Incremental Value of Digital PET/MRI over PET/CT in the Assessment of Neoplastic Liver Lesions

The objective of this study was to assess the performance of positron emission tomography/magnetic resonance imaging (PET/MRI) compared with PET/computed tomography (PET/CT) in the clinical management of patients with neoplastic hepatic lesions.

This is a retrospective study and includes a sample size of 15 patients, referred for diagnostic evaluation and staging of neoplastic hepatic lesions. The patients included in this study underwent a simultaneous PET/CT scan on uMI-Vista and a complementary liver PET/MRI scan on uPMR 790. PET/CT and PET/MRI were compared based on the number of detected lesions, the smallest detected lesion diameter, and tumor-to-liver ratio (TLR). The histopathological analysis was considered the standard of reference.

PET/MRI reported extra information in 87% (13/15) of patients, and additional lesions were identified in 73% (11/15) of patients. Furthermore, PET/MRI could identify subcentimeter liver lesions and added great value in the evaluation of lesion viability. Overall, 40 additional lesions were detected with PET/MRI in contrast with PET/CT within the given patient cohort. The smallest revealed lesion measured 2 mm in the long-axis diameter, and the average long-axis diameter of small lesions detected by PET/MRI across 15 patients was 3.4 mm with a standard deviation of 1.3 mm. These findings significantly affected the final outcomes in 12 out of 15 patients, leading to modifications in the response assessment category in 5 patients and defined the malignant hepatic lesions on staging/restaging scans (10/15).

PET/MRI has been found to outperform PET/CT in terms of conspicuity of liver lesions, with better sensitivity and specificity. Overall, coregistered PET and MR images have been shown to outperform PET/CT in the imaging of liver lesions, with better delineation of small lesions as well as reliable localization of lesions to the corresponding liver segment.

In addition to a significant decrease in radiation exposure, the PET/MRI combination resulted in higher detection rates and more precise characterization of small malignant liver lesions and tends to be more powerful than PET/CT, which has a direct impact on the patient's diagnosis, staging, and further therapeutic strategies.