MRI management of focal liver lesion: what a liver MRI beginner cannot fail to know

Vincenza Granata¹Roberta Fusco^1*Igino Simonetti¹Maria Giovanna Riga²Giuseppe Pellegrino³Serena Carriero⁴Gianpaolo Carrafiello^3,4Antonella Petrillo¹Francesco Izzo¹

• ¹G. Pascale National Cancer Institute Foundation (IRCCS), Naples, Italy
• ²Department of Radiology, University of Padova, Padova, Italy
• ³Diagnostic and Interventional Radiology, Università degli Studi di Milano, Milan, Italy
• ⁴Diagnostic and Interventional Radiology Department, IRCCS Ca' Granda Fondazione Ospedale Maggiore Policlinico, Milan, Italy

Magnetic Resonance Imaging (MRI) is currently recognized as the most suitable diagnostic tool in detection and characterization of focal liver lesions. Morphological and functional data allows, in different clinical scenarios, a high diagnostic performance for the characterization of even very small lesions and, therefore, improve patient management, reducing costs and times. Despite this premise, MRI should not be prescribed to all patients with focal liver lesions, but not only indications should be well known, but also individual patients should be considered. For different clinical scenario, according to the extrahepatic malignancy presence or known liver disease, MRI with contrast agent represents a useful diagnostic tool, although the choice of diagnostic tool will be subordinated to the operator experience, technology availability and patient specific characteristics. Standard protocol should include conventional sequences: T2-W sequences, T2-W sequences with fat suppression (FS), and in-op phase GRE T1 sequences and functional. Among functional, diffusion-weighted imaging (DWI) is mandatory, especially for detection of very small lesions, however diffusion restriction does not necessarily indicate that a lesion is malignant. Contrast-enhanced MR is the keystone of liver MR, especially for lesion categorization. Contrast agents can be classified as non-specific agents that distribute into vascular and extra-vascular extra-cellular spaces and specific agents acquired by hepatic cells, either taken up by Kupffer cells than by hepatocytes. The abbreviated protocol concept is subordinated to the idea that in less examination time it is possible to acquire all the information necessary for patient management using only part of the sequences that normally fall within a standardized protocol. Radiomics has emerged as a promising tool in the liver oncology field, particularly in colorectal liver metastases evaluation. To fully realize radiomics clinical value, it is essential to address several methodological hurdles, including the standardization of image acquisition and analysis workflows, rigorous validation across large and diverse patient cohorts. The aim of review, for a liver MRI beginner, is to provide a comprehensive overview of MRI management of focal liver lesion, with a focus on acquisition protocol, including abbreviated protocols, contrast media, and the capacity to report all relevant data to characterize focal liver lesions.