Intensity-modulated arc therapy simplified.
OBJECTIVE
We present a treatment planning strategy for intensity-modulated radiation therapy using gantry arcs with dynamic multileaf collimator, previously termed intensity-modulated arc therapy (IMAT).


METHODS
The planning strategy is an extension of the photon bar arc and asymmetric arc techniques and is classified into three levels of complexity, with increasing number of gantry arcs. This principle allows us to generalize the analysis of the number of arcs required for intensity modulation for a given treatment site. Using a phantom, we illustrate how the current technique is more flexible than the photon bar arc technique. We then compare plans from our strategy with conventional three-dimensional conformal treatment plans for three sites: prostate (prostate plus seminal vesicles), posterior pharyngeal wall, and chest wall.


RESULTS
Our strategy generates superior IMAT treatment plans compared to conventional three-dimensional conformal plans. The IMAT plans spare critical organs well, and the trade-off for simplicity is that the dose uniformity in the target volume may not rival that of true inverse treatment plans.


CONCLUSIONS
The analyses presented in this paper give a better understanding of IMAT plans. Our strategy is easier to understand and more efficient in generating plans than inverse planning systems; our plans are also simpler to modify, and quality assurance is more intuitive.
Wong
Eugene
E
Department of Oncology, London Regional Cancer Centre, 790 Commissioners Road East, London, Ontario, Canada N6A 4L6. ewong@phy.lrcc.on.ca
Chen
Jeff Z
JZ
Greenland
Jonathan
J
D006801:Humans; D008297:Male; D019047:Phantoms, Imaging; D010610:Pharyngeal Neoplasms / Q000532:radiotherapy; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000379:methods*; D013899:Thoracic Neoplasms / Q000532:radiotherapy