A novel software and conceptual design of the hardware platform for intensity modulated radiation therapy

Nguyen, Dan; Ruan, Dan; O’Connor, Daniel; Woods, Kaley; Low, Daniel A.; Boucher, S.; Sheng, Ke

doi:10.1118/1.4940353

Cited by 14 publications

(20 citation statements)

References 31 publications

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“…When solved using an algorithm based on a proximal-class primal-dual algorithm, the Chambolle-Pock algorithm, 24 we found a new methods, based on L2-norm fidelity terms and L1-norm regularization terms, 22,30 to incorporate fluence maps simplification into the dose domain optimization. In this study, we further developed the methods to solve the VMAT problem, which previously only had greedy heuristic solutions.…”

Section: Discussionmentioning

confidence: 99%

A comprehensive formulation for volumetric modulated arc therapy planning

et al. 2016

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Purpose: Volumetric modulated arc therapy (VMAT) is a widely employed radiation therapy technique, showing comparable dosimetry to static beam intensity modulated radiation therapy (IMRT) with reduced monitor units and treatment time. However, the current VMAT optimization has various greedy heuristics employed for an empirical solution, which jeopardizes plan consistency and quality. The authors introduce a novel direct aperture optimization method for VMAT to overcome these limitations. Methods: The comprehensive VMAT (comVMAT) planning was formulated as an optimization problem with an L2-norm fidelity term to penalize the difference between the optimized dose and the prescribed dose, as well as an anisotropic total variation term to promote piecewise continuity in the fluence maps, preparing it for direct aperture optimization. A level set function was used to describe the aperture shapes and the difference between aperture shapes at adjacent angles was penalized to control MLC motion range. A proximal-class optimization solver was adopted to solve the large scale optimization problem, and an alternating optimization strategy was implemented to solve the fluence intensity and aperture shapes simultaneously. Single arc comVMAT plans, utilizing 180 beams with 2• angular resolution, were generated for a glioblastoma multiforme case, a lung (LNG) case, and two head and neck cases-one with three PTVs (H&N 3PTV ) and one with foue PTVs (H&N 4PTV )-to test the efficacy. The plans were optimized using an alternating optimization strategy. The plans were compared against the clinical VMAT (clnVMAT) plans utilizing two overlapping coplanar arcs for treatment.Results: The optimization of the comVMAT plans had converged within 600 iterations of the block minimization algorithm. comVMAT plans were able to consistently reduce the dose to all organs-at-risk (OARs) as compared to the clnVMAT plans. On average, comVMAT plans reduced the max and mean OAR dose by 6.59% and 7.45%, respectively, of the prescription dose. Reductions in max dose and mean dose were as high as 14.5 Gy in the LNG case and 15.3 Gy in the H&N 3PTV case. PTV coverages measured by D95, D98, and D99 were within 0.25% of the prescription dose. By comprehensively optimizing all beams, the comVMAT optimizer gained the freedom to allow some selected beams to deliver higher intensities, yielding a dose distribution that resembles a static beam IMRT plan with beam orientation optimization. Conclusions: The novel nongreedy VMAT approach simultaneously optimizes all beams in an arc and then directly generates deliverable apertures. The single arc VMAT approach thus fully utilizes the digital Linac's capability in dose rate and gantry rotation speed modulation. In practice, the new single VMAT algorithm generates plans superior to existing VMAT algorithms utilizing two arcs. C 2016 American Association of Physicists in Medicine. [http://dx

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Section: Discussionmentioning

confidence: 99%

A comprehensive formulation for volumetric modulated arc therapy planning

et al. 2016

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“…However, increasing the number of leaves increases the delivery efficiency, as it enables the dose to certain regions of the fluence map to be delivered in parallel, as previously mentioned. Increasing this to more than two leaves per bank greatly increases the complexity of the system while providing only minor improvements in efficiency, as previously shown . Therefore, the preclinical SOC designed in this study features two leaves per bank.…”

Section: Methodsmentioning

confidence: 91%

“…Increasing this to more than two leaves per bank greatly increases the complexity of the system while providing only minor improvements in efficiency, as previously shown. 43 Therefore, the preclinical SOC designed in this study features two leaves per bank.…”

Section: A Soc Designmentioning

confidence: 99%

A sparse orthogonal collimator for small animal intensity‐modulated radiation therapy. Part II: hardware development and commissioning

et al. 2019

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Purpose A dose‐modulation device for small animal radiotherapy is required to use clinically analogous treatment techniques, which will likely increase the translatability of preclinical research results. Because the clinically used multileaf collimator (MLC) is impractical for miniaturization, we have developed a simpler, better‐suited sparse orthogonal collimator (SOC) for delivering small animal intensity‐modulated radiation therapy (IMRT) using a rectangular aperture optimization (RAO) treatment planning system. Methods The SOC system was modeled in computer‐aided design software and fabricated with machined tungsten leaves and three‐dimensional (3D) printed leaf housing. A graphical user interface was developed for controlling and calibrating the SOC leaves, which are driven by Arduino‐controlled stepper motors. A Winston‐Lutz test was performed to assess mechanical alignment, and abutting field and grid dose patterns were created to analyze intra‐ and intercalibration leaf positioning error. Leaf transmission and penumbra were measured over the full range of gantry angles and leaf positions, respectively. Three SOC test plans were delivered, and film measurements were compared to the intended dose distributions. The differences in maximum, mean, and minimum, as well as pixelwise absolute dose differences, were compared for each structure, and a gamma analysis was performed for the target structures using criteria of 4% dose difference and 0.3 mm distance to agreement. Results The Winston‐Lutz test revealed maximum directional offsets between the SOC and primary collimator axes of 0.53 mm at 0° and 0.68 mm over the full 360°. Upper and lower abutting field patterns had maximum dose deviations of 18.8 ± 3.1% and 15.5 ± 2.9%, respectively, and grid patterns showed intra‐ and intercalibration repeatability of 93% and 91%, respectively. Extremely low midleaf (0.15 ± 0.05%) and interleaf (0.27 ± 0.22%) transmission was measured, with no significant rotational variation. The average penumbra was ~0.8 mm for all leaves at field center, with a range of 0.17 mm for all leaf positions. A highly concave test plan was delivered with a ~ 95% gamma analysis pass rate, and a realistic mouse phantom liver irradiation plan achieved a pass rate of ~98%. A highly complex dose distribution was also created with 551 SOC apertures averaging 2.4 mm in size. Conclusions A sparse orthogonal collimator was developed and commissioned, with promising preliminary dosimetry results. The SOC design, with its limited moving components and high dose‐modulation resolution, is ideal for delivering high‐quality small animal IMRT with our RAO‐based treatment planning system.

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“…For SOC‐based IMRT, we have formulated the rectangular aperture optimization (RAO), which has been described in more detail previously, as

\begin{matrix} \begin{matrix} bold-italicargmin \\ α \end{matrix} \frac{1}{2} {(∥∥, W ()(, A R α - {bold-italicd}_{0}))}_{2}^{2} + bold-italicλ {(∥∥, bold-italicα)}_{1} \\ bold-italicsubjectto bold-italicα \geq 0 . \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

“…() and this update method are alternated until no more new apertures are added to

R

. A detailed explanation of the initial overrepresented set and the update method was previously described …”

Section: Methodsmentioning

confidence: 99%

A sparse orthogonal collimator for small animal intensity‐modulated radiation therapy part I: Planning system development and commissioning

et al. 2019

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Purpose To achieve more translatable preclinical research results, small animal irradiation needs to more closely simulate human radiotherapy. Although the clinical gold standard is intensity‐modulated radiation therapy (IMRT), the direct translation of this method for small animals is impractical. In this study we describe the treatment planning system for a novel dose modulation device to address this challenge. Methods Using delineated target and avoidance structures, a rectangular aperture optimization (RAO) problem was formulated to penalize deviations from a desired dose distribution and limit the number of selected rectangular apertures. RAO was used to create IMRT plans with highly concave targets in the mouse brain, and the plan quality was compared to that using a hypothetical miniaturized multileaf collimator (MLC). RAO plans were also created for a realistic application of mouse whole liver irradiation and for a highly complex two‐dimensional (2D) dose distribution as a proof‐of‐principle. Beam commissioning data, including output and off‐axis factors and percent depth dose (PDD) curves, were acquired for our small animal irradiation system and incorporated into the treatment planning system. A plan post‐processing step was implemented for aperture size‐specific dose recalculation and aperture weighting reoptimization. Results The first RAO test case achieved highly conformal doses to concave targets in the brain, with substantially better dose gradient, conformity, and target dose homogeneity than the hypothetical miniaturized MLC plans. In the second test case, a highly conformal dose to the liver was achieved with significant sparing of the kidneys. RAO also successfully replicated a complex 2D dose distribution with three prescription dose levels. Energy spectra for field sizes 1 to 20 mm were calculated to match the measured PDD curves, with maximum and mean dose deviations of 4.47 ± 0.30% and 1.71 ± 0.18%. The final reoptimization of aperture weightings for the complex RAO test plan was able to reduce the maximum and mean dose deviations between the optimized and recalculated dose distributions from 10.3% to 6.6% and 4.0% to 2.8%, respectively. Conclusions Using the advanced optimization techniques, complex IMRT plans were achieved using a simple dose modulation device. Beam commissioning data were incorporated into the treatment planning process to more accurately predict the resulting dose distribution. This platform substantially reduces the gap in treatment plan quality between clinical and preclinical radiotherapy, potentially increasing the value and flexibility of small animal studies.

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A novel software and conceptual design of the hardware platform for intensity modulated radiation therapy

Cited by 14 publications

References 31 publications

A comprehensive formulation for volumetric modulated arc therapy planning

A comprehensive formulation for volumetric modulated arc therapy planning

A sparse orthogonal collimator for small animal intensity‐modulated radiation therapy. Part II: hardware development and commissioning

A sparse orthogonal collimator for small animal intensity‐modulated radiation therapy part I: Planning system development and commissioning

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