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Braunstein L, Brüningk SC, Rivens I, Civale J, Haar GT. Characterization of Acoustic, Cavitation, and Thermal Properties of Poly(vinyl alcohol) Hydrogels for Use as Therapeutic Ultrasound Tissue Mimics. ULTRASOUND IN MEDICINE & BIOLOGY 2022; 48:1095-1109. [PMID: 35337687 DOI: 10.1016/j.ultrasmedbio.2022.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 01/19/2022] [Accepted: 02/06/2022] [Indexed: 06/14/2023]
Abstract
The thermal and mechanical effects induced in tissue by ultrasound can be exploited for therapeutic applications. Tissue-mimicking materials (TMMs), reflecting different soft tissue properties, are required for experimental evaluation of therapeutic potential. In the study described here, poly(vinyl alcohol) (PVA) hydrogels were characterized. Hydrogels prepared using different concentrations (5%-20% w/w) and molecular weights of PVA ± cellulose scatterers (2.5%-10% w/w) were characterized acoustically (sound speed, attenuation) as a function of temperature (25°C-45°C), thermally (thermal conductivity, specific heat capacity) and in terms of their cavitation thresholds. Results were compared with measurements in fresh sheep tissue (kidney, liver, spleen). Sound speed depended most strongly on PVA concentration, and attenuation, on cellulose content. For the range of formulations investigated, the PVA gel acoustic properties (sound speed: 1532 ± 17 to 1590 ± 9 m/s, attenuation coefficient: 0.08 ± 0.01 to 0.37 ± 0.02 dB/cm) fell within those measured in fresh tissue. Cavitation thresholds for 10% PVA hydrogels (50% occurrence: 4.1-5.4 MPa, 75% occurrence: 5.4-8.2 MPa) decreased with increasing cellulose content. In summary, PVA cellulose composite hydrogels may be suitable mimics of acoustic, cavitation and thermal properties of soft tissue for a number of therapeutic ultrasound applications.
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Affiliation(s)
- Lisa Braunstein
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom.
| | - Sarah C Brüningk
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom; Machine Learning & Computational Biology Lab, Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland; SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Ian Rivens
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - John Civale
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
| | - Gail Ter Haar
- Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
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Peek AT, Thomas GPL, Leotta DF, Yuldashev PV, Khokhlova VA, Khokhlova TD. Robust and durable aberrative and absorptive phantom for therapeutic ultrasound applications. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:3007. [PMID: 35649925 PMCID: PMC9071501 DOI: 10.1121/10.0010369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Phase aberration induced by soft tissue inhomogeneities often complicates high-intensity focused ultrasound (HIFU) therapies by distorting the field and, previously, we designed and fabricated a bilayer gel phantom to reproducibly mimic that effect. A surface pattern containing size scales relevant to inhomogeneities of a porcine body wall was introduced between gel materials with fat- and muscle-like acoustic properties-ballistic and polyvinyl alcohol gels. Here, the phantom design was refined to achieve relevant values of ultrasound absorption and scattering and make it more robust, facilitating frequent handling and use in various experimental arrangements. The fidelity of the interfacial surface of the fabricated phantom to the design was confirmed by three-dimensional ultrasound imaging. The HIFU field distortions-displacement of the focus, enlargement of the focal region, and reduction of focal pressure-produced by the phantom were characterized using hydrophone measurements with a 1.5 MHz 256-element HIFU array and found to be similar to those induced by an ex vivo porcine body wall. A phase correction approach was used to mitigate the aberration effect on nonlinear focal waveforms and enable boiling histotripsy treatments through the phantom or body wall. The refined phantom represents a practical tool to explore HIFU therapy systems capabilities.
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Affiliation(s)
- Alex T Peek
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Gilles P L Thomas
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Daniel F Leotta
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | | | - Vera A Khokhlova
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Tatiana D Khokhlova
- Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, Washington 98125, USA
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Gautam UC, Pydi YS, Selladurai S, Das CJ, Thittai AK, Roy S, Datla NV. A Poly-vinyl Alcohol (PVA)-based phantom and training tool for use in simulated Transrectal Ultrasound (TRUS) guided prostate needle biopsy procedures. Med Eng Phys 2021; 96:46-52. [PMID: 34565552 DOI: 10.1016/j.medengphy.2021.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 08/16/2021] [Accepted: 08/24/2021] [Indexed: 10/20/2022]
Abstract
Trans-rectal ultrasound-guided needle biopsy is a well-established diagnosis technique for prostate cancer. To enhance the needle manoeuvring skills under ultrasound (US) guidance, it is preferable to train medical practitioners in needle biopsy on tissue-mimicking phantoms. This phantom should mimic the morphology as well as mechanical and acoustic properties of the human male pelvic region to provide a surgical experience and feedback. In this study, polyvinyl alcohol (PVA) was used and evaluated for prostate phantom development, that is stiffness tunable, US-compatible and durable phantom material. Three samples, each with 5%, 10%, and 15% concentration of PVA material, were prepared, and their mechanical and shrinkage characteristics were investigated. The anatomy of male pelvic region was used to develop an anatomically correct phantom. Later US-guided needle biopsy was performed on the phantom. The range of elastic moduli of the PVA samples was 2∼146 kPa. Their elastic moduli and volumes were found to remain statistically close from seventh to eighth freeze-thaw cycle (p>0.05). Initial US scans of the phantom resulted in satisfactory B-mode images, with a clear distinction between the prostate and its surrounding organs. This study demonstrated the applicability of PVA hydrogel as a phantom material for training in US-guided needle biopsy.
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Affiliation(s)
- Umesh C Gautam
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India; Department of Applied Mechanics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Yeswanth S Pydi
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | | | - Chandan J Das
- Department of Radiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
| | - Arun K Thittai
- Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Sitikantha Roy
- Department of Applied Mechanics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Naresh V Datla
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
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Peek AT, Hunter C, Kreider W, Khokhlova TD, Rosnitskiy PB, Yuldashev PV, Sapozhnikov OA, Khokhlova VA. Bilayer aberration-inducing gel phantom for high intensity focused ultrasound applications. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 148:3569. [PMID: 33379925 PMCID: PMC8097711 DOI: 10.1121/10.0002877] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/04/2020] [Accepted: 11/15/2020] [Indexed: 05/19/2023]
Abstract
Aberrations induced by soft tissue inhomogeneities often complicate high-intensity focused ultrasound (HIFU) therapies. In this work, a bilayer phantom made from polyvinyl alcohol hydrogel and ballistic gel was built to mimic alternating layers of water-based and lipid tissues characteristic of an abdominal body wall and to reproducibly distort HIFU fields. The density, sound speed, and attenuation coefficient of each material were measured using a homogeneous gel layer. A surface with random topographical features was designed as an interface between gel layers using a 2D Fourier spectrum approach and replicating different spatial scales of tissue inhomogeneities. Distortion of the field of a 256-element 1.5 MHz HIFU array by the phantom was characterized through hydrophone measurements for linear and nonlinear beam focusing and compared to the corresponding distortion induced by an ex vivo porcine body wall of the same thickness. Both spatial shift and widening of the focal lobe were observed, as well as dramatic reduction in focal pressures caused by aberrations. The results suggest that the phantom produced levels of aberration that are similar to a real body wall and can serve as a research tool for studying HIFU effects as well as for developing algorithms for aberration correction.
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Affiliation(s)
- Alex T Peek
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Christopher Hunter
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Wayne Kreider
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Tatiana D Khokhlova
- Division of Gastroenterology, Department of Medicine, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA
| | - Pavel B Rosnitskiy
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Petr V Yuldashev
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Oleg A Sapozhnikov
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Vera A Khokhlova
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
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Nisar H, Moore J, Piazza R, Maneas E, Chen ECS, Peters TM. A simple, realistic walled phantom for intravascular and intracardiac applications. Int J Comput Assist Radiol Surg 2020; 15:1513-1523. [PMID: 32524216 PMCID: PMC7419379 DOI: 10.1007/s11548-020-02201-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 05/18/2020] [Indexed: 11/29/2022]
Abstract
PURPOSE This work aims to develop a simple, anatomically and haptically realistic vascular phantom, compatible with intravascular and intracardiac ultrasound. The low-cost, dual-layered phantom bridges the gap between traditional wall-only and wall-less phantoms by showing both the vessel wall and surrounding tissue in ultrasound imaging. This phantom can better assist clinical tool training, testing of intravascular devices, blood flow studies, and validation of algorithms for intravascular and intracardiac surgical systems. METHODS Polyvinyl alcohol cryogel (PVA-c) incorporating a scattering agent was used to obtain vessel and tissue-mimicking materials. Our specific design targeted the inferior vena cava and renal bifurcations which were modelled using CAD software. A custom mould and container were 3D-printed for shaping the desired vessel wall. Three phantoms were prepared by varying both the concentrations of scattering agent as well as the number of freeze-thaw cycles to which the phantom layers were subjected during the manufacturing process. Each phantom was evaluated using ultrasound imaging using the Foresight™ ICE probe. Geometrical validation was provided by comparing CAD design to a CT scan of the phantom. RESULTS The desired vascular phantom was constructed using 2.5% and 0.05% scattering agent concentration in the vessel and tissue-mimicking layers, respectively. Imaging of the three phantoms showed that increasing the number of freeze-thaw cycles did not significantly enhance the image contrast. Comparison of the US images with their CT equivalents resulted in an average error of 0.9[Formula: see text] for the lumen diameter. CONCLUSION The phantom is anatomically realistic when imaged with intracardiac ultrasound and provides a smooth lumen for the ultrasound probe and catheter to manoeuvre. The vascular phantom enables validation of intravascular and intracardiac image guidance systems. The simple construction technique also provides a workflow for designing complex, multi-layered arterial phantoms.
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Affiliation(s)
- Hareem Nisar
- Robarts Research Institute, Western University, London, Canada. .,School of Biomedical Engineering, Western University, London, Canada.
| | - John Moore
- Robarts Research Institute, Western University, London, Canada
| | - Roberta Piazza
- Department of Information Engineering, University of Pisa, Pisa, Italy
| | - Efthymios Maneas
- Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, London, UK.,Department of Medical Physics and Bioengineering, University College London, London, UK
| | - Elvis C S Chen
- Robarts Research Institute, Western University, London, Canada.,School of Biomedical Engineering, Western University, London, Canada.,Department of Medical Biophysics, Western University, London, Canada
| | - Terry M Peters
- Robarts Research Institute, Western University, London, Canada.,School of Biomedical Engineering, Western University, London, Canada.,Department of Medical Biophysics, Western University, London, Canada.,Department of Medical Imaging, Western University, London, Canada
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