Diffusion anisotropy in fresh and fixed prostate tissue ex vivo.

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Prostate Cancer Research

Background:

• Diffusion Tensor Imaging (DTI) provides insights into tissue microstructure.
• Understanding diffusion anisotropy in the prostate is crucial for accurate imaging interpretation.

Purpose of the Study:

• To investigate diffusion anisotropy in whole human prostate specimens using high-field MRI.
• To assess the impact of voxel size and tissue fixation on fractional anisotropy (FA) measurements.

Main Methods:

• Diffusion tensor imaging (DTI) performed on seven whole prostatectomy specimens at 9.4 Tesla.
• Diffusion tensors calculated from native data and progressively downsampled data.
• Analysis of fractional anisotropy (FA) in relation to voxel volume, fixation, and diffusion time.

Main Results:

• Fractional anisotropy (FA) decreased significantly with increasing voxel volume.
• Tissue fixation reduced mean FA, but did not alter principal eigenvector orientation.
• High FA (>0.6) was observed only in very small voxels (<0.5 mm³).
• At typical clinical voxel volumes (4-16 mm³), less than 50% of voxels had FA > 0.25.
• Peripheral zone FA was significantly lower than transition zone FA in most specimens.

Conclusions:

• Prostate diffusion anisotropy exhibits wide variability between individuals.
• The limited proportion of high-FA voxels at clinical sizes suggests minimal impact of anisotropy on standard ADC measurements in DWI.
• Findings inform the interpretation of diffusion-weighted imaging in prostate cancer assessment.