الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 126 |  |  |
| | | from | 126 | | |
Abstract
There is an overall agreement that there are significant changes of ADC levels after locoregional treatment of HCC lesions, this raise the need for pretreatment measurement of ADC and comparing it with post treatment values. we conclude that percentage of ADC change is highly impressive of early treatment response and furthermore we found that by confining specific cut off values for ADC change, gaining at least 22% increase in ADC value to predict complete response, and less than 15% increase in ADC to predict residual tumor viability. Sensitivity increases to 91.67% and specificity to 90% with values lying between 15% and 22% remain equivocal.
Thus we postulate that, the use of percentage of change of ADC pre and post-therapy is much more beneficial than subjective determining the facilitation and restriction to exclude the conflict of cut off values and also to exclude the fallacies resulting from high initial ADC level of well differentiated tumors with maximization of the technical parameters and unification of b value (between 800 and 1000) pre and post treatment are mandatory factors to increase accuracy.
Along with the known advantages of DWI compared to contrast study as improved liver lesion detection, no need for contrast, relative short time of acquisition and easily generated ADC maps.
Other benefits include DWI increases the sensitivity of dynamic MRI in the evaluation of the HCC response to TACE, especially in patients who cannot hold their breath for adequate time that degrade the DCE MR images quality, yet it has low specificity related to high number of false positive results preventing using it solely.
Also, DWIs is a reliable method in detection of small satellites, hypovascular lesions and for differentiation between active tumor residue and benign perilesional enhancement.
The DWI can overcome difficulties encountering the triphasic CT like the beam hardening induced by dense lipiodol lowering its sensitivity in predicting local tumor recurrent. Also hypovascular lesions and small satellite lesions are better detected by DWI rather than conventional dynamic CT or MRI.
In terms of using specific criteria for quantification of treatment response, mRECIST couldn’t be applied in some cases with multiple necrotic regions and is defective in defining criteria of tumor viability imaging, the new LI-RADS treatment response algorithm offers a comprehensive approach to assess treatment response for individual lesions after a variety of locoregional therapies. In addition to offering imaging criteria for viable and nonviable HCC, new concepts of nonevaluable tumors as well as tumors with equivocal viability are introduced.