Tuning of Acuros<scp>XB</scp> source size setting for small intracranial targets

Gardner, Stephen; Lu, Shu‐Ling; Liu, Chang; Chetty, Indrin J.

doi:10.1002/acm2.12091

Cited by 7 publications

(13 citation statements)

References 43 publications

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“…reports the need to adjust source size for small field intracranial SRS using AcurosXB in the Eclipse planning system to avoid >10% central axis dose discrepancies for small target volumes. 20 When treating multiple targets distant from the isocenter, extra requirements are needed for setup accuracy and limitation of patient motion during treatment. To remove any patient rotation at setup, a 6DOF couch should be used for treatment.…”

Section: Ma Et Al Published a Planning Study Comparing Plans For Gammamentioning

confidence: 99%

Institutional experience with SRS VMAT planning for multiple cranial metastases

Ballangrud

Kuo

Happersett

et al. 2018

J Applied Clin Med Phys

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Background and PurposeThis study summarizes the cranial stereotactic radiosurgery (SRS) volumetric modulated arc therapy (VMAT) procedure at our institution.Materials and MethodsVolumetric modulated arc therapy plans were generated for 40 patients with 188 lesions (range 2–8, median 5) in Eclipse and treated on a TrueBeam STx. Limitations of the custom beam model outside the central 2.5 mm leaves necessitated more than one isocenter pending the spatial distribution of lesions. Two to nine arcs were used per isocenter. Conformity index (CI), gradient index (GI) and target dose heterogeneity index (HI) were determined for each lesion. Dose to critical structures and treatment times are reported.ResultsLesion size ranged 0.05–17.74 cm3 (median 0.77 cm3), and total tumor volume per case ranged 1.09–26.95 cm3 (median 7.11 cm3). For each lesion, HI ranged 1.2–1.5 (median 1.3), CI ranged 1.0–2.9 (median 1.2), and GI ranged 2.5–8.4 (median 4.4). By correlating GI to PTV volume a predicted GI = 4/PTV0.2 was determined and implemented in a script in Eclipse and used for plan evaluation. Brain volume receiving 7 Gy (V 7 Gy) ranged 10–136 cm3 (median 42 cm3). Total treatment time ranged 24–138 min (median 61 min).ConclusionsVolumetric modulated arc therapy provide plans with steep dose gradients around the targets and low dose to critical structures, and VMAT treatment is delivered in a shorter time than conventional methods using one isocenter per lesion. To further improve VMAT planning for multiple cranial metastases, better tools to shorten planning time are needed. The most significant improvement would come from better dose modeling in Eclipse, possibly by allowing for customizing the dynamic leaf gap (DLG) for a special SRS model and not limit to one DLG per energy per treatment machine and thereby remove the limitation on the Y‐jaw and allow planning with a single isocenter.

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Section: Ma Et Al Published a Planning Study Comparing Plans For Gammamentioning

confidence: 99%

Institutional experience with SRS VMAT planning for multiple cranial metastases

Ballangrud

Kuo

Happersett

et al. 2018

J Applied Clin Med Phys

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“…Generally, adjustable parameters, such as the MLC parameters (i.e., dosimetric leaf gap (DLG) and MLC transmission factor (TF)) and focal spot size have attracted attention for the commissioning of RTPS. 3,[5][6][7][19][20][21] An important question is whether the uneven differences in VMAT calculated dose distributions could be compensated through the parameter adjustments or not. There are two concerns regarding this.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of differences and dosimetric influences of beam models using golden and multi‐institutional measured beam datasets in radiation treatment planning systems

Tani¹,

Wakita²,

Tohyama³

et al. 2020

Medical Physics

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Purpose The beam model in radiation treatment planning systems (RTPSs) plays a crucial role in determining the accuracy of calculated dose distributions. The purpose of this study was to ascertain differences in beam models and their dosimetric influences when a golden beam dataset (GBD) and multi‐institution measured beam datasets (MBDs) are used for beam modeling in RTPSs. Methods The MBDs collected from 15 institutions, and the MBDs' beam models, were compared with a GBD, and the GBD’s beam model, for Varian TrueBeam linear accelerator. The calculated dose distributions of the MBDs' beam models were compared with those of the GBD’s beam model for simple geometries in a water phantom. Calculated dose distributions were similarly evaluated in volumetric modulated arc therapy (VMAT) plans for TG‐119 C‐shape and TG‐244 head and neck, at several dose constraints of the planning target volumes (PTVs), and organs at risk. Results The agreements of the MBDs with the GBD were almost all within ±1%. The calculated dose distributions for simple geometries in a water phantom also closely corresponded between the beam models of GBD and MBDs. Nevertheless, there were considerable differences between the beam models. The maximum differences between the mean energy of the energy spectra of GBD and MBDs were −0.12 MeV (−10.5%) in AcurosXB (AXB, Eclipse) and 0.11 MeV (7.7%) in collapsed cone convolution (CCC, RayStation). The differences in the VMAT calculated dose distributions varied for each dose region, plan, X‐ray energy, and dose calculation algorithm. The ranges of the differences in the dose constraints were −5.6% to 3.0% for AXB and −24.1% to 2.8% for CCC. In several VMAT plans, the calculated dose distributions of GBD's beam model tended to be lower in high‐dose regions and higher in low‐dose regions than those of the MBDs' beam models. Conclusions We found that small differences in beam data have large impacts on the beam models, and on calculated dose distributions in clinical VMAT plan, even if beam data correspond within ±1%. GBD’s beam model was not a representative beam model. The beam models of GBD and MBDs and their calculated dose distributions under clinical conditions were significantly different. These differences are most likely due to the extensive variation in the beam models, reflecting the characteristics of beam data. The energy spectrum and radial energy in the beam model varied in a wide range, even if the differences in the beam data were <±1%. To minimize the uncertainty of the calculated dose distributions in clinical plans, it was best to use the institutional MBD for beam modeling, or the beam model that ensures the accuracy of calculated dose distributions.

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“…The 3% ΔD criterion was selected in this study because it is widely used, in combination with a range of Δd values, but the use of 3% as a ΔD criterion is not universal. Similarly, GAI values of 100% and 95% were selected as examples of extreme and commonly‐used PSQA action levels, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Recent surveys suggested that 3%/3 mm are currently the most commonly used gamma evaluation criteria, and the AAPM's task group report on IMRT commissioning (TG‐119) used 3%/3 mm and the AAPM's more recent task group report on modulated radiotherapy quality assurance (TG‐218) recommended 3%/2 mm. Investigations of cranial and extra‐cranial stereotactic radiotherapy have reported the use of 3%/2 mm, 3%/1.5 mm, 3%/1 mm and 3%/0.3 mm criteria.…”

Section: Methodsmentioning

confidence: 99%

Technical note: A modified gamma evaluation method for dose distribution comparisons

Kairn

Trapp

et al. 2019

J Applied Clin Med Phys

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Purpose In this work we have developed a novel method of dose distribution comparison, the inverse gamma (IG) evaluation, by modifying the commonly used gamma evaluation method. Methods The IG evaluation calculates the gamma criteria (dose difference criterion, ΔD, or distance‐to‐agreement criterion, Δd) that are needed to achieve a predefined pass rate or gamma agreement index (GAI). In‐house code for evaluating IG with a fixed ΔD of 3% was developed using Python (v3.5.2) and investigated using treatment plans and measurement data from 25 retrospective patient specific quality assurance tests (53 individual arcs). Results It was found that when the desired GAI was set to 95%, approximately three quarters of the arcs tested were able to achieve Δd within 1 mm (mean Δd: 0.7 ± 0.5 mm). The mean Δd required in order for all points to pass the gamma evaluation (i.e., GAI = 100%) was 4.5 ± 3.1 mm. The possibility of evaluating IG by fixing the Δd or ΔD/Δd, instead of fixing the ΔD at 3%, was also investigated. Conclusion The IG method and its indices have the potential to be implemented clinically to quantify the minimum dose and distance criteria based on a specified GAI. This method provides additional information to augment standard gamma evaluation results during patient specific quality assurance testing of individual treatment plans. The IG method also has the potential to be used in retrospective audits to determine an appropriate set of local gamma criteria and action levels based on a cohort of patient specific quality assurance plans.

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Tuning of AcurosXB source size setting for small intracranial targets

Cited by 7 publications

References 43 publications

Institutional experience with SRS VMAT planning for multiple cranial metastases

Institutional experience with SRS VMAT planning for multiple cranial metastases

Evaluation of differences and dosimetric influences of beam models using golden and multi‐institutional measured beam datasets in radiation treatment planning systems

Technical note: A modified gamma evaluation method for dose distribution comparisons

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