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Proton Range Verification in Homogeneous Materials Through Acoustic Measurements

W Nie

W Nie1*, K Jones2 , S Petro3 , A Kassaee4 , C Sehgal5 , S Avery6 , (1) ,Philadelphia, PA, (2) Rush University Medical Center, Chicago, IL, (3) University of Pennsylvania, Philadelphia, Pennsylvania, (4) Univ Pennsylvania, Glenmoore, PA, (5) University of Pennsylvania, Philadelphia, PA, (6) UNIVERSITY OF PENNSYLVANIA, Sicklerville, NJ


SU-I-GPD-T-145 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Clinical proton beam quality assurance (QA) requires a simple and accurate method to measure the Bragg peak (BP) depth. One potential QA method is protoacoustics, which measures proton range based on the time-of-flight (TOF) of acoustic waves emitted due to thermoacoustic conversion of heat to pressure. Protoacoustic signals were produced in aluminum, lead and polyethylene. Characteristics for a potential QA device are investigated with the accuracy comparable to currently used QA techniques.

Methods: Protoacoustic signals were produced and measured in rectangular (aluminum and lead) and cylindrical (polyethylene) homogeneous solid phantoms. Four different methods (M1-4) for measuring the TOF of the protoacoustic signal were analyzed and compared. For the proposed protoacoustic-based QA methods, psuedospectral wave-equation simulations (k-Wave MATLAB toolbox) were used to study the ideal material and geometry of phantoms.

Results: Data analysis shows that protoacoustic range calculation method M1 has less variation than M2 (st. dev. of 0.3 cm compared to 0.6 cm), but it produces more systematic bias. M3 implicitly characterizes the speed of sound in the material, but it results in the largest error (<1 cm). M4 best agrees with simulations and exhibits minimal error (0.1 - 0.2 cm), but it requires simulation to find the acoustic wave path of travel and assumes a homogeneous material. Therefore, M4 is only applicable for QA, not for heterogeneous tissue measurements. The rectangular polyethylene phantom was found to be the best phantom for protoacoustic-based QA based on accuracy, usability and stability.

Conclusion: Our study shows that protoacoustic measurements may potentially provide a low cost and simple QA method for determining proton beam range. Protoacoustics provides a novel, non-invasive method to measure the thermoacoustic features and to characterize the acoustic properties of various materials.

Funding Support, Disclosures, and Conflict of Interest: Acknowledgement: Research reported in this abstract was supported by the NATIONAL INSTITUTE OF BIOMEDICAL IMAGING AND BIOENGINEERING (NIBIB) of the National Institutes of Health under award numberR21 CA205063. The content is solely the responsibility of the authors and doesn't necessarily represent the official views of the National Institutes of Health.

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