Diffusion Tensor Imaging MRI With Spin-Echo Sequence and Long-Duration Measurement for Evaluation of Renal Fibrosis in a Rat Fibrosis Model

Background. Renal fibrosis (RF) is a well-known marker for chronic kidney disease (CKD) progression, including chronic renal injury after renal transplantation. However, invasive biopsy is an available examination for evaluation of RF. Diffusion MRI was once recognized as a promising option for RF. However, it is now controversial for RF evaluation in a unilateral ureteral obstruction (UUO) model. Methods. To seek an optimal imaging method applicable for RF in UUO model kidneys, we attempted a series of MRI methods, including proton density weighted imaging, T1-weighted imaging, T2-weighted imaging, T2*-weighted imaging, diffusion-weighted imaging, and diffusion tensor imaging (DTI). Results. We identified DTI MRI by spin-echo sequence plus a special kidney attachment as the best option for evaluation of renal UUO fibrosis, compared with normal kidney on the opposite side. To confirm these results, we applied this technique to a rat UUO therapeutic model with the anti-fibrotic reagent Fasudil. Fractional anisotropy values calculated from DTI MRI showed statistically significant linear correlation with the RF area measured by use of Sirius red or Masson trichrome staining of the positive area [cortex (r = 0.6397, P = .0283) and outer stripe of the outer medulla (r = 0.7810, P = .0039)]. Conclusions. By use of the DTI MRI with spin-echo sequence, it may be possible to accurately evaluate RF in CKD.