Water-equivalent plastic scintillation detectors for high-energy beam dosimetry: II. Properties and measurements

Beddar, Sam; Mackie, Thomas Rockwell; Attix, F.H.

doi:10.1088/0031-9155/37/10/007

Cited by 340 publications

(336 citation statements)

References 2 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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“…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%

“…[21][22][23][24] The main drawback of plastic scintillators is represented by the generation ofČerenkov light in the optical fibre guide when the scintillator is exposed to a radiation field. Two main approaches have been suggested to subtract thě Cerenkov light component: the method proposed by Beddar et al, 15,16 which uses a background optical fibre not coupled with a scintillating fibre, and the two-fibre or spectral method, proposed by Fontbonne et al 25 and reformulated by Guillot et al, 26 which is based on the dependence of the intensity of thě Cerenkov light on the length of the exposed fibre and measures the light signal by means of two different wavelength channels. Morin 22 has proposed a modification of the measurement procedure proposed by Guillot et al 26 to determine the Cerenkov spectrum with the detector placed with the stem parallel to the beam axis.…”

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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“…As such, in vivo dosimetry measurements were made of the anterior rectal wall using plastic scintillators. Plastic scintillators are well suited for in vivo dosimetry measurements as they are water‐equivalent; independent of angular incidence, dose rate, and energy; and have a linear relationship between dose deposited and light emitted 3 , 4 However, newer generations of plastic scintillating materials exhibit a temperature dependence not found in previously used materials 5 , 6 …”

Section: Introductionmentioning

confidence: 99%

Real‐time in vivo dosimetry for SBRT prostate treatment using plastic scintillating dosimetry embedded in a rectal balloon: a case study

Cantley

Cheng

Jesseph

et al. 2016

J Applied Clin Med Phys

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A novel FDA approved in vivo dosimetry device system using plastic scintillating detectors placed in an endorectal balloon to provide real‐time in vivo dosimetry for prostatic rectal interface was tested for use with stereotactic body radiotherapy (SBRT). The system was used for the first time ever to measure dose during linear accelerator based SBRT. A single patient was treated with a total dose of 36.25 Gy given in 5 fractions. Delivered dose was measured for each treatment with the detectors placed against the anterior rectal wall near the prostate rectal interface. Measured doses showed varying degrees of agreement with computed/ planned doses, with average combined dose found to be within 6% of the expected dose. The variance between measurements is most likely due to uncertainty of the detector location, as well as variation in the placement of a new balloon prior to each fraction. Distance to agreement for the detectors was generally found to be within a few millimeters, which also suggested that the differences in measured and calculated doses were due to positional uncertainty of the detectors during the SBRT, which had sharp dose falloff near the penumbra along the rectal wall. Overall, the use of a real time in vivo dosimeter provided a level of safety and improved confidence in treatment delivery. We are evaluating the device further in an IRB‐approved prospective partial prostate SBRT trial, and believe further clinical investigations are warranted.PACS number(s): 87.53.Bn, 87.53.Ly, 87.55.km

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Water-equivalent plastic scintillation detectors for high-energy beam dosimetry: II. Properties and measurements

Cited by 340 publications

References 2 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

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

Real‐time in vivo dosimetry for SBRT prostate treatment using plastic scintillating dosimetry embedded in a rectal balloon: a case study

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