Acoustic Analog Front End for Proton Range Detection in Hadron Therapy

Abstract

Clinical ions beams for cancer treatment provide maximum energy deposition (Bragg peak (BP)) at the end of their range and practically no dose behind. This enables a more efficient therapeutic option comparing with classical photon-based radiotherapy where maximum energy is deposited at the body interface. Obviously, minimum-error BP detection is, thus, a key aspect of this treatment. This paper investigates a promising detection technique, based on the so-called ionoacoustic effect. The BP energy deposition causes a small (millikelvin) heating of the surrounding volume that in turn induces a pressure variation. This generates a sound signal that can be detected by an acoustic sensor placed at a certain distance from the BP point. Thus, the sound time-of-flight measure aims, with sound speed, to detect the BP position with very high accuracy (<1 mm). This paper presents the results of a complete cross-domain model that starting from proton beam energy provides the induced pressure variation in water, emulates the propagation of sound waves in the medium, and finally, returns a voltage signal whose time evolution determines BP position with an average deviation from effective position of 1% accuracy.

Feasibility study of 3D time‐reversal reconstruction of proton‐induced acoustic signals for dose verification in the head and the liver: A simulation study

“…On top of that, acoustic sensors have a finite bandwidth in their frequency responses. Due to the underlying physics of signal generation, the frequency spectrum of proton‐induced acoustic waveforms mainly stays in the low‐frequency region (<50 kHz), 10,25 much lower than that of the transducers used in ultrasound imaging (~MHz). The physical size (cross‐section) of each sensor, if larger than the pixel size (3 mm), may also compromise the reconstruction accuracy.…”

Bragg Peak Localization with Piezoelectric Sensors for Proton Therapy Treatment

“…Each differential volume element of the irradiated source pressure emits a micro bipolar pressure wave. The pressure measured in the sensor is the sum of the micro-pressure waves emitted by each differential element of the volume [35]. Doubling the number of particles in a given pulse will double the resulting emitted pressure amplitude.…”

Ionoacoustic application of an optical hydrophone to detect proton beam range in water

“…They successfully evaluated the range error in anthropomorphic imaging phantom by coregistering IA and acoustic echo images 22,23 . Furthermore, to increase the SNR, a design of a low‐noise acoustic analog front‐end was presented by Riva et al 24 . and Vallicelli et al., 25 which was demonstrated to be useful in monitoring the high dose rate (FLASH) hadron therapy treatments 26 .…”

“…They successfully evaluated the range error in anthropomorphic imaging phantom by coregistering IA and acoustic echo images. 22,23 Furthermore, to increase the SNR, a design of a low-noise acoustic analog front-end was presented by Riva et al 24 and Vallicelli et al, 25 which was demonstrated to be useful in monitoring the high dose rate (FLASH) hadron therapy treatments. 26 Moreover, to increase the magnitude of pressure, we explored a fixed-field alternating gradient accelerator (FFA), a candidate accelerator in future proton therapy, 27,28 to generate a short-pulsed proton beam (σ∼27 ns).…”