/CT in guiding the management of HCC. Results: The literature review of dPET/CT showed it is a promising technique in many aspects for research; however, the capability of dynamic dPET/CT imaging in clinical practice has not been explored. For instance, FDG PET/CT has a low sensitivity for detecting HCC (36%-70%) due to the lack of vascular flow information. In our case study, a 79y male patient with a CT and MRI received the diagnosis of highly probable HCC. However, subsequent liver biopsy was non-diagnostic. FDG dPET/CT scan without contrast and was done for staging with dynamic information (arterial and venous) collected immediately after FDG injection similarly to CT or MRI multiphase protocols. The standard PET/CT images acquired 90 min post-injection did not show FDG uptake in the known liver lesion. However, dynamic dPET/CT imaging showed higher prefusion in the lesion. The overall PET scan read was HCC (based on positive arterial dynamic phase) but a well/moderately differentiated type (based on the negative standard delayed images). Subsequent repeated biopsy revealed well/moderately differentiated HCC. In the absence of the dynamic perfusion information, the interpretation would have been a false negative. Adding dynamic information avoided a false negative diagnosis and informed us regarding lesion biology and prognosis. Based on this case study, our institution has developed a prospective study to explore the potential impact of dynamic dPET/CT in HCC. Our hypothesis is that flow positive but standard delayed negative is more likely to be well/moderately differentiated but flow positive and standard delayed positive are more likely to be a poorly differentiated HCC. Conclusions: Overall, dynamic dPET/CT may provide useful information for lesion detection and characterization of HCC. With the new generation of dPET/CT, the clinical sensitivity and specificity for the diagnosis of HCC are expected to improve. Also, dynamic dPET/CT has advantages over CT and MRI as it provides critical prognostic information, lesion characterization, and detects unexpected extrahepatic metastasis. This case study gives insight on how dynamic dPET/CT can change the diagnostic accuracy, detection, and characterization for HCC and may add additional information not currently being provided by contrast enhanced multiphasic MRI or CT.