In vivo micro-imaging using alternating navigator echoes with applications to cancellous bone structural analysis

Area of Science:

• Biomedical Imaging
• Orthopedics
• Medical Physics

Background:

• Involuntary subject motion, even at the sub-millimeter level, significantly degrades the accuracy of micro-magnetic resonance imaging (micro-MRI) for assessing cancellous bone architecture.
• Accurate quantification of bone architectural parameters is crucial for understanding bone health and disease, but is often hindered by motion artifacts.

Purpose of the Study:

• To develop and evaluate a navigator-assisted three-dimensional spin-echo technique for high-resolution micro-MRI of human cancellous bone.
• To improve the accuracy and reproducibility of trabecular bone architectural parameter quantification in the presence of subject motion.

Main Methods:

• A navigator-assisted 3D spin-echo technique utilizing gradient navigator echoes for sensing translational displacements in x- and y-directions.
• Achieved a spatial resolution of 137 micrometers and temporal resolution of 0.2 seconds for motion sensing.
• Evaluated the technique on distal forearm micro-images, assessing parameters like bone volume fraction, transverse contiguity, and tubularity.

Main Results:

• The navigator-assisted technique significantly improved micro-images of the distal forearm.
• Demonstrated enhanced accuracy and reproducibility for key trabecular bone architectural parameters.
• Showed that reduced navigator sampling time and zero-filling improved correction accuracy while decreasing pulse repetition time and gradient heating.

Conclusions:

• Navigator-assisted micro-imaging effectively corrects sub-millimeter displacements in high-resolution MRI of cancellous bone.
• This technique offers a viable solution for accurate and reproducible micro-architectural analysis of bone tissue.
• The method holds promise for improved diagnosis and monitoring of bone-related conditions.