[Dynamic MRI of the liver with parallel acquisition technique: characterization of focal liver lesions and analysis of the hepatic vasculature in a single MRI session].
ABSTRACT To retrospectively evaluate the performance of breath-hold contrast-enhanced 3D dynamic parallel gradient echo MRI (pMRT) for the characterization of focal liver lesions (standard of reference: histology) and for the analysis of hepatic vasculature (standard of reference: contrast-enhanced 64-detector row computed tomography; MSCT) in a single MRI session.
Two blinded readers independently analyzed preoperative pMRT data sets (1.5T-MRT) of 45 patients (23 men, 22 women; 28 - 77 years, average age, 48 years) with a total of 68 focal liver lesions with regard to image quality of hepatic arteries, portal and hepatic veins, presence of variant anatomy of the hepatic vasculature, as well as presence of portal vein thrombosis and hemodynamically significant arterial stenosis. In addition, both readers were asked to identify and characterize focal liver lesions. Imaging parameters of pMRT were: TR/TE/matrix/slice thickness/acquisition time: 3.1 ms/ 1.4 ms/ 384 x 224 / 4 mm/ 15 - 17 s. MSCT was performed with a pitch of 1.2, an effective slice thickness of 1 mm and a matrix of 512 x 512.
Based on histology, the 68 liver lesions were found to be 42 hepatocellular carcinomas (HCC), 20 metastases, 3 cholangiocellular carcinomas (CCC) as well as 1 dysplastic nodule, 1 focal nodular hyperplasia (FNH) and 1 atypical hemangioma. Overall, the diagnostic accuracy was high for both readers (91 - 100 %) in the characterization of these focal liver lesions with an excellent interobserver agreement (kappa-values of 0.89 [metastases], 0.97 [HCC] and 1 [CCC]). On average, the image quality of all vessels under consideration was rated good or excellent in 89 % (reader 1) and 90 % (reader 2). Anatomical variants of the hepatic arteries, hepatic veins and portal vein as well as thrombosis of the portal vein were reliably detected by pMRT. Significant arterial stenosis was found with a sensitivity between 86 % and 100 % and an excellent interobserver agreement (kappa = 0.85).
Diagnostic image quality remains good or excellent in most cases when the data acquisition time is accelerated by means of parallel imaging in dynamic MRI. It allows reliable detection and characterization of focal liver lesions as well as the depiction of hepatic vascular variants, portal vein thrombosis, and arterial stenosis. Introducing pMRT in routine liver MRI may be another step towards a simplified diagnostic work-up prior to liver surgery.