SBRT of ventricular tachycardia using 4pi optimized trajectories

Reis, Cristiano Queiroz Melo Dos; Little, Brian; MacDonald, R. Lee; Syme, Alasdair; Thomas, Christopher G.; Robar, James L.

doi:10.1002/acm2.13454

Cited by 8 publications

(6 citation statements)

References 42 publications

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“…18 This F I G U R E 9 Comparison between measured dose (thin lines) and calculated dose (thick line) for the colli-DTRT plan of case 1 (top) and the NC-VMAT of case 6 (bottom). approach was also used for a planning study of ventricular tachycardia, 17 showing applicability in the thorax. For lung cases, the authors introduced a sampling score to maintain conformity 33 ; with dosimetrically motivated BAO as in our study, this was not needed.…”

Section: F I G U R Ementioning

confidence: 99%

“…4 MacDonald et al have automatically determined table angles and gantry-angle range for non-coplanar partial arcs with optimized collimator angle using overlap metrics to solve the BAO problem. 3 By considering partial arcs, the technique is more easily applicable to treatment sites in the body 17 where collision risk strongly limits the range of usable table angles for a full gantry rotation.…”

Section: Introductionmentioning

confidence: 99%

“…However, by not considering the dosimetric interplay between different beam directions during BAO, these geometric methods 3,17,18 may result in suboptimal beam angle selection.…”

Section: Introductionmentioning

confidence: 99%

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Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Bertholet,

Zhu,

Guyer

et al. 2023

Medical Physics

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BackgroundNon‐coplanar techniques have shown to improve the achievable dose distribution compared to standard coplanar techniques for multiple treatment sites but finding optimal beam directions is challenging. Dynamic collimator trajectory radiotherapy (colli‐DTRT) is a new intensity modulated radiotherapy technique that uses non‐coplanar partial arcs and dynamic collimator rotation.PurposeTo solve the beam angle optimization (BAO) problem for colli‐DTRT and non‐coplanar VMAT (NC‐VMAT) by determining the table‐angle and the gantry‐angle ranges of the partial arcs through iterative 4π fluence map optimization (FMO) and beam direction elimination.MethodsBAO considers all available beam directions sampled on a gantry‐table map with the collimator angle aligned to the superior‐inferior axis (colli‐DTRT) or static (NC‐VMAT). First, FMO is performed, and beam directions are scored based on their contributions to the objective function. The map is thresholded to remove the least contributing beam directions, and arc candidates are formed by adjacent beam directions with the same table angle. Next, FMO and arc candidate trimming, based on objective function penalty score, is performed iteratively until a desired total gantry angle range is reached. Direct aperture optimization on the final set of colli‐DTRT or NC‐VMAT arcs generates deliverable plans. colli‐DTRT and NC‐VMAT plans were created for seven clinically‐motivated cases with targets in the head and neck (two cases), brain, esophagus, lung, breast, and prostate. colli‐DTRT and NC‐VMAT were compared to coplanar VMAT plans as well as to class‐solution non‐coplanar VMAT plans for the brain and head and neck cases. Dosimetric validation was performed for one colli‐DTRT (head and neck) and one NC‐VMAT (breast) plan using film measurements.ResultsTarget coverage and conformity was similar for all techniques. colli‐DTRT and NC‐VMAT plans had improved dosimetric performance compared to coplanar VMAT for all treatment sites except prostate where all techniques were equivalent. For the head and neck and brain cases, mean dose reduction—in percentage of the prescription dose—to parallel organs was on average 0.7% (colli‐DTRT), 0.8% (NC‐VMAT) and 0.4% (class‐solution) compared to VMAT. The reduction in D2% for the serial organs was on average 1.7% (colli‐DTRT), 2.0% (NC‐VMAT) and 0.9% (class‐solution). For the esophagus, lung, and breast cases, mean dose reduction to parallel organs was on average 0.2% (colli‐DTRT) and 0.3% (NC‐VMAT) compared to VMAT. The reduction in D2% for the serial organs was on average 1.3% (colli‐DTRT) and 0.9% (NC‐VMAT). Estimated delivery times for colli‐DTRT and NC‐VMAT were below 4 min for a full gantry angle range of 720°, including transitions between arcs, except for the brain case where multiple arcs covered the whole table angle range. These times are in the same order as the class‐solution for the head and neck and brain cases. Total optimization times were 25%–107% longer for colli‐DTRT, including BAO, compared to VMAT.ConclusionsWe successfully developed dosimetrically motivated BAO for colli‐DTRT and NC‐VMAT treatment planning. colli‐DTRT and NC‐VMAT are applicable to multiple treatment sites, including body sites, with beneficial or equivalent dosimetric performances compared to coplanar VMAT and reasonable delivery times.

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Section: F I G U R Ementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Bertholet,

Zhu,

Guyer

et al. 2023

Medical Physics

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“…Recent work in the area of 4π radiotherapy has demonstrated the potential benefits of dynamic trajectories in radiotherapy (treatment deliveries in which the couch, gantry and collimator engage in continuous motion while the beam is on). The benefits include both a reduction in normal tissue doses and an increase in monitor unit efficiency 25–30 . In one clinical trial with 4π‐radiotherapy, treatment‐time tolerability for N = 11 cases was found to be tolerable (8.625 ± 2.64 out of 10) and was found to not cause nausea 31 .…”

Section: Introductionmentioning

confidence: 99%

“…The benefits include both a reduction in normal tissue doses and an increase in monitor unit efficiency. [25][26][27][28][29][30] In one clinical trial with 4𝜋-radiotherapy, treatment-time tolerability for N = 11 cases was found to be tolerable (8.625 ± 2.64 out of 10) and was found to not cause nausea. 31 To date, most of this research has focused on treatments delivered at the nominal isocenter of the treatment unit (i.e., conventional source-to-axis distance [SAD] treatments); however, the same capabilities that permit intra-treatment rotations of the couch also permit dynamic translations of the couch for the purpose of reducing the source-to-target distance.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of plan quality and treatment efficiency in cranial stereotactic radiosurgery treatment plans with a variable source‐to‐axis distance

et al. 2023

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Introduction: Radiotherapy deliveries with dynamic couch motions that shorten the source-to-axis distance (SAD) on a C-arm linac have the potential to increase treatment efficiency through the increase of the effective dose rate. In this investigation, we convert clinically deliverable volumetric modulated arc therapy (VMAT) and dynamic conformal arc (DCA) plans for cranial radiosurgery into virtual isocenter plans through implementation of couch trajectories that maintain the target at a shortened but variable SAD throughout treatment. Materials and Methods: A randomly sampled population of patients treated with cranial radiosurgery from within the last three years were separated into groups with one, two, and three lesions. All plans had a single isocenter (regardless of number of targets), and a single prescription dose. Patient treatment plans were converted from their original delivery at a standard isocenter to a dynamic virtual isocenter in MATLAB. The virtual isocenter plan featured a variable isocenter position based upon the closest achievable source-to-target distance (referred to herein as a virtual source-to-axis distance [vSAD]) which avoided collision zones on a TrueBeam STx platform. Apertures were magnified according to the vSAD and monitor units at a given control point were scaled based on the inverse square law. Doses were calculated for the plans with a virtual isocenter in the Eclipse (v13.6.23) treatment planning system (TPS) and were compared with the clinical plans. Plan metrics (MU, Paddick conformity index, gradient index, and the volume receiving 12 Gy or more), normal brain dose-volume differences, as well as maximum doses received by organs at risk (OARs) were assessed. The values were compared between standard and virtual isocenter plans with Wilcoxon Sign Ranked tests to determine significance. A subset of the plans were mapped to the MAX-HD anthropomorphic phantom which contained an insert housing EBT3 GafChromic film and a PTW 31010 microion chamber for dose verification on a linac. Results: Delivering plans at a virtual isocenter resulted in an average reduction of 20.9% (p = 3×10 −6 ) and 20.6% (p = 3.0×10 −6 ) of MUs across all VMAT and all DCA plans, respectively. There was no significant change in OAR max doses received by plans delivered at a virtual isocenter.The low dose wash (1.0-2.0 Gy or 5-11% of the prescription dose) was increased (by approximately 20 cc) for plans with three lesions. This was equivalent to a 2.7%-3.8% volumetric increase in normal tissue receiving the respective dose level when comparing the plan with a virtual isocenter to a plan with a standard isocenter. Gamma pass rates with a 5%/1mm analysis criteria were 96.40% ± 2.90% and 95.07% ± 3.10% for deliveries at standard and virtual isocenter, respectively. Absolute point dose agreements were within −0.36% ± 3.45% and −0.55% ± 3.39% for

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Evaluation of the feasibility of cardiac gating for SBRT of ventricular tachycardia based on real‐time ECG signal acquisition

Reis

Robar

2022

J Applied Clin Med Phys

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Purpose To investigate the feasibility of cardiac synchronized gating in stereotactic body radiation therapy (SBRT) of ventricular tachycardia (VT) using a real‐time electrocardiogram (ECG) signal acquisition. Methods and materials Stability of beam characteristics during simulated ECG gating was examined by developing a microcontroller interface to a Varian Clinac iX linear accelerator allowing gating at frequencies and duty cycles relevant to cardiac rhythm. Delivery accuracy was evaluated by measuring dose linearity with an ionization chamber, and flatness and symmetry with a two‐dimensional detector array, for different gating windows within typical human cardiac cycle periods. To establish a practical method of gating based on actual ECG signals, an AD8232 Heart Monitor board was used to acquire the ECG signal and synchronize the beam delivery. Real‐time cardiac gated delivery measurements were performed for a single 10 × 10 cm 2 field and for a VT‐SBRT plan using intensity‐modulated radiation therapy (IMRT). Results and discussion Dose per monitor unit (MU) values were found to be linear within most gating windows investigated with maximum differences relative to non‐gated delivery of <2% for gating windows ≥200 ms and for >10 MUs. Beam profiles for both gated and non‐gated modes were also found to agree with maximum differences of 0.5% relative to central axis dose for all sets of beam‐on/beam‐off combinations. Comparison of dose distributions for intensity‐modulated SBRT plans between non‐gating and cardiac gating modes provided a gamma passing rate of 97.2% for a 2% 2 mm tolerance. Conclusions Beam output is stable with respect to linearity, flatness, and symmetry for gating windows within cardiac cycle periods. Agreement between dose distributions for VT‐SBRT using IMRT in non‐gated and cardiac cycle gated delivery modes shows that the proposed methodology is feasible. Technically, gating for delivery of SBRT for VT is possible with regard to beam stability.

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SBRT of ventricular tachycardia using 4pi optimized trajectories

Cited by 8 publications

References 42 publications

Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Evaluation of plan quality and treatment efficiency in cranial stereotactic radiosurgery treatment plans with a variable source‐to‐axis distance

Evaluation of the feasibility of cardiac gating for SBRT of ventricular tachycardia based on real‐time ECG signal acquisition

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