Cortical bone water: in vivo quantification with ultrashort echo-time MR imaging

Area of Science:

• Biomedical Engineering
• Radiology
• Orthopedics

Background:

• Bone quality assessment is crucial for fracture risk prediction.
• Current methods like BMD do not fully capture bone's microstructural integrity.
• Bone water (BW) concentration is emerging as a potential indicator of bone health.

Purpose of the Study:

• To develop and validate an ultrashort echo-time radial MRI technique for in vivo quantification of cortical bone water (BW) concentration.
• To establish BW concentration as a novel metric for assessing bone quality.
• To compare BW concentration with bone mineral density (BMD) in different demographic groups.

Main Methods:

• Developed custom ultrashort echo-time radial MRI sequences at 3.0 T.
• Validated the method ex vivo using deuterium oxide exchange.
• Measured cortical BW concentration in healthy premenopausal and postmenopausal women, and patients undergoing hemodialysis.
• Compared BW concentration with BMD measurements from pQCT and DXA.

Main Results:

• Ex vivo validation showed excellent agreement between MRI-measured water and D(2)O exchange (r(2) = 0.99).
• In vivo, postmenopausal women had 65% higher BW concentration than premenopausal women (P < .001).
• Patients with renal osteodystrophy exhibited significantly higher BW concentration compared to both premenopausal (135%, P < .001) and postmenopausal (43%, P = .02) groups.
• BMD showed inverse but less pronounced group differences, suggesting BW reflects porosity.

Conclusions:

• Demonstrated a novel, noninvasive MRI-based method for quantifying bone water concentration.
• BW concentration serves as a surrogate marker for cortical porosity.
• This technique offers a new avenue for evaluating bone quality beyond traditional BMD measurements.