Application of plastic scintillating fibres to surface dosimetry in megavoltage photon and electron beams: considerations for Cerenkov correction

Monajemi, Thalat; Ruiz, E A

doi:10.1088/1361-6560/aad9b6

Cited by 5 publications

(15 citation statements)

References 23 publications

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“…However, it has been shown that Cerenkov will be produced in the scintillator itself. 8 To help understand how problematic the Cerenkov radiation could be in our SPSD, we have measured the directional dependence on the surface using a 16 MeV electron beam since this setup produces a relatively unidirectional beam of electrons which will, in turn, maximize the directionality of the Cerenkov emissions. The use of reflective tape in this setting is a first test of a simple correction strategy.…”

Section: Discussionmentioning

confidence: 99%

“…At depth, electron scattering should result in more isotropic Cerenkov emission, resulting in a smaller directional dependence. 8…”

Section: B Spsd Characterizationmentioning

confidence: 99%

“…2,6,7 Furthermore, it has been shown that Cerenkov radiation is produced in the scintillator itself, further complicating the correction. 8 Even with a correction, Cerenkov radiation can produce a dosimetric error greater than 10% in certain circumstances. 8 The Exradin W1 (Standard Imaging, Middleton, WI, USA) was the first commercially available scintillation detector specifically designed for radiotherapy applications.…”

Section: Introductionmentioning

confidence: 99%

“…8 Even with a correction, Cerenkov radiation can produce a dosimetric error greater than 10% in certain circumstances. 8 The Exradin W1 (Standard Imaging, Middleton, WI, USA) was the first commercially available scintillation detector specifically designed for radiotherapy applications. It uses a spectral discrimination technique to correct for Cerenkov contamination.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication and characterization of a stemless plastic scintillation detector

et al. 2020

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Purpose To fabricate a stemless plastic scintillation detector (SPSD) and characterize its linearity and reproducibility, and its dependence on energy and dose per pulse; and to apply it to clinical PDD and output factor measurements. Methods An organic bulk heterojunction photodiode was fabricated by spin coating a blend of P3HT and PCBM onto an ITO‐coated glass substrate and depositing aluminum top contacts. Eljen scintillators (~5 × 5 × 5 mm3; EJ‐204, EJ‐208, and EJ‐260) or Saint‐Gobain scintillators (~3 × 3 × 2 mm3; BC‐400 and BC‐412) were placed on the opposite side of the glass using a silicone grease (optical coupling agent) creating the SPSD. Energy dependence was measured by using 100, 180, and 300 kVp photon beams from an orthovoltage treatment unit (Xstrahl 300) and 6 and 10 MV photons from a Varian TrueBeam linear accelerator. Linearity, dose per pulse dependence, output factors, and PDDs were measured using a 6 MV photon beam. PDDs and output factors were compared to ion chamber measurements. A control device was fabricated by substituting polystyrene (PS) for the P3HT/PCBM layer. No photocurrent should be generated in the control device and so any current measured is due to Compton current in the electrodes, wires, and surroundings from the irradiation. Output factors were corrected by subtracting the signal measured using the control device from the photodiode measured signal to yield the photocurrent. Results Each SPSD had excellent linearity with dose having an r2 of 1 and sensitivities of 1.07 nC/cGy, 1.04 nC/cGy, 1.00 nC/cGy and 0.10 nC/cGy, and 0.10 nC/cGy for EJ‐204, EJ‐208, EJ‐260 (5 × 5 × 5 mm3 volumes), BC‐400, and BC‐412 (3 × 3 × 2 mm3 volumes), respectively. No significant dose per pulse dependence was measured. Output factors matched within 1% for the large scintillators for field sizes of 5 × 5 cm2 to 25 × 25 cm2, but there was a large under‐response at field sizes below 3 × 3 cm2. After correcting the signal of the small scintillators by subtracting the current measured using the PS control, the output factors agreed with the ion chamber measurements within 1% from field sizes 1 × 1 cm2 to 20 × 20 cm2. The impact of Cerenkov emissions in the scintillator was effectively corrected with a simple reflective coating on the scintillator. In comparison to a 6 MV photon beam, the large scintillator SPSDs exhibited 37%, 52%, and 73% of the response at energies 100 kVp, 180 kVp and 300 kVp, respectively. Conclusion The principle of the SPSD was demonstrated. Devices had excellent linearity, reproducibility, and no significant dose per pulse dependence, and a simple reflective coating was sufficient to correct for Cerenkov emissions from within the scintillator. The devices demonstrated similar energy dependence to other scintillator detectors used in a radiotherapy setting.

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Section: Discussionmentioning

confidence: 99%

“…At depth, electron scattering should result in more isotropic Cerenkov emission, resulting in a smaller directional dependence. 8…”

Section: B Spsd Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fabrication and characterization of a stemless plastic scintillation detector

et al. 2020

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“…a dose rate dependence less than 1%) [14,15,16], irradiation angle independence [13,14,15], high spatial resolutions [17,18] and real time responses [11,19]. PSDs have been used effectively for small field dosimetry [20,21,22] and in vivo dosimetry [23,24,25] with clinical LINACs. Given these qualities and their non-ferromagnetic composition, PSDs are promising 2 prospects for MRI-LINAC dosimetry.…”

Section: Introductionmentioning

confidence: 99%

First measurements with a plastic scintillation dosimeter at the Australian MRI-LINAC

Madden

Archer

et al. 2019

Phys. Med. Biol.

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MRI-LINACs combine MRI and LINAC technologies with the potential for image guided radiation therapy with optimal soft-tissue contrast. In this work, we present the advantages and limitations of plastic scintillation dosimeters (PSDs) for relative dosimetry with MRI-LINACs. PSDs possess many desirable qualities, including magnetic field insensitivity and irradiation angle independence, which are expected to make them suitable for dosimetry with MRI-LINACs. An in-house PSD was used to measure field size output factors as well as a percent depth dose distribution and the beam quality index TPR20/10 at a [Formula: see text] cm2 field size. Measurements were repeated with a Scanditronix/Wellhofer FC65-G ionisation chamber and PTW 60019 microDiamond detector for comparison. Relative differences were calculated between the three detectors, where the mean difference in dose was 1.2% between the PSD and ionisation chamber, 1.9% between the PSD and microDiamond detector and 1.3% between the microDiamond detector and the ionisation chamber. The closeness between the three mean differences in doses suggests that PSDs are feasible for relative dosimetry with MRI-LINACs.

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Development of a real‐time in vivo dosimetry tool for electron beam therapy using a flexible thin film solar cell coated with scintillator powder

Jeong

Kwon

et al. 2022

Medical Physics

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Purpose A real‐time solar cell based in vivo dosimetry system (SC‐IVD) was developed using a flexible thin film solar cell and scintillating powder. The present study evaluated the clinical feasibility of the SC‐IVD in electron beam therapy. Methods A thin film solar cell was coated with 100 mg of scintillating powder using an optical adhesive to enhance the sensitivity of the SC‐IVD. Calibration factors were obtained by dividing the dose, measured at a reference depth for 6–20 MeV electron beam energy, by the signal obtained using the SC‐IVD. Dosimetric characteristics of SC‐IVDs containing variable quantities of scintillating powder (0–500 mg) were evaluated, including energy, dose rate, and beam angle dependencies, as well as dose linearity. To determine the extent to which the SC‐IVD affected the dose to the medium, doses at R90 were compared depending on whether the SC‐IVD was on the surface. Finally, the accuracy of surface doses measured using the SC‐IVD was evaluated by comparison with surface doses measured using a Markus chamber. Results Charge measured using the SC‐IVD increased linearly with dose and was within 1% of the average signal according to the dose rate. The signal generated by the SC‐IVD increased as the beam angle increased. The presence of the SC‐IVD on the surface of a phantom resulted in a 0.5%–2.2% reduction in dose at R90 for 6–20 MeV electron beams compared with the bare phantom. Surface doses measured using the SC‐IVD system and Markus chamber differed by less than 5%. Conclusions The dosimetric characteristics of the SC‐IVD were evaluated in this study. The results showed that it accurately measured the surface dose without a significant difference of dose in the medium when compared with the Markus chamber. The flexibility of the SC‐IVD allows it to be attached to a patient's skin, enabling real‐time and cost‐effective measurement.

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Application of plastic scintillating fibres to surface dosimetry in megavoltage photon and electron beams: considerations for Cerenkov correction

Cited by 5 publications

References 23 publications

Fabrication and characterization of a stemless plastic scintillation detector

Fabrication and characterization of a stemless plastic scintillation detector

First measurements with a plastic scintillation dosimeter at the Australian MRI-LINAC

Development of a real‐time in vivo dosimetry tool for electron beam therapy using a flexible thin film solar cell coated with scintillator powder

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