Dose rate response of Digital Megavolt Imager detector for flattening filter‐free beams

Xu, Zhigang; Kim, Jinkoo; Han, James; Hsia, A; Ryu, Samuel

doi:10.1002/acm2.12358

Cited by 9 publications

(9 citation statements)

References 11 publications

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“…Xu et al. found that the gamma passing rate decreased from 99.9% to 91.5% when the dose rate was increased from 400 to 1200 MU/min for 10X FFF beams on a DMI imager . While decreasing the dose rate may improve the PD analysis, it is not recommended since ASTRO guidelines state that “same files to be used for the patient delivery should be used for the QA measurements.”…”

Section: Discussionmentioning

confidence: 99%

Assessing the feasibility of single target radiosurgery quality assurance with portal dosimetry

Covington

Snyder

et al. 2019

J Applied Clin Med Phys

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Purpose To assess the feasibility of using portal dosimetry (PD) for pre‐treatment quality assurance of single target, flattening filter free (FFF), volumetric arc therapy intracranial radiosurgery plans. Methods A PD algorithm was created for a 10X FFF beam on a Varian Edge linear accelerator (Varian Inc, Palo Alto, CA, USA). Treatment plans that were previously evaluated with Gafchromic EBT‐XD (Ashland, Bridgewater, NJ, USA) film were measured via PD and analyzed with the ARIA Portal Dosimetry workspace. Absolute dose evaluation for film and PD was done by computing the mean dose in the region receiving greater than or equal to 90% of the max dose and comparing to the mean dose in the same region calculated by the treatment planning system (TPS). Gamma analysis with 10% threshold and 3%/2 mm passing criteria was performed on film and portal images. Results Thirty‐six PD verification plans were delivered and analyzed. The average PD to TPS dose was 0.989 ± 0.01 while film to TPS dose was 1.026 ± 0.01. All PD plans passed the gamma analysis with 100% of points having gamma <1. Overall, PD to TPS dose agreement was found to be target size dependent. As target size decreases, PD to TPS dose ratio decreased from 1.004 for targets with diameters between 15–31 mm and 0.978 for targets with diameters less than 15 mm. Conclusion The agreement of PD to TPS mean dose in the high dose region was found to be dependent on target size. Film measurements did not exhibit size dependence. All PD plans passed the 3%/2 mm gamma analysis, but caution should be used when using PD to assess overall dosimetric accuracy of the treatment plan for small targets.

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Section: Discussionmentioning

confidence: 99%

Assessing the feasibility of single target radiosurgery quality assurance with portal dosimetry

Covington

Snyder

et al. 2019

J Applied Clin Med Phys

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“…33 Xu et al found that the detector panel has a saturation in case of high dose-rate beams, but it was clinically insignificant even at the maximum dose rate of 2400 MU/min. 34 Pardo et al and Miri et al investigated FFF beam dosimetry plans and found no clinically relevant deviations, but in these studies plans were not included using beams over ca. 1000 MU.…”

Section: Discussionmentioning

confidence: 99%

“…found that the detector panel has a saturation in case of high dose-rate beams, but it was clinically insignificant even at the maximum dose rate of 2400 MU/min. 34 Pardo et al . and Miri et al .…”

Section: Discussionmentioning

confidence: 99%

Verification of an optimizer algorithm by the beam delivery evaluation of intensity-modulated arc therapy plans

Pócza

Szegedi

Major

et al. 2021

Radiology and Oncology

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Background In the case of dynamic radiotherapy plans, the fractionation schemes can have dosimetric effects. Our goal was to define the effect of the fraction dose on the plan quality and the beam delivery. Materials and methods Treatment plans were created for 5 early-stage lung cancer patients with different dose schedules. The planned total dose was 60 Gy, fraction dose was 2 Gy, 3 Gy, 5 Gy, 12 Gy and 20 Gy. Additionally renormalized plans were created by changing the prescribed fraction dose after optimization. The dosimetric parameters and the beam delivery parameters were collected to define the plan quality and the complexity of the treatment plans. The accuracy of dose delivery was verified with dose measurements using electronic portal imaging device (EPID). Results The plan quality was independent from the used fractionation scheme. The fraction dose could be changed safely after the optimization, the delivery accuracy of the treatment plans with changed prescribed dose was not lower. According to EPID based measurements, the high fraction dose and dose rate caused the saturation of the detector, which lowered the gamma passing rate. The aperture complexity score, the gantry speed and the dose rate changes were not predicting factors for the gamma passing rate values. Conclusions The plan quality and the delivery accuracy are independent from the fraction dose, moreover the fraction dose can be changed safely after the dose optimization. The saturation effect of the EPID has to be considered when the action limits of the quality assurance system are defined.

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“…Xu et al investigated the dose rate response characteristics of the Digital Megavolt Imager (DMI) detector for flattening filterfree (FFF) beams (19) . They measured as a function of dose rate on a Varian TrueBeam machine.…”

Section: Gul and Inanmentioning

confidence: 99%

The impacts of dose rate in sliding window intensity modulated radiation therapy quality assurance

Gül

İNAN

2021

Int J Radiat Res

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Background:The present study aims to compare the impacts of dose rate in intensity-modulated radiation therapy (IMRT) plan delivery by using the gamma agreement between the calculated and measured doses by pretreatment quality assurance (QA). Materials and Methods: Ten nasopharynx cancer patients who underwent IMRT treatment were included in this study. The treatment plans were performed using Varian DHX eclipse treatment planning system (TPS) version 15.1. and the QA plans were generated for the dose rates of 300, 400, 500 and 600 MU/min. All measurements were performed by aS1000 Electronic Portal Imaging Device (Epid) integrated into Varian DHX linear accelerator and 2D array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (2%/2 mm and 3%/3 mm) for dose agreement and distance to agreement parameters. Statistical analyses were evaluated by using Mann-Whitney Test and a p-value of p <0.05 was considered to be significant. Results: There was a significant decrease in the percentage gamma pass rate when the dose rate was increased from 300 MU/min to 600 MU/min (p<0.05). There was a significant difference between Epid and Epiqa for all dose rates (p<0.05). The total number of MU was correlated to the dose rate. When comparing MU from 300 MU/min to 600 MU/min dose rate, it was observed that the MU of IMRT plans increaed as the dose rate was increased. Conclusion: In this study, we have demonstrated that IMRT delivery using sliding window method is affected by the dose rate.

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Dose rate response of Digital Megavolt Imager detector for flattening filter‐free beams

Cited by 9 publications

References 11 publications

Assessing the feasibility of single target radiosurgery quality assurance with portal dosimetry

Assessing the feasibility of single target radiosurgery quality assurance with portal dosimetry

Verification of an optimizer algorithm by the beam delivery evaluation of intensity-modulated arc therapy plans

The impacts of dose rate in sliding window intensity modulated radiation therapy quality assurance

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