<scp>TG</scp>‐51 reference dosimetry for the Halcyon™: A clinical experience

Lloyd, Samantha A. M.; Lim, Tze Yee; Fave, Xenia; Flores‐Martinez, Everardo; Atwood, Todd; Moiseenko, Vitali

doi:10.1002/acm2.12349

Cited by 29 publications

(46 citation statements)

References 7 publications

(12 reference statements)

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“…The beam quality was recorded following TG‐51 guidelines as % dd (10) . The beam was not filtered with lead for these measurements however Lloyd et al has shown this to impact the measured % dd (10) by less than 0.7% on the Halcyon . This ranged from 59.85% for a 5 cm square field to 68.5% for 28 cm square field.…”

Section: Resultsmentioning

confidence: 99%

“…18 The beam was not filtered with lead for these measurements however Lloyd et al has shown this to impact the measured %dd(10) by less than 0.7% on the Halcyon. 19 This ranged from 59.85% for a 5 cm square field to 68.5% for 28 cm square field. For all distances past dmax, the measured data agreed with the TPS data to within 1% for all field sizes.…”

Section: A Dosimetric Parametersmentioning

confidence: 96%

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Technical Note: Dosimetric characterization of the dynamic beam flattening MLC sequence on a ring shaped, Jawless Linear Accelerator with double stacked MLC

Bollinger

Laugeman

et al. 2020

Medical Physics

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Purpose To characterize the dosimetric features and limitations of the dynamic beam flattening (DBF) on the Halcyon 2.0 linear accelerator (Varian Medical Systems). Methods A predefined multi‐leaf collimator (MLC) sequence was introduced and used to flatten the 6 MV flattening filter free (FFF) beam on the Halcyon 2.0. Dosimetric characterizations of the flattened beams, including beam flatness, symmetry, percent depth dose (PDD), output factor and MU linearity, were investigated. Flatness and symmetry were obtained from profile measurements with both radiographic films (EDR2) and a two dimensional ion‐chamber array (IC Profiler, Sun Nuclear Corporation). MU linearity, output factors, and PDDs were measured in a water tank with a CC13 ion chamber (Scanditronix Wellhöfer, Nuremburg, Germany). In addition, the effect of the DBF sequence on 3D plan quality was evaluated by creating DBF plans for a 4‐field box rectum and an AP/PA spine plan. Patient specific QA was performed on these plans. Results At 100 cm SSD and 10 cm depth, a flatness of <3% was observed on both transversal and radial profiles for all square field sizes ≥10 cm with DBF. For both larger and smaller field sizes the flatness showed a tendency to increase as the fields got bigger or smaller, respectively. Similar trends in flatness were observed at all depths measured. All measured output factors for square field sizes ≥5 cm were within 1% of the TPS prediction. Linearity was ≤2.02% for all measurements. For both treatment sites, the MD judged the plans created for the Halcyon without the use of DBF not to be clinically acceptable, however considered both the TrueBeam plan and the Halcyon plan with the DBF sequence to be clinically acceptable. Conclusions The DBF sequence on the Halcyon and its characteristics were investigated. The analysis indicates that the DBF sequence can be used on the Halcyon to generate clinically acceptable 3D treatment plans.

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Section: Resultsmentioning

confidence: 99%

Section: A Dosimetric Parametersmentioning

confidence: 96%

Technical Note: Dosimetric characterization of the dynamic beam flattening MLC sequence on a ring shaped, Jawless Linear Accelerator with double stacked MLC

Bollinger

Laugeman

et al. 2020

Medical Physics

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“…Halcyon plans: The Halcyon is a ring-based delivery system [13,[22][23][24]. It consists of a linear accelerator capable of producing a 6MV flattening filter-free (FFF) photon beam delivering (when calibrated to deliver 1.0Gy per 100 monitor units (MU) at the reference conditions of source-surface distance (SSD) 100 cm at d max depth of 1.3 cm) a maximum dose rate of 800MU/min.…”

Section: The Treatment Planning Techniques and Featuresmentioning

confidence: 99%

Treatment planning comparison of volumetric modulated arc therapy employing a dual-layer stacked multi-leaf collimator and helical tomotherapy for cervix uteri

et al. 2020

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Purpose: To ascertain the dosimetric performance of a new delivery system (the Halcyon system, H) equipped with dual-layer stacked multi-leaf collimator (MLC) for risk-adapted targets in cervix uteri cancer patients compared to another ring-based system in clinical operation (Helical Tomotherapy, HT). Methods: Twenty patients were retrospectively included in a treatment planning study (10 with positive lymph nodes and 10 without). The dose prescription (45Gy to the primary tumour volume and a simultaneously integrated boost up to 55Gy for the positive patients) and the clinical planning objectives were defined consistently as recommended by an ongoing multicentric clinical trial. Halcyon plans were optimised for the volumetric modulated arc therapy. The plan comparison was performed employing the quantitative analysis of the dose-volume histograms.Results: The coverage of the primary and nodal target volumes was comparable for both techniques and both subsets of patients. The primary planning target volume (PTV) receiving at least 95% of the prescription isodose ranged from 97.2 ± 1.1% (node-negative) to 99.1 ± 1.2% (node-positive) for H and from 96.5 ± 1.9% (node-negative) to 98.3 ± 0.9% (node-positive) for HT. The uncertainty is expressed at one standard deviation from the cohort of patient per each group. For the nodal clinical target volumes, the dose received by 98% of the planning target volume ranged 55.5 ± 0.1 to 56.0 ± 0.8Gy for H and HT, respectively. The only significant and potentially relevant differences were observed for the bowels. In this case, V 40Gy resulted 226.3 ± 35.9 and 186.9 ± 115.9 cm 3 for the node-positive and node-negative patients respectively for Halcyon. The corresponding findings for HT were: 258.9 ± 60.5 and 224.9 ± 102.2 cm 3 . On the contrary, V 15Gy resulted 1279.7 ± 296.5 and 1557.2 ± 359.9 cm 3 for HT and H respectively for node-positive and 1010.8 ± 320.9 versus 1203.8 ± 332.8 cm 3 for node-negative. Conclusion: This retrospective treatment planning study, based on the dose constraints derived from the Embrace II study protocol, suggested the essential equivalence between Halcyon based and Helical Tomotherapy based plans for the intensity-modulated rotational treatment of cervix uteri cancer. Different levels of sparing were observed for the bowels with H better protecting in the high-dose region and HT in the mid-low dose regions. The clinical impact of these differences should be further addressed.

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“…There are a number of publications that either evaluate the operation of the Halcyon or provide recommendations on its clinical use . A recent publication provided a risk assessment of Halcyon acceptance testing and commissioning processes using the TG‐100 methodology .…”

Section: Introductionmentioning

confidence: 99%

“…There are a number of publications that either evaluate the operation of the Halcyon or provide recommendations on its clinical use. [1][2][3][4][5][6][7][8][9][10][11] A recent publication provided a risk assessment of Halcyon acceptance testing and commissioning processes using the TG-100 methodology. 12 In that work, 142 failure modes were identified with the top risk priority number (RPN) values ranging from 85.5 to 95.0 for the acceptance testing and commissioning, respectively.…”

Section: Introductionmentioning

confidence: 99%

Clinical safety assessment of the Halcyon system

et al. 2019

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Purpose The Halcyon consists of precommissioned linear accelerator and treatment planning algorithms that were designed to simplify the acceptance, commissioning, and clinical workflow for image‐guided intensity‐modulated radiotherapy. The purpose of this work was to perform a comprehensive safety assessment for the clinical use of the Halcyon. Methods Systems‐Theoretic Process Analysis was used as the safety assessment tool. As part of the analysis, a number of control loops and control actions are created to describe system function. Safety is assessed by determining unsafe control actions and a corresponding list of causal scenarios that leads to accidents. The scope of the analysis was from the acceptance of the Halcyon to routine patient treatments. All aspects of treating patients were considered including the roles of physicians, physicists, dosimetrists, and therapists. The analysis was completed by four physicists with input from other members of the radiation therapy team. The causal scenarios were summarized using the causality categories from the consensus recommendations for incident learning database structures in radiation oncology (Med Phys, Vol. 39, No. 12, Dec 2012). Results Twenty‐three (23) control loops containing 52 control actions were created for the clinical use of the Halcyon. One hundred forty‐four (144) unsafe control actions were identified with 385 associated causal scenarios. Twenty‐seven percent (27%) of the causal scenarios were related to equipment technical issues, while 73% of the causal scenarios were predominantly related to procedural issues, human behavior, and organizational management. Conclusions For routine clinical use of closed or largely automated radiation therapy equipment, the majority of safety concerns is related to nontechnical issues. The Halcyon and other similar systems may present opportunities to streamline, reduce, or eliminate some traditional equipment commissioning and routine quality assurance activities in exchange for an increased focus on issues related to organizational management, procedures, and human behavior.

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TG‐51 reference dosimetry for the Halcyon™: A clinical experience

Cited by 29 publications

References 7 publications

Technical Note: Dosimetric characterization of the dynamic beam flattening MLC sequence on a ring shaped, Jawless Linear Accelerator with double stacked MLC

Technical Note: Dosimetric characterization of the dynamic beam flattening MLC sequence on a ring shaped, Jawless Linear Accelerator with double stacked MLC

Treatment planning comparison of volumetric modulated arc therapy employing a dual-layer stacked multi-leaf collimator and helical tomotherapy for cervix uteri

Clinical safety assessment of the Halcyon system

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