A sliding-window approach for improved VMAT dose calculation accuracy

Alahmad, Haitham; Park, Ji-Yeon; Potter, Nicholas J.; Lü, Bo; Yan, G; Liu, Chihray; Li, Jonathan G.

doi:10.1016/j.meddos.2019.11.001

Cited by 2 publications

(1 citation statement)

References 12 publications

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“…However, a finer CP spacing increases the optimization computation time and beamlet dose calculation time as well as the necessary computer memory. A dose calculation for VMAT including interpolation of the MLC leaves between CPs has been proposed by Alahmad et al (2020). However, our results show that consideration of interpolation of the MLC leaves between CPs only in the final dose calculation still leads to a large OCE.…”

Section: Discussionmentioning

confidence: 82%

Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Guyer¹,

Mueller²,

Koechli³

et al. 2022

Phys. Med. Biol.

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Objective: The purpose of this study is to develop a treatment planning process (TPP) for non-isocentric dynamic trajectory radiotherapy (DTRT) using dynamic gantry rotation, collimator rotation, table rotation, longitudinal, vertical and lateral table translations and intensity modulation and to validate the dosimetric accuracy. Approach: The TPP consists of two steps. First, a path describing the dynamic gantry rotation, collimator rotation and dynamic table rotation and translations is determined. Second, an optimization of the intensity modulation along the path is performed. We demonstrate the TPP for three use cases. First, a non-isocentric DTRT plan for a brain case is compared to an isocentric DTRT plan in terms of dosimetric plan quality and delivery time. Second, a non-isocentric DTRT plan for a craniospinal irradiation (CSI) case is compared to a multi-isocentric intensity modulated radiotherapy (IMRT) plan. Third, a non-isocentric DTRT plan for a bilateral breast case is compared to a multi-isocentric volumetric modulated arc therapy (VMAT) plan. The non-isocentric DTRT plans are delivered on a TrueBeam in developer mode and their dosimetric accuracy is validated using radiochromic films. Main results: The non-isocentric DTRT plan for the brain case is similar in dosimetric plan quality and delivery time to the isocentric DTRT plan but is expected to reduce the risk of collisions. The DTRT plan for the CSI case shows similar dosimetric plan quality while reducing the delivery time by 45% in comparison with the IMRT plan. The DTRT plan for the breast case showed better treatment plan quality in comparison with the VMAT plan. The gamma passing rates between the measured and calculated dose distributions are higher than 95% for all three plans. Significance: The versatile benefits of non-isocentric DTRT are demonstrated with three use cases, namely reduction of collision risk, reduced setup and delivery time and improved dosimetric plan quality.

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Section: Discussionmentioning

confidence: 82%

Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Guyer¹,

Mueller²,

Koechli³

et al. 2022

Phys. Med. Biol.

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A polar‐coordinate‐based pencil beam algorithm for VMAT dose computation with high‐resolution gantry angle sampling

et al. 2022

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Purpose: Most commercially available treatment planning systems (TPSs) approximate the continuous delivery of volumetric modulated arc therapy (VMAT) plans with a series of discretized static beams for treatment planning, which can make VMAT dose computation extremely inefficient. In this study, we developed a polar-coordinate-based pencil beam (PB) algorithm for efficient VMAT dose computation with high-resolution gantry angle sampling that can improve the computational efficiency and reduce the dose discrepancy due to the angular under-sampling effect. Methods and Materials: 6 MV 1 × 1 mm 2 pencil beams were simulated on a uniform cylindrical phantom under an EGSnrc Monte Carlo (MC) environment. The MC-generated PB kernels were collected in the polar coordinate system for each bixel on a 40 × 40 cm 2 fluence map and subsequently fitted via a series of Gaussians. The fluence was calculated using a detectors' eye view with off -axis and MLC transmission factors corrected. Doses of VMAT arc on the phantom were computed by summing the convolution results between the corresponding PB kernels and fluence for each bixel in the polar coordinate system. The convolution was performed using fast Fourier transform to expedite the computing speed. The calculated doses were converted to the Cartesian coordinate system and compared with the reference dose computed by a collapsed cone convolution (CCC) algorithm of the TPS. A heterogeneous phantom was created to study the heterogeneity corrections using the proposed algorithm. Ten VMAT arcs were included to evaluate the algorithm performance. Gamma analysis and computation complexity theory were used to measure the dosimetric accuracy and computational efficiency, respectively. Results: The dosimetric comparisons on the homogeneous phantom between the proposed PB algorithm and the CCC algorithm for 10 VMAT arcs demonstrate that the proposed algorithm can achieve a dosimetric accuracy comparable to that of the CCC algorithm with average gamma passing rates of 96% (2%/2mm) and 98% (3%/3mm). In addition, the proposed algorithm can provide better computational efficiency for VMAT dose computation using a PC equipped with a 4-core processor, compared to the CCC algorithm utilizing a dual 10-core server. Moreover, the computation complexity theory reveals that the proposed algorithm has a great advantage with regard to computational efficiency for VMAT dose computation on homogeneous medium, especially when a fine angular sampling rate is applied. This can support a reduction in dose errors from the angular under-sampling effect by using a finer angular sampling rate, while still preserving a practical computing speed. For dose calculation on 4026

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A sliding-window approach for improved VMAT dose calculation accuracy

Cited by 2 publications

References 12 publications

Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

A polar‐coordinate‐based pencil beam algorithm for VMAT dose computation with high‐resolution gantry angle sampling

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