External respiratory motion: shape analysis and custom realistic respiratory trace generation.
OBJECTIVE
The authors developed a realistic respiratory trace generating (RTG) tool for use with phantom and simulation studies.


METHODS
The authors analyzed the extent of abdominal wall motion from a real-time position management system database comprised of 125 lung, liver, and abdominal patients to determine the shape and extent of motion. Using Akaike's information criterion (AIC), the authors compared different model types to find the optimal realistic model of respiratory motion.


RESULTS
The authors compared a family of sigmoid curves and determined a four parameter sigmoid fit was optimal for over 98% patient inhale and exhale traces. This fit was also better than sin (2)(x) for 98% of patient exhale and 70% of patient inhale traces and better than sin (x) for 100% of both patient inhale and exhale traces. This analysis also shows that sin (2)(x) is better than sin (x) for over 95% of patient inhale and exhale traces. With results from shape and extent of motion analysis, we developed a realistic respiratory trace generating (RTG) software tool. The software can be run in two modes: population and user defined. In population mode, the RTG draws entirely from the population data including inter- and intra fraction amplitude and period variability and baseline drift. In user-defined mode, the user customizes the respiratory parameters by inputting the peak-to-peak amplitude, period, end exhale position, as well as controls variability in these parameters and baseline drift.


CONCLUSIONS
This work provides a method of generating custom respiratory data that can be used for initial implementation and testing of new technologies.
Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alberta T2N 4N2, Canada. sarah.quirk@gmail.com
Sarah
S
Quirk
Nathan
N
Becker
Wendy
W
Smith
D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging*; D008168:Lung / Q000000981:diagnostic imaging*; D015233:Models, Statistical; D009038:Motion; D011860:Radiography, Abdominal / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012119:Respiration; D015656:Respiratory Mechanics; D012984:Software; D013997:Time Factors