3-D Protoacoustic Imaging Through a Planar Ultrasound Array: A Simulation Workflow.

Area of Science:

• Medical Physics
• Acoustic Imaging
• Radiation Oncology

Background:

• Proton therapy faces challenges with Bragg peak range uncertainties, impacting treatment precision.
• Pulsed proton beams produce protoacoustic emissions, which correlate with absorbed energy and contain dosimetry information.

Purpose of the Study:

• To derive and model 3D protoacoustic imaging using an ultrasound array.
• To investigate the frequency characteristics of protoacoustic emissions.
• To assess the feasibility of image reconstruction under noisy conditions.

Main Methods:

• Development of a formalism to characterize protoacoustic signals, considering transducer bandwidth and proton beam pulse duration.
• Acquisition of experimental proton beam intensity data from a Mevion S250 clinical machine.
• Utilizing ultrasound arrays for 3D image reconstruction from acoustic emissions.

Main Results:

• Demonstrated the possibility of 3D protoacoustic image reconstruction, even when noise exceeds signal amplitude.
• Characterized protoacoustic signals based on beam properties and transducer specifications.
• Identified that MHz range signals can be generated by a 4μs Gaussian proton pulse with sufficient temperature gradients.

Conclusions:

• Protoacoustic imaging offers a novel method for dosimetry and 3D imaging in proton therapy.
• The developed formalism provides a framework for understanding and optimizing protoacoustic signal detection.
• The technique shows promise for robust image reconstruction in clinically relevant scenarios.