Automatic generation of anatomy-based MLC fields in aperture-based IMRT.
We have developed an algorithm to automatically generate anatomy-based MLC fields. For each beam, a first field is adjusted to the projection of the target in a beam's eye view, allowing subsequent fields to be derived from this conformal field by removing the overlapping surface of each organ at risk, respectively. The projections are based on a surface sampling of the anatomical structures. On top of the MLC mechanical constraints, verification constraints are imposed on the MLC segments, in order to get reliable dosimetry using a commercial dose calculation engine. Thus, in each direction, the aperture's cross-section must be greater than a specified threshold, in our case 2 cm. Furthermore, junctions are not tolerated in order to avoid underdosage, for instance from the tongue-and-groove effect. The use of such MLC fields simplifies the verification process. The performance of the algorithm is illustrated for head and neck, thorax and prostate cases. Only a fraction of a second of CPU time is required to perform the segmentation for each beam.
Beaulieu
Frédéric
F
Département de Physique, de Génie Physique et d'Optique, Université Laval, Québec G1K 7P4, Canada. frederic.beaulieu@mail.chuq.qc.ca
Beaulieu
Luc
L
Tremblay
Daniel
D
Lachance
Bernard
B
Roy
René
R
D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000706:statistics & numerical data*; D013953:Thymus Neoplasms / Q000473:pathology / Q000532:radiotherapy