Intravoxel Incoherent Motion Diffusion-weighted MRI Assessing the Effect of the Vascular Disrupting Agent CA4P on VX2 Liver Tumors in Rabbits

Objective: This study aimed to assess the response of combretastatin-A4-phosphate (CA4P) in rabbit VX2 liver tumors using intravoxel incoherent motion diffusion-weighted MRI (IVIM DW-MRI). Methods: Forty rabbits with implanted VX2 liver tumors underwent baseline MRI and were then given 10 mg/kg CA4P (n=20) or saline (n=20). After 4 h, 10 rabbits from each group underwent an MRI examination and were then sacrificed. The remaining rabbits underwent MRI after 1, 3, and 7 days and were then sacrificed. Liver samples were processed for H&E and immunohistochemical staining. IVIM parameters (D, f, D*) were compared in the treatment and control groups, and the correlations of IVIM parameters with microvascular density (MVD) were determined. Results: At 4 h, the two treatment groups had significantly different f and D* values (p<0.001), and these values were at their minimum in the treatment group. The treatment group had moderate correlations between MVD and f at 4 h (r=0.676, p=0.032) and 7 days (r=0.656, p=0.039) and with D* at 4 h (r=0.732, p=0.016) and 7 days (r=0.748, p=0.013), but no correlation was reported between MVD and f or D* in the control group (all P>0.05). Conclusion: IVIM DW-MRI is a sensitive imaging technique. It successfully evaluated the effect of CA4P on VX2 liver tumors in rabbits. The f and D* values correlated with MVD at 4 h and 7 days after using CA4P, indicating that these parameters have the potential to be used as indicators of tumor angiogenesis after treatment.