High-speed spectroscopic imaging for cancellous bone marrow R(2)* mapping and lipid quantification

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Quantitative Imaging

Background:

• Accurate in-vivo lipid quantification and R(2)* measurement are crucial for assessing bone marrow composition.
• Existing methods like Dixon-type techniques have limitations in spectral approximation.
• High-resolution imaging with fast scan times is essential for clinical applicability.

Purpose of the Study:

• To design, implement, and evaluate an interleaved multiple-gradient-echo chemical shift imaging (IMGE-CSI) technique.
• To achieve high-resolution lipid quantification and R(2)* measurement in cancellous bone marrow in-vivo.
• To compare IMGE-CSI performance against existing methods and assess its reproducibility.

Main Methods:

• Development and implementation of the IMGE-CSI technique at 1.5T and 4T.
• Utilizing spectroscopic bandwidth extension by interleaving gradient-echo trains.
• Employing multi-line spectral curve fitting for R(2)* determination.

Main Results:

• IMGE-CSI accurately measures true fat volume fraction, outperforming Dixon-type methods.
• High correlation (r(2) > 0.99) was observed between IMGE-CSI volume fractions and volumetry.
• The technique quantifies regional bone marrow composition with 2.5 x 2.5 x 5 mm(3) resolution.
• R(2)* measurements in cancellous bone marrow showed good agreement with time-domain methods and superiority in mixed constituents.
• Excellent inter-scan reproducibility (1% coefficient of variation) was demonstrated.

Conclusions:

• IMGE-CSI enables highly accurate in-vivo lipid quantification.
• The technique provides precise measurement of cancellous bone marrow R(2)*.
• IMGE-CSI achieves resolutions and scan times compatible with clinical protocols.