PURPOSE: To design a diffusion tensor imaging (DTI) protocol and determine the principal diffusion coefficients and anisotropy index of the healthy testicles.
MATERIALS AND METHODS: All protocols were approved by the institutional Internal Review Board of Sheba Medical Center and a signed informed consent was obtained from all participants. Between June 2017 to March 2018, 16 healthy volunteers (mean age: 34 y, range:22-67 y) were prospectively scanned at 3T MRI using T2-weighted sequence and high in-plane spatial resolution (1.2*1.2*5 mm3) DTI protocol with 24 directional diffusion gradients and two separated pairs of b-values (0/700 s/mm2 and 100/700 s/mm2). Pixel by pixel image processing of the two DTI datasets yielded for each pair the diffusion vector maps and parametric maps of their corresponding principal diffusion coefficients λ1, λ2, λ3, mean diffusivity (MD), and fractional anisotropy (FA).
RESULTS: The results demonstrated the feasibility of DTI to obtain parametric maps of the testicles. The mean values of the diffusion parameters in the testicles (n=32) of all healthy volunteers were: λ1= 1.36±0.21 (x10-3 mm2/sec), λ2 =1.17±0.20 (x10-3 mm2/sec), λ3= 1.03±0.18 (x10-3 mm2/sec), MD= 1.18±0.13 (x10-3 mm /sec) and FA= 0.13±0.05. DTI parameters were not age nor side dependent. The diffusion coefficients derived from datasets with b-values 0/700 were found to be slightly but significantly higher than those derived from datasets with b-values 100/700 s/mm2 by 4-5% (p<0.05), while FA values remained indifferent (p=0.15) using the 100 s/mm2 b-value as the reference.
CONCLUSION: DTI enables the characterization of the 3-dimensional diffusion process in the testicles. Despite the clear anisotropic architecture of the microtubules, the measured anisotropic diffusivity was relatively low. Furthermore, application of a high reference b-value, resulted in slightly decreased diffusivity, suggesting a mild contribution from intravoxel incoherent motion (IVIM) in the low b-values regime.
