The effect of beam interruption during VMAT delivery on the delivered dose distribution

Heo, Taemin; Ye, Sung Joon; Carlson, Joel; Park, Jong Min

doi:10.1016/j.ejmp.2015.01.014

Cited by 5 publications

(6 citation statements)

References 14 publications

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“…The main characteristic of this metric is that it can condense a verification measurement into a single value; this is both the advantage and pitfall of this metric. If implemented carefully, it can be used to streamline QA by making it possible to choose decision thresholds for a passing rate, thereby reducing the analysis time [26][27][28][29][30]. The disadvantage is that the passing rate does not provide any details of where failed points are.…”

Section: Further Considerations Of the Gamma Index Computationmentioning

confidence: 99%

Challenges in calculation of the gamma index in radiotherapy – Towards good practice

2017

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Section: Further Considerations Of the Gamma Index Computationmentioning

confidence: 99%

Challenges in calculation of the gamma index in radiotherapy – Towards good practice

2017

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“…Volumetric modulated arc therapy (VMAT) delivers prescription doses to target volumes while minimizing the dose to normal tissue by modulating photon beams through modulations of multi-leaf collimator (MLC) positions, gantry rotation speed and dose-rate simultaneously (Brahme 1988, Otto 2008. Recently, VMAT has been widely adopted in the clinic due to its ability to rapidly deliver dose distributions which are equal to or better than those of intensity modulated radiation therapy (IMRT) (Park et al 2012, 2014a, 2014c, Kim et al 2014, Mattes et al 2014, Heo et al 2015. For VMAT, the mechanical uncertainty of MLC movements, gantry rotations and beam control systems as well as inaccurate dose calculations of small or irregular fields result in discrepancies between planned dose distributions as intended to be delivered to the patient, and the actual delivery to the patient (Ezzell et al 2003, Fredh et al 2013, Heilemann et al 2013, Kim et al 2014, Heo et al 2015, Park et al 2015a.…”

Section: Introductionmentioning

confidence: 99%

Modulation index for VMAT considering both mechanical and dose calculation uncertainties

Park

Kim

2015

Phys. Med. Biol.

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The aim of this study is to present a modulation index considering both mechanical and dose calculation uncertainties for volumetric modulated arc therapy (VMAT). As a modulation index considering only mechanical uncertainty of VMAT, MIt has been previously suggested. In this study, we developed a weighting factor which represents dose calculation uncertainty based on the aperture shapes of fluence maps at every control point of VMAT plans. In order to calculate the weighting factor, the thinning algorithm of image processing techniques was applied to measure field aperture irregularity. By combining this weighting factor with the previously suggested modulation index, MIt, comprehensive modulation index (MIc) was designed. To evaluate the performance of MIc, gamma passing rates, differences in mechanical parameters between plans and log files and differences in dose-volume parameters between plans and the plans reconstructed from log files were acquired with a total of 52 VMAT plans. Spearman's correlation coefficients (rs) between the values of MIc and measures of VMAT delivery accuracy were calculated. The rs values of MIc (f = 0.5) to global gamma passing rates with 2%/2 mm, 1%/2 mm and 2%/1 mm were -0.728,-0.847 and -0.617, respectively (p< 0.001). Those to local gamma passing rates were -0.765,-0.767 and -0.748, respectively (p < 0.001). The rs values of MIc (f = 0.5) to multi-leaf collimator and gantry angle errors were 0.800 and -0.712, respectively (p < 0.001). The MIc (f = 0.5) showed a total of 20 rs values (p < 0.05) to the differences in dose-volumetric parameters from a total of 35 tested cases. The MIc (f = 0.5) demonstrated considerable power to predict VMAT delivery accuracy showing strong correlations to various measures of VMAT delivery accuracy.

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“…Oh et al . and Heo et al . demonstrated that a small number of beam interruptions were clinically acceptable in VMAT delivery and show only minimal changes in gamma passing rate, dose volume parameters, and log file analysis.…”

Section: Discussionmentioning

confidence: 99%

“…suggested that the curative dose could increase by 20% or more compared with the planned dose if the interruption time extended to 30 min or longer in carbon‐ion radiotherapy, and it should be considered if a longer dose‐delivery procedure time was anticipated. Beam interruption is known to be caused by the gating parameters and by sudden movements of the patient, such as a cough . An insufficient correlation between the external surrogate marker and the internal tumor motion can be another reason for an interruption.…”

Section: Discussionmentioning

confidence: 99%

Comparing phase‐ and amplitude‐gated volumetric modulated arc therapy for stereotactic body radiation therapy using 3D printed lung phantom

Lee

Yoon

Cho

et al. 2019

J Applied Clin Med Phys

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PurposeTo compare the dosimetric impact and treatment delivery efficacy of phase‐gated volumetric modulated arc therapy (VMAT) vs amplitude‐gated VMAT for stereotactic body radiation therapy (SBRT) for lung cancer by using realistic three‐dimensional‐printed phantoms.MethodsFour patient‐specific moving lung phantoms that closely simulate the heterogeneity of lung tissue and breathing patterns were fabricated with four planning computed tomography (CT) images for lung SBRT cases. The phantoms were designed to be bisected for the measurement of two‐dimensional dose distributions by using EBT3 dosimetry film. The dosimetric accuracy of treatment under respiratory motion was analyzed with the gamma index (2%/1 mm) between the plan dose and film dose measured under phase‐ and amplitude‐gated VMAT. For the validation of the direct usage of the real‐time position management (RPM) data for respiratory motion, the relationship between the RPM signal and the diaphragm position was measured by four‐dimensional CT. By using data recorded during the beam delivery of both phase‐ and amplitude‐gated VMAT, the total time intervals were compared for each treatment mode.ResultsFilm dosimetry showed a 5.2 ± 4.2% difference of gamma passing rate (2%/1 mm) on average between the phase‐ vs amplitude‐gated VMAT [77.7% (72.7%–85.9%) for the phase mode and 82.9% (81.4%–86.2%) for the amplitude mode]. For delivery efficiency, frequent interruptions were observed during the phase‐gated VMAT, which stopped the beam delivery and required a certain amount of time before resuming the beam. This abnormality in phase‐gated VMAT caused a prolonged treatment delivery time of 366 s compared with 183 s for amplitude‐gated VMAT.ConclusionsConsidering the dosimetric accuracy and delivery efficacy between the gating methods, amplitude mode is superior to phase mode for gated VMAT treatment.

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The effect of beam interruption during VMAT delivery on the delivered dose distribution

Cited by 5 publications

References 14 publications

Challenges in calculation of the gamma index in radiotherapy – Towards good practice

Challenges in calculation of the gamma index in radiotherapy – Towards good practice

Modulation index for VMAT considering both mechanical and dose calculation uncertainties

Comparing phase‐ and amplitude‐gated volumetric modulated arc therapy for stereotactic body radiation therapy using 3D printed lung phantom

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