On the sensitivity of quantitative susceptibility mapping for measuring trabecular bone density

Area of Science:

• Biomedical Imaging
• Medical Physics
• Radiology

Background:

• Trabecular bone density is a critical indicator of bone health.
• Quantitative Susceptibility Mapping (QSM) offers potential for non-invasive bone assessment.
• Simultaneous measurement of R2* and magnetic susceptibility in bone marrow is challenging.

Purpose of the Study:

• To develop a framework for simultaneous measurement of R2* and magnetic susceptibility in trabecularized yellow bone marrow.
• To evaluate the sensitivity of Quantitative Susceptibility Mapping (QSM) for determining trabecular bone density.
• To utilize a non-UTE multi-gradient echo sequence for enhanced imaging.

Main Methods:

• Employed a time-interleaved multi-gradient-echo (TIMGRE) sequence on 16 healthy volunteers and 2 patients.
• Implemented field mapping and background field removal techniques.
• Applied three QSM dipole inversion schemes and compared results with R2* maps, bone volume fraction (BV/TV), and CT attenuation.

Main Results:

• Susceptibility maps effectively depicted calcaneus trabecularization, correlating well with high-resolution MR and CT.
• Demonstrated a linear relationship between QSM-derived susceptibility, R2*, and bone volume to total volume (BV/TV) ratio.
• Observed a strong linear correlation (R² = 0.88) between in vivo susceptibility and R2* in the ankle.

Conclusions:

• A novel multi-parametric mapping method combining R2* and QSM was successfully developed.
• The study highlights the good sensitivity of QSM for measuring trabecular bone density.
• This technique provides a promising approach for quantitative assessment of bone marrow microarchitecture.