Breath-hold imaging and respiratory triggering have been suggested as techniques to overcome these problems. DTI is a development from diffusion-weighted MRI, which allows the quantification of diffusion in different directions. Diffusion anisotropy is related to structural organization and therefore could be compromised in a pathological process. Molecular diffusion, however, is a three-dimensional process which can occur with different probabilities in each direction, i.e. in an anisotropic manner. This is the case in the kidney, which has a well-defined structure with tubules, collecting ducts and vessels radially oriented towards the pelvis and in which molecules move in a preferential direction. The measurement of global diffusion and the direction of the diffusion is necessary to investigate molecular diffusion in the kidney. DTI can provide three indices related to the magnitude of diffusivity from the mathematical description of the system. These indices are the mean, axial and radial diffusivity. MD is the average of the average diffusion coefficient in all three directions and is a reflection of the magnitude of the tensor that describes the system. AD is the first eigenvalue, and occurs in the longitudinal direction of the tensor. RD is the average of the second and third eigenvalues. It is related to diffusion along the radial direction. The three indices are related to diffusional anisotropy and fractional anisotropy. The measurement of MD, AD, RD and FA in a healthy kidney has not yet been reported in the literature. The aim of our study was to evaluate the diffusivity characteristics of the renal cortex and medulla and provide baseline data for future studies. In this pilot study, we identified significantly higher mean cortical MD, l2, l3, and RD. The primary eigenvalue l1 was the largest and least restricted diffusivity and, in a medullary tubule, reflected motion along the length of the tubule. This included intratubular flow, whose direction was specified by the primary diffusion eigenvector, The secondary and tertiary eigenvalues reflected lower restricted diffusion orthogonal to l1. In the medulla this corresponded to cross-tubule or transtubular motion. These differences in DTI indices reflected the renal Vismodegib 879085-55-9 anatomic and physiological structure. The chief function of the kidney is filtration of plasma and formation of urine. The renal blood flow, in particular blood flow to the renal cortex, is much greater than that needed for the metabolic requirements of the kidney. Most blood is directed towards the renal cortex to optimize glomerular filtration and reabsorption of solute. The renal cortex requires rich perfusion to function properly, while the renal medulla requires limited blood flow. The maintenance of a relatively low medullary blood flow appears to be critical for maintaining the cortical-medullary solute gradient and, therefore, urinary concentrating mechanisms. Blood is supplied to the renal medulla from the vasa recta capillaries. The vasa recta capillaries arise from the efferent arterioles of the juxtamedullary glomeruli, which comprise about 10% of all glomeruli in the kidney. While all blood flow to the kidney enters the renal cortex, only about 10% reaches the renal medulla.