Technical Note: Range verification of pulsed proton beams from fixed‐field alternating gradient accelerator by means of time‐of‐flight measurement of ionoacoustic waves

Nakamura, Yuta; Takayanagi, T.; Uesaka, Tomoki; Ünlü, Mehmet; Kuriyama, Y.; Ishi, Y.; Uesugi, T.; Kobayashi, Masanori; Kudo, Nobuki; Tanaka, Sodai; Umegaki, Kikuo; Tomioka, Satoshi; Matsuura, Tetsuya

doi:10.1002/mp.15060

Cited by 4 publications

(19 citation statements)

References 41 publications

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“…The number of protons per pulse was between 1.07 and 1.22 × 10 8 throughout the measurement which corresponds to the BP dose of 0.5−0.6 Gy. As demonstrated in previous studies, 29,30 the short pulse of FFA is beneficial to the increase in the acoustic signal amplitude. Beam size and range were measured using a radiochromic film EBT3 (Ashland Inc., Wayne, New Jersey, USA).…”

Section: Measurement Of Ffa Beam Propertiessupporting

confidence: 62%

“…The measured waveforms, absolute pressure, SNR, and BP dose necessary for the range verification were compared with those in previous measurements using PH 29,30 and/or simulation. In this study, the BP dose necessary for the range verification is defined as the BP dose per pulse times the number of averaging, which was necessary to suppress the maximum range variation among 100 measurements to 1 mm for the γ-wave and the number of averaging that was necessary to suppress the intensity fluctuation (standard deviation) at the resonance frequency to 7% for SPIRE.…”

Section: Discussionmentioning

confidence: 99%

“…In each setup, the distance from the GM to the OH was set the same as the previous measurement using PH, namely, 25 and 28 mm, respectively. 29,30 To measure the variation in the SPIRE amplitude against the hydrophone misalignment, the hydrophone was independently shifted by ± 2 mm at maximum in the y and z directions. Though this measurement was performed only in the lateral setup due to the limitations of our jig design, we expect similar results to be obtained in the distal setup, considering the spherically symmetric shape of SPIRE.…”

Section: Geometrymentioning

confidence: 99%

“…However, for the IA wave from BP (referred to as γ-wave below), a BP dose of about 1.8 Gy was necessary using an off -the-shelf detection system. 29 We also investigated the use of a spherical IA wave with resonant frequency (1.52 MHz) (SPIRE) generated from a spherical gold fiducial marker (GM), which is used for patient alignment in clinics. 30 By molding the hydrophone surface to match the spherical wavefront and customizing the low-noise charge amplifier and band-pass filter to focus on the resonance frequency, a high SNR and submillimeter range accuracy were achieved with a single pulse measurement (a dose of about 0.35 Gy at BP).…”

Section: Introductionmentioning

confidence: 99%

“…Piezoelectric hydrophones (PH) were used for sensing IA waves in the aforementioned studies of IA range verification. [16][17][18][19][20][21][22][23]29,30 Because hydrophones must be placed on a patient's surface, the detector should be as small as possible to avoid narrowing the range of available beam angles and disturbing the real-time images during beam delivery such as in X-ray fluoroscopy. In fact, several researchers proposed the use of multiple detectors (from four to more than 200) to increase the estimated range reliability and/or to reconstruct dose distributions.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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Background Proton range uncertainty has been the main factor limiting the ability of proton therapy to concentrate doses to tumors to their full potential. Ionoacoustic (IA) range verification is an approach to reducing this uncertainty by detecting thermoacoustic waves emitted from an irradiated volume immediately following a pulsed proton beam delivery; however, the signal weakness has been an obstacle to its clinical application. To increase the signal‐to‐noise ratio (SNR) with the conventional piezoelectric hydrophone (PH), the detector‐sensitive volume needs to be large, but it could narrow the range of available beam angles and disturb real‐time images obtained during beam delivery. Purpose To prevent this issue, we investigated a millimeter‐sized optical hydrophone (OH) that exploits the laser interferometric principle. For two types of IA waves [γ‐wave emitted from the Bragg peak (BP) and a spherical IA wave with resonant frequency (SPIRE) emitted from the gold fiducial marker (GM)], comparisons were made with PH in terms of waveforms, SNR, range detection accuracy, and signal intensity robustness against the small detector misalignment, particularly for SPIRE. Methods A 100‐MeV proton beam with a 27 ns pulse width and 4 mm beam size was produced using a fixed‐field alternating gradient accelerator and was irradiated to the water phantom. The GM was set on the beam's central axis. Acrylic plates of various thicknesses, up to 12 mm, were set in front of the phantoms to shift the proton range. OH was set distal and lateral to the beam, and the range was estimated using the time‐of‐flight method for γ‐wave and by comparing with the calibration data (SPIRE intensity versus the distance between the GM and BP) derived from an IA wave transport simulation for SPIRE. The BP dose per pulse was 0.5–0.6 Gy. To measure the variation in SPIRE amplitude against the hydrophone misalignment, the hydrophone was shifted by ± 2 mm at a maximum in lateral directions. Results Despite its small size, OH could detect γ‐wave with a higher SNR than the conventional PH (diameter, 29 mm), and a single measurement was sufficient to detect the beam range with a submillimeter accuracy in water. In the SPIRE measurement, OH was far more robust against the detector misalignment than the focused PH (FPH) used in our previous study [5%/mm (OH) versus 80%/mm (FPH)], and the correlation between the measured SPIRE intensity and the distance between the GM and BP agreed well with the simulation results. However, the OH sensitivity was lower than the FPH sensitivity, and about 5.6‐Gy dose was required to decrease the intensity variation among measurements to less than 10%. Conclusion The miniature OH was found to detect weak IA signals produced by proton beams with a BP dose used in hypofractionated regimens. The OH sensitivity improvement at the MHz regime is worth exploring as the next step.

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Section: Measurement Of Ffa Beam Propertiessupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Section: Geometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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Accuracy verification of protoacoustic measurements in a heterogeneous phantom by an optical hydrophone

Chen,

Kasamatsu,

Kuriyama

et al. 2024

Medical Physics

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BackgroundProtoacoustics has emerged as a promising real‐time range measurement method for proton therapy. Optical hydrophones (OHs) are considered suitable to detect protoacoustic waves owing to their ultracompact size and high sensitivity. In our previous research, we demonstrated that the time‐of‐arrival (TOA) measured by an OH showed good agreement with the simulated ground truth in a homogeneous medium.PurposeThe purpose of the study was to experimentally evaluate the accuracy of the TOA and compression peak pressures detected by the OH. Protoacoustic waves that undergo the typical distortions occurring in the human body were investigated. In such cases, the use of small detectors such as OHs is desirable to minimize the effects of detector size and directivity.MethodsA 100‐MeV proton pencil beam emitted from a fixed‐field alternating gradient accelerator was irradiated onto a homogeneous water phantom and a water phantom with a half‐ or full‐sized silicone plate downstream of the Bragg peak (BP) or a bone plate that covered half of the beam cross‐section in the beam path. The OH was shifted 70 mm laterally across the beam axis downstream of the BP to measure the protoacoustic waves. The k‐WAVE acoustic wave transport simulation was employed as the ground truth. The TOA and the first compression peak pressures were compared between the simulation and experiment.ResultsThe TOA deviation against the ground truth was primarily attributed to alignment errors of the measurement devices and phantoms, with deviations of < 1 mm. The peak pressure distribution closely resembled the ground truth, with FWHM differences of 0.0%–3.0% for the tested geometries.ConclusionThe OH was able to determine the TOA and peak pressures with sufficient accuracy in heterogeneous phantoms, even without considering the effect of the size of the detector or directivity on the measurements.

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Ionic-resolution protoacoustic microscopy: A feasibility study

Pandey,

Gonzalez,

Cheong

et al. 2024

Applied Physics Letters

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Visualizing micro- and nano-scale biological entities requires high-resolution imaging and is conventionally achieved via optical microscopic techniques. Optical diffraction limits their resolution to ∼200 nm. This limit can be overcome by using ions with ∼1 MeV energy. Such ions penetrate through several micrometers in tissues, and their much shorter de Broglie wavelengths indicate that these ion beams can be focused to much shorter scales and hence can potentially facilitate higher resolution as compared to the optical techniques. Proton microscopy with ∼1 MeV protons has been shown to have reasonable inherent contrast between sub-cellular organelles. However, being a transmission-based modality, it is unsuitable for in vivo studies and cannot facilitate three-dimensional imaging from a single raster scan. Here, we propose proton-induced acoustic microscopy (PrAM), a technique based on pulsed proton irradiation and proton-induced acoustic signal collection. This technique is capable of label-free, super-resolution, 3D imaging with a single raster scan. Converting radiation energy into ultrasound enables PrAM with reflection mode detection, making it suitable for in vivo imaging and probing deeper than proton scanning transmission ion microscopy (STIM). Using a proton STIM image of HeLa cells, a coupled Monte Carlo+k-wave simulations-based feasibility study has been performed to demonstrate the capabilities of PrAM. We demonstrate that sub-50 nm lateral (depending upon the beam size and energy) and sub-micron axial resolution (based on acoustic detection bandwidth and proton beam pulse width) can be obtained using the proposed modality. By enabling visualization of biological phenomena at cellular and subcellular levels, this high-resolution microscopic technique enhances understanding of intricate cellular processes.

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Technical Note: Range verification of pulsed proton beams from fixed‐field alternating gradient accelerator by means of time‐of‐flight measurement of ionoacoustic waves

Cited by 4 publications

References 41 publications

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

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

Accuracy verification of protoacoustic measurements in a heterogeneous phantom by an optical hydrophone

Ionic-resolution protoacoustic microscopy: A feasibility study

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