Quantitative Backscattered Electron Imaging of Bone Using a Thermionic or a Field Emission Electron Source.

Area of Science:

• Biomaterials science
• Materials characterization
• Medical imaging

Background:

• Quantitative backscattered electron imaging is a validated technique for mapping bone mineral content and determining bone mineralization density distribution (BMDD).
• Initial validation was performed on scanning electron microscopes (SEM) with tungsten hairpin cathodes (thermionic emission).
• Field emission scanning electron microscopes (FE-SEM) offer superior spatial resolution due to smaller electron source sizes.

Purpose of the Study:

• To compare BMDD measurements between thermionic SEM and FE-SEM to validate the transferability of the imaging technique.
• To assess the impact of FE-SEM's higher spatial resolution on BMDD parameters.
• To establish new reference BMDD curves for FE-SEM analysis.

Main Methods:

• Quantitative backscattered electron imaging was performed on both thermionic SEM and FE-SEM instruments.
• Bone samples were analyzed at varying pixel resolutions (1.76, 0.88, and 0.57 μm) on the FE-SEM.
• Bone mineralization density distribution (BMDD) and mean calcium content were quantified and compared between the two SEM types.

Main Results:

• Transitioning to higher pixel resolutions on FE-SEM resulted in shifts of the BMDD peak and width to higher values.
• Inter-device reproducibility of mean calcium content showed differences up to 1 wt% Ca.
• Technical variance within each device was reduced to less than 0.5 wt% Ca.

Conclusions:

• Quantitative backscattered electron imaging methodology is transferable to FE-SEM, but requires careful parameter adjustment and validation.
• Differences in BMDD parameters and calcium content necessitate using device-specific reference data.
• New reference BMDD curves for adults were generated for FE-SEM data comparison to ensure accurate clinical interpretation.