Experimental Study On MR-DWI In Evaluating The Therapeutic Efficacy Of Transarterial Embolization Ablation

Objective:To evaluate the role of Diffusion Weighted Imaging (DWI) in VX-2liver tumor after Transarterial Embolization Ablation (TEA).Materials and Methods:Thirty one New Zealand white rabbits were included in the study, VX-2implanted models of liver tumor were established by percutaneous puncture under CT-guidance. Two weeks later, all the rabbits underwent conventional MRI (T1WI, T2WI), DWI,(b=100,400,600,800,1000s/mm2) and Transarterial Embolization Ablation. MR imaging was acquired one week after TEA. Then, all the rabbits were sacrificed to get the specimens, which processed for Hematoxylin and Eosin (HE) staining and CD31immunohistochemical staining to count the Microvessel Density (MVD).Results:Eighteen rabbit VX-2liver tumor models were successfully established. When b=100,400,600,800and1000s/mm2, the mean Apparent Diffusion Coefficient (ADC) values of the tumor pre-operation were (1.69±0.15)×10-3mm2/s,(1.45±0.11)×10-3mm2/s,(1.26±0.08)×10-3mm2/s,(1.20±0.08)×10-3mm2/s,(1.09±0.07)×10-3mm2/s, respectively; The mean ADC values post-operation were (2.74±0.19)×10-3mm2/s,(2.45±0.16)×10-3mm2/s,(2.25±0.14)×10-3mm2/s,(2.03±0.14)×10-3mm2/s,(1.83±0.12)×10-3mm2/s, respectively. The mean ADC values were decreased with the b-value increased in pre-operation and post-operation, the mean ADC values showed significant statistic difference (P<0.001) in pre-operation and post-operation under the same b value, and the mean ADC values post-operation were increased (P<0.001). The contrast was better when we chose the b=600s/mm2, combining with pathology, the ADC value of the necrotic portions post-operation was (2.18±0.32)×10-3mm2/s, compared with the ADC value of viable tumor portions (1.5±0.30)×10-3mm2/s, showing significant statistic difference (P<0.001). There was a significant difference of ADC value in the viable tumor portions (1.50±.30)×10-3mm2/s and the normal liver tissue portions (2.28±0.35)×10-3mm2/s (P<0.001). There was a significant difference of ADC value in the viable tumor portions (1.86±0.41)×10-3mm2/s mm2/s and the necrotic portions of the normal liver tissue (1.86±0.41)×10-3mm2/s (P=0.005<0.05). There was a significant difference of ADC value in the normal liver tissue portions (1.86±0.41)×10-3mm2/s and the necrotic portions of the normal liver tissue (1.86±0.41)×10-3mm2/s (P<0.001). The maximum ADCdifference value pre-operation was (0.28±0.10)×10-3mm2/s, compared with the maximum ADCdifference value post-operation (0.47±0.10)×10-3mm2/s, showing significantly statistic difference (P<0.001). When the b=600s/mm2, the mean ADC values of the tumor were not significantly correlated with MVD values (r=0.221, P=0.379>0.05), and the ADC values of viable tumor portions were not significantly correlated with MVD values (r=-0.044, P=0.862>0.05). The maximum ADCdifference values post-operation correlated positively with MVD values (F=12.247, P=0.003<0.05).Conclusions:DWI is an effective method to evaluate the therapeutic efficacy of TEA, which can distinguish the tumor necrotic portions and viable portions. The maximum ADCdifference offers a promising new method of non-invasively, which can reflect the level of tumor angiogenesis.