A new algorithm for determining collimator angles that favor efficiency in MLC based IMRT delivery

Wang, David; Hill, R; Lam, S

doi:10.1118/1.1696708

Cited by 4 publications

(7 citation statements)

References 13 publications

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“…Use of anatomy-based segments with each beam angle combination has also been considered (Beaulieu et al 2004a(Beaulieu et al , 2004b. Optimization of collimator angle should also not be overlooked as the orientation of the multileaf collimator has an impact on the efficacy of the IMRT treatment plan (Wang et al 2004a).…”

Section: Introductionmentioning

confidence: 99%

Direct-aperture optimization applied to selection of beam orientations in intensity-modulated radiation therapy

Bedford

Webb²

2006

Phys. Med. Biol.

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Direct-aperture optimization (DAO) was applied to iterative beam-orientation selection in intensity-modulated radiation therapy (IMRT), so as to ensure a realistic segmental treatment plan at each iteration. Nested optimization engines dealt separately with gantry angles, couch angles, collimator angles, segment shapes, segment weights and wedge angles. Each optimization engine performed a random search with successively narrowing step sizes. For optimization of segment shapes, the filtered backprojection (FBP) method was first used to determine desired fluence, the fluence map was segmented, and then constrained direct-aperture optimization was used thereafter. Segment shapes were fully optimized when a beam angle was perturbed, and minimally re-optimized otherwise. The algorithm was compared with a previously reported method using FBP alone at each orientation iteration. An example case consisting of a cylindrical phantom with a hemi-annular planning target volume (PTV) showed that for three-field plans, the method performed better than when using FBP alone, but for five or more fields, neither method provided much benefit over equally spaced beams. For a prostate case, improved bladder sparing was achieved through the use of the new algorithm. A plan for partial scalp treatment showed slightly improved PTV coverage and lower irradiated volume of brain with the new method compared to FBP alone. It is concluded that, although the method is computationally intensive and not suitable for searching large unconstrained regions of beam space, it can be used effectively in conjunction with prior class solutions to provide individually optimized IMRT treatment plans.

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Section: Introductionmentioning

confidence: 99%

Direct-aperture optimization applied to selection of beam orientations in intensity-modulated radiation therapy

Bedford

Webb²

2006

Phys. Med. Biol.

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“…It was evident that non-0 17,19,20 Wang et al found that the number of MUs was largely reduced without compromising plan quality when collimator angles were determined with a new algorithm. 30 Furthermore,…”

Section: Discussionmentioning

confidence: 99%

“…In 30 Furthermore, Milette suggested that comparable dose distributions and better delivery efficiency were possible with the rotating aperture optimization technique. 31 Additionally, the innovation of the current study was that it proposed to adopt MATLAB to write code, combined with analytical methods to obtain the best collimator angle (CLx) in gastric cancer for the first time.…”

Section: Discussionmentioning

confidence: 99%

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Dosimetric effects related to collimator angle optimization in intensity‐modulated radiotherapy planning for gastric cancer

Zhao

Zhang

et al. 2021

Precision Radiation Oncology

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Objective To investigate the dosimetric impact of different collimator angle optimization methods in intensity‐modulated radiotherapy of gastric cancer. Methods A total of 10 gastric cases were retrospectively selected in this study. Three sets of plans were generated with different collimator angle optimization: setting the collimator angle to 0° (CL0), applying Eclipse automatic collimator angle optimization (CLA), and setting the collimator angle corresponding to the minimum X‐jaw gap (CLX). Different dosimetric metrics were applied in comparison of the target volume and normal tissues. Delivery efficiency was accessed in terms of control points, split fields, monitor units, and treatment time. All plans were verified using the 2‐D array MatriXX, and the γ‐index analysis was carried out by using different criteria. Results There was no significant difference in dosimetric comparison of planning target volume and organs at risk. Compared with CL0, Both CLA and CLX can significantly reduce control points, split fields, and monitor units, except that CLA increased treatment time. For dose verification, the γ passing rate showed a tendency of CLx > CLA > CL0. Conclusion For intensity‐modulated radiotherapy for gastric cancer, CLA and CLX can obtain comparable dosimetry distribution in respect to CL0. However, CLX can significantly increase the dose delivery efficiency and verification passing rates. It was suggested that CLx was beneficial in intensity‐modulated radiotherapy for gastric cancer.

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“…The beam isocenter in the treated plans was positioned automatically by the TPS at the center of the tumor. The collimator angle was determined so that the movement direction of HDMLC (high definition MLC) aligning with the minimum dimension of the target for best conformal plan . The treated plans were created with the intention to have more uniform dose in the target and the conventional P‐IDL (averagely (91.7 ± 0.5, ±1.7)% of the maximum dose.…”

Section: Methodsmentioning

confidence: 99%

Strategies to optimize stereotactic radiosurgery plans for brain tumors with volumetric‐modulated arc therapy

Wang

DeNittis

2020

J Applied Clin Med Phys

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Purpose Prescription practice in SRS plans for brain tumors differs significantly for different modalities. In this retrospective study, the strategies to optimize SRS plans for brain tumors with volumetric arc therapy (VMAT) were presented. Methods Fifty clinically treated cases were stratified by the maximum target size into two groups (≥ 2 cm in 25 cases and <2 cm but ≥1 cm in 25 cases), which were optimized using traditional LINAC MLC‐based approaches with the average prescription isodose line (P‐IDL) of (91.4 ± 0.6)%. Four to five plans have been created for each case with variation of the P‐IDL from 65% to 90%. The optimization strategies to select an optimal P‐IDL, to use tuning structures within the target and beyond as well as to use NTO (normal tissue objectives), were applied to all new plans. Results The optimal P‐IDL was found to be around 75%. After applying the new optimization strategies with an average P‐IDL of 74.8%, the mean modified gradient index (mGI) and V12 were reduced by 25% and 35%, respectively for both groups. The Paddick conformity index (PCI) was averagely improved by 8%. The average homogeneity index (HI) and focal index (FI) were increased by 22% and 50%, respectively. The mGI was inversely proportional to the PTV volumes. The shape of the dose distribution in target was also changed from concave to convex. The comparison of PCI with historical data from other institutes and modalities shows that the plans in this study have the best conformity near the target. Conclusions With the new optimization strategies for VMAT SRS plan of brain tumor more conformal plans in both high and intermediate dose region (~50% of the PD) were created, in which the dose in the core of the target was notably increased while V12 and mGI were significantly decreased, and PCI was improved. The mGI was inversely proportional to the PTV volumes. The optimal P‐IDL is around 75%. The average PCI is the best in this study compared with the published historical data. These strategies are applicable to treatment planning for multiple brain and liver tumors where sparing the tissue peripheral to the target is critical.

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A new algorithm for determining collimator angles that favor efficiency in MLC based IMRT delivery

Cited by 4 publications

References 13 publications

Direct-aperture optimization applied to selection of beam orientations in intensity-modulated radiation therapy

Direct-aperture optimization applied to selection of beam orientations in intensity-modulated radiation therapy

Dosimetric effects related to collimator angle optimization in intensity‐modulated radiotherapy planning for gastric cancer

Strategies to optimize stereotactic radiosurgery plans for brain tumors with volumetric‐modulated arc therapy

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