Measuring Anisotropic Diffusion in Kidney Using MRI

Rationale and Objectives To measure the anisotropic diffusion in kidney and to demonstrate the feasibility of renal tractography. Materials and Methods Diffusion tensor imaging was acquired in kidney from 10 healthy volunteers and 5 patients with chronic kidney disease. Diffusion indices were calculated from the tensor, including fractional anisotropy, intervoxel diffusion coherence, and mean/axial/radial diffusivity. Results Acquisitions with respiratory triggering could provide improved image quality in all diffusion indices, as compared to that by breathhold. It is sufficient to use five to seven scan averages when the measured diffusion indices converge to a steady state in medulla, which reduced the acquisition time in a triggered measurement down to a clinically tolerable limit. Second, the measured diffusion indices can be affected by the diffusion weighting. An increased diffusion weighting will lead to an underestimation in all diffusion indices. Finally the direction of water diffusion is consistent in the kidney cortex, which was properly reflected in intervoxel diffusion coherence. In a feasibility study in healthy volunteers and patients, renal tractography was performed that visualized the organized renal structure and as it declined with the progress of chronic kidney disease. Conclusion When compared to conventional breath hold technique, the significant improvement in image quality compensated for the prolonged acquisition time. Therefore, triggered acquisition is preferred in a clinical setting because it required less from patient cooperation.