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Simulation Study Using Thermoacoustics to Image Proton Dose and Range in Water and Skull Phantom

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K Stantz

K Stantz1*, V Moskvin2 , (1) Purdue University, West Lafayette, IN, (2) St. Jude Children's Research Hospital, Memphis, TN


SU-E-J-140 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: In this study, thermoacoustic pressure signals generated from a proton beam were simulated in water and currently within a skull phantom to investigate the sensitivity of radioacoustic CT imaging in the brain.

Methods:Thermoacoustically generated pressure signals from a pulse pencil proton beam (12, 15, 20, and 27cm range) were simulated in water. These simulated pressure signal are detected using a (71) transducer array placed along the surface of a cylinder (30cm x 40cm) and rotated over 2π (in 2 degree increments), where the normal vector to the surface of each transducer intersects the isocenter of the scanner. Currently, a software skull phantom is positioned at isocenter, where the scattering, absorption and speed of dispersion of the thermoacoustic signal through a three layer cortical-trabecular-cortical structure is being simulated. Based on data obtained from the literature, the effects of acoustic attenuation and speed-of-sound (dispersion) will be applied within the 3D FBP algorithm to obtain dosimetric images.

Results:Based on hydrophone detector specifications, a 0.5MHz bandwidth and 50dB re 1μPa per Hz^1/2, a 1.6cGy sensitivity at the Bragg peak was demonstrated while maintaining a 1.0 mm (FWHM) range resolution along the central axis of the beam. Utilizing this same information, the integral dose within the Bragg peak and distal edge compared to MC had a 2% (statistical) and 5% voxel-based RMS at this same dose sensitivity. We plan to present preliminary data determining the range sensitivity for a head phantom for this scanner design and the feasibility of imaging the proton dose in patients with a brain tumor undergoing therapy.

Conclusion:RACT scanner provides 3D dosimetric images with 1.6cGy (Bragg peak) sensitivity with 1mm range sensitivity. Simulations will be performed to determine feasibility to treat brain cancer patients.

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