Characterization of prostate microstructure using water diffusion and NMR relaxation.

Area of Science:

• Biophysics
• Medical Imaging
• Cellular Biology

Background:

• Early pathological changes occur at the cellular level, often below MRI's direct resolution.
• Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool limited in resolving cellular structures.
• Water diffusion and NMR relaxation offer indirect insights into microscopic tissue alterations.

Purpose of the Study:

• To present a physical model of water diffusion and NMR relaxation in the heterogeneous human prostate.
• To differentiate contributions from cellular and luminal compartments to water diffusion.
• To explore MRI's potential for non-invasive prostate cancer grading.

Main Methods:

• Utilized transverse NMR relaxation to identify distinct tissue compartments (cellular and luminal).
• Applied the random permeable barrier model (RPBM) to analyze restricted diffusion in the cellular compartment.
• Re-analyzed data from 38 prostate cancer cases to validate findings.

Main Results:

• Identified fast and slow T2 components corresponding to luminal and cellular compartments.
• Measured average lumen diameter in healthy prostates as 217.7±188.7 μm.
• Derived fiber diameter (19.8±8.1 μm) and membrane permeability (0.044±0.045 μm/ms) using RPBM, consistent with histology.
• Observed a consistent dynamical exponent (ϑ = 1/2) in both tumor and benign prostate tissues.

Conclusions:

• Water diffusion and NMR relaxation provide a biophysical characterization of prostate tissue heterogeneity.
• Multi-parametric MRI combined with biophysical modeling shows promise for non-invasive prostate cancer grading.
• This approach may reduce reliance on invasive biopsies for prostate cancer diagnosis.