A scintillating gas detector for 2D dose measurements in clinical carbon beams

Seravalli, Enrica; Boer, M. de; Geurink, F; Huizenga, J.; Kreuger, R.; Schippers, J.M.; Eijk, C.W.E. van; Voss, B.

doi:10.1088/0031-9155/53/17/013

Cited by 28 publications

(34 citation statements)

References 23 publications

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“…We have recently demonstrated that in an alpha particle beam (Seravalli et al 2007) and clinical carbon ion beam (Seravalli et al 2008b), the scintillating GEM detector response underestimation of the Bragg peak dose is much smaller than the one presented by state-ofthe-art 2D dosimeters with a millimeter resolution (e.g. Boon 1998a, Spielberger et al 2003.…”

Section: Introductionmentioning

confidence: 93%

“…The GEMs used in this work have double conical holes and are glued onto 1 mm thick Al frames. For a detailed description of the detector, we refer to (Seravalli et al 2008b).…”

Section: The Scintillating Gem Detectormentioning

confidence: 99%

“…The photons produced in the electron avalanches are detected by means of a low darkcurrent CCD camera coupled with a zoom lens (Seravalli et al 2008b and2008c). The CCD signal per pixel is expressed in analog-to-digital units (ADU), 1 ADU being equivalent to 8.4 electrons' collected charge.…”

Section: The Scintillating Gem Detectormentioning

confidence: 99%

“…The currents are measured by means of nanoamperemeters connected in series with the high voltage line which supplies each GEM surface (Seravalli et al 2008b).…”

Section: The Scintillating Gem Detectormentioning

confidence: 99%

“…A gas-filled detector is expected to have a smaller energy dependence and a faster response (Seravalli 2008a) than radiographic films and scintillating screens. We are developing a position-sensitive scintillating gas detector based on GEMs (Sauli 1997) for relative 2D dose measurements in charged particle beams.…”

Section: Introductionmentioning

confidence: 99%

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2D dosimetry in a proton beam with a scintillating GEM detector

Seravalli¹,

Boer²,

Geurink³

et al. 2009

Phys. Med. Biol.

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A two-dimensional position-sensitive dosimetry system based on a scintillating gas detector is being developed for pre-treatment verification of dose distributions in particle therapy. The dosimetry system consists of a chamber filled with an Ar/CF 4 scintillating gas mixture, inside which two gas electron multiplier (GEM) structures are mounted (Seravalli et al 2008b Med. Phys. Biol. 53 4651-65). Photons emitted by the excited Ar/CF 4 gas molecules during the gas multiplication in the GEM holes are detected by a mirrorlens-CCD camera system. The intensity distribution of the measured light spot is proportional to the 2D dose distribution. In this work, we report on the characterization of the scintillating GEM detector in terms of those properties that are of particular importance in relative dose measurements, e.g. response reproducibility, dose dependence, dose rate dependence, spatial and time response, field size dependence, response uniformity. The experiments were performed in a 150 MeV proton beam. We found that the detector response is very stable for measurements performed in succession (σ = 0.6%) and its response reproducibility over 2 days is about 5%. The detector response was found to be linear with the dose in the range 0.05-19 Gy. No dose rate effects were observed between 1 and 16 Gy min −1 at the shallow depth of a water phantom and 2 and 38 Gy min −1 at the Bragg peak depth. No field size effects were observed in the range 120-3850 mm 2 . A signal rise and fall time of 2 μs was recorded and a spatial response of 1 mm was measured.

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Section: Introductionmentioning

confidence: 93%

“…The GEMs used in this work have double conical holes and are glued onto 1 mm thick Al frames. For a detailed description of the detector, we refer to (Seravalli et al 2008b).…”

Section: The Scintillating Gem Detectormentioning

confidence: 99%

Section: The Scintillating Gem Detectormentioning

confidence: 99%

“…The currents are measured by means of nanoamperemeters connected in series with the high voltage line which supplies each GEM surface (Seravalli et al 2008b).…”

Section: The Scintillating Gem Detectormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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2D dosimetry in a proton beam with a scintillating GEM detector

Seravalli¹,

Boer²,

Geurink³

et al. 2009

Phys. Med. Biol.

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AAPM task group 224: Comprehensive proton therapy machine quality assurance

et al. 2019

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Purpose: Task Group (TG) 224 was established by the American Association of Physicists in Medicine's Science Council under the Radiation Therapy Committee and Work Group on Particle Beams. The group was charged with developing comprehensive quality assurance (QA) guidelines and recommendations for the three commonly employed proton therapy techniques for beam delivery: scattering, uniform scanning, and pencil beam scanning. This report supplements established QA guidelines for therapy machine performance for other widely used modalities, such as photons and electrons (TG 142, TG 40, TG 24, TG 22, TG 179, and Medical Physics Practice Guideline 2a) and shares their aims of ensuring the safe, accurate, and consistent delivery of radiation therapy dose distributions to patients. Methods: To provide a basis from which machine‐specific QA procedures can be developed, the report first describes the different delivery techniques and highlights the salient components of the related machine hardware. Depending on the particular machine hardware, certain procedures may be more or less important, and each institution should investigate its own situation. Results: In lieu of such investigations, this report identifies common beam parameters that are typically checked, along with the typical frequencies of those checks (daily, weekly, monthly, or annually). The rationale for choosing these checks and their frequencies is briefly described. Short descriptions of suggested tools and procedures for completing some of the periodic QA checks are also presented. Conclusion: Recommended tolerance limits for each of the recommended QA checks are tabulated, and are based on the literature and on consensus data from the clinical proton experience of the task group members. We hope that this and other reports will serve as a reference for clinical physicists wishing either to establish a proton therapy QA program or to evaluate an existing one.

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A GEMPix‐based integrated system for measurements of 3D dose distributions in water for carbon ion scanning beam radiotherapy

et al. 2020

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Purpose: Commercially available systems for ion beam reference dosimetry in water are mainly based on ionization chambers. In those systems, a large number of small detectors are typically arranged in a two-dimensional (2D) array or matrix to achieve high spatial resolution (order of several millimeters) and large field coverage at the same time. The goal of this work was to investigate the reliability of a detector of superior spatial resolution to perform three-dimensional (3D) ionization measurements in carbon ion pencil beams. Methods: The GEMPix is a small gaseous detector with a highly pixelated readout, consisting of a drift region (with 2.8 cm 3 9 2.8 cm 3 9 0.3 cm 3 volume), three gas electron multipliers (GEMs) for signal amplification and four Timepix ASICs with 55 µm pixel pitch and a total of 262,144 pixels. An integrated system was designed and built, which consists of a commercial water phantom with a three-axis motorized arm, a reference large-area ionization chamber for signal normalization to the beam output and the GEMPix itself. Measurements at different depths in water have been performed at the Italian National Centre for Oncological Hadrontherapy (CNAO) with three carbon ion beam energies. Lateral beam profiles measured with the GEMPix at the shallowest depth were compared to those measured with radiochromic EBT3 films in air in the position of the reference ionization chamber. The Timepix readout was calibrated in energy by using one independent depth scan with carbon ions of 150 mm range. Bragg peak curves were also simulated using the Monte Carlo FLUKA code as a reference. Results: Beam profiles measured with the GEMPix were smooth and showed similar shape and full width at half maximum when compared to those measured with radiochromic EBT3 films. Smooth, reproducible Bragg curves were obtained with statistical uncertainties of about 2%, matching FLUKA simulations of the Bragg curves within 15% for most data points. This difference is partially explained for the measurement with carbon ions of 150 mm range by a saturation effect in the GEMs. The high granularity of the readout allowed to produce 2D images of the deposited dose at different depths, as well as 3D data distributions. Conclusions: This paper demonstrates the capability of the GEMPix detector to measure the 3D dose distribution of carbon ions in water for a clinical pencil beam reliably. In the future, the detector area will be increased to cover fields of scanned beams. Measurements at higher beam intensities and with protons are planned.

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A scintillating gas detector for 2D dose measurements in clinical carbon beams

Cited by 28 publications

References 23 publications

2D dosimetry in a proton beam with a scintillating GEM detector

2D dosimetry in a proton beam with a scintillating GEM detector

AAPM task group 224: Comprehensive proton therapy machine quality assurance

A GEMPix‐based integrated system for measurements of 3D dose distributions in water for carbon ion scanning beam radiotherapy

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