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PET/MRI accurate in detecting liver metastases

Researchers found that the use of positron emission tomography with [¹⁸F]FDG in combination with magnetic resonance imaging was more accurate in detecting liver metastases compared with positron emission tomography with computed tomography, according to published findings.

“While [CT] represents the clinical standard in abdominal tumor staging, [MRI] of the liver, with its excellent soft tissue contrast, offers a higher sensitivity especially in liver lesions sized [less than] 10 mm,” the researchers wrote. “Positron emission tomography … with [¹⁸F]FDG, usually in combination with CT, enables a further characterization of liver lesions based on their glucose metabolism. … MRI, however, is known to show a higher sensitivity and accuracy in the detection of small liver lesions compared with CT, as well as with PET/CT, making it is a promising alternative to CT in hybrid imaging.”

To determine which system has the higher accuracy, researchers analyzed data of 32 patients with malignancies who underwent positron emission tomography (PET)/MRI with [¹⁸F]FDG and PET/CT of the liver. They sought to determine the sensitivity, specificity, positive predictive value and negative predictive value (NPV) of each patient from both systems, used the area under the receiver operating characteristic (ROC) curve for accuracy and calculated conspicuity and diagnostic confidence using Wilcoxon-sign-rank test.

Overall, 113 liver lesions were found in 26 patients, of which 45 were malignant and 68 were benign. Twelve patients had liver metastases (38%).

PET/CT was able to identify 11 of 12 patients with metastases (92%), whereas PET/MRI identified all 12 patients. Analyses showed PET/MRI had a higher accuracy rate compared with PET/CT (96.1% vs. 82.4%; P < .001), as well as higher sensitivity (92.2% vs. 67.8%; P < .01) and NPV (95.1% vs. 82%; P < .05) compared with PET/CT.

Additionally, compared with PET/CT, PET/MRI had higher lesion conspicuity (2.8 ± 0.5 vs. 2.0±1.1 vs.; P < .001) and higher diagnostic confidence (2.6 ± 0.6 vs. 2 ± 0.8; P < .001). PET/MRI also detected additional PET-negative metastases versus PET/CT.

The researchers concluded: “The results of this study indicate that [¹⁸F]FDG-PET/MRI is superior to PET/CT for the detection and characterization of liver lesions. Hence, PET/MRI may become a new reference method in oncologic liver imaging as a modality offering a higher diagnostic accuracy at a reduced radiation dose compared to PET/CT.” – by Melinda Stevens

Disclosures: The researchers report no relevant financial disclosures.