Thermoacoustic range verification using a clinical ultrasound array provides perfectly co-registered overlay of the Bragg peak onto an ultrasound image

Abstract

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.

Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

“…In the same year, Patch et al. performed intrinsically co‐registered ionoacoustic and ultrasonic acquisitions of water and a gelatine phantom by another specially manipulated non‐clinical low‐energy (50 MeV) proton source using a cardiac ultrasound transducer array . This measurement required a signal integration of 1024 pulses corresponding to over 2000 Gy of total dose delivery.…”

“…The newest clinical sources, synchrocyclotrons, clinically deliver approximately 3.5 ls FWHM Gaussian proton pulses, 16 which are predicted to be ideal for acoustic wave generation. 62 To experimentally characterize proton-induced thermoacoustics, researchers have first used accessible nonclinical proton sources, 64,65 and modified others. 66 To generate detectable acoustic signals using a clinical IBA 230 cyclotron, Jones et al modified the proton pulse output by modulating the proton current entering the cyclotron with a function generator.…”

“…70 In the same year, Patch et al performed intrinsically co-registered ionoacoustic and ultrasonic acquisitions of water and a gelatine phantom by another specially manipulated non-clinical low-energy (50 MeV) proton source using a cardiac ultrasound transducer array. 65 This measurement required a signal integration of 1024 pulses corresponding to over 2000 Gy of total dose delivery. For clinical proton energies, dedicated devices will need to be developed in order to provide the required frequency spectra for ultrasound imaging (MHz) and proto/ionoacoustic sensing (kHz), ideally integrated in a single system for intrinsic co-registration.…”

A review of microwave-induced thermoacoustic imaging: Excitation source, data acquisition system and biomedical applications

“…With the publication of above reports, more and more researchers are aware of the advantages of TAI and put their e®orts into improving TAI system. Nowadays, the main TAI groups in this¯eld are Patch et al, [28][29][30][31][32][33] Ntziachristos et al, [34][35][36][37] Jiang et al, [38][39][40][41][42][43] Xin et al, [44][45][46][47][48][49] Arbabian et al, 50,51 Zheng et al, [52][53][54] Xing et al [80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98] and others. Under the e®orts of these researchers, the excitation source, data acquisition system and image algorithm have been improved greatly, and it can be revealed that TAI is e±cient in detecting the area with anomalous microwave absorption in biological tissue, particularly for breast cancer.…”

Two‐stage ionoacoustic range verification leveraging Monte Carlo and acoustic simulations to stably account for tissue inhomogeneity and accelerator–specific time structure – A simulation study

“…23,24 Thermoacoustic emissions from 20 MeV pulses as short as 8 ns duration and microsecond-duration pulses of protons with energies exceeding 200 MeV into water baths have been detected using single element piezoelectric transducers 25,26 and hydrophones 27,28 respectively. Ionoacoustic range verification by overlaying the Bragg peak on an ultrasound (US) image 29 was performed using 50 MeV protons. The recent review 30 expands upon this summary.…”