IBA Dosimetry GmbH

Schwarzenbruck, Germany

IBA Dosimetry GmbH

Schwarzenbruck, Germany
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Togno M.,TU Munich | Togno M.,IBA Dosimetry GmbH | Wilkens J.J.,TU Munich | Menichelli D.,IBA Dosimetry GmbH | And 3 more authors.
Medical Physics | Year: 2016

Purpose: To characterize a new air vented ionization chamber technology, suitable to build detector arrays with small pixel pitch and independence of sensitivity on dose per pulse. Methods: The prototype under test is a linear array of air vented ionization chambers, consisting of 80 pixels with 3.5 mm pixel pitch distance and a sensitive volume of about 4 mm3. The detector has been characterized with 60Co radiation and MV x rays from different linear accelerators (with flattened and unflattened beam qualities). Sensitivity dependence on dose per pulse has been evaluated under MV x rays by changing both the source to detector distance and the beam quality. Bias voltage has been varied in order to evaluate the charge collection efficiency in the most critical conditions. Relative dose profiles have been measured for both flattened and unflattened distributions with different field sizes. The reference detectors were a commercial array of ionization chambers and an amorphous silicon flat panel in direct conversion configuration. Profiles of dose distribution have been measured also with intensity modulated radiation therapy (IMRT), stereotactic radiosurgery (SRS), and volumetric modulated arc therapy (VMAT) patient plans. Comparison has been done with a commercial diode array and with Gafchromic EBT3 films. Results: Repeatability and stability under continuous gamma irradiation are within 0.3%, in spite of low active volume and sensitivity (∼200 pC/Gy). Deviation from linearity is in the range [0.3%, -0.9%] for a dose of at least 20 cGy, while a worsening of linearity is observed below 10 cGy. Charge collection efficiency with 2.67 mGy/pulse is higher than 99%, leading to a ±0.9% sensitivity change in the range 0.09-2.67 mGy/pulse (covering all flattened and unflattened beam qualities). Tissue to phantom ratios show an agreement within 0.6% with the reference detector up to 34 cm depth. For field sizes in the range 2 × 2 to 15 × 15 cm2, the output factors are in agreement with a thimble chamber within 2%, while with 25 × 25 cm2 field size, an underestimation of 4.0% was found. Agreement of field and penumbra width measurements with the flat panel is of the order of 1 mm down to 1 × 1 cm2 field size. Flatness and symmetry values measured with the 1D array and the reference detectors are comparable, and differences are always smaller than 1%. Angular dependence of the detector, when compared to measurements taken with a cylindrical chamber in the same phantom, is as large as 16%. This includes inhomogeneity and asymmetry of the design, which during plan verification are accounted for by the treatment planning system (TPS). The detector is capable to reproduce the dose distributions of IMRT and VMAT plans with a maximum deviation from TPS of 3.0% in the target region. In the case of VMAT and SRS plans, an average (maximum) deviation of the order of 1% (4%) from films has been measured. Conclusions: The investigated technology appears to be useful both for Linac QA and patient plan verification, especially in treatments with steep dose gradients and nonuniform dose rates such as VMAT and SRS. Major limitations of the present prototype are the linearity at low dose, which can be solved by optimizing the readout electronics, and the underestimation of output factors with large field sizes. The latter problem is presently not completely understood and will require further investigations. © 2016 American Association of Physicists in Medicine.


Grant
Agency: European Commission | Branch: FP7 | Program: MC-ITN | Phase: FP7-PEOPLE-2011-ITN | Award Amount: 3.92M | Year: 2012

ARDENT is a multi-site ITN that will provide training for 15 ESRs in the field of advanced instrumentation for radiation dosimetry. This training initiative is founded on actions aiming to strengthen and enrich international cooperation amongst all partners involved (7 Full and 5 Associate), promoting the technological transfer of the research results to industry through the active involvement of four industrial partners (3 Full and 1 Associate). The project focuses on three main technologies: gas detectors (gas electron multipliers and tissue equivalent proportional counters), solid state detectors (Medipix and silicon microdosimeters) and track detectors (CR-39 and nanodosimeters). It addresses the development of these types of instruments for mixed-field dosimetry, microdosimetry, spectrometry, beam monitoring. The applications range from the characterization of mixed radiation fields around particle accelerators, in particular accelerators for cancer therapy with electron, proton and carbon ions, on board commercial flights and in space, to the measurement of the secondary dose to patients undergoing radiation therapy, and can equally be employed for measurement of the properties of clinical hadron beams. The overall goal of ARDENT is to train young researchers in a sector that is very important for the future of European research, at the same time fostering the development of the European private sector. Some of the institutes involved in ARDENT have a long-standing bilateral collaboration but at present there is no global collaboration amongst all partners involved in this ITN. ARDENT therefore also represents an excellent opportunity to strengthen existing links and to create a new network among all partners. A series of network-wide activities, in terms of both training and collaborative research, and a strong programme of secondments are an essential part of this ITN. Several outreach activities complete the ARDENT programme.


PubMed | TU Munich, University of California at San Francisco and IBA Dosimetry GmbH
Type: Journal Article | Journal: Medical physics | Year: 2016

To characterize a new air vented ionization chamber technology, suitable to build detector arrays with small pixel pitch and independence of sensitivity on dose per pulse.The prototype under test is a linear array of air vented ionization chambers, consisting of 80 pixels with 3.5 mm pixel pitch distance and a sensitive volume of about 4 mm(3). The detector has been characterized with (60)Co radiation and MV x rays from different linear accelerators (with flattened and unflattened beam qualities). Sensitivity dependence on dose per pulse has been evaluated under MV x rays by changing both the source to detector distance and the beam quality. Bias voltage has been varied in order to evaluate the charge collection efficiency in the most critical conditions. Relative dose profiles have been measured for both flattened and unflattened distributions with different field sizes. The reference detectors were a commercial array of ionization chambers and an amorphous silicon flat panel in direct conversion configuration. Profiles of dose distribution have been measured also with intensity modulated radiation therapy (IMRT), stereotactic radiosurgery (SRS), and volumetric modulated arc therapy (VMAT) patient plans. Comparison has been done with a commercial diode array and with Gafchromic EBT3 films.Repeatability and stability under continuous gamma irradiation are within 0.3%, in spite of low active volume and sensitivity (200 pC/Gy). Deviation from linearity is in the range [0.3%, -0.9%] for a dose of at least 20 cGy, while a worsening of linearity is observed below 10 cGy. Charge collection efficiency with 2.67 mGy/pulse is higher than 99%, leading to a 0.9% sensitivity change in the range 0.09-2.67 mGy/pulse (covering all flattened and unflattened beam qualities). Tissue to phantom ratios show an agreement within 0.6% with the reference detector up to 34 cm depth. For field sizes in the range 2 2 to 15 15 cm(2), the output factors are in agreement with a thimble chamber within 2%, while with 25 25 cm(2) field size, an underestimation of 4.0% was found. Agreement of field and penumbra width measurements with the flat panel is of the order of 1 mm down to 1 1 cm(2) field size. Flatness and symmetry values measured with the 1D array and the reference detectors are comparable, and differences are always smaller than 1%. Angular dependence of the detector, when compared to measurements taken with a cylindrical chamber in the same phantom, is as large as 16%. This includes inhomogeneity and asymmetry of the design, which during plan verification are accounted for by the treatment planning system (TPS). The detector is capable to reproduce the dose distributions of IMRT and VMAT plans with a maximum deviation from TPS of 3.0% in the target region. In the case of VMAT and SRS plans, an average (maximum) deviation of the order of 1% (4%) from films has been measured.The investigated technology appears to be useful both for Linac QA and patient plan verification, especially in treatments with steep dose gradients and nonuniform dose rates such as VMAT and SRS. Major limitations of the present prototype are the linearity at low dose, which can be solved by optimizing the readout electronics, and the underestimation of output factors with large field sizes. The latter problem is presently not completely understood and will require further investigations.


Lin L.,University of Pennsylvania | Ainsley C.G.,University of Pennsylvania | Mertens T.,IBA Dosimetry GmbH | De Wilde O.,IBA Particle Therapy | And 2 more authors.
Physics in Medicine and Biology | Year: 2013

To investigate the profile measurement capabilities of an IBA-Dosimetry scintillation detector and to assess its feasibility for determining the low-intensity tails of pencil-beam scanning spots, the responses of the scintillation detector and Gafchromic EBT2 film to a 115 MeV proton spot were measured in-air at the isocenter. Pairs of irradiations were made: one lower-level irradiation insufficient to cause saturation, and one higher-level irradiation which deliberately saturated the central region of the spot, but provided magnification of the tails. By employing the pair/magnification technique, agreement between the film and scintillation detector measurements of the spot profile can be extended from 4% of the central spot dose down to 0.01%. Gamma analysis between these measurements shows 95% and 99% agreement within a ±9 cm bound using criteria of 3 mm/3% and 5 mm/5%, respectively. Above 4%, our 115 MeV proton spot can be well-described by Gaussian function; below 4%, non-Gaussian, diamond-shaped tails predominate. © 2013 Institute of Physics and Engineering in Medicine.


PubMed | IBA Dosimetry GmbH, University of Pennsylvania and Proton Therapy
Type: Journal Article | Journal: Medical physics | Year: 2017

Proton radiography and proton computed tomography (PCT) can be used to measure proton stopping power directly. However, practical and cost effective proton imaging detectors are not widely available. In this study, the authors investigated the feasibility of proton imaging using a silicon diode array.A one-dimensional silicon-diode detector array (1DSDA) was aligned with the central axis (CAX) of the proton beam. Polymethyl methacrylate (PMMA) slabs were used to find the correspondence between the water equivalent thickness (WET) and 1DSDA channel number. 2D proton radiographs (PR) were obtained by translation and rotation of a phantom relative to CAX while the proton nozzle and 1DSDA were kept stationary. A PCT image of one slice of the phantom was reconstructed using filtered backprojection.PR and PCT images of the PMMA cube were successfully acquired using the 1DSDA. The WET of the phantom was measured using PR data with an accuracy of 4.2% or better. Structures down to 1 mm in size could be resolved. Reconstruction of a PCT image showed very good agreement with simulation. Limitations in spatial resolution are attributed to limited spatial sampling, beam collimation, and proton scatter.The results demonstrate the feasibility of using silicon diode arrays for proton imaging. Such a device can potentially offer fast image acquisition, high spatial and energy resolution for PR and PCT.


PubMed | IBA University, IBA Dosimetry GmbH, University of Pennsylvania and Proton Therapy
Type: Journal Article | Journal: Medical physics | Year: 2016

Proton radiography (PR) and proton computed tomography (PCT) can be used to measure proton stopping power directly. However, practical and cost effective proton imaging detectors are not widely available. In this study, the authors investigated the feasibility of proton imaging using a silicon diode array.A one-dimensional silicon diode detector array (1DSDA) was aligned with the central axis (CAX) of the proton beam. Polymethyl methacrylate (PMMA) slabs were used to find the correspondence between the water equivalent thickness (WET) and 1DSDA channel number. Two-dimensional proton radiographs were obtained by translation and rotation of a phantom relative to CAX while the proton nozzle and 1DSDA were kept stationary. A PCT image of one slice of the phantom was reconstructed using filtered backprojection.PR and PCT images of the PMMA cube were successfully acquired using the 1DSDA. The WET of the phantom was measured using PR data. The resolution and maximum error in WET measurement are 2.0 and 1.5 mm, respectively. Structures down to 2.0 mm in size could be resolved completely. Reconstruction of a PCT image showed very good agreement with simulation. Limitations in spatial resolution are attributed to limited spatial sampling, beam collimation, and proton scatter.The results demonstrate the feasibility of using silicon diode arrays for proton imaging. Such a device can potentially offer fast image acquisition and high spatial and energy resolution for PR and PCT.


Pelzer G.,Friedrich - Alexander - University, Erlangen - Nuremberg | Weber T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Anton G.,Friedrich - Alexander - University, Erlangen - Nuremberg | Ballabriga R.,CERN | And 16 more authors.
Optics Express | Year: 2013

We have carried out grating-based x-ray differential phasecontrast measurements with a hybrid pixel detector in 16 energy channels simultaneously. A method for combining the energy resolved phase-contrast images based on energy weighting is presented. An improvement in contrast-to-noise ratio by 58.2% with respect to an emulated integrating detector could be observed in the final image. The same image quality could thus be achieved with this detector and with energy weighting at 60.0% reduced dose compared to an integrating detector. The benefit of the method depends on the object, spectrum, interferometer design and the detector efficiency. © 2013 Optical Society of America.


Gabris F.,IBA Dosimetry GmbH | Zeman J.,IBA Dosimetry GmbH | Valenta J.,IBA Dosimetry GmbH | Selbach H.-J.,Physikalisch - Technische Bundesanstalt
Metrologia | Year: 2012

A secondary standard of the BEV, calibrated at the PTB in terms of D w,1 cm, was used for calibration of the well-type chamber-based measuring systems used in clinics. In addition to the calibration, we tried to employ it for assessment of treatment planning systems (TPS) used for each particular afterloader. The dose to water at 1cm distance from the source position was calculated by the TPS, using reference data from the source producer certificate. The values were compared directly with the dose measured at the same distance from the source. The comparison has been carried out for GammaMed Plus and MicroSelectron HDR sources. Differences of secondary standard measurements and TPS calculations were lower than ±5%, which is below the achievable uncertainty of both dose measurement and dose determination by the TPS. Nevertheless, it is higher than generally accepted in the case of external beam radiotherapy. Additional direct measurements in terms of Dw,1 cm may improve the safety and reliability of patient treatment. © 2012 BIPM & IOP Publishing Ltd.


Zeman J.,IBA Dosimetry GmbH | Valenta J.,IBA Dosimetry GmbH | Gabris F.,IBA Dosimetry GmbH | Grezdo J.,St Elisabeth Oncology Institute OUSA | Stastna S.,Faculty Hospital Na Bulovce FNB
Metrologia | Year: 2012

IBA Dosimetry GmbH participated in the Joint Research Project Increasing cancer treatment efficacy using 3D brachytherapy as a non-funded partner in the work package which was mostly dedicated to the determination of dose-to-water distribution from a high-dose-rate (HDR) brachytherapy source. The dose distribution was measured with a MatriXX (MXX) 2D detector array and compared with Dose Cube Data, calculated by treatment planning systems (TPS). All measurements and calculations were performed in cooperation with OUSA, Bratislava and FNB, Prague. The comparison has been carried out for three irradiation geometries: single source position, single line and four line motions of the source, and with the effective point of measurement in a plane at 6mm, 10mm and 20mm distance from the source position. The comparison of the MXX measurements and the TPS calculations was evaluated by the commercial IBA Dosimetry software OmniPro I'mRT (1) as the difference between maximum of measured and calculated values and (2) as the maximum difference between the two-dimensional distributions of measured and calculated values. The dose distribution was evaluated by the gamma method with parameters 3mm and 3%. All differences of comparison of the MXX measurements and TPS calculations were within the range ±10% and the γ-index was less than 1 for 96% (or 97%, respectively) of the dose distribution in the plane at 10mm distance from the source position. © 2012 BIPM & IOP Publishing Ltd.


Fiedler F.,Helmholtz Center Dresden | Shakirin G.,Helmholtz Center Dresden | Skowron J.,Helmholtz Center Dresden | Skowron J.,IBA Dosimetry GmbH | And 12 more authors.
Physics in Medicine and Biology | Year: 2010

At present, in-beam positron emission tomography (PET) is the only method for in vivo and in situ range verification in ion therapy. At the GSI Helmholtzzentrum für Schwerionenforschung GmbH (GSI) Darmstadt, Germany, a unique in-beam PET installation has been operated from 1997 until the shut down of the carbon ion therapy facility in 2008. Therapeutic irradiation by means of 12C ion beams of more than 400 patients have been monitored. In this paper a first quantitative study on the accuracy of the in-beam PET method to detect range deviations between planned and applied treatment in clinically relevant situations using simulations based on clinical data is presented. Patient treatment plans were used for performing simulations of positron emitter distributions. For each patient a range difference of 6 mm in water was applied and compared to simulations without any changes. The comparisons were performed manually by six experienced evaluators for data of 81 patients. The number of patients required for the study was calculated using the outcome of a pilot study. The results indicate a sensitivity of (91 ± 3)% and a specificity of (96 ± 2)% for detecting an overrange, a reduced range is recognized with a sensitivity of (92 ± 3)% and a specificity of (96 2)%. The positive and the negative predictive value of this method are 94% and 87%, respectively. The interobserver coefficient of variation is between 3 and 8%. The in-beam PET method demonstrated a high sensitivity and specificity for the detection of range deviations. As the range is a most indicative factor of deviations in the dose delivery, the promising results shown in this paper confirm the in-beam PET method as an appropriate tool for monitoring ion therapy. © 2010 Institute of Physics and Engineering in Medicine.

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