Fast 2D phantom dosimetry for scanning proton beams

Boon, S. N.; Luijk, Peter van; Schippers, J.M.; Meertens, H.; Denis, Jm.; Vynckier, Stefaan; Medin, Joakim; Grusell, Erik

doi:10.1118/1.598221

Cited by 110 publications

(107 citation statements)

References 33 publications

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“…The use of stacks of films (Lomax et al 2001) gives dose information with very high spatial resolution, but the film measurement evaluation is time consuming. Scintillating screens (Boon et al 1998, Safai et al 2004 coupled to a CCD camera allow online measurements of dose distributions with a 2D spatial resolution nearly as good as the film in a plane perpendicular to the beam. However, their response suffers from saturation.…”

Section: Introductionmentioning

confidence: 99%

“…However, their response suffers from saturation. The saturation is due to the combination of three effects: a quenching of the light production process due to the ionization density of the particle tracks, the non-tissue equivalence of the scintillator material and the non-infinitesimal thickness of the detection volume (Boon et al 1998).…”

Section: Introductionmentioning

confidence: 99%

“…The intensity distribution of the measured light spot is proportional to the two-dimensional hadron dose distribution deposited in the detector sensitive volume. The system is a follow-up of the scintillating Gd 2 O 2 S:Tb ('Lanex') screen setup (Boon et al 1998(Boon et al , 2000.…”

Section: Introductionmentioning

confidence: 99%

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

Seravalli¹,

Boer²,

Geurink

et al. 2008

Phys. Med. Biol.

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A two-dimensional position sensitive dosimetry system based on a scintillating gas detector has been developed for pre-treatment verification of dose distributions in hadron therapy. The dosimetry system consists of a chamber filled with an Ar/CF 4 scintillating gas mixture, inside which two cascaded gas electron multipliers (GEMs) are mounted. A GEM is a thin kapton foil with copper cladding structured with a regular pattern of sub-mm holes. The primary electrons, created in the detector's sensitive volume by the incoming beam, drift in an electric field towards the GEMs and undergo gas multiplication in the GEM holes. During this process, photons are emitted by the excited Ar/CF 4 gas molecules and detected by a mirror-lens-CCD camera system. Since the amount of emitted light is proportional to the dose deposited in the sensitive volume of the detector by the incoming beam, the intensity distribution of the measured light spot is proportional to the 2D hadron dose distribution. For a measurement of a 3D dose distribution, the scintillating gas detector is mounted at the beam exit side of a water-bellows phantom, whose thickness can be varied in steps. In this work, the energy dependence of the output signal of the scintillating gas detector has been verified in a 250 MeV/u clinical 12 C ion beam by means of a depth-dose curve measurement. The underestimation of the measured signal at the Bragg peak depth is only 9% with respect to an airfilled ionization chamber. This is much smaller than the underestimation found for a scintillating Gd 2 O 2 S:Tb ('Lanex') screen under the same measurement conditions (43%). Consequently, the scintillating gas detector is a promising device for verifying dose distributions in high LET beams, for example to check hadron therapy treatment plans which comprise beams with different energies.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Seravalli¹,

Boer²,

Geurink

et al. 2008

Phys. Med. Biol.

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“…radiographic films (Butson et al 2003, Spielberger et al 2001 and scintillating screens (Boon et al 1998b, Safai et al 2004) depends on the particle energy. A correction for this energy dependence cannot be applied when multiple proton energies are contributing to the local dose.…”

Section: Introductionmentioning

confidence: 99%

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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“…[1][2][3][4][5][6] However, the dynamic nature of IMPT as well as the necessity to use thousands of scanning proton beamlets makes treatment verification both time consuming and difficult to perform. [7][8][9][10][11] We have previously studied the feasibility of using a three-dimensional liquid scintillator (LS) detector system to rapidly verify proton treatments. 12,13 Using a tank of LS and a high sensitivity CCD camera, we have shown that monitoring the passage of a proton beam is feasible.…”

Section: Introductionmentioning

confidence: 99%

Verification of proton range, position, and intensity in IMPT with a 3D liquid scintillator detector system

et al. 2012

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Purpose: Intensity-modulated proton therapy (IMPT) using spot scanned proton beams relies on the delivery of a large number of beamlets to shape the dose distribution in a highly conformal manner. The authors have developed a 3D system based on liquid scintillator to measure the spatial location, intensity, and depth of penetration (energy) of the proton beamlets in near real-time. Methods: The detector system consists of a 20 Â 20 Â 20 cc liquid scintillator (LS) material in a light tight enclosure connected to a CCD camera. This camera has a field of view of 25.7 by 19.3 cm and a pixel size of 0.4 mm. While the LS is irradiated, the camera continuously acquires images of the light distribution produced inside the LS. Irradiations were made with proton pencil beams produced with a spot-scanning nozzle. Pencil beams with nominal ranges in water between 9.5 and 17.6 cm were scanned to irradiate an area of 10 Â 10 cm square on the surface of the LS phantom. Image frames were acquired at 50 ms per frame. Results: The signal to noise ratio of a typical Bragg peak was about 170. Proton range measured from the light distribution produced in the LS was accurate to within 0.3 mm on average. The largest deviation seen between the nominal and measured range was 0.6 mm. Lateral position of the measured pencil beam was accurate to within 0.4 mm on average. The largest deviation seen between the nominal and measured lateral position was 0.8 mm; however, the accuracy of this measurement could be improved by correcting light scattering artifacts. Intensity of single proton spots were measured with precision ranging from 3 % for the smallest spot intensity (0.005 MU) to 0.5 % for the largest spot (0.04 MU). Conclusions: Our LS detector system has been shown to be capable of fast, submillimeter spatial localization of proton spots delivered in a 3D volume. This system could be used for beam range, intensity and position verification in IMPT.

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Fast 2D phantom dosimetry for scanning proton beams

Cited by 110 publications

References 33 publications

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

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

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

Verification of proton range, position, and intensity in IMPT with a 3D liquid scintillator detector system

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