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Journal ArticleDOI

Characterization of a commercial scintillation detector for 2-D dosimetry in scanned proton and carbon ion beams.

TL;DR: Preliminary results have shown that Lynx is suitable to be used for commissioning and QA checks for proton and carbon ion scanning beams; the cross-check with EBT3 films showed a good agreement between the two detectors, for both single spot and scanned field measurements.
About: This article is published in Physica Medica.The article was published on 2017-02-01. It has received 72 citations till now. The article focuses on the topics: Dosimetry & Pencil-beam scanning.
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Journal ArticleDOI
TL;DR: Dose rates exceeding 40 Gy/s were obtained, enabling uniform irradiation for radiobiology investigations of small animals in a modified clinical proton beam line, which was not possible with the conventional clinical mode of the existing beamline.
Abstract: Purpose Recent in vivo investigations have shown that short pulses of electrons at very high dose rates (FLASH) are less harmful to healthy tissues but just as efficient as conventional dose-rate radiation to inhibit tumor growth. In view of the potential clinical value of FLASH and the availability of modern proton therapy infrastructures to achieve this goal, we herein describe a series of technological developments required to investigate the biology of FLASH irradiation using a commercially available clinical proton therapy system. Methods and Materials Numerical simulations and experimental dosimetric characterization of a modified clinical proton beamline, upstream from the isocenter, were performed with a Monte Carlo toolkit and different detectors. A single scattering system was optimized with a ridge filter and a high current monitoring system. In addition, a submillimetric set-up protocol based on image guidance using a digital camera and an animal positioning system was also developed. Results The dosimetric properties of the resulting beam and monitoring system were characterized; linearity with dose rate and homogeneity for a 12 × 12 mm2 field size were assessed. Dose rates exceeding 40 Gy/s at energies between 138 and 198 MeV were obtained, enabling uniform irradiation for radiobiology investigations of small animals in a modified clinical proton beam line. Conclusions This approach will enable us to conduct FLASH proton therapy experiments on small animals, specifically for mouse lung irradiation. Dose rates exceeding 40 Gy/s were achieved, which was not possible with the conventional clinical mode of the existing beamline.

163 citations

Journal ArticleDOI
TL;DR: The goal of this review article is to present the current state of this intriguing radiotherapy technique by reviewing existing publications on FLASH radiotherapy (RT) in terms of its physical and biological aspects.
Abstract: Ultrahigh dose-rate radiotherapy (RT), or 'FLASH' therapy, has gained significant momentum following various in vivo studies published since 2014 which have demonstrated a reduction in normal tissue toxicity and similar tumor control for FLASH-RT when compared with conventional dose-rate RT. Subsequent studies have sought to investigate the potential for FLASH normal tissue protection and the literature has been since been inundated with publications on FLASH therapies. Today, FLASH-RT is considered by some as having the potential to 'revolutionize radiotherapy'. FLASH-RT is considered by some as having the potential to 'revolutionize radiotherapy'. The goal of this review article is to present the current state of this intriguing RT technique and to review existing publications on FLASH-RT in terms of its physical and biological aspects. In the physics section, the current landscape of ultrahigh dose-rate radiation delivery and dosimetry is presented. Specifically, electron, photon and proton radiation sources capable of delivering ultrahigh dose-rates along with their beam delivery parameters are thoroughly discussed. Additionally, the benefits and drawbacks of radiation detectors suitable for dosimetry in FLASH-RT are presented. The biology section comprises a summary of pioneering in vitro ultrahigh dose-rate studies performed in the 1960s and early 1970s and continues with a summary of the recent literature investigating normal and tumor tissue responses in electron, photon and proton beams. The section is concluded with possible mechanistic explanations of the FLASH normal-tissue protection effect (FLASH effect). Finally, challenges associated with clinical translation of FLASH-RT and its future prospects are critically discussed; specifically, proposed treatment machines and publications on treatment planning for FLASH-RT are reviewed.

115 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe the methods used for beam monitoring in the FLASH mode with emphasis on techniques that provide proportional, time-resolved dosimetry of radiation at the submicrosecond time scale.
Abstract: Most anticancer radiation therapy facilities are based on linear electron accelerators with electron–photon conversion providing dose-rates in the range 0.03-0.40 Gy.s−1, and treatment plans usually involve daily fractions of 2 Gy cumulated for up to reaching a total dose close to the limit of tolerance of the normal tissues that surround tumors. We recently developed another methodology named “FLASH” that relies on very high dose-rate facilities and consists in delivering ≥ 10 Gy in a single microsecond pulse of relativistic electrons, or else in a limited number of pulses of 1-2 Gy each given in ≤ 100 ms temporal sequence. In mice FLASH was found to elicit a dramatic decrease of damage to normal tissues whilst keeping the anti-tumor efficiency unchanged. In the following we describe the methods used for beam monitoring in the FLASH mode with emphasis on techniques that provide proportional, time-resolved dosimetry of radiation at the submicrosecond time scale. These methods include measurement of the electron fluence, optically monitored chemical dosimeters in water, solid scintillation and Cerenkov light emission. An application to the calibration of Gafchromic™ films is described and the minimal requirements for dose monitoring in preclinical assays are discussed. Good repeatability and linearity of these techniques in a range of peak dose-rates from 2x102 to 4x107 Gy.s−1 and from 1 mGy to over 30 Gy per microsecond pulse have been obtained with an overall precision better than ± 2%.

33 citations

Journal ArticleDOI
TL;DR: A dual-ring double scattering system was designed to produce irradiation fields of two sizes starting from a fix pencil beam at 148 MeV, and results indicate that dose uniformity above 92.9% is obtained at the entrance channel as well as in the middle SOBP in the target regions for both irradiated fields.

31 citations

Journal ArticleDOI
TL;DR: The use of novel QA devices such as the Sphinx in conjunction with the Lynx, PPC05 ion chamber, HexaCheck/MIMI phantoms, and myQA software was shown to provide a comprehensive and efficient method for performing daily QA of a number of system parameters for a modern proton PBS‐dedicated treatment delivery unit.
Abstract: Purpose The main purpose of this study is to demonstrate the clinical implementation of a comprehensive pencil beam scanning (PBS) daily quality assurance (QA) program involving a number of novel QA devices including the Sphinx/Lynx/parallel-plate (PPC05) ion chamber and HexaCheck/multiple imaging modality isocentricity (MIMI) imaging phantoms. Additionally, the study highlights the importance of testing the connectivity among oncology information system (OIS), beam delivery/imaging systems, and patient position system at a proton center with multi-vendor equipment and software. Methods For dosimetry, a daily QA plan with spot map of four different energies (106, 145, 172, and 221 MeV) is delivered on the delivery system through the OIS. The delivery assesses the dose output, field homogeneity, beam coincidence, beam energy, width, distal-fall-off (DFO), and spot characteristics - for example, position, size, and skewness. As a part of mechanical and imaging QA, a treatment plan with the MIMI phantom serving as the patient is transferred from OIS to imaging system. The HexaCheck/MIMI phantoms are used to assess daily laser accuracy, imaging isocenter accuracy, image registration accuracy, and six-dimensional (6D) positional correction accuracy for the kV imaging system and robotic couch. Results The daily QA results presented herein are based on 202 daily sets of measurements over a period of 10 months. Total time to perform daily QA tasks at our center is under 30 min. The relative difference (Δrel ) of daily measurements with respect to baseline was within ± 1% for field homogeneity, ±0.5 mm for range, width and DFO, ±1 mm for spots positions, ±10% for in-air spot sigma, ±0.5 spot skewness, and ±1 mm for beam coincidence (except 1 case: Δrel = 1.3 mm). The average Δrel in dose output was -0.2% (range: -1.1% to 1.5%). For 6D IGRT QA, the average absolute difference (Δabs ) was ≤0.6 ± 0.4 mm for translational and ≤0.5° for rotational shifts. Conclusion The use of novel QA devices such as the Sphinx in conjunction with the Lynx, PPC05 ion chamber, HexaCheck/MIMI phantoms, and myQA software was shown to provide a comprehensive and efficient method for performing daily QA of a number of system parameters for a modern proton PBS-dedicated treatment delivery unit.

31 citations


Cites methods from "Characterization of a commercial sc..."

  • ...A detailed description of the Lynx is provided by Russo et al.13 For imaging quality assurance, the multiple imaging modality isocentricity (MIMI) phantom along with the HexaCheck phantom (Standard Imaging, Middleton, WI, USA) are used to perform daily, six‐dimensional (6D) image‐guided radiation therapy (IGRT) QA of the IBA adaPT‐Insight software and LEONI (LEONI Healthcare, Chartres France) robotic couch....

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  • ...A detailed description of the Lynx is provided by Russo et al.(13) For imaging quality assurance, the multiple imaging modality isocentricity (MIMI) phantom along with the HexaCheck phantom (Standard Imaging, Middleton, WI, USA) are used to perform daily, six‐dimensional (6D) image‐guided radiation therapy (IGRT) QA of the IBA adaPT‐Insight software and LEONI (LEONI Healthcare, Chartres France) robotic couch....

    [...]

References
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Journal ArticleDOI
TL;DR: The design and technical realization of the magnetic scanning system at GSI combines features of both scan techniques and it was found that both methods lead to nearly identical results.
Abstract: Beams of heavy ions have favourable physical and biological properties for the use in radiotherapy. These advantages are most pronoucced if the beam is delivered in a tumor-conform way by active beam scanning. A magnetic scanning technique is used to spread the beam laterally. The range of the particles in tissue is controlled by the variation of the beam energy in the accelerator. Computer simulations were used to compare a discrete scan mode (pixel scan) with a continous scan mode (raster scan). It was found that both methods lead to nearly identical results. The design and technical realization of the magnetic scanning system at GSI combines features of both scan techniques. First results using the lateral beam scanning method as well as the combination of the active energy variation with the magnetic beam scanning are presented.

728 citations

Journal ArticleDOI
TL;DR: Results of clinical phase I-II trials provide evidence that carbon-ion radiotherapy might be beneficial in several tumor entities, and the progress in heavy-ion therapy is reviewed, including physical and technical developments, radiobiological studiesmore and models, as well as radiooncological studies.
Abstract: High-energy beams of charged nuclear particles (protons and heavier ions) offer significant advantages for the treatment of deep-seated local tumors in comparison to conventional megavolt photon therapy. Their physical depth-dose distribution in tissue is characterized by a small entrance dose and a distinct maximum (Bragg peak) near the end of range with a sharp fall-off at the distal edge. Taking full advantage of the well-defined range and the small lateral beam spread, modern scanning beam systems allow delivery of the dose with millimeter precision. In addition, projectiles heavier than protons such as carbon ions exhibit an enhanced biological effectiveness in the Bragg peak region caused by the dense ionization of individual particle tracks resulting in reduced cellular repair. This makes them particularly attractive for the treatment of radio-resistant tumors localized near organs at risk. While tumor therapy with protons is a well-established treatment modality with more than 60 000 patients treated worldwide, the application of heavy ions is so far restricted to a few facilities only. Nevertheless, results of clinical phase I-II trials provide evidence that carbon-ion radiotherapy might be beneficial in several tumor entities. This article reviews the progress in heavy-ion therapy, including physical and technical developments, radiobiological studiesmore » and models, as well as radiooncological studies. As a result of the promising clinical results obtained with carbon-ion beams in the past ten years at the Heavy Ion Medical Accelerator facility (Japan) and in a pilot project at GSI Darmstadt (Germany), the plans for new clinical centers for heavy-ion or combined proton and heavy-ion therapy have recently received a substantial boost.« less

619 citations

Journal ArticleDOI
TL;DR: The pencil beam dose model used for treatment planning at the PSI proton gantry, the only system presently applying proton therapy with a beam scanning technique, is presented, including the nuclear beam halo, which can predict quite precisely the dose directly from treatment planning without renormalization measurements.
Abstract: In this paper we present the pencil beam dose model used for treatment planning at the PSI proton gantry, the only system presently applying proton therapy with a beam scanning technique. The scope of the paper is to give a general overview on the various components of the dose model, on the related measurements and on the practical parametrization of the results. The physical model estimates from first physical principles absolute dose normalized to the number of incident protons. The proton beam flux is measured in practice by plane-parallel ionization chambers (ICs) normalized to protons via Faraday-cup measurements. It is therefore possible to predict and deliver absolute dose directly from this model without other means. The dose predicted in this way agrees very well with the results obtained with ICs calibrated in a cobalt beam. Emphasis is given in this paper to the characterization of nuclear interaction effects, which play a significant role in the model and are the major source of uncertainty in the direct estimation of the absolute dose. Nuclear interactions attenuate the primary proton flux, they modify the shape of the depth-dose curve and produce a faint beam halo of secondary dose around the primary proton pencil beam in water. A very simple beam halo model has been developed and used at PSI to eliminate the systematic dependences of the dose observed as a function of the size of the target volume. We show typical results for the relative (using a CCD system) and absolute (using calibrated ICs) dosimetry, routinely applied for the verification of patient plans. With the dose model including the nuclear beam halo we can predict quite precisely the dose directly from treatment planning without renormalization measurements, independently of the dose, shape and size of the dose fields. This applies also to the complex non-homogeneous dose distributions required for the delivery of range-intensity-modulated proton therapy, a novel therapy technique developed at PSI.

322 citations

Journal ArticleDOI
TL;DR: This review summarizes technical aspects associated with the establishment of reference radiochromic film dosimetry and its subsequent use for either clinical or research applications.

214 citations

Journal ArticleDOI
TL;DR: The goal of this study was to find an efficient method of correcting for light scattering, and to compare dose distribution supplied by Gafchromic™ EBT with the distribution obtained with a 2D ion-chamber detector system.
Abstract: The Gafchromic™ EBT was recently introduced in filmdosimetry for external beam therapy (EBT). The high spatial resolution, weak energy dependence, and near-tissue equivalence of EBT films make them suitable for measurement of dose distributions in radiotherapy, especially intensity-modulated radiation therapy(IMRT). Starting with a sensitometric curve and dose uncertainty relative to the flatbed scanner, the goal of this study was to find an efficient method of correcting for light scattering, and to compare dose distribution supplied by Gafchromic™ EBT with the distribution obtained with a 2D ion-chamber detector system. Light scattering was analyzed for different levels of dose, and was found to depend on the red-scale value as well as the position of the pixel on the scanner. Many “uniform” films were exposed at different levels of dose to create a two-dimensional matrix correction to take this effect into account. The dose distribution obtained for three clinical beams ( 10 × 10 , 15 × 15 cm open fields and 12 × 12 cm wedge 60 ° field) were in agreement with those supplied by the 2D array. Gamma index 1 (using 5 mm distance and 5% dose as constraints) for the three fields considered was reached in an average of 98% of the points.

161 citations

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