Effects of 10 MV and Flattening-Filter-Free Beams on Peripheral Dose in a Cohort of Pediatric Patients

Bouchta, Youssef Ben; Goddard, Karen; Petric, Martin; Bergman, Alanah

doi:10.1016/j.ijrobp.2018.07.2002

Cited by 5 publications

(4 citation statements)

References 28 publications

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“…41 As monitor unit (MU) in the use of IMRT or VMAT is usually higher than that in conventional RT, effect of neutron dose in IMRT and VMAT has been studied and reported. [42][43][44][45] Peripheral dose of thermal neutron in VMAT with 10 MV was less than 100 micro-Gray of kerma equivalent. 45 All the mean energies of the photon simulated in this study were less than 10 MeV and only 0.08% for 10 MV was over 10 MeV, we did not consider effect of the neutron dose in film measurement.…”

Section: Discussionmentioning

confidence: 97%

Feasibility of a GATE Monte Carlo platform in a clinical pretreatment QA system for VMAT treatment plans using TrueBeam with an HD120 multileaf collimator

Lee

Jeong

Chung

et al. 2019

J Applied Clin Med Phys

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PurposeTo evaluate the quality of patient‐specific complicated treatment plans, including commercialized treatment planning systems (TPS) and commissioned beam data, we developed a process of quality assurance (QA) using a Monte Carlo (MC) platform. Specifically, we constructed an interface system that automatically converts treatment plan and dose matrix data in digital imaging and communications in medicine to an MC dose‐calculation engine. The clinical feasibility of the system was evaluated.Materials and MethodsA dose‐calculation engine based on GATE v8.1 was embedded in our QA system and in a parallel computing system to significantly reduce the computation time. The QA system automatically converts parameters in volumetric‐modulated arc therapy (VMAT) plans to files for dose calculation using GATE. The system then calculates dose maps. Energies of 6 MV, 10 MV, 6 MV flattening filter free (FFF), and 10 MV FFF from a TrueBeam with HD120 were modeled and commissioned. To evaluate the beam models, percentage depth dose (PDD) values, MC calculation profiles, and measured beam data were compared at various depths (Dmax, 5 cm, 10 cm, and 20 cm), field sizes, and energies. To evaluate the feasibility of the QA system for clinical use, doses measured for clinical VMAT plans using films were compared to dose maps calculated using our MC‐based QA system.ResultsA LINAC QA system was analyzed by PDD and profile according to the secondary collimator and multileaf collimator (MLC). Values for MC calculations and TPS beam data obtained using CC13 ion chamber (IBA Dosimetry, Germany) were consistent within 1.0%. Clinical validation using a gamma index was performed for VMAT treatment plans using a solid water phantom and arbitrary patient data. The gamma evaluation results (with criteria of 3%/3 mm) were 98.1%, 99.1%, 99.2%, and 97.1% for energies of 6 MV, 10 MV, 6 MV FFF, and 10 MV FFF, respectively.ConclusionsWe constructed an MC‐based QA system for evaluating patient treatment plans and evaluated its feasibility in clinical practice. We observed robust agreement between dose calculations from our QA system and measurements for VMAT plans. Our QA system could be useful in other clinical settings, such as small‐field SRS procedures or analyses of secondary cancer risk, for which dose calculations using TPS are difficult to verify.

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Section: Discussionmentioning

confidence: 97%

Feasibility of a GATE Monte Carlo platform in a clinical pretreatment QA system for VMAT treatment plans using TrueBeam with an HD120 multileaf collimator

Lee

Jeong

Chung

et al. 2019

J Applied Clin Med Phys

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“…The mean testicular dose from para-aortic irradiation alone was measured as 0.65 ± 0.35 cGy with shielding and 1.86 ± 0.86 cGy without shielding [ 7 ]. Unfortunately, lead is not an effective shield against secondary neutrons; however, neutrons can be avoided through use of beam energies 10 MV and lower [ 59 ].…”

Section: Strategies For Reducing Out-of-field Dosementioning

confidence: 99%

Preservation of male fertility in patients undergoing pelvic irradiation

Ramirez-Fort,

Kardoust-Parizi,

Flannigan

et al. 2024

Rep Pract Oncol Radiother.

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As the number of cancer survivors increases, so does the demand for preserving male fertility after radiation. It is important for healthcare providers to understand the pathophysiology of radiation-induced testicular injury, the techniques of fertility preservation both before and during radiation, and their role in counseling patients on the risks to their fertility and the means of mitigating these risks. Impaired spermatogenesis is a known testicular toxicity of radiation in both the acute and the late settings, as rapidly dividing spermatogonial germ cells are exquisitely sensitive to irradiation. The threshold for spermatogonial injury and subsequent impairment in spermatogenesis is ~ 0.1 Gy and the severity of gonadal injury is highly dose-dependent. Total doses < 4 Gy may allow for recovery of spermatogenesis and fertility potential, but with larger doses, recovery may be protracted or impossible. All patients undergoing gonadotoxic radiation therapy should be counseled on the possibility of future infertility, offered the opportunity for semen cryopreservation, and offered referral to a fertility specialist. In addition to this, every effort should be made to shield the testes (if not expected to contain tumor) during therapy.

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“…The flattening-filter-free 10 MV beam model (10 FFF) is generally used to reduce the delivery time, and it can achieve better target coverage and less peripheral dose. 7,8 However, the 10 FFF SBRT with more monitor units (MU) and higher beam rate can bring a risk of more induced activity.…”

Section: Introductionmentioning

confidence: 99%

“…Compared with the conventional fractionation, SBRT is characterized by higher fractional dose, fewer fractions, and longer delivery time. The flattening‐filter‐free 10 MV beam model (10 FFF) is generally used to reduce the delivery time, and it can achieve better target coverage and less peripheral dose 7,8 . However, the 10 FFF SBRT with more monitor units (MU) and higher beam rate can bring a risk of more induced activity.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

et al. 2021

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The induced radioactivity in stereotactic body radiation therapy with a flattening-filter-free 10 MV beam model (10 FFF SBRT) was investigated for the risk to therapists. Methods: This study was performed on a Varian TrueBeam linac. The induced radioisotopes were identified by γ spectroscopy. The dose rate from the induced activity was measured for 12 treatment cycles in 4 h continuously. The impacts of the characteristic factors of 10 FFF SBRT on the dose rate were investigated, including monitor units (MU), beam rate, field size, and flattening filter. The dose rate was compared between the SBRT plans and conventional fractionation plans. A mathematical model was used to analyze the results and estimate the annual dose to therapists. Results: (a) The induced radioisotopes included 24 Na, 28 Al, 38 Cl, 56 Mn, 66 Cu, 187 W, and 196 Au. (b) In 4 h, the total dose contribution ratios were more than 70% for 28 Al, about 20% for 56 Mn, and 10% for all other long-lived radioisotopes, combining doses at the isocenter and end of the treatment couch. (c) The dose rate showed a nonlinear growth with increasing MU and beam rate. The variation of the dose rate was complicated with the jaw field and not sensitive to the MLC field. The removal of the flattening filter reduced the dose rate by about 40%. The dose level of SBRT was two to three times that of conventional fractionation. (d) The estimated annual dose to therapists was up to 0.20 mSv/y. Conclusions: The induced radioactivity in 10 FFF SBRT was higher compared with that in 10 MV conventional fractionation. More MU and higher beam rate were the primary factors that caused the increase. The therapists should wait longer after beam-off to reduce the occupational dose. In addition, aluminum and manganese should be less used in the treatment room.

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Effects of 10 MV and Flattening-Filter-Free Beams on Peripheral Dose in a Cohort of Pediatric Patients

Cited by 5 publications

References 28 publications

Feasibility of a GATE Monte Carlo platform in a clinical pretreatment QA system for VMAT treatment plans using TrueBeam with an HD120 multileaf collimator

Feasibility of a GATE Monte Carlo platform in a clinical pretreatment QA system for VMAT treatment plans using TrueBeam with an HD120 multileaf collimator

Preservation of male fertility in patients undergoing pelvic irradiation

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

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