Choreographing couch and collimator in volumetric modulated arc therapy Journal Article
| Authors: | Yang, Y.; Zhang, P.; Happersett, L.; Xiong, J.; Yang, J.; Chan, M.; Beal, K.; Mageras, G.; Hunt, M. |
| Article Title: | Choreographing couch and collimator in volumetric modulated arc therapy |
| Abstract: | Purpose: To design and optimize trajectory-based, noncoplanar subarcs for volumetric modulated arc therapy (VMAT) deliverable on both Varian TrueBEAM system and traditional accelerators; and to investigate their potential advantages for treating central nervous system (CNS) tumors. Methods and Materials: To guide the computerized selection of beam trajectories consisting of simultaneous couch, gantry, and collimator motion, a score function was implemented to estimate the geometric overlap between targets and organs at risk for each couch/gantry angle combination. An initial set of beam orientations is obtained as a function of couch and gantry angle, according to a minimum search of the score function excluding zones of collision. This set is grouped into multiple continuous and extended subarcs subject to mechanical limitations using a hierarchical clustering algorithm. After determination of couch/gantry trajectories, a principal component analysis finds the collimator angle at each beam orientation that minimizes residual target-organ at risk overlaps. An in-house VMAT optimization algorithm determines the optimal multileaf collimator position and monitor units for control points within each subarc. A retrospective study of 10 CNS patients compares the proposed method of VMAT trajectory with dynamic gantry, leaves, couch, and collimator motion (Tra-VMAT); a standard noncoplanar VMAT with no couch/collimator motion within subarcs (Std-VMAT); and noncoplanar intensity-modulated radiotherapy (IMRT) plans that were clinically used. Results: Tra-VMAT provided improved target dose conformality and lowered maximum dose to brainstem, optic nerves, and chiasm by 7.7%, 1.1%, 2.3%, and 1.7%, respectively, compared with Std-VMAT. Tra-VMAT provided higher planning target volume minimum dose and reduced maximum dose to chiasm, optic nerves, and cochlea by 6.2%, 1.3%, 6.3%, and 8.4%, respectively, and reduced cochlea mean dose by 8.7%, compared with IMRT. Tra-VMAT averaged beam-on time was comparable to Std-VMAT but significantly (45%) less than IMRT. Conclusion: Optimized couch, gantry, and collimator trajectories may be integrated into VMAT with improved mechanical flexibility and may provide better dosimetric properties and improved efficiency in the treatment of CNS tumors. © 2011 Elsevier Inc. |
| Keywords: | clinical article; intensity modulated radiation therapy; treatment planning; cancer radiotherapy; radiation dose; radiotherapy; retrospective study; central nervous system tumor; intensity-modulated radiotherapy; physical therapy; tumors; central nervous systems; collimator; optic nerve; brain stem; eye protection; optic chiasm; optimization; volumetric modulated arc therapy; mean dose; cochlea; risk perception; organs at risks; principal component analysis; brainstem; gantry angles; monitor units; optimal multileaf collimator; planning target volumes; trajectories; volumetric arc modulated therapy; cns tumors; trajectory based; beam orientation; beam trajectories; cns tumor; control point; dose conformality; dosimetric properties; hierarchical clustering algorithms; mechanical flexibility; non-coplanar; optimization algorithms; score function; sub-arc; clustering algorithms; mechanical properties; optical collimators; beam therapy; target organ |
| Journal Title: | International Journal of Radiation Oncology, Biology, Physics |
| Volume: | 80 |
| Issue: | 4 |
| ISSN: | 0360-3016 |
| Publisher: | Elsevier Inc. |
| Date Published: | 2011-07-15 |
| Start Page: | 1238 |
| End Page: | 1247 |
| Language: | English |
| DOI: | 10.1016/j.ijrobp.2010.10.016 |
| PROVIDER: | scopus |
| PUBMED: | 21377811 |
| DOI/URL: | |
| Notes: | --- - "Export Date: 17 August 2011" - "CODEN: IOBPD" - "Source: Scopus" |
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