Recording of natural head position using stereophotogrammetry: a new technique and reliability study

Area of Science:

• Medical Imaging
• Computer Graphics
• Biomedical Engineering

Background:

• Accurate 3D facial reconstruction requires precise patient head positioning.
• Existing stereophotogrammetry (SP) methods may lack consistent orientation protocols.
• Digital mesh models need reliable alignment to natural head positions for clinical applications.

Purpose of the Study:

• To develop a repeatable technique for orienting digital mesh models to a natural head position using stereophotogrammetry (SP).
• To establish a method for recording physical references to ensure consistent SP machine calibration and patient image capture.

Main Methods:

• A reference board was digitally modeled using SP, aligned to true vertical with a plumb bob, and to a laser plane.
• Parameters from the reference board's digital mesh model were used to calibrate roll, pitch, and yaw for subsequent patient facial captures.
• The calibration's validity was maintained until the next machine recalibration.

Main Results:

• The reference board placement demonstrated high repeatability.
• Standard deviations for pitch and yaw angles were less than 0.1°.
• Standard deviations for roll angles were less than 0.15°.

Conclusions:

• The developed SP technique provides a reliable method for orienting digital mesh models to a natural head position.
• This technique enhances the accuracy and consistency of 3D facial reconstructions in clinical settings.
• The repeatable calibration process ensures precise alignment for patient imaging.