Implementation of respiratory‐gated VMAT on a Versa HD linear accelerator

Snyder, John Evan; Flynn, R; Hyer, Daniel E.

doi:10.1002/acm2.12160

Cited by 8 publications

(7 citation statements)

References 8 publications

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“…However, these systems are not as widely available as C‐arm linacs where motion mitigation strategies such as gating are applied in clinical practice 15 . Free‐breathing gating, however, imposes frequent beam‐on/off switching, making it potentially more difficult to deliver for dynamic techniques 18,19 . To apply free‐breathing gating for DTRT, several challenges and questions need to be answered: Is the machine capable of applying free‐breathing gating DTRT for realistic motion traces?…”

Section: Introductionmentioning

confidence: 99%

Technical note: Feasibility of gating for dynamic trajectory radiotherapy – Mechanical accuracy and dosimetric performance

et al. 2023

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BackgroundDynamic trajectory radiotherapy (DTRT) extends state‐of‐the‐art volumetric modulated arc therapy (VMAT) by dynamic table and collimator rotations during beam‐on. The effects of intrafraction motion during DTRT delivery are unknown, especially regarding the possible interplay between patient and machine motion with additional dynamic axes.PurposeTo experimentally assess the technical feasibility and quantify the mechanical and dosimetric accuracy of respiratory gating during DTRT delivery.MethodsA DTRT and VMAT plan are created for a clinically motivated lung cancer case and delivered to a dosimetric motion phantom (MP) placed on the table of a TrueBeam system using Developer Mode. The MP reproduces four different 3D motion traces. Gating is triggered using an external marker block, placed on the MP. Mechanical accuracy and delivery time of the VMAT and DTRT deliveries with and without gating are extracted from the logfiles. Dosimetric performance is assessed by means of gamma evaluation (3% global/2 mm, 10% threshold).ResultsThe DTRT and VMAT plans are successfully delivered with and without gating for all motion traces. Mechanical accuracy is similar for all experiments with deviations <0.14° (gantry angle), <0.15° (table angle), <0.09° (collimator angle) and <0.08 mm (MLC leaf positions). For DTRT (VMAT), delivery times are 1.6–2.3 (1.6– 2.5) times longer with than without gating for all motion traces except one, where DTRT (VMAT) delivery is 5.0 (3.6) times longer due to a substantial uncorrected baseline drift affecting only DTRT delivery. Gamma passing rates with (without) gating for DTRT/VMAT were ≥96.7%/98.5% (≤88.3%/84.8%). For one VMAT arc without gating it was 99.6%.ConclusionGating is successfully applied during DTRT delivery on a TrueBeam system for the first time. Mechanical accuracy is similar for VMAT and DTRT deliveries with and without gating. Gating substantially improved dosimetric performance for DTRT and VMAT.

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Section: Introductionmentioning

confidence: 99%

Technical note: Feasibility of gating for dynamic trajectory radiotherapy – Mechanical accuracy and dosimetric performance

et al. 2023

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“…Others in the literature have reported considerably smaller beam-on latencies than those reported in this work using the modular or end-to-end approaches. 5,8 Within the control system of the LINAC, several parameters can be adjusted to alter the temporal characteristics of gated delivery, particularly with regards to beam-on latency. 9,11 It is expected that the beam-on latencies reported in this work could be reduced by altering these parameters.…”

Section: Resultsmentioning

confidence: 99%

“…Several authors have presented methods for measuring gating latencies using the displacement of a radio‐opaque moving target captured using film or the LINACs electronic portal imaging device (EPID). 4 , 5 , 6 , 7 Such methods can be used to measure the end‐to‐end latencies of the gating system but do not allow for analysis of the individual components included in the system. Modern gating systems are typically composed of multiple components, or subsystems, each having their own latency.…”

Section: Introductionmentioning

confidence: 99%

“…End‐to‐end latency refers to the total time delay of the entire gating system. Several authors have presented methods for measuring gating latencies using the displacement of a radio‐opaque moving target captured using film or the LINACs electronic portal imaging device (EPID) 4–7 . Such methods can be used to measure the end‐to‐end latencies of the gating system but do not allow for analysis of the individual components included in the system.…”

Section: Introductionmentioning

confidence: 99%

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Measurement of the temporal latency of a respiratory gating system using two distinct approaches

Stock

Chu

Fontenot

2022

J Applied Clin Med Phys

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Purpose To develop a methodology that can be used to measure the temporal latency of a respiratory gating system. Methods The gating system was composed of an automatic gating interface (Response) and an in‐house respiratory motion monitoring system featuring an optically tracked surface marker. Two approaches were used to measure gating latencies. A modular approach involved measuring separately the latency of the gating system's complementary metal–oxide–semiconductor tracking camera, tracking software, and a gating latency of the LINAC. Additionally, an end‐to‐end approach was used to measure the total latency of the gating system. End‐to‐end latencies were measured using the displacement of a radiographic target moving at known velocities during the gating process. Results Summing together the latencies of each of the modular components investigated yielded a total beam‐on latency of 1.55 s and a total beam‐off latency of 0.49 s. End‐to‐end beam‐on and beam‐off latency was found to be 1.49 and 0.34 s, respectively. In each case, no statistically significant differences were found between the end‐to‐end latency of the gating system and the summation of the individually measured components. Conclusion Two distinct approaches to quantify gating latencies were presented. Measuring the end‐to‐end latency of the gating system provided an independent means of validating the modular approach. It is expected that the beam‐on latencies reported in this work could be reduced by altering the control system configuration of the LINAC. The modular approach can be used to decouple the individual latencies of the gating system, but future improvements in the temporal resolution of the service graphing feature are needed to reduce the uncertainty of LINAC‐related gating latencies measured using this approach. Both approaches are generalizable and can be used together when designing a quality assurance program for a respiratory gating system.

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“…The linear accelerator must be characterized before the application of this complex technique to reduce the beam-on delay, to study the efficiency of the delivery, and to investigate the influence of frequent beam interruptions on the dosimetric accuracy of gated deliveries (17)(18)(19)(20)(21) . This technique is time-consuming, and its benefits must be further validated before its application in a clinical scenario.…”

Section: Discussionmentioning

confidence: 99%

Choosing the optimal gated window for defining target volume in lung stereotactic ablative radiotherapy

Nardone¹,

Sangiovanni

Scala

et al. 2021

Int J Radiat Res

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Background: This study aims to compare retrospectively generated gated internal target volumes (ITVs) and to evaluate whether gated ITVs can reduce planned target volumes (PTVs) compared with standard ITV expansions. Materials and Methods:In this study, we retrospectively generated respiratory-gated ITVs and PTVs for our cohort of patients who underwent four-dimensional computed tomography for thoracic radiotherapy in our department between August 2018 and February 2019. We calculated the standard ITVs and two gated ITVs to analyze the volumetric reduction. Further, we considered a PTV reduction of >10% to be significant, and we analyzed the role of the localization and the size of the gross tumor volumes. Results:We included 38 patients with a median age of 70 years (mean = 68, SD ± 13,4, range =43-89), of whom 18 (47%) were females and 20 (52%) were males. The two gated PTVs (PTV 30%-70% and PTV 80%-20%) were significantly smaller than the standard PTVs (p-value < 0,001 for both PTVs). Considering the volume of the gross target volume (GTV), we found a significant correlation between GTV30cc and ITV30%-70% (chi-square analysis, p:0,006) and between GTV5cc and ITV80%-20% (p:0,003). We also found a correlation between the localization of the target lesion (mediastinal/ central/peripheral lesion) for both the gated ITVs (p: 0,030 for ITV 30%-70% and p:0,018 for ITV 80%-20%). Conclusion: Gated ITV plans could be useful for the sparing of normal tissues. Our results show that this approach could be useful for small lesions and for certain localizations (island tumors).

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Implementation of respiratory‐gated VMAT on a Versa HD linear accelerator

Cited by 8 publications

References 8 publications

Technical note: Feasibility of gating for dynamic trajectory radiotherapy – Mechanical accuracy and dosimetric performance

Technical note: Feasibility of gating for dynamic trajectory radiotherapy – Mechanical accuracy and dosimetric performance

Measurement of the temporal latency of a respiratory gating system using two distinct approaches

Choosing the optimal gated window for defining target volume in lung stereotactic ablative radiotherapy

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