High-resolution MRI of internal field diffusion-weighting in trabecular bone

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Skeletal Biology

Background:

• Trabecular bone structure significantly impacts skeletal strength and fracture risk.
• Conventional MRI methods for bone structure analysis rely on susceptibility differences and linewidth measurements (1/T(2)').

Purpose of the Study:

• To spatially resolve a novel MRI contrast method based on internal gradients and diffusion weighting at the microscopic trabecular level.
• To confirm the interpretation of bulk measurements and compare the structural sensitivity of this new method with T(2)'.
• To assess the potential of this technique for evaluating trabecular bone properties relevant to fracture risk.

Main Methods:

• Microscopic MRI imaging with 0.156 mm in-plane resolution was performed on trabecular bone samples.
• A novel approach using internal gradients to encode diffusion weighting was employed.
• Signal decay analysis was used to extract structural information, specifically the decay due to diffusion in the internal field (DDIF).

Main Results:

• DDIF contrast was found to be maximal near trabecular bone surfaces.
• Lower resolution scans utilizing DDIF contrast effectively probed surface abundance, offering advantages over conventional proton density or T(1)-weighted imaging.
• Microscopic analysis revealed that DDIF contrast is more localized around trabecular walls compared to the internal field itself.

Conclusions:

• The DDIF MRI contrast method provides a more specific measure of trabecular bone properties, such as trabecular number, compared to T(2)'.
• This technique has the potential to enhance the assessment of skeletal strength and fracture risk by providing detailed microstructural information.
• The findings validate the interpretation of DDIF contrast from bulk measurements and highlight its localized sensitivity to trabecular surfaces.