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

Casar, Božidar; Gershkevitsh, E.; Méndez, Ignasi; Jurković, Slaven; Huq, M. Saiful

doi:10.1002/mp.13894

Cited by 22 publications

(22 citation statements)

References 38 publications

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“…42 determined CFs exhibit a difference of up to 4% for 0.5 × 0.5 cm 2 field, although for 10 MV beam this difference decreases to approximately 2.5 %. For PTW31023, the difference in CF measured in this study and that of Casar et al 24 is <1.5% for fields smaller than 1 × 1 cm 2 for both energies. Whereas a substantial deviation has been observed for smaller fields.…”

Section: Discussioncontrasting

confidence: 69%

“…However, It has been characterized for reference and relative dosimetry in the conventional fields by Bushing et al and Bruggmoser et al 22,23 Recently, it has also been studied by Casar et al for determination of CFs in radial and axial orientations. 24 However, the response has not been corrected for polarity and recombination effects as recommended by TRS483. Similarly, RNC, the smallest commercially available IC, has been characterized for different dosimetric parameters specially the polarity and stem effects.…”

Section: Introductionmentioning

confidence: 99%

“…[28][29][30] Casar et al has also determined the CFs for this detector in radial and axial directions without correcting its response for polarity effect. 24 However, before deploying these detectors for small field relative dosimetry further assessment is needed. Furthermore, the measurement setup is not uniform, as per recommendation of TRS 483, in most of the above-mentioned studies.…”

Section: Introductionmentioning

confidence: 99%

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Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams

Gul

Fukuda

Mizuno

et al. 2020

J Applied Clin Med Phys

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This study assesses the feasibility of using stereotactic field diode (SFD) as an alternate to gaf chromic films for field output factor (FF) measurement and further evaluating three new detectors for small field dosimetry. Varian 21EX linear accelerator was used to generate 6 and 10 MV beams of nominal square fields ranging from 0.5 × 0.5 cm2 to 10 × 10 cm2. One passive (EBT3 films) and five active detectors including IBA RAZOR diode(RD), SFD, RAZOR nanochamber (RNC), pinpoint chamber (PTW31023), and semiflex chamber (PTW31010) were employed. FFs were measured using films and SFD while beam profiles and percentage depth dose (PDD) distribution were acquired with active detectors. Polarity (kpol) and recombination (ks) effects of ion chambers were determined and corrected for output ratio measurement. Correction factors (CF) of RD, RNC, and PTW31023 in axial and radial orientation were also measured. Stereotactic field diode measured FFs have shown good agreement with films (with difference of <1%). RD and RNC measured beam profiles were within 3% deviation from the SFD values. Variation in kpol with field size for RNC and PTW31023 was up to 4% and 0.4% (for fields ≥ 1 × 1 cm2), respectively, while variation in ks of PTW31023 was <0.2 %. The maximum values of CF have been calculated to be 5.2%, 2.0%, 13.6%, and 25.5% for RD, RNC, PTW31023‐axial, and PTW31023‐radial respectively. This study concludes that SFD with appropriate CFs as given in TRS 483 may be used for measuring FFs as an alternate to EBT3 films. Whereas RD and RNC may be used for beam profile and PDD measurement in small fields. Considering the limit of usability of 2%, RNC may be used without CF for FF measurement in the smallfields investigated in this study.

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Section: Discussioncontrasting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams

Gul

Fukuda

Mizuno

et al. 2020

J Applied Clin Med Phys

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“…It requires determination of detector specific correction factors, which have to be utilized individually for the selected detector and are associated with additional uncertainties. 24 , 25 , 26 The latter can pose a problem to conduct such a study with sufficient reliability and robustness.…”

Section: Discussionmentioning

confidence: 99%

Experimental validation of Monte Carlo based treatment planning system in bone density equivalent media

Radojcic

Casar

Rajlić

et al. 2020

Radiology and Oncology

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IntroductionAdvanced, Monte Carlo (MC) based dose calculation algorithms, determine absorbed dose as dose to medium-in-medium (Dm,m) or dose to water-in-medium (Dw,m). Some earlier studies identified the differences in the absorbed doses related to the calculation mode, especially in the bone density equivalent (BDE) media. Since the calculation algorithms built in the treatment planning systems (TPS) should be dosimetrically verified before their use, we analyzed dose differences between two calculation modes for the Elekta Monaco TPS. We compared them with experimentally determined values, aiming to define a supplement to the existing TPS verification methodology.Materials and methodsIn our study, we used a 6 MV photon beam from a linear accelerator. To evaluate the accuracy of the TPS calculation approaches, measurements with a Farmer type chamber in a semi-anthropomorphic phantom were compared to those obtained by two calculation options. The comparison was made for three parts of the phantom having different densities, with a focus on the BDE part.ResultsMeasured and calculated doses were in agreement for water and lung equivalent density materials, regardless of the calculation mode. However, in the BDE part of the phantom, mean dose differences between the calculation options ranged from 5.7 to 8.3%, depending on the method used. In the BDE part of the phantom, neither of the two calculation options were consistent with experimentally determined absorbed doses.ConclusionsBased on our findings, we proposed a supplement to the current methodology for the verification of commercial MC based TPS by performing additional measurements in BDE material.

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“…In 2019, Francescon et al [121] investigated the sensitivity of dosimetric correction factors to interunit variation and reported variation up to 9% between the measured data corrected using the recommendations of TRS-483 and Monte Carlo results. Casar et al [122] provided detector-specific output correction factors for small-field sizes using the recommendations of TRS-483.…”

Section: Monte Carlo Studies For Small-field Dosimetrymentioning

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

Cited by 22 publications

References 38 publications

Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams

Feasibility study of using Stereotactic Field Diode for field output factors measurement and evaluating three new detectors for small field relative dosimetry of 6 and 10 MV photon beams

Experimental validation of Monte Carlo based treatment planning system in bone density equivalent media

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

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