Monte Carlo dose calculation of segmental IMRT delivery to a moving phantom using dynamic MLC and gating log files.
Respiratory gating is emerging as a tool to limit the effect of motion for liver and lung tumors. In order to study the impact of target motion and gated intensity modulated radiation therapy (IMRT) delivery, a computer program was developed to simulate segmental IMRT delivery to a moving phantom. Two distinct plans were delivered to a rigid-motion phantom with a film insert in place under four conditions: static, sinusoidal motion, gated sinusoidal motion with a duty cycle of 25% and gated sinusoidal motion with duty cycle of 50% under motion conditions of a typical patient (A = 1 cm, T = 4 s). The MLC controller log files and gating log files were retained to perform a retrospective Monte Carlo dose calculation of the plans. Comparison of the 2D planar dose distributions between simulation and measurement demonstrated that our technique had at least 94% of the points passing gamma criteria of 3% for dose difference and 3 mm as the distance to agreement. This note demonstrates that the use of dynamic multi-leaf collimator and respiratory monitoring system log files together with a fast Monte Carlo dose calculation algorithm is an accurate and efficient way to study the dosimetric effect of motion for gated or non-gated IMRT delivery on a rigidly-moving body.
Oliver
Mike
M
Department of Medical Biophysics, University of Western Ontario, London, ON, Canada. michael.oliver@lhsc.on.ca
Staruch
Robert
R
Gladwish
Adam
A
Craig
Jeff
J
Chen
Jeff
J
Wong
Eugene
E
D006801:Humans; D015640:Ion Channel Gating; D008175:Lung Neoplasms / Q000503:physiopathology / Q000532:radiotherapy; D008954:Models, Biological; D009010:Monte Carlo Method; D009068:Movement; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012119:Respiration