Aperture maneuver with compelled breath (AMC) for moving tumors: a feasibility study with a moving phantom.
Respiration causes target motion, which is known to be one of the technical bottlenecks in radiotherapy, especially for stereotactic radio-surgery and intensity modulated radiotherapy (IMRT). To overcome this problem, aperture maneuver with compelled breath (AMC) has been developed. In order to simulate compelled respiratory motion, a moving phantom using a ventilator was designed. As the air flow was forced to the bellows, which simulates the lungs, by a ventilator, a film connected to the ventilator moved like the respiratory target motion. A software was developed to transfer multileaf collimator motion from breathless to actual periodic breathing conditions. Static fields as well as step-and-shoot IMRT fields were modified in accordance with moving shapes to follow the target position, using the software with the controlled breathing information. Film dosimetry for a small field and for IMRT fields with a moving phantom was performed. To evaluate clinical implementation, five healthy volunteers were tested to breathe through a ventilator, and all of them could adapt the compelled breath without any difficulties. Additive margins for a moving target with AMC were not larger than 3 mm for respiratory organ motions up to 18 mm, while those with the static beam were 9 mm. For IMRT fields, large discrepancies were present between a static target and a moving target with the static beam, while they coincided well with AMC. Clinical acceptable differences between the dose distributions from a static target with the static beam and from a moving target with AMC revealed that this technique could be applied clinically.
Suh
Y
Y
Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnap-dong Songpa-gu, Seoul, 138-736, Korea.
Yi
B
B
Ahn
S
S
Kim
J
J
Lee
S
S
Shin
S
S
Shin
S
S
Choi
E
E
D000465:Algorithms; D005240:Feasibility Studies; D005246:Feedback; D006801:Humans; D009038:Motion; D009068:Movement; D009369:Neoplasms / Q000503:physiopathology* / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D012119:Respiration; D012680:Sensitivity and Specificity