The Value Of Diffusion Weighted Imaging In Evaluating The High Intensity Focused Ultrasound Treatment For Rabbit VX2Liver Tumor Model

Objective To study the changes of tumor tissue in a rabbit VX2liver cancer model on diffusion weighted imaging before and after high intensity focused ultrasound ablation.Methods Magnetic resonance imaging(MRI) including non-enhanced T1W1, T2WI, contrast-enhanced T1W1(with LAVA sequence) and diffusion weighted imaging(DWI) were obtained before within12hours,1day,3,7,14and21days after high intensity focused ultrasound ablation in a rabbit VX2liver cancer model. Experimental rabbit of each observation time point was executed death after MRI examination and pathological examination was carried out. Changes on ADC value were observed and compared with pathological findings.Results The success rate of implantation of VX2liver cancer in our experiment was93%(56/60).Six rabbit liver cancer models were execute death after MR scanning but before HIFU ablation to use for pathological examination and for observing the diffusion of hydrogen.45of50rabbit VX2liver cancer models survival, the success rate of experiment was75%.Hypointensity signal on TIWI, hyper-intensity or heterogeneous signal on T2WI, three pattern of enhancement (well-distributed, nonuniform and circular enhancement) on LAVA sequence, hyper-intensity or heterogeneous signals, hypo-intensity or heterogeneous signals on ADC maps were found in the45models before HIFU ablation. All models were confirmed pathologically with well-differentiated squamous cancer. Hypointensity signal on TIWI, hypo-intensity or heterogeneous signal on T2WI, three pattern of enhancement (no, heterogeneous, and circular enhancement) on LAVA sequence, hypo-intensity or heterogeneous signals on DWI, hyper-intensity or heterogeneous signals on ADC maps were found in the45models after HIFU ablation. The tissues in rabbit VX2liver cancer models (29/45,64%) which showed hyper-intensity on ADC maps1,3,7,14and21days after HIFU ablation were necrosis tissue pathologically, and their ADC value were higher that those before HIFU ablation (P<0.05). The tissues in rabbit VX2liver cancer models (16/45,36%) which showed heterogeneous signals on ADC maps3,7,14and21days after HIFU ablation were necrosis tissue(hyper-intensity signal region, and their ADC values were higher that those before HIFU ablation, P<0.05) and survival tumor tissue (hypo-intensity signal region, no difference between their ADC values and those before HIFU ablation, P>0.05), respectively Conclusion DWI and ADC value can be an important modality in evaluation the curative effect of HIFU ablation for rabbit VX2liver cancer, which can demonstrate accurately the tumor necrosis and survival tumor tissue.