Novel spirometry based on optical surface imaging.

Area of Science:

• Medical Imaging
• Respiratory Physiology

Background:

• Accurate measurement of dynamic torso volume changes is crucial for respiratory monitoring.
• Existing methods may have limitations in capturing real-time, non-invasive volumetric data.

Purpose of the Study:

• To evaluate the feasibility and accuracy of optical surface imaging (OSI) for measuring dynamic tidal volume (TV) of the human torso during free breathing.
• To assess OSI's potential as a respiratory surrogate in clinical settings.

Main Methods:

• Experiments were conducted using geometric and deformable phantoms, comparing OSI measurements with geometric calculations and CT scans.
• High-speed OSI was applied to three healthy volunteers, synchronized with spirometric measurements.
• Custom MATLAB programs were developed for volume of interest definition, thorax/abdomen separation, and automatic calculation of thoracic and abdominal volumes and breathing patterns.

Main Results:

• OSI showed high accuracy in phantom studies, with discrepancies of 0.0% ± 1.6% for geometric phantoms and 1.2% ± 2.1% for deformable phantoms compared to CT.
• In volunteers, OSI tidal volume measurements had a relative error of -2.2% ± 4.9% and correlated strongly (r=0.98) with spirometry.
• Distinct volumetric breathing patterns were observed among individual volunteers.

Conclusions:

• Optical surface imaging is a feasible and accurate method for measuring dynamic breathing tidal volumes and patterns.
• This study presents the first use of OSI for dynamic tidal volume and breathing pattern measurement.
• OSI-derived torso movement shows promise as a novel respiratory surrogate for radiation therapy.