Evaluation of dosimetric parameters of small fields of 6 MV flattening filter free photon beam measured using various detectors against Monte Carlo simulation – CORRIGENDUM

Mamballikalam, Gopinath; Senthilkumar, S.; Jayadevan, P. M.; bos, R. C. Jaon; Basith, P. M. Ahamed; Inippully, Rohit; Shine, N. S.; Clinto, C O

doi:10.1017/s1460396920000321

Cited by 3 publications

(1 citation statement)

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“…In MLC based Intensity Modulated Radiotherapy (IMRT) required fluence distribution can be achieved by modulating the un-flattened non-uniform fluence distribution directly [11]. The fluence of photons that comes out of an unflattened beam is dosimetrically different from a flattened beam [12,13]. Beam hardening does not occur since there is no flattening filter, and the fluence of photons contains a larger number of low energy photons (< 1 MeV).…”

Section: Introductionmentioning

confidence: 99%

Time motion study to evaluate the impact of flattening filter free beam on overall treatment time for frameless intracranial radiosurgery using Varian TrueBeam® linear accelerator

Mamballikalam

Senthilkumar

Clinto

et al. 2021

Rep Pract Oncol Radiother.

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background:The aim was to study the impact of the flattening filter free (FFF) beam on overall treatment time for frameless intracranial radiosurgery using TrueBeam® LINac.The development of frameless stereotactic radiosurgery (srs) is possible due to the incorporation of image guidance in the delivery of treatment. It is important to analyze the cost and benefits of FFF beams for treating srs by understanding the impact of FFF beams in reducing the treatment time.Materials and methods: Dynamic conformal arc (Dca) and volumetric arc therapy (VMaT) plans were generated using 6 MV with a flattening filter (FF) and FFF beams. Overall treatment time was divided into beam on time (BOT) and beam off time (BFT). percentage beam on time reduction (pBOTr) and percentage total time reduction (pTTr) factors were defined for the comparison. results: BOT reduction was observed to be significant for higher dose per fraction but subjected to the treatment technique and modulation differences. pBOTr values are much higher than pTTr values. The 39.9% of pBOTr resulted in only 8% pTTr for Dca and 65.3% resulted in 15.9% pTTr for VMaT. conclusion: Major BFT was utilized for imaging and verification. FFF beam significantly reduced the beam on time and was found to be most effective if the fractional dose was as high as that for srs. Newly defined pBOTr and pTTr factors are very useful indicators to evaluate the efficacy of FFF beams in terms of time reduction.

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Section: Introductionmentioning

confidence: 99%

Time motion study to evaluate the impact of flattening filter free beam on overall treatment time for frameless intracranial radiosurgery using Varian TrueBeam® linear accelerator

Mamballikalam

Senthilkumar

Clinto

et al. 2021

Rep Pract Oncol Radiother.

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Monte Carlo simulation of linac using PRIMO

Sun

Liang

et al. 2022

Radiat Oncol

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Background Monte Carlo simulation is considered as the most accurate method for dose calculation in radiotherapy. PRIMO is a Monte-Carlo program with a user-friendly graphical interface. Material and method A VitalBeam with 6MV and 6MV flattening filter free (FFF), equipped with the 120 Millennium multileaf collimator was simulated by PRIMO. We adjusted initial energy, energy full width at half maximum (FWHM), focal spot FWHM, and beam divergence to match the measurements. The water tank and ion-chamber were used in the measurement. Percentage depth dose (PDD) and off axis ratio (OAR) were evaluated with gamma passing rates (GPRs) implemented in PRIMO. PDDs were matched at different widths of standard square fields. OARs were matched at five depths. Transmission factor and dose leaf gap (DLG) were simulated. DLG was measured by electronic portal imaging device using a sweeping gap method. Result For the criterion of 2%/2 mm, 1%/2 mm and 1%/1 mm, the GPRs of 6MV PDD were 99.33–100%, 99–100%, and 99–100%, respectively; the GPRs of 6MV FFF PDD were 99.33–100%, 98.99–99.66%, and 97.64–98.99%, respectively; the GPRs of 6MV OAR were 96.4–100%, 90.99–100%, and 85.12–98.62%, respectively; the GPRs of 6MV FFF OAR were 95.15–100%, 89.32–100%, and 87.02–99.74%, respectively. The calculated DLG matched well with the measurement (6MV: 1.36 mm vs. 1.41 mm; 6MV FFF: 1.07 mm vs. 1.03 mm, simulation vs measurement). The transmission factors were similar (6MV: 1.25% vs. 1.32%; 6MV FFF: 0.8% vs. 1.12%, simulation vs measurement). Conclusion The calculated PDD, OAR, DLG and transmission factor were all in good agreement with measurements. PRIMO is an independent (with respect to analytical dose calculation algorithm) and accurate Monte Carlo tool.

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Point dose verification of Cranial Stereotactic Radiosurgery using micro Ionization Chamber and EBT3 film for 6MV FF and FFF beams in Varian TrueBeam^® LINAC

Mamballikalam

Senthilkumar

Ahamed

et al. 2020

Polish Journal of Medical Physics and Engineering

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Introduction: Achieving high positional and dosimetric accuracy in small fields is very challenging due to the imbalance of charged particle equilibrium (CPE), occlusion of the primary radiation source, and overlapping penumbra regions. These factors make the choice of the detector for Stereotactic Radiosurgery (SRS) patient-specific quality assurance (PSQA) difficult. The aim of the study is to compare the suitability of EBT3 Gafchromic film against CC01 pinpoint chamber for the purpose of SRS and stereotactic Radiotherapy (SRT) dose verification.Material and Method: EBT3 Gafchromic film was calibrated against Treatment Planning System (TPS) doses (1 Gy – 35 Gy). CC01 pinpoint chamber and EBT3 film was used to verify Patient-Specific point doses of 21 intracranial lesions each planned with Static, Dynamic Conformal Arc (DCA), and Volumetric Arc Therapy (VMAT) using Varian TrueBeam Accelerator 6MV Flattening Filter (FF) and 6MV Flattening Filter Free (FFF) beams. The lesion sizes varied from 0.4 cc to 2.9 cc. The lesions were categorized into <1cc, 1cc-2cc and 2cc-3cc.Results: High variations in measured doses from TPS calculated dose were observed with small lesion volumes irrespective of the dosimeter. As the sizes decreased high uncertainty was observed in ion chamber results. CC01 was observed under-responding to film in small lesion sizes (<1cc), where nearly 50% of results under-responded in comparison with Film results. Film results were more or less consistent for static and DCA plans. Static and DCA plans were consistent passing more than 73% of the plans of the smallest lesion size category. VMAT showed very poor PSQA agreement for all three volumes (32.1% for <1cc, 14.3% for 2cc-3cc and 39.3% for 2cc-3cc). No significant difference was observed between 6MVFF and 6MVFFF beams from the chi-squared test.Conclusion: EBT3 Film was observed to be a more suitable detector for small lesion sizes less than 1cc, compared to CC01. As the volume increases, the response of CC01 and EBT3 film have no significant difference in performing PSQA for intracranial SRS/SRT. VMAT techniques for intra cranial SRS shows deviation from TPS planned dose for both EBT3 film and CC01 and should not be preferred choice of verification tools.

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Evaluation of dosimetric parameters of small fields of 6 MV flattening filter free photon beam measured using various detectors against Monte Carlo simulation – CORRIGENDUM

Cited by 3 publications

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Time motion study to evaluate the impact of flattening filter free beam on overall treatment time for frameless intracranial radiosurgery using Varian TrueBeam® linear accelerator

Time motion study to evaluate the impact of flattening filter free beam on overall treatment time for frameless intracranial radiosurgery using Varian TrueBeam® linear accelerator

Monte Carlo simulation of linac using PRIMO

Point dose verification of Cranial Stereotactic Radiosurgery using micro Ionization Chamber and EBT3 film for 6MV FF and FFF beams in Varian TrueBeam^® LINAC

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Evaluation of dosimetric parameters of small fields of 6 MV flattening filter free photon beam measured using various detectors against Monte Carlo simulation – CORRIGENDUM

Cited by 3 publications

References 0 publications

Time motion study to evaluate the impact of flattening filter free beam on overall treatment time for frameless intracranial radiosurgery using Varian TrueBeam® linear accelerator

Time motion study to evaluate the impact of flattening filter free beam on overall treatment time for frameless intracranial radiosurgery using Varian TrueBeam® linear accelerator

Monte Carlo simulation of linac using PRIMO

Point dose verification of Cranial Stereotactic Radiosurgery using micro Ionization Chamber and EBT3 film for 6MV FF and FFF beams in Varian TrueBeam® LINAC

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Product

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Point dose verification of Cranial Stereotactic Radiosurgery using micro Ionization Chamber and EBT3 film for 6MV FF and FFF beams in Varian TrueBeam^® LINAC