Perfusion-sensitive parameters of intravoxel incoherent motion MRI in rectal cancer: evaluation of reproducibility and correlation with dynamic contrast-enhanced MRI.

Background: Intravoxel incoherent motion magnetic resonance imaging (IVIM-MRI) acquires tumor perfusion information without injection of contrast medium, which is promising in tumor assessment. However, its consistency with dynamic contrast-enhanced MRI (DCE-MRI), a more widely used method for tumor perfusion evaluation, is not revealed in rectal cancer.

Purpose: In this study, we aimed to investigate the correlation of perfusion-sensitive parameters derived from IVIM-MRI with DCE-MRI and measurement reproducibility of IVIM-MRI parameters in rectal cancer.

Material And Methods: Forty-seven rectal cancer patients underwent IVIM-MRI with 16 b-values and DCE-MRI. The perfusion fraction ( f), pseudo-diffusion coefficient ( D*), and f· D* were measured by two radiologists independently and correlated with the transfer constant ( K), reflux constant ( k), and extravascular extracellular fractional volume ( v) obtained from DCE-MRI.

Results: Pearson's correlation analyses of IVIM-MRI and DCE-MRI parameters showed fair to moderate correlation between f and K ( r = 0.461, P = 0.001), followed by f and k ( r = 0.430, P = 0.003), f·D*, and K ( r = 0.425, P = 0.003), f·D*, and k ( r = 0.384, P = 0.008). There was no significant correlation between v and f, v and D*, v and f· D*, D* and K, and D* and k. The reproducibility of IVIM-MRI measurements was moderate. For parameter f, intraclass correlation coefficient (ICC) = 0.71 (0.53-0.82), coefficient of variation (CV) = 13.05 ± 0.02%, limit of agreement (LoA) = -0.05-0.04; for parameter D*, ICC = 0.55 (0.32-0.72), CV = 20.28 ± 3.23%, LoA = -9.6-8.4.

Conclusion: Perfusion-sensitive parameters derived from IVIM-MRI correlated fairly to moderately with DCE-MRI in rectal cancer patients and showed moderate measurement reproducibility. IVIM-MRI supplements routine high-resolution MRI without contrast enhancement to provide information of tumor microcirculation.