Transcatheter arterial chemoembolization (TACE) is a well-accepted method for Treatment of unresectable hepatocellular carcinoma (HCC). Determining the success of treatment by imaging studies would 
help to guide subsequent therapeutic planning. Diffusion-weighted imaging (DWI) with calculation of 
corresponding apparent diffusion coefficient (ADC) maps can give us an impression about the extent of 
the tumor necrosis after TACE. Also rapid image acquisition and dispensing of contrast are considered 
superior pros. Objective: To investigate changes in apparent diffusion coefficient (ADC) levels pre and 
post TACE to monitor early therapeutic response of hepatocellular carcinoma (HCC) to transcatheter 
arterial chemoembolization (TACE). Patients and methods: 20 patients with 22 lesions included in the 
study, underwent TACE for HCC lesions, All patients had MR-DWI pre TACE and 1 month after TACE 
with calculation of ADC values and comparing the percentage of change in ADC level pre and post 
TACE in 1 month after TACE with the results of contrast enhanced Dynamic MRI 3 or 6 month after 
TACE based on MRECIST criteria. Results: Of about 20 patients, 22 lesions was treated, ADC levels 1 
month post-operative showed 75% sensitivity, 80% specificity and about 77.27% accuracy. It was found 
that the specificity of degree of ADC change is maximized by gaining at least 22% increase in ADC 
value, and the sensitivity is maximized by gaining less than 15% increase in ADC. At these points 
sensitivity increased to 91.67% and specificity up to 90%. Conclusion: the calculation of percentage of 
change in ADC levels 1 month after TACE with addition of specific Cut off values can improve the 
accuracy of assessment of early response to TACE and create proper planning for achievement of 
treatment goals. Although larger, more definitive and quantitative studies with clinical end points are 
needed.