Comparison of Intravoxel incoherent motion imaging and multiecho dynamic contrast-based MRI in rectal cancer.

Background Dynamic contrast-based MRI and intravoxel incoherent motion imaging (IVIM) MRI are both methods showing promise as diagnostic and prognostic tools in rectal cancer. Both methods aim at measuring perfusion-related parameters, but the relationship between them is unclear. Purpose To investigate the relationship between perfusion- and permeability-related parameters obtained by IVIM-MRI, T-1-weighted dynamic contrast-enhanced (DCE)-MRI and T-2*-weighted dynamic susceptibility contrast (DSC)-MRI. Study Type Prospective. Subjects In all, 94 patients with histologically confirmed rectal cancer. Field Strength/Sequence Subjects underwent pretreatment 1.5T clinical procedure MRI, and in addition a study-specific diffusion-weighted sequence (b = 0, 25, 50, 100, 500, 1000, 1300 s/mm(2)) and a multiecho dynamic contrast-based echo-planer imaging sequence. Assessment Median tumor values were obtained from IVIM (perfusion fraction [f], pseudodiffusion [D*], diffusion [D]), from the extended Tofts model applied to DCE data (K-trans, k(ep), v(p), v(e)) and from model free deconvolution of DSC (blood flow [BF] and area under curve). A subgroup of the excised tumors underwent immunohistochemistry with quantification of microvessel density and vessel size. Statistical Test Spearman's rank correlation test. Results D* was correlated with BF (r(s) = 0.47, P < 0.001), and f was negatively correlated with k(ep) (r(s) = -0.31, P = 0.002). BF was correlated with K-trans (r(s) = 0.29, P = 0.004), but this correlation varied extensively when separating tumors into groups of low (r(s) = 0.62, P < 0.001) and high (r(s) = -0.06, P = 0.68) BF. K-trans was negatively correlated with vessel size (r(s) = -0.82, P = 0.004) in the subgroup of tumors with high BF. Data Conclusion We found an association between D* from IVIM and BF estimated from DSC-MRI. The relationship between IVIM and DCE-MRI was less clear. Comparing parameters from DSC-MRI and DCE-MRI highlights the importance of the underlying biology for the interpretation of these parameters. Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019.