Linearization of dose–response curve of the radiochromic film dosimetry system

Dević, Slobodan; Tomic, Nada; Aldelaijan, Saad; DeBlois, F; Seuntjens, J; Chan, M; Lewis, D.G.

doi:10.1118/1.4736800

Cited by 70 publications

(67 citation statements)

References 21 publications

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“…However, as a matter of clinical practice, it is difficult to achieve a scanning time window within

\pm 5 min

for the 30‐min protocol. Furthermore, Devic et al (25) demonstrated the use of a functional argument to linearize the inherently nonlinear response of a radiochromic film‐based reference dosimetry system, and showed that relative dosimetry can be conveniently performed using a radiochromic film dosimetry system without establishing a calibration curve. The radiochromic film response to the postirradiation time is not important for the measurement of relative dose, but it is important for the absolute dose.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a single‐scan protocol for radiochromic film dosimetry

Shimohigashi

Araki

Maruyama

et al. 2015

J Applied Clin Med Phys

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The purpose of this study was to evaluate a single‐scan protocol using Gafchromic EBT3 film (EBT3) by comparing it with the commonly used 24‐hr measurement protocol for radiochromic film dosimetry. Radiochromic film is generally scanned 24 hr after film exposure (24‐hr protocol). The single‐scan protocol enables measurement results within a short time using only the verification film, one calibration film, and unirradiated film. The single‐scan protocol was scanned 30 min after film irradiation. The EBT3 calibration curves were obtained with the multichannel film dosimetry method. The dose verifications for each protocol were performed with the step pattern, pyramid pattern, and clinical treatment plans for intensity‐modulated radiation therapy (IMRT). The absolute dose distributions for each protocol were compared with those calculated by the treatment planning system (TPS) using gamma evaluation at 3% and 3 mm. The dose distribution for the single‐scan protocol was within 2% of the 24‐hr protocol dose distribution. For the step pattern, the absolute dose discrepancies between the TPS for the single‐scan and 24‐hr protocols were 2.0±1.8 cGy and 1.4±1.2 cGy at the dose plateau, respectively. The pass rates were 96.0% for the single‐scan protocol and 95.9% for the 24‐hr protocol. Similarly, the dose discrepancies for the pyramid pattern were 3.6±3.5 cGy and 2.9±3.3 cGy, respectively, while the pass rates for the pyramid pattern were 95.3% and 96.4%, respectively. The average pass rates for the four IMRT plans were 96.7%±1.8% for the single‐scan protocol and 97.3%±1.4% for the 24‐hr protocol. Thus, the single‐scan protocol measurement is useful for dose verification of IMRT, based on its accuracy and efficiency.PACS number: 87.55.Qr

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“…However, as a matter of clinical practice, it is difficult to achieve a scanning time window within

\pm 5 min

Section: Discussionmentioning

confidence: 99%

Evaluation of a single‐scan protocol for radiochromic film dosimetry

Shimohigashi

Araki

Maruyama

et al. 2015

J Applied Clin Med Phys

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“…Finally, inter‐ and intrafilm lot and scanner variation can result in inconsistent dose mapping between film lots, scanner models, and environmental processing conditions 10. Recent improvements in technology and techniques, such as multiple‐channel dosimetry,11 simplified calibration and intralot recalibration,10 calibration‐less relative dosimetry,12 and film that is less sensitive to light have significantly mitigated these concerns. They have not, however, eliminated them entirely.…”

Section: Introductionmentioning

confidence: 99%

Initial testing of a pixelated silicon detector prototype in proton therapy

Wroe

McAuley

Teran

et al. 2017

J Applied Clin Med Phys

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As technology continues to develop, external beam radiation therapy is being employed, with increased conformity, to treat smaller targets. As this occurs, the dosimetry methods and tools employed to quantify these fields for treatment also have to evolve to provide increased spatial resolution. The team at the University of Wollongong has developed a pixelated silicon detector prototype known as the dose magnifying glass (DMG) for real‐time small‐field metrology. This device has been tested in photon fields and IMRT. The purpose of this work was to conduct the initial performance tests with proton radiation, using beam energies and modulations typically associated with proton radiosurgery. Depth dose and lateral beam profiles were measured and compared with those collected using a PTW parallel‐plate ionization chamber, a PTW proton‐specific dosimetry diode, EBT3 Gafchromic film, and Monte Carlo simulations. Measurements of the depth dose profile yielded good agreement when compared with Monte Carlo, diode and ionization chamber. Bragg peak location was measured accurately by the DMG by scanning along the depth dose profile, and the relative response of the DMG at the center of modulation was within 2.5% of that for the PTW dosimetry diode for all energy and modulation combinations tested. Real‐time beam profile measurements of a 5 mm 127 MeV proton beam also yielded FWHM and FW90 within ±1 channel (0.1 mm) of the Monte Carlo and EBT3 film data across all depths tested. The DMG tested here proved to be a useful device at measuring depth dose profiles in proton therapy with a stable response across the entire proton spread‐out Bragg peak. In addition, the linear array of small sensitive volumes allowed for accurate point and high spatial resolution one‐dimensional profile measurements of small radiation fields in real time to be completed with minimal impact from partial volume averaging.

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“…The film piece was scanned 24 h after irradiation and the transmission signal from the red colour channel was converted into relative dose using radiochromic film dose-response linearization method. 17 The size of the hole was measured at 50% of the maximum dose.…”

Section: Grid Treatment Planning System Commissioningmentioning

confidence: 99%

Effective spatially fractionated GRID radiation treatment planning for a passive grid block

Nobah¹,

Mohiuddin²,

Dević³

et al. 2015

BJR

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Objective: To commission a grid block for spatially fractionated grid radiation therapy (SFGRT) treatments and describe its clinical implementation and verification through the record and verify (R&V) system. Methods: SFGRT was developed as a treatment modality for bulky tumours that cannot be easily controlled with conventionally fractionated radiation. Treatment is delivered in the form of open-closed areas. Currently, SFGRT is performed by either using a commercially available grid block or a multileaf collimator (MLC) of a linear accelerator. In this work, 6-MV photon beam was used to study dosimetric characteristics of the grid block. We inserted the grid block into a commercially available treatment planning system (TPS), and the feasibility of delivering such treatment plans on a linear accelerator using a R&V system was verified. Dose measurements were performed using a miniature PinPoint TM ion chamber (PTW, Freiburg, Germany) in a water phantom and radiochromic film within solid water slabs. PinPoint ion chamber was used to measure the output factors, percentage depth dose (PDD) curves and beam profiles at two depths, depth of maximum dose (z max ) and 10 cm.Film sheets were used to measure dose profiles at z max and 10-cm depth.Results: The largest observed percentage difference between output factors for the grid block technique calculated by the TPS and measured with the PinPoint ion chamber was 3.6% for the 5 3 5-cm 2 field size. Relatively significant discrepancies between measured and calculated PDD values appear only in the build-up region, which was found to amount to ,4%, while a good agreement (differences ,2%) at depths beyond z max was observed. Dose verification comparisons performed between calculated and measured dose distributions were in clinically acceptable agreements. When comparing the MLC-based with the grid block technique, the advantage of treating large tumours with a single field reduces treatment time by at least 3-5 times, having significant impact on patient throughput. Conclusion:The proposed method supports and helps to standardize the clinical implementation of the grid block in a safer and more accurate way. Advances in knowledge: This work describes the method to implement treatment planning for the grid block technique in radiotherapy departments.

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Linearization of dose–response curve of the radiochromic film dosimetry system

Cited by 70 publications

References 21 publications

Evaluation of a single‐scan protocol for radiochromic film dosimetry

Evaluation of a single‐scan protocol for radiochromic film dosimetry

Initial testing of a pixelated silicon detector prototype in proton therapy

Effective spatially fractionated GRID radiation treatment planning for a passive grid block

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