Role of MRI in Characterization of Benign Hepatic Focal Lesions

Abstract

Background: nowadays, magnetic resonance plays a key role in management of liver lesions, using a radiation-free technique and a safe contrast agent profile. The heightened soft-tissue resolution and sensitivity to intravenous contrast agents provided by magnetic resonance imaging (MRI) makes it an invaluable problem-solving tool for fully characterizing focal liver lesions (FLL). Diffusion-weighted imaging (DWI) sequences have been shown to be an emerging contributor for liver MRI and are being incorporated in most abdominal MR protocols. Aims: To determine the role of MRI in characterization of benign hepatic focal lesions. Patients and methods: This study included 30 patients (11 M, 19 F with mean age of 47.7 years) with benign hepatic focal lesions. They were simple cyst (n =6), hemangioma (n = 11), abscess (n = 4), adenoma (n = 2), focal nodular hyperplasia (n = 3), Hydatid cyst (n=1) and regenerative nodules (n = 3). They underwent routine MR imaging and diffusion MR weighted imaging using 1.5 tesla MR unit (Philips Achieva). Diffusion MR imaging was done using spin echo type of single shot echo planar imaging (EPI) with b value of 0, &800 mm2/sec. The apparent diffusion coefficient (ADC) map was reconstructed and ADC value was measured. The mean ADC values correlated with histopathological results as well as followup imaging results. Results: The mean ADC values were significantly different within benign hepatic focal lesions (P < 0.001). There was highly statically significant relation between cyst and hemangioma (p-value < 0.001), cyst and abscess (p-value <0.001), hemngioma and abscess (p-value < 0.001), while there was no statically significance relation between adenoma and focal nodular hyperplasia (p-value < 0.74), adenoma and regenerative nodules (p-value < 0.67) and focal nodular hyperplasia and regenerative nodules (p-value < 0.41). Conclusions: benign liver lesions are frequently encountered in clinical practice and their characterization may be sometimes difficult. The problem of lesion characterization is mainly crucial and may influence therapeutic decisions and patient’s management. The role of imaging is therefore a mainstay and MRI, with its multi parametric potentialities, is a highly accurate method for lesion detection and characterization. Nevertheless, benign lesions may be sometimes “non-typic” in their cellular content and vascular behavior and lesions biopsy can be necessary for definitive characterization.