FDG PET/MR for liver metastases: a systematic review and meta-analysis of diagnostic accuracy and technical protocols with a proposed reporting framework

This systematic review and meta-analysis evaluated the diagnostic performance of FDG PET/MR for detecting hepatic metastases from extrahepatic primary malignancies, together with acquisition protocols, reconstruction parameters, and technical heterogeneity.

A systematic search was conducted through September 2026. Eligible studies evaluated FDG PET/MR for hepatic metastases and reported diagnostic performance data and/or technical protocol information. Summary estimates of sensitivity and specificity were obtained using a bivariate random-effects model. A structured qualitative assessment of PET and MR acquisition, reconstruction parameters, and image interpretation strategies was also performed.

Fifteen studies involving 861 patients met the inclusion criteria. Eight studies (53%) provided sufficient data for the diagnostic accuracy meta-analysis, whereas all contributed to the qualitative technical assessment. The meta-analysis demonstrated a summary sensitivity estimate of 0.94 (95% CI, 0.89-0.97) and a summary specificity estimate of 0.99 (95% CI, 0.92-1.00) for detecting hepatic metastases. Sensitivity showed substantial between-study heterogeneity (I² = 0.83), whereas specificity showed low heterogeneity (I² = 0.21). Technical assessment revealed marked variability in PET acquisition, MR protocols, reconstruction parameters, and reporting, with frequent underreporting of voxel size, filtering, and motion correction. Hepatobiliary contrast agents were used in only a minority of studies, and dedicated PET motion correction was rarely implemented.

FDG PET/MR demonstrates high lesion-level diagnostic accuracy for the detection of hepatic metastases, with high summary sensitivity and specificity. However, substantial between-study variability in sensitivity, together with variability and frequent underreporting of technical parameters, highlights the need for standardized acquisition protocols and reporting frameworks to improve reproducibility, comparability, and clinical translation.