Acoustical properties of the human skull

Area of Science:

• Biomedical Engineering
• Acoustics
• Materials Science

Background:

• Human skull's acoustic properties are crucial for medical imaging.
• Previous studies have explored insertion loss but lacked detailed component analysis.

Purpose of the Study:

• To quantitatively measure acoustic properties (insertion loss, reflection loss, sound speed) of human skulls.
• To investigate the influence of skull layers, particularly the diploe, on acoustic wave propagation.
• To assess the feasibility of transkull diagnostic imaging.

Main Methods:

• Acoustic measurements (0.25-6 MHz) on fresh and formalin-fixed human skulls.
• Utilized an axisymmetric focused beam and piezoelectric ceramic receivers.
• Sectioned skulls to analyze individual layer components (e.g., diploe).

Main Results:

• A three-layer analytical model effectively explained insertion and reflection losses.
• The diploe (middle cancellous bone layer) significantly impacts acoustic losses.
• New data on diploe acoustic scattering, sound velocity, dispersion, and attenuation were obtained.
• Sound beam distortion and shifts were observed after transmission.

Conclusions:

• The diploe is the primary determinant of acoustic loss in adult human skulls.
• Appropriate frequency selection (0.5-1.0 MHz) and beam configuration can enable clinically significant transkull diagnostic imaging.
• This research provides foundational data for developing advanced neuroimaging techniques.