Measuring bone mineral density with fat-water MRI: comparison with computed tomography

Area of Science:

• Biomedical Imaging
• Radiology
• Orthopedics

Background:

• Accurate bone mineral density (BMD) measurement is crucial for diagnosing osteoporosis and assessing fracture risk.
• Quantitative computed tomography (QCT) is a standard method, but involves ionizing radiation.
• Developing radiation-free alternatives for BMD assessment is a significant clinical need.

Purpose of the Study:

• To establish and validate a magnetic resonance imaging (MRI) based method for quantifying bone mineral density (BMD).
• To compare the accuracy of the novel MRI technique against the established quantitative computed tomography (QCT) method.

Main Methods:

• A mathematical model correlating MRI signal intensity with hydroxyapatite concentration was developed using calibration standards.
• Proton-density-weighted in-phase images from multi-fat-peak T2*-IDEAL MRI were acquired.
• BMD was computed for patellar voxels using the MRI signal model and validated against QCT measurements via linear regression.

Main Results:

• A robust linear relationship (r = 0.98, P < 0.01) was found between hydroxyapatite concentration and MRI signal intensity in calibration standards.
• MRI-derived BMD measurements in the patella showed significant correlation with QCT-derived BMD (r = 0.82, P < 0.001).
• The regression analysis yielded a slope of 1.02 and an intercept of -0.26, indicating good agreement.

Conclusions:

• A standardized phantom method using hydroxyapatite and water enables accurate in vivo BMD quantification via MRI.
• This MRI technique offers a promising, radiation-free alternative for bone mineral density assessment.
• The findings support the potential of MRI as a valuable tool in osteoporosis diagnosis and management.