Small field output factors: Comparison of measurements with various detectors and effects of detector orientation with primary jaw setting

Godson, Henry Finlay; Ravikumar, M; Ganesh, K M; Sathiyan, S; Ponmalar, Y Retna

doi:10.1016/j.radmeas.2015.12.038

Cited by 12 publications

(21 citation statements)

References 53 publications

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“…The uncorrected output factor values measured in this work agree with previous work by Godson 12 who used the IBA EFD, IBA PFD, and PTW 60018 SRS diodes and Pinpoint PTW 31014 ionization chamber. Cone diameters ranging between 10 and 40 mm (in 5 mm increments) and field sizes between 1 cm × 1 cm and 10 cm × 10 cm (in 1 cm × 1 cm increments) were examined, at the same SSD and depth as this investigation.…”

Section: D | Ptw 60019 Microdiamond Intracomparison In the Stereotasupporting

confidence: 89%

“…Cone diameters ranging between 10 and 40 mm (in 5 mm increments) and field sizes between 1 cm × 1 cm and 10 cm × 10 cm (in 1 cm × 1 cm increments) were examined, at the same SSD and depth as this investigation. Overall Godson reported reasonable consistency in uncorrected output factors (for all detectors) when using field sizes ≥2 cm × 2 cm. Whilst no correction factors were applied to the results, it was reported for smaller cone and field sizes that the IBA PFD diode over‐estimated the output factors, as occurred in this study.…”

Section: Discussionmentioning

confidence: 75%

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Evaluation of the IAEA‐TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors

Smith

Montesari

Oliver³

et al. 2019

J Applied Clin Med Phys

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The IAEA TRS 483 protocol1 for the dosimetry of small static fields in radiotherapy was used to calculate output factors for the Elekta Synergy linac at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Small field output factors for both square and circular fields were measured using nine different detectors. The “corrected” output factors (ratio of detector readings multiplied by the appropriate correction factor from the protocol) showed better consistency compared to the “uncorrected” output factors (ratio of detector readings only), with the relative standard deviation decreasing by approximately 1% after the application of the relevant correction factors. Comparisons relative to an arbitrarily chosen PTW 60019 microDiamond detector showed a reduction of maximal variation for the corrected values of approximately 3%. A full uncertainty budget was prepared to analyze the consistency of the output factors. Agreement within uncertainties between all detectors and field sizes was found, except for the 15 mm circular field. The results of this study show that the application of IAEA TRS 4831 when measuring small fields will improve the consistency of small field measurements when using multiple detectors contained within the protocol.

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Section: D | Ptw 60019 Microdiamond Intracomparison In the Stereotasupporting

confidence: 89%

Section: Discussionmentioning

confidence: 75%

Evaluation of the IAEA‐TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors

Smith

Montesari

Oliver³

et al. 2019

J Applied Clin Med Phys

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show abstract

“…The reasons for recommending perpendicular orientation for the determination of field output factors in small fields is that there was a lack of high quality data in the published literature for output correction factors determined in parallel orientation for various combinations of chambers and beam energies obtained from different linear accelerators. 4 Indeed, while the determination of output correction factors for ionization chambers in the perpendicular orientation has been extensively investigated by a number of research groups and for a range of ionization chambers, only a few studies have reported results for k f clin ;f ref Q clin ;Q ref for a few small volume ionization chambers [14][15][16]18,19,31 in small fields determined in parallel or for both orientations.…”

Section: Introductionmentioning

confidence: 99%

“…1.080 (15) 1.051 141.01 1.054 (13) 1.020 (12) 1.057 (13) 1.076 (13) 1.035 (12) 1.047 (13) 1.040 (12) 1.50 1.012 (11) 1.003 (11) 1.020 (11) 1.016 (11) 1.010 (11) 1.010 (11) 1.018 (11) 2.00 1.000 (11) 0.995 (11) 1.003 (12) 1.002 (12) 0.999 (11) 1.000 (11) 1.011 (12) 3.03 1.001 (11) 1.001 (11) 1.001 (11) 0.999 (11) 0.999 (11) 0.998 (11) 1.012 (11) 4.03 1.000 (11) 1.002 (11) 1.001 (11) 0.998 (11) 1.000 (11) 0.997 (11) 1.010 (11) 5.02 0.997 (10) 0.999 (10) 0.998 (10) 0.996 (10) 0.998 (10) 0.995 (10) 1.005 (10) 151.49 1.004 (14) 0.999 141.012 141.008 141.000 141.003 141.022 141.99 0.999 (14) 0.996 141.003…”

mentioning

confidence: 99%

Output correction factors for small static fields in megavoltage photon beams for seven ionization chambers in two orientations — perpendicular and parallel

et al. 2019

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The goal of the present work was to provide a large set of detector-specific output correction factors for seven small volume ionization chambers on two linear accelerators in four megavoltage photon beams utilizing perpendicular and parallel orientation of ionization chambers in the beam for nominal field sizes ranging from 0.5 cm 2 9 0.5 cm 2 to 10 cm 2 9 10 cm 2. The present study is the second part of an extensive research conducted by our group. Methods: Output correction factors k f clin ;f ref Q clin ;Q ref were experimentally determined on two linacs, Elekta Versa HD and Varian TrueBeam for 6 and 10 MV beams with and without flattening filter for nine square fields ranging from 0.5 cm 2 9 0.5 cm 2 to 10 cm 2 9 10 cm 2 , for seven mini and micro ionization chambers, IBA CC04, IBA Razor, PTW 31016 3D PinPoint, PTW 31021 3D Semiflex, PTW 31022 3D PinPoint, PTW 31023 PinPoint, and SI Exradin A16. An Exradin W1 plastic scintillator and EBT3 radiochromic films were used as the reference detectors. Results: For all ionization chambers, values of output correction factors k f clin ;f ref Q clin ;Q ref were lower for parallel orientation compared to those obtained in the perpendicular orientation. Five ionization chambers from our study set, IBA Razor, PTW 31016 3D PinPoint, PTW 31022 3D PinPoint, PTW 31023 PinPoint, and SI Exradin A16, fulfill the requirement recommended in the TRS-483 Code of Practice, that is, 0:95\k

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“…This is done with the help of collimating system available on medical electron linear accelerators (linacs), which includes secondary jaws, multi-leaf collimators (MLCs), tertiary collimators, etc. [1]. The small photon beams differ from traditionally used radiation fields (4 cm Â 4cmupto40cmÂ 40 cm) in terms of their size.…”

Section: Introductionmentioning

confidence: 99%

Prospective Monte Carlo Simulation for Choosing High Efficient Detectors for Small-Field Dosimetry

Donya¹,

Seniwal²,

Darwesh³

et al. 2019

Theory, Application, and Implementation of Monte Carlo Method in Science and Technology

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In this chapter, a detailed study on physics and methodology of small field dosimetry are reported. It introduces talking about how small radiation fields came into existence and the importance of accurate small-field dosimetry. In addition, it discusses small and long cavity theories for evaluating accurate dose response. It sheds the spot on pencil beam algorithms for evaluating dose response and uses Monte Carlo (MC) simulation in categorizing primary and scattering components of the radiotherapeutic photon beam. Moreover, it summarizes all commercial dosimeters used in small-field dosimetry. It gives good knowledge about detectors and equipment like ionization chambers for reference dosimetry in small and nonreference fields and different types of solid-state detector. The importance and applications of Monte Carlo techniques in small-field dosimetry and radiotherapeutic treatment methods based on small field are reported. For this purpose, different commonly used Monte Carlo codes are handled like Electron Gamma Shower (EGSnrc), Geant4, PENELOPE, and Monte Carlo N-Particle (MCNP). A review on the recent studies of using Monte Carlo simulation particularly on the small-field dosimetric studies is also reported. This chapter also discusses the recommendations of the code of practices (COPs) for dosimetry of small radiation fields. It mentions all recommendations provided by TRS-483 for accurate beam data collection and accurate dosimetric measurements. It gives good knowledge to the user for selecting a suitable dosimeter in small-field dosimetry through investigation of different practical methods and Monte Carlo simulations.

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Small field output factors: Comparison of measurements with various detectors and effects of detector orientation with primary jaw setting

Cited by 12 publications

References 53 publications

Evaluation of the IAEA‐TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors

Evaluation of the IAEA‐TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors

Output correction factors for small static fields in megavoltage photon beams for seven ionization chambers in two orientations — perpendicular and parallel

Prospective Monte Carlo Simulation for Choosing High Efficient Detectors for Small-Field Dosimetry

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