High Quality Clinical Stereotactic Radiosurgery Planning and Delivery With Standard Resolution (5 mm) Multileaf Collimation and Multiple Isocenters

Robinson, M.; Tunstall, Clare; Heuvel, Frank Van den; Hobbs, Claire; Pothapregada, Sriram

doi:10.1016/j.prro.2020.03.004

Cited by 5 publications

(4 citation statements)

References 12 publications

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“…However, the number of cases with GPR below 90% decreased from 10 to 1 when the dose criterion changed from 3% 42 The 5% dose criterion has been also used for analysis of the accuracy of VMAT-based SIMT SRS using measurement-based 3D dose reconstructions. 4,45,46 In contrast to our derived 5% accuracy level for the VIPER software, some authors used tighter dose criterion for the gamma analysis. For example, Ahmed et al investigated the accuracy of a commercial hybrid volumetric dose verification system for SIMT cranial SRS.…”

Section: Discussionmentioning

confidence: 95%

“…The 5% accuracy found in our study for the VIPER software is compatible with the 5%–6% criterion established in the NCS 25 guideline for stereotactic treatment verification 42 . The 5% dose criterion has been also used for analysis of the accuracy of VMAT‐based SIMT SRS using measurement‐based 3D dose reconstructions 4,45,46 …”

Section: Discussionmentioning

confidence: 99%

“…An increase in stereotactic radiosurgery (SRS) treatments for multiple (≥4) intracranial metastases has been described in the literature 1,2 . Traditionally, each lesion was treated using one or more isocenters, and the patient had to be shifted during a single session for repositioning according to the isocenter for each lesion 3,4 . A clear drawback of this approach is the longer time required to deliver a single fraction treatment with the corresponding discomfort of the patient.…”

Section: Introductionmentioning

confidence: 99%

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Validation of virtual water phantom software for pre‐treatment verification of single‐isocenter multiple‐target stereotactic radiosurgery

Calvo-Ortega

Greer

Hermida-López

et al. 2021

J Applied Clin Med Phys

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The aim of this study was to benchmark the accuracy of the VIrtual Phantom Epid dose Reconstruction (VIPER) software for pre-treatment dosimetric verification of multiple-target stereotactic radiosurgery (SRS). VIPER is an EPID-based method to reconstruct a 3D dose distribution in a virtual phantom from in-air portal images. Validation of the VIPER dose calculation was assessed using several MLC-defined fields for a 6 MV photon beam. Central axis percent depth doses (PDDs) and output factors were measured with an ionization chamber in a water tank, while dose planes at a depth of 10 cm in a solid flat phantom were acquired with radiochromic films. The accuracy of VIPER for multiple-target SRS plan verification was benchmarked against Monte Carlo simulations. Eighteen multiple-target SRS plans designed with the Eclipse treatment planning system were mapped to a cylindrical water phantom. For each plan, the 3D dose distribution reconstructed by VIPER within the phantom was compared with the Monte Carlo simulation, using a 3D gamma analysis. Dose differences (VIPER vs. measurements) generally within 2% were found for the MLC-defined fields, while film dosimetry revealed gamma passing rates (GPRs) ≥95% for a 3%/1 mm criteria. For the 18 multiple-target SRS plans, average 3D GPRs greater than 93% and 98% for the 3%/2 mm and 5%/2 mm criteria, respectively. Our results validate the use of VIPER as a dosimetric verification tool for pre-treatment QA of single-isocenter multiple-target SRS plans. The method requires no setup time on the linac and results in an accurate 3D characterization of the delivered dose.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Validation of virtual water phantom software for pre‐treatment verification of single‐isocenter multiple‐target stereotactic radiosurgery

Calvo-Ortega

Greer

Hermida-López

et al. 2021

J Applied Clin Med Phys

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“…These MLCs have been shown to provide better conformity for single-target SRS [12][13][14]. However, not all of the benefits of smaller MLC leaves realized for single-target SRS have been recognized in SIMT [15,16]. Herein, the effect of small and large MLCs on hippocampal avoidance in SIMT is investigated.…”

Section: Introductionmentioning

confidence: 99%

Hippocampal Avoidance in Multitarget Radiosurgery

Gude

Adamson

Kirkpatrick

et al. 2021

Cureus

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Brain metastases are a common complication for patients diagnosed with cancer. As stereotactic radiosurgery (SRS) becomes a more prevalent treatment option for patients with many brain metastases, further research is required to better characterize the ability of SRS to treat large numbers of metastases (≥4) and the impact on normal brain tissue and, ultimately, neurocognition and quality of life (QOL). This study serves first as an evaluation of the feasibility of hippocampal avoidance for SRS patients, specifically receiving single-isocenter multitarget treatments (SIMT) planned with volumetric modulated arc therapy (VMAT). Second, this study analyzes the effects of standard-definition (SD) multileaf collimators (MLCs) (5 mm width) on plan quality and hippocampal avoidance.The 40 patients enrolled in this Institutional Review Board (IRB)-approved study had between four and 10 brain metastases and were treated with SIMT using VMAT. From the initial 40 patients, eight hippocampi across seven patients had hippocampal doses exceeding the maximum biologically effective dose (BED) constraint given by RTOG 0933. With the addition of upper constraints in the optimization objectives and one arc angle adjustment in one patient plan, four out of seven patient plans were able to meet the maximum hippocampal BED constraint, avoiding five out of eight total hippocampi at risk. High-definition (HD) MLCs allowed for an average decrease of 29% ± 23% (p = 0.007) in the maximum BED delivered to all eight hippocampi at risk.The ability to meet dose constraints depended on the distance between the hippocampus and the nearest planning target volume (PTV). Meeting the maximum hippocampal BED constraint in re-optimized plans was equally likely with the use of SD-MLCs (five out of eight hippocampi at risk were avoided) but resulted in increased dose to normal tissue volumes (23.67% ± 16.3% increase in V50%[cc] of normal brain tissue, i.e., brain volume subtracted by the total PTV) when compared to the HD-MLC re-optimized plans. Comparing the effects of SD-MLCs on plans not optimized for hippocampal avoidance resulted in increases of 48.2% ± 32.2% (p = 0.0056), 31.5% ± 16.3% (p = 0.024), and 16.7% ± 8.5% (p = 0.022) in V20%[cc], V50% [cc], and V75%[cc], respectively, compared to the use of HD-MLCs. The conformity index changed significantly neither when plans were optimized for hippocampal avoidance nor when SD-MLC leaves were used for treatment. In plans not optimized for hippocampal avoidance, mean hippocampal dose increased with the use of SD-MLCs by 38.0% ± 37.5% (p = 0.01). However, the use of SD-MLCs did not result in an increased number of hippocampi at risk.

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Fricke gel xylenol orange dosimeter layers for stereotactic radiosurgery: A preliminary approach

Pérez

Torres

Bruna³

et al. 2021

Applied Radiation and Isotopes

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High Quality Clinical Stereotactic Radiosurgery Planning and Delivery With Standard Resolution (5 mm) Multileaf Collimation and Multiple Isocenters

Cited by 5 publications

References 12 publications

Validation of virtual water phantom software for pre‐treatment verification of single‐isocenter multiple‐target stereotactic radiosurgery

Validation of virtual water phantom software for pre‐treatment verification of single‐isocenter multiple‐target stereotactic radiosurgery

Hippocampal Avoidance in Multitarget Radiosurgery

Fricke gel xylenol orange dosimeter layers for stereotactic radiosurgery: A preliminary approach

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