Use of genetic algorithm for PTV optimization in single isocenter multiple metastases radiosurgery treatments with Brainlab Elements™

Rojas-López, José Alejandro; Moreno, Rogelio Manuel Díaz; Venencia, C

doi:10.1016/j.ejmp.2021.05.031

Cited by 13 publications

(29 citation statements)

References 40 publications

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“…The PTV was created following an institutional geometric margin criterion based on Kuntz et al and others. 6,[32][33][34][35] If the GTV is located less than 50 mm from the isocenter, a margin of 0•5 mm was assigned. If the GTV is located more than 50 mm from the isocenter or its volume was less than 0•1 cc, a margin of 1 mm was assigned.…”

Section: Plan Selectionmentioning

confidence: 99%

“…If the GTV is located more than 50 mm from the isocenter or its volume was less than 0•1 cc, a margin of 1 mm was assigned. 32…”

Section: Plan Selectionmentioning

confidence: 99%

“…Rotations were not included in TPS. In a previous work 32 , we worked out on the DICOM files handling to perform rotations of the targets with respect to a single point (isocenter). Additionally, it is known that the group of rotation transformations is non-commutative.…”

Section: Rotation-induced Displacementsmentioning

confidence: 99%

“…The software technical description is shown in literature. 32 It works under the assumption that if displacements are relatively small with respect to the relevant anatomical dimensions and the radiological path of the treatment beams towards the targets, this approach is valid for an arc treatment. 12 It allows to handle each structure from the DICOM structure file, applying rotations in any direction with respect to isocenter plan, while the CT and dose DICOM files remained fixed to display dosimetric calculations.…”

Section: Rotation-induced Displacementsmentioning

confidence: 99%

“…Additionally, dosimetric differences due to rotation-induced displacements were studied for both MLC following the previous study of our work group. 32…”

Section: Introductionmentioning

confidence: 99%

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Rotational effect and dosimetric impact: HDMLC vs 5-mm MLC leaf width in single isocenter multiple metastases radiosurgery with Brainlab Elements™

Venencia¹,

Rojas-López

Moreno³

et al. 2022

J Radiother Pract

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Purpose: To analyse the impact of multileaf collimator (MLC) leaf width in multiple metastases radiosurgery (SRS) considering the target distance to isocenter and rotational displacements. Methods: Ten plans were optimised. The plans were created with Elements Multiple Mets SRS v2·0 (Brainlab AG, Munchen, Germany). The mean number of metastases per plan was 5 ± 2 [min 3, max 9], and the mean volume of gross tumour volume (GTV) was 1·1 ± 1·3 cc [min 0·02, max 5·1]. Planning target volume margin criterion was based on GTV-isocenter distance and target dimensions. Plans were performed using 6 MV with high-definition MLC (HDMLC) and reoptimised using 5-mm MLC (MLC-5). Plans were compared using Paddick conformity index (PCI), gradient index, monitor units , volume receiving half of prescription isodose (PIV50), maximum dose to brainstem, optic chiasm and optic nerves, and V12Gy, V10Gy and V5Gy for healthy brain were analysed. The maximum displacement due to rotational combinations was optimised by a genetic algorithm for both plans. Plans were reoptimised and compared using optimised margin. Results: HDMLC plans had better conformity and higher dose falloff than MLC-5 plans. Dosimetric differences were statistically significant (p < 0·05). The smaller the lesion volume, the higher the dosimetric differences between both plans. The effect of rotational displacements produced for each target in SRS was not dependent on the MLC (p > 0·05). Conclusions: The finer HDMLC offers dosimetric advantages compared with the MLC-5 in terms of target conformity and dose to the surrounding organs at risk. However, only dose falloff differences due to rotations depend on MLC.

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Section: Plan Selectionmentioning

confidence: 99%

“…If the GTV is located more than 50 mm from the isocenter or its volume was less than 0•1 cc, a margin of 1 mm was assigned. 32…”

Section: Plan Selectionmentioning

confidence: 99%

Section: Rotation-induced Displacementsmentioning

confidence: 99%

Section: Rotation-induced Displacementsmentioning

confidence: 99%

“…Additionally, dosimetric differences due to rotation-induced displacements were studied for both MLC following the previous study of our work group. 32…”

Section: Introductionmentioning

confidence: 99%

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Rotational effect and dosimetric impact: HDMLC vs 5-mm MLC leaf width in single isocenter multiple metastases radiosurgery with Brainlab Elements™

Venencia¹,

Rojas-López

Moreno³

et al. 2022

J Radiother Pract

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Automatic measurement of beam‐positioning accuracy at off‐isocenter positions

Ono

Kido

Nakamura

et al. 2022

J Applied Clin Med Phys

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Purpose This study performed an automatic measurement of the off‐axis beam‐positioning accuracy at a single isocenter via the TrueBeam Developer mode and evaluated the beam‐positioning accuracy considering the effect of couch rotational errors. Methods TrueBeam STx and the Winston–Lutz test‐dedicated phantom, with a 3 mm diameter steel ball, were used in this study. The phantom was placed on the treatment couch, and the Winston–Lutz test was performed at the isocenter for four gantry angles (0°, 90°, 180°, and 270°) using an electronic portal imaging device. The phantom offset positions were at distances of 0, 25, 50, 75, and 100 mm from the isocenter along the superior–inferior, anterior–posterior, and left–right directions. Seventeen patterns of multileaf collimator‐shaped square fields of 10 × 10 mm2 were created at the isocenter and off‐axis positions for each gantry angle. The beam‐positioning accuracy was evaluated with couch rotation along the yaw‐axis (0°, ± 0.5°, and ± 1.0°). Results The mean beam‐positioning errors at the isocenter and off‐isocenter distances (from the isocenter to ±100 mm) were 0.46–0.60, 0.44–0.91, and 0.42–1.11 mm for the couch angles of 0°, ±0.5°, and ±1°, respectively. The beam‐positioning errors increased as the distance from the isocenter and couch rotation increased. Conclusion These findings suggest that the beam‐positioning accuracy at the isocenter and off‐isocenter positions can be evaluated quickly and automatically using the TrueBeam Developer mode. The proposed procedure is expected to contribute to an efficient evaluation of the beam‐positioning accuracy at off‐isocenter positions.

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Dosimetric effects of rotational errors for single isocenter multiple targets in HyperArc plans: A phantom and retrospective imaging analysis study

Golmakani,

McGrath,

Williams

2023

J Applied Clin Med Phys

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PurposeThis study uses a phantom to investigate the dosimetric impact of rotational setup errors for Single Isocenter Multiple Targets (SIMT) HyperArc plans. Additionally, it evaluates intra‐fractional rotational setup errors in patients treated with Encompass immobilization system.MethodsThe Varian HyperArc system (Varian Medical systems) was used to create plans targeting spherical PTVs with diameters of 5, 10, and 15 mm and with offsets of 1.3–5.3 cm from the isocenter. Dosimetric parameters, including mean and maximum dose, D99% and D95% were evaluated for various rotational setup errors ranging from 0.5° to 2° for the PTVs and certain CTVs created within PTVs. These rotational errors were applied in an order and direction that resulted in the maximum displacement of targets. The rotation was applied both uniformly around all three axes and individually around each axis. Furthermore, to link the findings to actual treatment scenarios, the intra‐fractional rotational setup errors were obtained for stereotactic cranial patients treated with the Encompass system using CBCT images acquired during treatments.ResultsThe maximum displacement of 2.7 mm was observed for targets located at 4.4 and 4.5 cm from the isocenter with rotational setup errors of 2°. The dose reduction for D99% values corresponding to this displacement were about 50%, 40%, and 30% for PTVs with diameters of 5, 10, and 15 mm, respectively. Both D99% and D95% showed a consistent trend of dose reduction across various rotational errors and PTV volumes. While the maximum dose remained consistent for different targets with various rotational errors, the mean dose decreased by approximately 25%, 12%, and 6% for PTVs with diameters of 5, 10, and 15 cm, respectively, with rotational errors of 2°. In addition, by analyzing CBCT images, the absolute mean rotational setup errors obtained during treatment with Encompass for pitch, roll, and yaw were 0.17° ± 0.13°, 0.11° ± 0.10°, and 0.12° ± 0.10° respectively. This data, combined with existing studies, suggest that a 0.5° rotational setup error is a safe choice to consider for calculating additional PTV margin to ensure adequate CTV coverage.Therefore, the assessment of maximum displacement and dosimetric parameters in this study, for a 0.5° rotational error, highlights the need for an additional 0.7 mm PTV margin for targets positioned at distances of 4.4 cm or greater from the isocenter.ConclusionsFor SIMT Plans, a 0.5° rotational setup error is recommended as a basis for calculating additional PTV margins to ensure adequate CTV coverage when using the Encompass system.

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Use of genetic algorithm for PTV optimization in single isocenter multiple metastases radiosurgery treatments with Brainlab Elements™

Cited by 13 publications

References 40 publications

Rotational effect and dosimetric impact: HDMLC vs 5-mm MLC leaf width in single isocenter multiple metastases radiosurgery with Brainlab Elements™

Rotational effect and dosimetric impact: HDMLC vs 5-mm MLC leaf width in single isocenter multiple metastases radiosurgery with Brainlab Elements™

Automatic measurement of beam‐positioning accuracy at off‐isocenter positions

Dosimetric effects of rotational errors for single isocenter multiple targets in HyperArc plans: A phantom and retrospective imaging analysis study

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