Variation of kQclin,Qmsrfclin,fmsr for the small‐field dosimetric parameters percentage depth dose, tissue‐maximum ratio, and off‐axis ratio

Francescon, P.; Beddar, Sam; Satariano, N; Das, Indra J.

doi:10.1118/1.4895978

Cited by 77 publications

(142 citation statements)

References 51 publications

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“…The air core FOD is a cylindrical scintillation dosimeter with a sensitive volume of 1 mm diameter and 1 mm length, manufactured for use in external beam dosimetry, has been shown to be dosimetrically water‐equivalent, have no directional dependence, and have sufficient spatial resolution for use in field sizes as small as 4 mm in diameter 10 , 19 , 21 . Scintillation dosimeters are a good choice as a reference detector for small field work 15 , 22 as their response has been shown to be independent of dose rate, energy, and temperature, and they provide a linear response with delivered dose 23 , 24 . Scintillation dosimeters have been benchmarked against film 10 , 21 and Monte Carlo (25) and have a smaller measurement uncertainty than film.…”

Section: Methodsmentioning

confidence: 99%

Small field detector correction factors: effects of the flattening filter for Elekta and Varian linear accelerators

Tyler

Liu

Lee

et al. 2016

J Applied Clin Med Phys

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Flattening filter‐free (FFF) beams are becoming the preferred beam type for stereotactic radiosurgery (SRS) and stereotactic ablative radiation therapy (SABR), as they enable an increase in dose rate and a decrease in treatment time. This work assesses the effects of the flattening filter on small field output factors for 6 MV beams generated by both Elekta and Varian linear accelerators, and determines differences between detector response in flattened (FF) and FFF beams. Relative output factors were measured with a range of detectors (diodes, ionization chambers, radiochromic film, and microDiamond) and referenced to the relative output factors measured with an air core fiber optic dosimeter (FOD), a scintillation dosimeter developed at Chris O'Brien Lifehouse, Sydney. Small field correction factors were generated for both FF and FFF beams. Diode measured detector response was compared with a recently published mathematical relation to predict diode response corrections in small fields. The effect of flattening filter removal on detector response was quantified using a ratio of relative detector responses in FFF and FF fields for the same field size. The removal of the flattening filter was found to have a small but measurable effect on ionization chamber response with maximum deviations of less than ±0.9% across all field sizes measured. Solid‐state detectors showed an increased dependence on the flattening filter of up to ±1.6%. Measured diode response was within ±1.1% of the published mathematical relation for all fields up to 30 mm, independent of linac type and presence or absence of a flattening filter. For 6 MV beams, detector correction factors between FFF and FF beams are interchangeable for a linac between FF and FFF modes, providing that an additional uncertainty of up to ±1.6% is accepted.PACS number(s): 87.55.km, 87.56.bd, 87.56.Da

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Section: Methodsmentioning

confidence: 99%

Small field detector correction factors: effects of the flattening filter for Elekta and Varian linear accelerators

Tyler

Liu

Lee

et al. 2016

J Applied Clin Med Phys

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“…The choice of a particular detector should consider the following: ready availability, multiple independent validations within the literature and with a full validation using Monte Carlo techniques to check for radiological water equivalence. In either situation, detector orientation plays an important role in dose and profile measurements that had been described by Franscescon et el (11) for percent depth dose (PDD), tissue maximum ratio (TMR) and off axis ratio (OAR). There is also a list of detectors and associated kΩ values tabulated by Azangwe et al (21).…”

Section: Detectorsmentioning

confidence: 99%

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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“…9,14 Owing to their water equivalence and good spatial resolution, plastic scintillation detectors (PSDs) could play an important role in small-field dosimetry. Several authors have studied PSDs in recent years: 10,[15][16][17][18][19][20] their linear response to absorbed dose, dose rate and energy independence are well known. Consequently, PSDs have just found large application in small-field dosimetry.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric characterization and behaviour in small X-ray fields of a microchamber and a plastic scintillator detector

Pasquino

Cutaia

Radici

et al. 2017

BJR

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Objective: The aim of this work was to investigate the main dosimetric characteristics and the performance of an A26 Exradin ionization microchamber (A26 IC) and a W1 Exradin plastic scintillation detector (W1 PSD) in small photon beam dosimetry for treatment planning system commissioning and quality assurance programme. Methods: Detector characterization measurements (short-term stability, dose linearity, angular dependence and energy dependence) were performed in water for field sizes up to 10 3 10 cm 2 . Polarity effect (P pol ) was examined for the A26 IC. The behaviour of the detectors in small field relative dosimetry [percentage depth dose, dose profiles often called the off-axis ratio and output factors (OFs)] was investigated for field sizes ranging from 1 3 1 to 3 3 3 cm 2 . Results: Results were compared with those obtained with other detectors we already use for small photon beam dosimetry. A26 IC and W1 PSD showed a linear dose response. While the A26 IC showed no energy dependence, the W1 PSD showed energy dependence within 2%; no angular dependence was registered. P pol values for A26 IC were below 0.9% (0.5% for field size .2 3 2 cm 2 ). A26 IC and W1 PSD depth-dose curves and lateral profiles agreed with those obtained with an EDGE diode. No differences were observed among the detectors in OF measurement for field sizes larger than 1 3 1 cm 2 , with average differences ,1%. For field sizes ,1 3 1 cm 2 , the effective volume of ionization chamber and non-water equivalence of EDGE diode become significant. A26 IC OF values were significantly lower than EDGE diode and W1 PSD values, with percentage differences of about 223 and 213% for the smallest field, respectively. W1 PSD OF values lay between ion chambers and diode values, with a maximum percentage difference of about 210% with respect to the EDGE diode, for a 6 3 6-mm 2 field size. Conclusion: The results of our investigation confirm that A26 IC and W1 PSD could play an important role in small field relative dosimetry. Advances in knowledge: Dosimetric characteristics of Exradin A26 ionization microchamber and W1 plastic scintillation detector for small field dosimetry.

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Variation of kQclin,Qmsrfclin,fmsr for the small‐field dosimetric parameters percentage depth dose, tissue‐maximum ratio, and off‐axis ratio

Cited by 77 publications

References 51 publications

Small field detector correction factors: effects of the flattening filter for Elekta and Varian linear accelerators

Small field detector correction factors: effects of the flattening filter for Elekta and Varian linear accelerators

Small field dosimetry: What have we learnt?

Dosimetric characterization and behaviour in small X-ray fields of a microchamber and a plastic scintillator detector

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