Use of flattening filter free photon beams for off-axis targets in conformal arc stereotactic body radiation therapy

Smith, A.; Kim, S; Serago, Christopher F.; Hintenlang, Kathleen M.; Hintenlang, David E.; Heckman, Michael G.

doi:10.1007/978-3-319-19387-8_109

Cited by 5 publications

(8 citation statements)

References 17 publications

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“…16,18 The disadvantage of OAG plans is that they require longer treatment delivery times compared to CAG FFF plans, related to the off-axis distance of the PTV. 16 A further potential concern of OAG is the magnification of misalignment errors in the collimator or couch rotations at the off-axis position. However, these potential errors (<0.5°at the isocenter) were not found to have a clinically significant effect on dose distributions for OAG conventional (flattened) or FFF plans.…”

Section: Introductionmentioning

confidence: 99%

“…However, these potential errors (<0.5°at the isocenter) were not found to have a clinically significant effect on dose distributions for OAG conventional (flattened) or FFF plans. 16 To verify the dosimetric and geometric accuracy of SABR treatment deliveries, patient-specific quality assurance (QA) is required. A number of two-dimensional (2D)/three-dimensional (3D) dose measurement systems are commercially available and have been commissioned for such work; these typically comprise film, ionization chamber arrays, or semiconductor diode arrays.…”

Section: Introductionmentioning

confidence: 99%

“…This then requires large lateral couch shifts to be applied to relocate the patient in the off‐centered couch position following verification. OAG, on the other hand, positions the isocenter at the midline of the patient, thus eliminating clearance issues and enables the patient setup to be verified in the treatment position . Furthermore, OAG FFF treatment plans are dosimetrically comparable to CAG plans .…”

Section: Introductionmentioning

confidence: 99%

“…OAG, on the other hand, positions the isocenter at the midline of the patient, thus eliminating clearance issues and enables the patient setup to be verified in the treatment position . Furthermore, OAG FFF treatment plans are dosimetrically comparable to CAG plans . The disadvantage of OAG plans is that they require longer treatment delivery times compared to CAG FFF plans, related to the off‐axis distance of the PTV .…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Improvement of off‐axis SABR plan verification results by using adapted dose reconstruction algorithms for the Octavius 4D system

et al. 2018

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The errors in QA phantom measurements due to dose reconstruction at off-axis target geometry have been demonstrated for conformal arcs and clinical VMAT SABR plans. A novel software solution implemented by the vendor to allow accurate pass rates has been tested. This solution enables high-resolution arrays with small active detection areas to be used for quality assurance of SABR treatment plans in the off-axis treatment position.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Improvement of off‐axis SABR plan verification results by using adapted dose reconstruction algorithms for the Octavius 4D system

et al. 2018

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“…Similar to the recent use of modified DCAT to liver SBRT [ 31 ] either with or without flattening-filter-free beams [ 32 ], DrMAT is also easily applicable to other abdominal cancers that are particularly associated with respiratory tumor motion such as liver and pancreas cancers.…”

Section: Discussionmentioning

confidence: 99%

Improving Delivery Accuracy of Stereotactic Body Radiotherapy to a Moving Tumor Using Simplified Volumetric Modulated Arc Therapy

et al. 2016

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PurposeTo develop a simplified volumetric modulated arc therapy (VMAT) technique for more accurate dose delivery in thoracic stereotactic body radiation therapy (SBRT).Methods and MaterialsFor each of the 22 lung SBRT cases treated with respiratory-gated VMAT, a dose rate modulated arc therapy (DrMAT) plan was retrospectively generated. A dynamic conformal arc therapy plan with 33 adjoining coplanar arcs was designed and their beam weights were optimized by an inverse planning process. All sub-arc beams were converted into a series of control points with varying MLC segment and dose rates and merged into an arc beam for a DrMAT plan. The plan quality of original VMAT and DrMAT was compared in terms of target coverage, compactness of dose distribution, and dose sparing of organs at risk. To assess the delivery accuracy, the VMAT and DrMAT plans were delivered to a motion phantom programmed with the corresponding patients’ respiratory signal; results were compared using film dosimetry with gamma analysis.ResultsThe plan quality of DrMAT was equivalent to that of VMAT in terms of target coverage, dose compactness, and dose sparing for the normal lung. In dose sparing for other critical organs, DrMAT was less effective than VMAT for the spinal cord, heart, and esophagus while being well within the limits specified by the Radiation Therapy Oncology Group. Delivery accuracy of DrMAT to a moving target was similar to that of VMAT using a gamma criterion of 2%/2mm but was significantly better using a 2%/1mm criterion, implying the superiority of DrMAT over VMAT in SBRT for thoracic/abdominal tumors with respiratory movement.ConclusionWe developed a DrMAT technique for SBRT that produces plans of a quality similar to that achieved with VMAT but with better delivery accuracy. This technique is well-suited for small tumors with motion uncertainty.

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Evaluation of HyperArc™ using film and portal dosimetry quality assurance

Kamst

Desai

2022

Phys Eng Sci Med

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HyperArc ™ is a stereotactic radiotherapy modality designed for targeting multiple brain metastases using a single isocenter with multiple non-coplanar arcs. The purpose of this study was to assess the e cacy of two patient speci c quality assurance methods, lm and the Varian Portal Dosimetry System with Varian's HyperArc ™ technique and raise important considerations in the customisation of patient speci c quality assurance to accommodate HyperArc ™ delivery. Assessment criteria included gamma analysis and mean dose at full width half maximum. The minimum met size, maximum off-axis distance and suitable energy were identi ed and validated. Patient speci c quality assurance procedures were applied to a range of clinically relevant brain met plans. Initial investigation into energy selection showed no signi cant differences in gamma pass rates using 6MV, 6MV FFF or 10MV FFF for met sizes greater than 15 mm diameter at the isocenter. Gamma pass rates (2%/2mm) for 15 mm mets at the isocenter for all energies were greater than 96.0% for portal dosimetry and greater than 98.7% for lm. Fields of size 15 mm placed at various distances (10-70 mm) from the isocenter resulted in a maximum mean dose difference of 1.5% between lm and planned. Clinically relevant plans resulted in maximum mean dose difference for selected mets of 1.0% between lm and plan and maximum point dose difference of 2.9% between portal dose and plan. Portal dose image prediction was found to be a quick and convenient quality assurance tool for mets larger than 15 mm near the isocenter but provided diminished geometrical relevance for off-axis mets. Film QA required exacting procedures but offered the ability to assess the accuracy of geometrical targeting for off-axis mets and provided dosimetric accuracy for mets to well below 15 mm diameter.

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Use of flattening filter free photon beams for off-axis targets in conformal arc stereotactic body radiation therapy

Cited by 5 publications

References 17 publications

Improvement of off‐axis SABR plan verification results by using adapted dose reconstruction algorithms for the Octavius 4D system

Improvement of off‐axis SABR plan verification results by using adapted dose reconstruction algorithms for the Octavius 4D system

Improving Delivery Accuracy of Stereotactic Body Radiotherapy to a Moving Tumor Using Simplified Volumetric Modulated Arc Therapy

Evaluation of HyperArc™ using film and portal dosimetry quality assurance

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