Diffusion-weighted magnetic resonance imaging to evaluate microvascular density after transarterial embolization...

To evaluate the correlation between findings from diffusion weighted imaging (DWI) and microvascular density (MVD) measurements in VX2 liver tumors after transarterial embolization ablation (TEA).

Eighteen New Zealand white rabbits were used in this study. VX2 tumor cells were implanted in livers by percutaneous puncture under computed tomography (CT) guidance. Two weeks later, all rabbits underwent conventional magnetic resonance imaging (MRI) (T1 and T2 imaging), DWI, (b=100, 600, and 1000s/mm(2)) and TEA. MRI was performed again1 week after TEA. Liver tissue was then harvested and processed for hematoxylin and eosin (H&E) staining and immunohistochemical staining for CD31to determine MVD.

VX2 liver tumors were successfully established in all 18 rabbits. Optimal contrast was achieved with a b value of 600s/mm(2).The maximum pre-operative apparent diffusion coefficient (ADC)difference value was 0.28×10(-3)±0.10×10(-3)mm(2)/s, and was significantly different (P<0.001) from the maximum postoperative ADCdifference value of 0.47×10(-3)±0.10×10(-3)mm(2)/s. However, the mean ADC value for the entire tumor was not significantly correlated with MVD (r=0.221, P=0.379), nor was the ADC value for the regions of viable tumor (r=-0.044, P=0.862). However, the maximum postoperative ADCdifference value was positively correlated with MVD(r=0.606, F=12.247, P=0.003).

DWI is effective to evaluate the therapeutic efficacy of TEA. The maximum ADCdifference offers a promising new method to noninvasively assess tumor angiogenesis.