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T. Gimpel - One of the best experts on this subject based on the ideXlab platform.
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Thermoacoustic range verification using a clinical ultrasound array provides perfectly co-registered overlay of the Bragg Peak onto an ultrasound image.
Physics in medicine and biology, 2016Co-Authors: S. K. Patch, M. Kireeff Covo, A Jackson, Y M Qadadha, K S Campbell, R.a. Albright, P Bloemhard, Alexander P. Donoghue, C R Siero, T. GimpelAbstract:The potential of particle therapy due to focused dose deposition in the Bragg Peak has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg Peak location with target structure, by overlaying the location of the Bragg Peak onto a standard ultrasound image. Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the cyclotron inflector. The chopper limited the train of bunches so that 2 Gy were delivered in [Formula: see text]. The ion pulse generated thermoacoustic pulses that were detected by a cardiac ultrasound array, which also produced a grayscale ultrasound image. A filtered backprojection algorithm focused the received signal to the Bragg Peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg Peak. Phantom experiments performed with the cavity both empty and filled with olive oil confirmed that displacement of the Bragg Peak due to anatomical change could be detected. Thermoacoustic range measurements in the waterbath agreed with Monte Carlo simulation within 1.2 mm. In the phantom, thermoacoustic range estimates and first-order range estimates from CT images agreed to within 1.5 mm.
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TU-FG-BRB-09: Thermoacoustic Range Verification with Perfect Co-Registered Overlay of Bragg Peak onto Ultrasound Image.
Medical Physics, 2016Co-Authors: S. K. Patch, M. Kireeff Covo, A Jackson, Y M Qadadha, K S Campbell, R.a. Albright, P Bloemhard, Alexander P. Donoghue, C R Siero, T. GimpelAbstract:Purpose: The potential of particle therapy has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg Peak location with target structure, by overlaying thermoacoustic localization of the Bragg Peak onto an ultrasound image. Methods: Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the inflector of the 88″ cyclotron at Lawrence Berkeley National Lab. 2 Gy were delivered in 2 µs by a beam with Peak current of 2 µA. Thermoacoustic emissions were detected by a cardiac array and Verasonics V1 ultrasound system, which also generated a grayscale ultrasound image. 1024 thermoacoustic pulses were averaged before filtering and one-way beamforming focused signal onto the Bragg Peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg Peak. Experiments were performed with the cavity both empty and filled with olive oil. Results: In the waterbath overlays of the Bragg Peak agreed with Monte Carlo simulations to within 800±170 µm. Agreement within 1.3 ± 0.2 mm was achieved in the gelatin phantom, although relative stopping powers were estimated only to first order from CT scans. Protoacoustic signals were detected after travel from the Bragg Peak through 29 mm and 65 mm of phantom material when the cavity was empty and full of olive oil, respectively. Conclusion: Protoacoustic range verification is feasible with a commercial clinical ultrasound array, but at doses exceeding the clinical realm. Further optimization of both transducer array and injection line chopper is required to enable range verification within a 2 Gy dose limit, which would enable online adaptive treatment. This work was supported in part by a UWM Intramural Instrumentation Grant and by the Director, Office of Science, Office of Nuclear Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. YMQ was supported by a UWM-OUR summer fellowship.
Aswin L. Hoffmann - One of the best experts on this subject based on the ideXlab platform.
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First application of a high resolution silicon detector for proton beam Bragg Peak detection in a 0.95 T magnetic field
Medical physics, 2019Co-Authors: Trent Causer, Susanna Guatelli, Sonja M Schellhammer, Armin Lühr, Aswin L. Hoffmann, S. Gantz, Peter E Metcalfe, Anatoly B. Rosenfeld, Marco Petasecca, Bradley M ObornAbstract:PURPOSE To report on experimental results of a high spatial resolution silicon-based detector exposed to therapeutic quality proton beams in a 0.95 T transverse magnetic field. These experimental results are important for the development of accurate and novel dosimetry methods in future potential real-time MRI-guided proton therapy systems. METHODS A permanent magnet device was utilized to generate a 0.95 T magnetic field over a 4 × 20 × 15 cm3 volume. Within this volume, a high-resolution silicon diode array detector was positioned inside a PMMA phantom of 4 × 15 × 12 cm3 . This detector contains two orthogonal strips containing 505 sensitive volumes spaced at 0.2 mm apart. Proton beams collimated to a circle of 10 mm diameter with nominal energies of 90 MeV, 110 MeV, and 125 MeV were incident on the detector from an edge-on orientation. This allows for a measurement of the Bragg Peak at 0.2 mm spatial resolution in both the depth and lateral profile directions. The impact of the magnetic field on the proton beams, that is, a small deflection was also investigated. A Geant4 Monte Carlo simulation was performed of the experimental setup to aid in interpretation of the results. RESULTS The nominal Bragg Peak for each proton energy was successfully observed with a 0.2 mm spatial resolution in the 0.95 T transverse magnetic field in both a depth and lateral profiles. The proton beam deflection (at 0.95 T) was a consistent 2 ±0.5 mm at the center of the magnetic volume for each beam energy. However, a pristine Bragg Peak was not observed for each energy. This was caused by the detector packaging having small air gaps between layers of the phantom material surrounding the diode array. These air gaps act to degrade the shape of the Bragg Peak, and further to this, the nonwater equivalent silicon chip acts to separate the Bragg Peak into multiple Peaks depending on the proton path taken. Overall, a promising performance of the silicon detector array was observed, however, with a qualitative assessment rather than a robust quantitative dosimetric evaluation at this stage of development. CONCLUSIONS For the first time, a high-resolution silicon-based radiation detector has been used to measure proton beam Bragg Peak deflections in a phantom due to a strong magnetic field. Future efforts are required to optimize the detector packaging to strengthen the robustness of the dosimetric quantities obtained from the detector. Such high-resolution silicon diode arrays may be useful in future efforts in MRI-guided proton therapy research.
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technical note experimental verification of magnetic field induced beam deflection and Bragg Peak displacement for mr integrated proton therapy
Medical Physics, 2018Co-Authors: Sonja M Schellhammer, S. Gantz, Armin Lühr, Bradley M Oborn, Michael Bussmann, Aswin L. HoffmannAbstract:PURPOSE Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi-continuous energy loss and energy-dependent electromagnetic deflection at the same time, giving rise to a deflected beam trajectory and an altered dose distribution with a displaced Bragg Peak. So far, these effects have only been predicted using Monte Carlo and analytical models, but no clear consensus has been reached and experimental benchmark data are lacking. We measured proton beam trajectories and Bragg Peak displacement in a homogeneous phantom placed inside a magnetic field and compared them to simulations. METHODS Planar dose distributions of proton pencil beams (80-180 MeV) traversing the field of a 0.95 T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were measured using EBT3 radiochromic films and simulated using the Geant4 toolkit. Deflected beam trajectories and the Bragg Peak displacement were extracted from the measured planar dose distributions and compared against the simulations. RESULTS The lateral beam deflection was clearly visible on the EBT3 films and ranged from 1 to 10 mm for 80 to 180 MeV, respectively. Simulated and measured beam trajectories and Bragg Peak displacement agreed within 0.8 mm for all studied proton energies. CONCLUSIONS These results prove that the magnetic field-induced Bragg Peak displacement is both measurable and accurately predictable in a homogeneous phantom at 0.95 T, and allows Monte Carlo simulations to be used as gold standard for proton beam trajectory prediction in similar frameworks for MR-integrated proton therapy.
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Technical Note: Experimental verification of magnetic field‐induced beam deflection and Bragg Peak displacement for MR‐integrated proton therapy
Medical physics, 2018Co-Authors: Sonja M Schellhammer, S. Gantz, Armin Lühr, Bradley M Oborn, Michael Bussmann, Aswin L. HoffmannAbstract:PURPOSE Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi-continuous energy loss and energy-dependent electromagnetic deflection at the same time, giving rise to a deflected beam trajectory and an altered dose distribution with a displaced Bragg Peak. So far, these effects have only been predicted using Monte Carlo and analytical models, but no clear consensus has been reached and experimental benchmark data are lacking. We measured proton beam trajectories and Bragg Peak displacement in a homogeneous phantom placed inside a magnetic field and compared them to simulations. METHODS Planar dose distributions of proton pencil beams (80-180 MeV) traversing the field of a 0.95 T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were measured using EBT3 radiochromic films and simulated using the Geant4 toolkit. Deflected beam trajectories and the Bragg Peak displacement were extracted from the measured planar dose distributions and compared against the simulations. RESULTS The lateral beam deflection was clearly visible on the EBT3 films and ranged from 1 to 10 mm for 80 to 180 MeV, respectively. Simulated and measured beam trajectories and Bragg Peak displacement agreed within 0.8 mm for all studied proton energies. CONCLUSIONS These results prove that the magnetic field-induced Bragg Peak displacement is both measurable and accurately predictable in a homogeneous phantom at 0.95 T, and allows Monte Carlo simulations to be used as gold standard for proton beam trajectory prediction in similar frameworks for MR-integrated proton therapy.
George D. Sergiadis - One of the best experts on this subject based on the ideXlab platform.
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Ionoacoustic tomography of the proton Bragg Peak in combination with ultrasound and optoacoustic imaging.
Scientific reports, 2016Co-Authors: Stephan Kellnberger, Walter Assmann, S. Reinhardt, Sebastian Lehrack, Peter G. Thirolf, Günther Dollinger, George D. Sergiadis, Daniel Queirós, Katia Parodi, Vasilis NtziachristosAbstract:Ions provide a more advantageous dose distribution than photons for external beam radiotherapy, due to their so-called inverse depth dose deposition and, in particular a characteristic dose maximum at their end-of-range (Bragg Peak). The favorable physical interaction properties enable selective treatment of tumors while sparing surrounding healthy tissue, but optimal clinical use requires accurate monitoring of Bragg Peak positioning inside tissue. We introduce ionoacoustic tomography based on detection of ion induced ultrasound waves as a technique to provide feedback on the ion beam profile. We demonstrate for 20 MeV protons that ion range imaging is possible with submillimeter accuracy and can be combined with clinical ultrasound and optoacoustic tomography of similar precision. Our results indicate a simple and direct possibility to correlate, in-vivo and in real-time, the conventional ultrasound echo of the tumor region with ionoacoustic tomography. Combined with optoacoustic tomography it offers a well suited pre-clinical imaging system.
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we d brf 02 acoustic signal from the Bragg Peak for range verification in proton therapy
Medical Physics, 2014Co-Authors: S. Reinhardt, Walter Assmann, Stephan Kellnberger, Peter G. Thirolf, M. Moser, Günther Dollinger, Murad Omar, A Fink, C Gaebisch, George D. SergiadisAbstract:Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams. Aim of this work is to study the feasibility of determining the ion range with sub-mm accuracy by use of high frequency ultrasonic (US) transducers and to image the Bragg Peak by tomography. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity, length and repetition rate. The acoustic signal of single proton pulses was measured by different PZT-based US detectors (3.5 MHz and 10 MHz central frequencies). For tomography a 64 channel US detector array was used and moved along the ion track by a remotely controlled motor stage. Results: A clear signal of the Bragg Peak was visible for an energy deposition as low as 1012 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Range measurements were reproducible within +/− 20 micrometer and agreed well with Geant4 simulations. The tomographic reconstruction does not only allow to measure the ion range but also the beam spot size at the Bragg Peak position. Conclusion: Range verification by acoustic means is a promising new technique for treatment modalities where the tumor can be localized by US imaging. Further improvement of sensitivity is required to account for higher attenuation of the US signal in tissue, as well as lower energy density in the Bragg Peak in realistic treatment cases due to higher particle energy and larger spot sizes. Nevertheless, the acoustic range verification approach could offer the possibility of combining anatomical US imaging with Bragg Peak imaging in the near future. The work was funded by the DFG cluster of excellence Munich Centre for Advanced Photonics (MAP).
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WE‐D‐BRF‐02: Acoustic Signal From the Bragg Peak for Range Verification in Proton Therapy
Medical Physics, 2014Co-Authors: S. Reinhardt, Walter Assmann, Stephan Kellnberger, Peter G. Thirolf, M. Moser, Günther Dollinger, Murad Omar, A Fink, C Gaebisch, George D. SergiadisAbstract:Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams. Aim of this work is to study the feasibility of determining the ion range with sub-mm accuracy by use of high frequency ultrasonic (US) transducers and to image the Bragg Peak by tomography. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity, length and repetition rate. The acoustic signal of single proton pulses was measured by different PZT-based US detectors (3.5 MHz and 10 MHz central frequencies). For tomography a 64 channel US detector array was used and moved along the ion track by a remotely controlled motor stage. Results: A clear signal of the Bragg Peak was visible for an energy deposition as low as 1012 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Range measurements were reproducible within +/− 20 micrometer and agreed well with Geant4 simulations. The tomographic reconstruction does not only allow to measure the ion range but also the beam spot size at the Bragg Peak position. Conclusion: Range verification by acoustic means is a promising new technique for treatment modalities where the tumor can be localized by US imaging. Further improvement of sensitivity is required to account for higher attenuation of the US signal in tissue, as well as lower energy density in the Bragg Peak in realistic treatment cases due to higher particle energy and larger spot sizes. Nevertheless, the acoustic range verification approach could offer the possibility of combining anatomical US imaging with Bragg Peak imaging in the near future. The work was funded by the DFG cluster of excellence Munich Centre for Advanced Photonics (MAP).
S. Reinhardt - One of the best experts on this subject based on the ideXlab platform.
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Ionoacoustic tomography of the proton Bragg Peak in combination with ultrasound and optoacoustic imaging.
Scientific reports, 2016Co-Authors: Stephan Kellnberger, Walter Assmann, S. Reinhardt, Sebastian Lehrack, Peter G. Thirolf, Günther Dollinger, George D. Sergiadis, Daniel Queirós, Katia Parodi, Vasilis NtziachristosAbstract:Ions provide a more advantageous dose distribution than photons for external beam radiotherapy, due to their so-called inverse depth dose deposition and, in particular a characteristic dose maximum at their end-of-range (Bragg Peak). The favorable physical interaction properties enable selective treatment of tumors while sparing surrounding healthy tissue, but optimal clinical use requires accurate monitoring of Bragg Peak positioning inside tissue. We introduce ionoacoustic tomography based on detection of ion induced ultrasound waves as a technique to provide feedback on the ion beam profile. We demonstrate for 20 MeV protons that ion range imaging is possible with submillimeter accuracy and can be combined with clinical ultrasound and optoacoustic tomography of similar precision. Our results indicate a simple and direct possibility to correlate, in-vivo and in real-time, the conventional ultrasound echo of the tumor region with ionoacoustic tomography. Combined with optoacoustic tomography it offers a well suited pre-clinical imaging system.
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Ionoacoustic characterization of the proton Bragg Peak with submillimeter accuracy.
Medical physics, 2015Co-Authors: Walter Assmann, Stephan Kellnberger, S. Reinhardt, Sebastian Lehrack, A. Edlich, Peter G. Thirolf, M. Moser, Günther Dollinger, Murad Omar, Vasilis NtziachristosAbstract:Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams in tissue (ionoacoustics). Aim of this work was to study experimentally the achievable position resolution of ionoacoustics under idealized conditions using high frequency ultrasonic transducers and a specifically selected probing beam. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity and length. The acoustic signal of single proton pulses was measured by different PZT-based ultrasound detectors (3.5 and 10 MHz central frequencies). The proton dose distribution in water was calculated by Geant4 and used as input for simulation of the generated acoustic wave by the matlab toolbox k-WAVE. Results: In measurements from this study, a clear signal of the Bragg Peak was observed for an energy deposition as low as 1012 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Bragg Peak position measurements were reproducible within ±30 μm and agreed with Geant4 simulations to better than 100 μm. The ionoacoustic signal pattern allowed for a detailed analysis of the Bragg Peak and could be well reproduced by k-WAVE simulations. Conclusions: The authors have studied the ionoacoustic signal of the Bragg Peak in experiments using a 20 MeV proton beam with its correspondingly localized energy deposition, demonstrating submillimeter position resolution and providing a deep insight in the correlation between the acoustic signal and Bragg Peak shape. These results, together with earlier experiments and new simulations (including the results in this study) at higher energies, suggest ionoacoustics as a technique for range verification in particle therapy at locations, where the tumor can be localized by ultrasound imaging. This acoustic range verification approach could offer the possibility of combining anatomical ultrasound and Bragg Peak imaging, but further studies are required for translation of these findings to clinical application.
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we d brf 02 acoustic signal from the Bragg Peak for range verification in proton therapy
Medical Physics, 2014Co-Authors: S. Reinhardt, Walter Assmann, Stephan Kellnberger, Peter G. Thirolf, M. Moser, Günther Dollinger, Murad Omar, A Fink, C Gaebisch, George D. SergiadisAbstract:Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams. Aim of this work is to study the feasibility of determining the ion range with sub-mm accuracy by use of high frequency ultrasonic (US) transducers and to image the Bragg Peak by tomography. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity, length and repetition rate. The acoustic signal of single proton pulses was measured by different PZT-based US detectors (3.5 MHz and 10 MHz central frequencies). For tomography a 64 channel US detector array was used and moved along the ion track by a remotely controlled motor stage. Results: A clear signal of the Bragg Peak was visible for an energy deposition as low as 1012 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Range measurements were reproducible within +/− 20 micrometer and agreed well with Geant4 simulations. The tomographic reconstruction does not only allow to measure the ion range but also the beam spot size at the Bragg Peak position. Conclusion: Range verification by acoustic means is a promising new technique for treatment modalities where the tumor can be localized by US imaging. Further improvement of sensitivity is required to account for higher attenuation of the US signal in tissue, as well as lower energy density in the Bragg Peak in realistic treatment cases due to higher particle energy and larger spot sizes. Nevertheless, the acoustic range verification approach could offer the possibility of combining anatomical US imaging with Bragg Peak imaging in the near future. The work was funded by the DFG cluster of excellence Munich Centre for Advanced Photonics (MAP).
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WE‐D‐BRF‐02: Acoustic Signal From the Bragg Peak for Range Verification in Proton Therapy
Medical Physics, 2014Co-Authors: S. Reinhardt, Walter Assmann, Stephan Kellnberger, Peter G. Thirolf, M. Moser, Günther Dollinger, Murad Omar, A Fink, C Gaebisch, George D. SergiadisAbstract:Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams. Aim of this work is to study the feasibility of determining the ion range with sub-mm accuracy by use of high frequency ultrasonic (US) transducers and to image the Bragg Peak by tomography. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity, length and repetition rate. The acoustic signal of single proton pulses was measured by different PZT-based US detectors (3.5 MHz and 10 MHz central frequencies). For tomography a 64 channel US detector array was used and moved along the ion track by a remotely controlled motor stage. Results: A clear signal of the Bragg Peak was visible for an energy deposition as low as 1012 eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Range measurements were reproducible within +/− 20 micrometer and agreed well with Geant4 simulations. The tomographic reconstruction does not only allow to measure the ion range but also the beam spot size at the Bragg Peak position. Conclusion: Range verification by acoustic means is a promising new technique for treatment modalities where the tumor can be localized by US imaging. Further improvement of sensitivity is required to account for higher attenuation of the US signal in tissue, as well as lower energy density in the Bragg Peak in realistic treatment cases due to higher particle energy and larger spot sizes. Nevertheless, the acoustic range verification approach could offer the possibility of combining anatomical US imaging with Bragg Peak imaging in the near future. The work was funded by the DFG cluster of excellence Munich Centre for Advanced Photonics (MAP).
S. K. Patch - One of the best experts on this subject based on the ideXlab platform.
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Thermoacoustic range verification using a clinical ultrasound array provides perfectly co-registered overlay of the Bragg Peak onto an ultrasound image.
Physics in medicine and biology, 2016Co-Authors: S. K. Patch, M. Kireeff Covo, A Jackson, Y M Qadadha, K S Campbell, R.a. Albright, P Bloemhard, Alexander P. Donoghue, C R Siero, T. GimpelAbstract:The potential of particle therapy due to focused dose deposition in the Bragg Peak has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg Peak location with target structure, by overlaying the location of the Bragg Peak onto a standard ultrasound image. Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the cyclotron inflector. The chopper limited the train of bunches so that 2 Gy were delivered in [Formula: see text]. The ion pulse generated thermoacoustic pulses that were detected by a cardiac ultrasound array, which also produced a grayscale ultrasound image. A filtered backprojection algorithm focused the received signal to the Bragg Peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg Peak. Phantom experiments performed with the cavity both empty and filled with olive oil confirmed that displacement of the Bragg Peak due to anatomical change could be detected. Thermoacoustic range measurements in the waterbath agreed with Monte Carlo simulation within 1.2 mm. In the phantom, thermoacoustic range estimates and first-order range estimates from CT images agreed to within 1.5 mm.
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TU-FG-BRB-09: Thermoacoustic Range Verification with Perfect Co-Registered Overlay of Bragg Peak onto Ultrasound Image.
Medical Physics, 2016Co-Authors: S. K. Patch, M. Kireeff Covo, A Jackson, Y M Qadadha, K S Campbell, R.a. Albright, P Bloemhard, Alexander P. Donoghue, C R Siero, T. GimpelAbstract:Purpose: The potential of particle therapy has not yet been fully realized due to inaccuracies in range verification. The purpose of this work was to correlate the Bragg Peak location with target structure, by overlaying thermoacoustic localization of the Bragg Peak onto an ultrasound image. Methods: Pulsed delivery of 50 MeV protons was accomplished by a fast chopper installed between the ion source and the inflector of the 88″ cyclotron at Lawrence Berkeley National Lab. 2 Gy were delivered in 2 µs by a beam with Peak current of 2 µA. Thermoacoustic emissions were detected by a cardiac array and Verasonics V1 ultrasound system, which also generated a grayscale ultrasound image. 1024 thermoacoustic pulses were averaged before filtering and one-way beamforming focused signal onto the Bragg Peak location with perfect co-registration to the ultrasound images. Data was collected in a room temperature water bath and gelatin phantom with a cavity designed to mimic the intestine, in which gas pockets can displace the Bragg Peak. Experiments were performed with the cavity both empty and filled with olive oil. Results: In the waterbath overlays of the Bragg Peak agreed with Monte Carlo simulations to within 800±170 µm. Agreement within 1.3 ± 0.2 mm was achieved in the gelatin phantom, although relative stopping powers were estimated only to first order from CT scans. Protoacoustic signals were detected after travel from the Bragg Peak through 29 mm and 65 mm of phantom material when the cavity was empty and full of olive oil, respectively. Conclusion: Protoacoustic range verification is feasible with a commercial clinical ultrasound array, but at doses exceeding the clinical realm. Further optimization of both transducer array and injection line chopper is required to enable range verification within a 2 Gy dose limit, which would enable online adaptive treatment. This work was supported in part by a UWM Intramural Instrumentation Grant and by the Director, Office of Science, Office of Nuclear Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. YMQ was supported by a UWM-OUR summer fellowship.