Validation of 4D Monte Carlo dose calculations using a programmable deformable lung phantom. (August 2020)

• Record Type: Journal Article
• Authors: Gholampourkashi, Sara; Cygler, Joanna E.; Lavigne, Bernie; Heath, Emily
• Is Part Of: Physica medica. Volume 76(2020)
• Page Start: 16
• Page End: 27
• Publication Date: 2020-08
• Subjects: Monte Carlo -- 4D dose calculation -- Programmable deformable lung phantom -- Realistic breathing motion -- VMAT; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2020.05.019
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: A recently developed lung phantom is modified to be programmed and move according to realistic breathing traces. RADPOS recorded phantom motion during deliveries is used in 4DMC simulations. 4DdefDOSXYZnrc user code accurately simulates delivered dose to the phantom in the presence of irregular breathing motion. 4DMC simulations present similar sensitivity as in measurements to the starting phase of the breathing motion. RADPOS combined with our 4DMC code is a potential tool to verify treatment deliveries involving respiratory motion. Abstract: Purpose: To validate the accuracy of 4D Monte Carlo (4DMC) simulations to calculate dose deliveries to a deforming anatomy in the presence of realistic respiratory motion traces. A previously developed deformable lung phantom comprising an elastic tumor was modified to enable programming of arbitrary motion profiles. 4D simulations of the dose delivered to the phantom were compared with the measurements. Methods: The deformable lung phantom moving with irregular breathing patterns was irradiated using static and VMAT beam deliveries. Using the RADPOS 4D dosimetry system, point doses were measured inside and outside the tumor. Dose profiles were acquired using films along the motion path of the tumor (S-I). In addition to dose measurements, RADPOS was used to record the motion of the tumor during dose deliveries. Dose measurements were then compared against 4DMC simulations with EGSnrc/4DdefDOSXYZnrc using the recorded tumor motion. Results: The agreements between dose profiles from measurements and simulations were determined to be within 2%/2 mm. Point dose agreements were within 2σ of experimental and/or positional/dose reading uncertainties. 4DMC simulations were shown to accurately predict the sensitivity of delivered dose to the starting phase of breathing motions. We have demonstrated that our 4DMC method, combined with RADPOS, can accurately simulate realistic dose deliveries to a deforming anatomy moving with realistic breathing traces. This 4DMC tool has the potential to be used as a quality assurance tool to verify treatments involving respiratory motion. Adaptive treatment delivery is another area that may benefit from the potential of this 4DMC tool.