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Pandey PK, Gonzalez G, Cheong F, Chen CB, Bettiol AA, Chen Y, Xiang L. Ionic-resolution protoacoustic microscopy: A feasibility study. APPLIED PHYSICS LETTERS 2024; 124:053702. [PMID: 38313557 PMCID: PMC10838192 DOI: 10.1063/5.0188650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 01/16/2024] [Indexed: 02/06/2024]
Abstract
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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Affiliation(s)
- Prabodh Kumar Pandey
- Department of Radiological Sciences, University of California, Irvine, California 92697, USA
| | - Gilberto Gonzalez
- Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | - Frederick Cheong
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Ce-Belle Chen
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Andrew A. Bettiol
- Centre for Ion Beam Applications, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Yong Chen
- Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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Mast TD, Johnstone DA, Dumoulin CL, Lamba MA, Patch SK. Reconstruction of thermoacoustic emission sources induced by proton irradiation using numerical time reversal. Phys Med Biol 2023; 68:10.1088/1361-6560/acabfc. [PMID: 36595327 PMCID: PMC9976196 DOI: 10.1088/1361-6560/acabfc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022]
Abstract
Objective.Mapping of dose delivery in proton beam therapy can potentially be performed by analyzing thermoacoustic emissions measured by ultrasound arrays. Here, a method is derived and demonstrated for spatial mapping of thermoacoustic sources using numerical time reversal, simulating re-transmission of measured emissions into the medium.Approach.Spatial distributions of thermoacoustic emission sources are shown to be approximated by the analytic-signal form of the time-reversed acoustic field, evaluated at the time of the initial proton pulse. Given calibration of the array sensitivity and knowledge of tissue properties, this approach approximately reconstructs the acoustic source amplitude, equal to the product of the time derivative of the radiation dose rate, mass density, and Grüneisen parameter. This approach was implemented using two models for acoustic fields of the array elements, one modeling elements as line sources and the other as rectangular radiators. Thermoacoustic source reconstructions employed previously reported measurements of emissions from proton energy deposition in tissue-mimicking phantoms. For a phantom incorporating a bone layer, reconstructions accounted for the higher sound speed in bone. Dependence of reconstruction quality on array aperture size and signal-to-noise ratio was consistent with previous acoustic simulation studies.Main results.Thermoacoustic source distributions were successfully reconstructed from acoustic emissions measured by a linear ultrasound array. Spatial resolution of reconstructions was significantly improved in the azimuthal (array) direction by incorporation of array element diffraction. Source localization agreed well with Monte Carlo simulations of energy deposition, and was improved by incorporating effects of inhomogeneous sound speed.Significance.The presented numerical time reversal approach reconstructs thermoacoustic sources from proton beam radiation, based on straightforward processing of acoustic emissions measured by ultrasound arrays. This approach may be useful for ranging and dosimetry of clinical proton beams, if acoustic emissions of sufficient amplitude and bandwidth can be generated by therapeutic proton sources.
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Affiliation(s)
- T Douglas Mast
- Biomedical Engineering, University of Cincinnati, United States of America
| | - David A Johnstone
- Radiation Oncology, University of Cincinnati, United States of America
| | - Charles L Dumoulin
- Radiology, Cincinnati Children's Hospital Medical Center, United States of America
| | - Michael A Lamba
- Radiation Oncology, University of Cincinnati, United States of America
| | - Sarah K Patch
- Acoustic Range Estimates, Chicago, Illinois, United States of America
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Sueyasu S, Takayanagi T, Miyazaki K, Kuriyama Y, Ishi Y, Uesugi T, Unlu MB, Kudo N, Chen Y, Kasamatsu K, Fujii M, Kobayashi M, Rohringer W, Matsuura T. Ionoacoustic application of an optical hydrophone to detect proton beam range in water. Med Phys 2022; 50:2438-2449. [PMID: 36565440 DOI: 10.1002/mp.16189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/22/2022] [Accepted: 12/14/2022] [Indexed: 12/25/2022] Open
Abstract
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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Affiliation(s)
- Shota Sueyasu
- Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Taisuke Takayanagi
- Hitachi Ltd, Research and Development Group, Center for Technology Innovation-Energy, Hitachi-shi, Ibaraki, Japan
| | - Koichi Miyazaki
- Hitachi Ltd, Research and Development Group, Center for Technology Innovation-Energy, Hitachi-shi, Ibaraki, Japan
| | - Yasutoshi Kuriyama
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan
| | - Yoshihiro Ishi
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan
| | - Tomonori Uesugi
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan
| | - Mehmet Burcin Unlu
- Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan.,Department of Physics, Bogazici University, Bebek, Istanbul, Turkey
| | - Nobuki Kudo
- Faculty of Information Science and Technology, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Ye Chen
- Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Koki Kasamatsu
- Graduate School of Biomedical Science and Engineering, Hokkaido University, Sapporo, Hokkaido, Japan
| | | | - Masanori Kobayashi
- Planetary Exploration Research Institute, Chiba Institute of Technology, Narashino, Chiba, Japan
| | | | - Taeko Matsuura
- Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan.,Proton Beam Therapy Center, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
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