The Diffusion Tensor Imaging Properties of the Normal Testicles at 3 Tesla Magnetic Resonance Imaging

The testicles are structured in a well-defined microtubular network formation, which is expected to be reflected in high anisotropic diffusivity. However, preliminary studies reported on low values of fractional-anisotropy (FA) in the normal testicles. Our aim was to design and apply a diffusion-tensor imaging (DTI) protocol in order to elucidate the diffusivity properties of the testicles and their determining factors.

16 healthy volunteers were prospectively scanned at 3T. The protocol included T₂-weighted and DTI sequences, the latter using 24 directional diffusion gradients and 3 b-values (0, 100, and 700 s/mm²) that were separated for analysis based on the reference b-value of 0 or 100 s/mm². Image processing of the two DTI datasets yielded the diffusion vector maps and parametric maps of their corresponding principal diffusion coefficients λ₁, λ₂, λ₃, mean diffusivity and FA.

The results demonstrated the feasibility of DTI to provide parametric maps of the testicles. The diffusion tensor parameters obtained using the pair of 0 and 700 s/mm² b-values, exhibited relatively low diffusivity, with mean λ₁ values of 1.36 ± 0.21 × 10^-3 mm²/s and low anisotropy, with mean FA values of 0.13 ± 0.05. Analysis of DTI using the 100 and 700 s/mm² b-values yielded a slight decrease in the diffusivity of 4%-5%, whereas FA remained similar.

The diffusivity of the normal testicles is relatively slow, closed-to isotropic and hardly affected by the low b-values regime exclusion. Thus, DTI parameters of the normal testicles are neither dictated by the underlying architectural anisotropy nor microperfusion effects.