Characterization of optical-surface-imaging-based spirometry for respiratory surrogating in radiotherapy

Area of Science:

• Medical Imaging
• Respiratory Physiology
• Biomedical Engineering

Background:

• Accurate measurement of respiratory parameters is crucial for understanding physiological processes and predicting internal organ motion.
• Conventional spirometry has limitations in capturing complex breathing patterns and torso motion.

Purpose of the Study:

• To characterize a novel optical surface imaging (OSI) technique for precise tidal volume (TV) measurement, dynamic airflow (TV') calculation, and breathing pattern (BP) estimation.
• To evaluate the OSI technique across various breathing patterns: free breathing (FB), belly breathing (BB), chest breathing (CB), and breath hold (BH).

Main Methods:

• Optical surface imaging (OSI) was employed to capture torso surface motion during respiration.
• Concurrent measurements using OSI and conventional spirometry were performed on 11 healthy volunteers.
• The OSI technique calculates TV from torso volume changes and airflow from the rate of volume change, applying volume conservation principles.

Main Results:

• OSI-based spirometry demonstrated good accuracy for tidal volume (-3.5% ± 6.3%) and airflow (-5% ± 30%) compared to conventional spirometry.
• High correlations were observed between OSI and spirometric measurements for TV (R²=0.95-0.98) and airflow.
• The technique quantified substantial breathing irregularities and irreproducibility, providing insights into breathing pattern variations.

Conclusions:

• The OSI-based technique offers an accurate and comprehensive method for measuring tidal volume, airflow, and breathing patterns.
• This non-invasive approach is applicable to diverse breathing styles and can quantify breathing irregularities.
• The quantified breathing parameters hold potential for improving the accuracy of tumor motion predictions in clinical settings.