Time delay measurement for linac based treatment delivery in synchronized respiratory gating radiotherapy.
A time delay in a respiratory gating system could cause an unexpected phase mismatch for synchronized gating radiotherapy. This study presents a method of identifying and measuring the time delay in a gating system. Various port films were taken for a motion phantom at different gating window levels with a very narrow window size. The time delay for the gating system was determined by comparing the motion curve (the position of a moving object versus the gating time) measured in the port films to the motion curve determined by the video cameras. The measured time delay for a linac-based gating system was 0.17+/-0.03 s. This time delay could induce target missing if it was not properly taken into account for the synchronized gating radiotherapy. Measurement/verification of the time delay should be considered as an important part of the accepting/commissioning test before the clinical use of the gating system.
Jin
Jian-Yue
JY
Henry Ford Hospital, Detroit, Michigan 48202, USA. jjin1@hfhs.org
Yin
Fang-Fang
FF
D004867:Equipment Design; D019544:Equipment Failure Analysis; D005373:Film Dosimetry / Q000379:methods*; D006801:Humans; D009068:Movement; D010315:Particle Accelerators / Q000295:instrumentation*; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D015656:Respiratory Mechanics; D013997:Time Factors