Mineral content changes in bone associated with damage induced by the electron beam

Area of Science:

• Materials Science
• Biomineralization
• Analytical Chemistry

Background:

• Energy-dispersive X-ray (EDX) spectroscopy and backscattered electron (BSE) imaging are crucial for analyzing mineral content in bone at microscopic levels.
• Electron beam bombardment during these analyses can induce tissue damage, potentially leading to inaccurate mineral content interpretations.

Purpose of the Study:

• To quantify the deleterious effects of electron beam exposure on bone mineral content analysis.
• To investigate the impact of scanning time, mode (scan vs. point), magnification, and embedding medium (PMMA) on analytical results.

Main Methods:

• Undemineralized human cortical bone specimens were analyzed using coupled BSE/EDX.
• Specimens were examined under varying conditions: 200x embedded, 200x unembedded, and 1000x embedded.
• Elemental (Ca, P, C) proportions and mineral content (BSE gray levels) were measured across five consecutive analyses.

Main Results:

• Point mode analysis at 200x showed significant increases in Ca (7.2%) and decreases in C (-3.2%) by the second measurement.
• Higher magnification (1000x) resulted in significantly larger variations in Ca, P, and C proportions.
• BSE gray levels increased by up to 23% in point mode, suggesting increased mineral content due to beam damage.

Conclusions:

• Coupled BSE/EDX analyses in PMMA-embedded bone can yield reliable mineral content measurements.
• Utilizing lower magnifications in scan mode and minimizing electron beam exposure are critical for accurate results.
• For point mode analysis of small regions, adjustments to accelerating voltage and probe current may be necessary to mitigate beam-induced damage.