Role of Diffusion Weighted Magentic Resonance Imaging in Evaluation of Hepatocellular Carcinoma Post Chemoembolization

Abstract

Background:  Hepatocellular carcinoma (HCC) is the fifth most common type of cancer in the world and the third most prevalent frequent death reason in patients who suffers from malignant tumors. The apparent diffusion coefficient (ADC) is a method for measurement of  the water movement within tissues. Tumors that are viable have a high cellularity, and the cells' membranes are intact which water molecules' mobility is restricted, leading to a small ADC. But from the other hand, necrosis increases the permeability of the cell of the membrane, permitting water molecules to circulate freely and resulting in an elevation in the ADC's relative value. This study aimed to describe the use of diffusion weighted MRI to evaluate hepatocellular carcinoma in the setting of trans-arterial chemoembolization (TACE). Methods: This study was carried out on 30 patient (males: 22, eight females) aged 42 to 75 years with biopsy-proven HCC, candidate for trans arterial hepatic chemoembolization as a plan of treatment. They were referred from Oncology Department to MRI unit in radiology department over a period of 1 year starting in June 2018 to June 2019. Results: According to diffusion weighted Imaging (DWIs) and ADC values, there were 4 TP (13.33%), 22 TN (73.33%), 2 FP (6.66%) and 2 FN (6.66%) studies. The P-value by Fisher’s Exact was <0.05 denoting agreement between the DWI and ADC findings and the standard of references. Regarding the false negative studies by diffusion MRI, On diffusion images, there was a loss of signal or a mild sustained hyperintensity with a bright ADC map, so it was considered as well ablated lesion. Follow up triphasic CT or dynamic MRI after 3-6 months shows lesion enhancement at arterial phase and wash out at both venous and delayed phases with restricted diffusion. The optimal cutoff value for sensitivity and specificity is 1.069; at this ADC value, the sensitivity is 66.66 percent and the specificity is 91.66 percent. Conclusions: ADC obtained from diffusion-weighted magnetic resonance imaging has developed into a a useful biomarker for the response of tumours to therapy.  Analysis of the ADC value is helpful in detecting the presence of residuals in non-successfully ablated lesions.