1
|
Zhao X, Yang C, Lyu Y, Xu Y, Han Z, Zhao H. Tissue ultrasound imaging based on wavelet correlation analysis and pulse-inversion technique. Technol Health Care 2024; 32:31-53. [PMID: 37781821 DOI: 10.3233/thc-220403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
BACKGROUND Pulse-inversion-based tissue harmonic imaging has been utilized for many years because it can effectively eliminate the harmonic leakage and produce low side-lobe. However, the pulse inversion method is sensitive to imaging object movements, which may result in motion artifacts. Spatial resolution and contrast were limited. OBJECTIVE To improve ultrasound image quality by a new pulse-inversion-based tissue harmonic imaging technique. METHODS Continuous wavelet transform is applied to investigate the correlation between mother wavelet and the received echoes from two opposite pulses. To get a better correlation, a novel mother wavelet named 'tissue wavelet' is designed based on the Khokhlov-Zabolotskaya- Kuznetsov (KZK) wave equation. Radio frequency data were obtained from open Ultrasonix SonixTouch imaging system. Experiments were carried on ultrasonic tissue phantom, human carotid artery and human liver. RESULTS The average improvement of lateral spatial resolution is 49.52% compared to pulse-inversion-based tissue second-harmonic Imaging (PIHI). Contrast ratio (CR) and contrast-to-noise ratio (CNR) increased by 5.55 dB and 1.40 dB over PIHI. Tissue wavelet performs better than Mexh and Morl wavelet in lateral spatial resolution, CR, and CNR. CONCLUSION The proposed technique effectively improves the imaging quality in lateral spatial resolution, CR, and CNR.
Collapse
Affiliation(s)
- Xiaoyan Zhao
- Department of Information Engineering, School of Information Science and Technology, Qingdao University of Science and Technology, Tsingtao, Shandong, China
| | - Cuiyun Yang
- Department of Information Engineering, School of Information Science and Technology, Qingdao University of Science and Technology, Tsingtao, Shandong, China
| | - Yuchao Lyu
- Department of Information Engineering, School of Information Science and Technology, Qingdao University of Science and Technology, Tsingtao, Shandong, China
| | - Yinghao Xu
- Department of Information Engineering, School of Information Science and Technology, Qingdao University of Science and Technology, Tsingtao, Shandong, China
| | - Zhihui Han
- Department of Biomedical Engineering, School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, Hefei, Anhui, China
| | - Haien Zhao
- Orthopedic Department of the Second Hospital, Air Force Military Medical University, Xi'an, Shaanxi, China
| |
Collapse
|
2
|
He Y, Liu X, Zhang J, Peng C. A Backing-Layer-Shared Miniature Dual-Frequency Ultrasound Probe for Intravascular Ultrasound Imaging: In Vitro and Ex Vivo Validations. BIOSENSORS 2023; 13:971. [PMID: 37998146 PMCID: PMC10669229 DOI: 10.3390/bios13110971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 10/29/2023] [Accepted: 10/31/2023] [Indexed: 11/25/2023]
Abstract
Intravascular ultrasound (IVUS) imaging has been extensively utilized to visualize atherosclerotic coronary artery diseases and to guide coronary interventions. To receive ultrasound signals within the vessel wall safely and effectively, miniaturized ultrasound transducers that meet the strict size constraints and have a simple manufacturing procedure are highly demanded. In this work, the first known IVUS probe that employs a backing-layer-shared dual-frequency structure and a single coaxial cable is introduced, featuring a small thickness and easy interconnection procedure. The dual-frequency transducer is designed to have center frequencies of 30 MHz and 80 MHz, and both have an aperture size of 0.5 mm × 0.5 mm. The total thickness of the dual-frequency transducer is less than 700 µm. In vitro phantom imaging and ex vivo porcine coronary artery imaging experiments are conducted. The low-frequency transducer achieves spatial resolutions of 40 µm axially and 321 µm laterally, while the high-frequency transducer exhibits axial and lateral resolutions of 17 µm and 247 µm, respectively. A bandpass filter is utilized to separate the ultrasound images. Combining in vitro phantom imaging analysis with ex vivo imaging validation, a comprehensive demonstration of the promising application of the proposed miniature ultrasound probe is established.
Collapse
Affiliation(s)
- Yashuo He
- School of Biomedical Engineering, ShanghaiTech University, Shanghai 201210, China
| | - Xi Liu
- School of Biomedical Engineering, ShanghaiTech University, Shanghai 201210, China
| | - Jiayi Zhang
- School of Biomedical Engineering, ShanghaiTech University, Shanghai 201210, China
| | - Chang Peng
- School of Biomedical Engineering, ShanghaiTech University, Shanghai 201210, China
| |
Collapse
|
3
|
Shin EJ, Park S, Kang S, Kim J, Chang JH. Improving the quality of ultrasound images acquired using a therapeutic transducer. ULTRASONICS 2023; 134:107063. [PMID: 37300907 DOI: 10.1016/j.ultras.2023.107063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 05/01/2023] [Accepted: 05/30/2023] [Indexed: 06/12/2023]
Abstract
To enhance the effectiveness and safety of focused ultrasound (FUS) therapy, ultrasound image-based guidance and treatment monitoring are crucial. However, the use of FUS transducers for both therapy and imaging is impractical due to their low spatial resolution, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). To address this issue, we propose a new method that significantly improve the quality of images obtained by a FUS transducer. The proposed method employs coded excitation to enhance SNR and Wiener deconvolution to solve the problem of low axial resolution resulting from the narrow spectral bandwidth of FUS transducers. Specifically, the method eliminates the impulse response of a FUS transducer from received ultrasound signals using Wiener deconvolution, and pulse compression is performed using a mismatched filter. Simulation and commercial phantom experiments confirmed that the proposed method significantly improves the quality of images acquired by the FUS transducer. The -6 dB axial resolution was improved 1.27 mm to 0.37 mm that was similar to the resolution achieved by the imaging transducer, i.e., 0.33 mm. SNR and CNR also increased from 16.5 dB and 0.69 to 29.1 dB and 3.03, respectively, that were also similar to those by the imaging transducer (27.8 dB and 3.16). Based on the results, we believe that the proposed method has great potential to enhance the clinical utility of FUS transducers in ultrasound image-guided therapy.
Collapse
Affiliation(s)
- Eui-Ji Shin
- Department of Electronic Engineering, Sogang University, Seoul, Korea
| | - Sunghun Park
- Department of Electronic Engineering, Sogang University, Seoul, Korea
| | - Sungwoo Kang
- Department of Electrical Engineering and Computer Science, DGIST (Daegu Gyeongbuk Institute of Science and Technology), Daegu, Korea
| | - Jinwoo Kim
- Department of Electrical Engineering and Computer Science, DGIST (Daegu Gyeongbuk Institute of Science and Technology), Daegu, Korea
| | - Jin Ho Chang
- Department of Electrical Engineering and Computer Science, DGIST (Daegu Gyeongbuk Institute of Science and Technology), Daegu, Korea.
| |
Collapse
|
4
|
Collins GC, Brumfiel TA, Bercu ZL, Desai JP, Lindsey BD. Dual-Resonance (16/32 MHz) Piezoelectric Transducer With a Single Electrical Connection for Forward-Viewing Robotic Guidewire. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:1428-1441. [PMID: 35143395 PMCID: PMC9013008 DOI: 10.1109/tuffc.2022.3150746] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Peripheral artery disease (PAD) affects more than 200 million people globally. Minimally invasive endovascular procedures can provide relief and salvage limbs while reducing injury rates and recovery times. Unfortunately, when a calcified chronic total occlusion is encountered, ~25% of endovascular procedures fail due to the inability to advance a guidewire using the view provided by fluoroscopy. To enable a sub-millimeter, robotically steerable guidewire to cross these occlusions, a novel single-element, dual-band transducer is developed that provides simultaneous multifrequency, forward-viewing imaging with high penetration depth and high spatial resolution while requiring only a single electrical connection. The design, fabrication, and acoustic characterization of this device are described, and proof-of-concept imaging is demonstrated in an ex vivo porcine artery after integration with a robotically steered guidewire. Measured center frequencies of the developed transducer were 16 and 32 MHz, with -6 dB fractional bandwidths of 73% and 23%, respectively. When imaging a 0.2-mm wire target at a depth of 5 mm, measured -6 dB target widths were 0.498 ± 0.02 and 0.268 ± 0.01 mm for images formed at 16 and 32 MHz, respectively. Measured SNR values were 33.3 and 21.3 dB, respectively. The 3-D images of the ex vivo artery demonstrate high penetration for visualizing vessel morphology at 16 MHz and ability to resolve small features close to the transducer at 32 MHz. Using images acquired simultaneously at both frequencies as part of an integrated forward-viewing, guidewire-based imaging system, an interventionalist could visualize the best path for advancing the guidewire to improve outcomes for patients with PAD.
Collapse
|
5
|
Liang S, Su M, Liu B, Liu R, Zheng H, Qiu W, Zhang Z. Evaluation of Blood Induced Influence for High-Definition Intravascular Ultrasound (HD-IVUS). IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:98-105. [PMID: 34437062 DOI: 10.1109/tuffc.2021.3108163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
High-definition intravascular ultrasound (HD-IVUS) utilizing more than 80 MHz frequency to assess atherosclerotic plaque, can theoretically achieve an axial resolution of less than [Formula: see text]. However, the blood is a high-attenuation source at high frequency, which would affect the imaging quality. There has been no research evaluating the blood-induced influence on HD-IVUS imaging. And whether a temporary removal of blood is needed for HD-IVUS is unknown. In this study, an ultrahigh-frequency (100 MHz) ultrasound transducer was developed to evaluate the blood-induced attenuation for HD-IVUS imaging. A series of tungsten-wire phantom images in saline and blood at varying hematocrits were obtained. The images showed that blood did influence the ultrahigh-frequency imaging quality greatly. The signal-to-noise ratio (SNR) decrease by 71.7% in porcine whole blood compared to that in saline at the same depth of 2.3 mm. Moreover, the potential flushing schemes for HD-IVUS were studied in varying hematocrits. Three flushing agents commonly used in intravascular optical coherence tomography (IV-OCT) were investigated, including iohexol, mannitol, and dextran 5% and saline as the control group. The attenuation of blood in varying hematocrits/flushing agents was measured from 90 to 110 MHz. The result indicated dextran 5% was a suitable flushing agent for HD-IVUS due to its less signal attenuation compared to others.
Collapse
|
6
|
Choi BE, Lee HS, Sung JH, Jeong EY, Park CY, Jeong JS. Polarization Inverted Ultrasound Transducer Based on Composite Structure for Tissue Harmonic and Frequency Compound Imaging. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:273-282. [PMID: 34464259 DOI: 10.1109/tuffc.2021.3109458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Ultrasound transducer with polarization inversion technique (PIT) can provide dual-frequency feature for tissue harmonic imaging (THI) and frequency compound imaging (FCI). However, in the conventional PIT, the ultrasound intensity is reduced due to the multiple resonance characteristics of the combined piezoelectric element, and it is challenging to handle the thin piezoelectric layer required to make a PIT-based acoustic stack. In this study, an improved PIT using a piezo-composite layer was proposed to compensate for those problems simultaneously. The novel PIT-based acoustic stack also consists of two piezoelectric layers with opposite poling directions, in which the piezo-composite layer is located on the front side and the bulk-type piezoelectric layer is located on the back side. The thickness ratio between two piezoelectric layers is 0.5:0.5, but unlike a typical PIT model, it can generate dual-frequency spectrum. A finite element analysis (FEA) simulation was conducted, and subsequently, the prototype transducer was fabricated for performance demonstration. In the simulation and experiment, the intensity was increased by 56.76% and 30.88% compared to the conventional PIT model with the thickness ratio of 0.3:0.7. Thus, the proposed PIT-based transducer is expected to be useful in implementation of THI and FCI.
Collapse
|
7
|
Sung JH, Chang JH. Mechanically Rotating Intravascular Ultrasound (IVUS) Transducer: A Review. SENSORS (BASEL, SWITZERLAND) 2021; 21:3907. [PMID: 34198822 PMCID: PMC8201242 DOI: 10.3390/s21113907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/31/2021] [Accepted: 06/03/2021] [Indexed: 12/30/2022]
Abstract
Intravascular ultrasound (IVUS) is a valuable imaging modality for the diagnosis of atherosclerosis. It provides useful clinical information, such as lumen size, vessel wall thickness, and plaque composition, by providing a cross-sectional vascular image. For several decades, IVUS has made remarkable progress in improving the accuracy of diagnosing cardiovascular disease that remains the leading cause of death globally. As the quality of IVUS images mainly depends on the performance of the IVUS transducer, various IVUS transducers have been developed. Therefore, in this review, recently developed mechanically rotating IVUS transducers, especially ones exploiting piezoelectric ceramics or single crystals, are discussed. In addition, this review addresses the history and technical challenges in the development of IVUS transducers and the prospects of next-generation IVUS transducers.
Collapse
Affiliation(s)
| | - Jin-Ho Chang
- Department of Information and Communication Engineering, Deagu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea;
| |
Collapse
|
8
|
Peng C, Wu H, Kim S, Dai X, Jiang X. Recent Advances in Transducers for Intravascular Ultrasound (IVUS) Imaging. SENSORS (BASEL, SWITZERLAND) 2021; 21:3540. [PMID: 34069613 PMCID: PMC8160965 DOI: 10.3390/s21103540] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 05/11/2021] [Accepted: 05/17/2021] [Indexed: 12/16/2022]
Abstract
As a well-known medical imaging methodology, intravascular ultrasound (IVUS) imaging plays a critical role in diagnosis, treatment guidance and post-treatment assessment of coronary artery diseases. By cannulating a miniature ultrasound transducer mounted catheter into an artery, the vessel lumen opening, vessel wall morphology and other associated blood and vessel properties can be precisely assessed in IVUS imaging. Ultrasound transducer, as the key component of an IVUS system, is critical in determining the IVUS imaging performance. In recent years, a wide range of achievements in ultrasound transducers have been reported for IVUS imaging applications. Herein, a comprehensive review is given on recent advances in ultrasound transducers for IVUS imaging. Firstly, a fundamental understanding of IVUS imaging principle, evaluation parameters and IVUS catheter are summarized. Secondly, three different types of ultrasound transducers (piezoelectric ultrasound transducer, piezoelectric micromachined ultrasound transducer and capacitive micromachined ultrasound transducer) for IVUS imaging are presented. Particularly, the recent advances in piezoelectric ultrasound transducer for IVUS imaging are extensively examined according to their different working mechanisms, configurations and materials adopted. Thirdly, IVUS-based multimodality intravascular imaging of atherosclerotic plaque is discussed. Finally, summary and perspectives on the future studies are highlighted for IVUS imaging applications.
Collapse
Affiliation(s)
- Chang Peng
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA; (C.P.); (H.W.)
| | - Huaiyu Wu
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA; (C.P.); (H.W.)
| | | | - Xuming Dai
- Department of Cardiology, New York-Presbyterian Queens Hospital, Flushing, NY 11355, USA;
| | - Xiaoning Jiang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA; (C.P.); (H.W.)
| |
Collapse
|
9
|
Kang S, Lee J, Chang JH. Effectiveness of synthetic aperture focusing and coherence factor weighting for intravascular ultrasound imaging. ULTRASONICS 2021; 113:106364. [PMID: 33517139 DOI: 10.1016/j.ultras.2021.106364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 12/21/2020] [Accepted: 01/15/2021] [Indexed: 06/12/2023]
Abstract
Synthetic aperture focusing (SAF) and coherence factor weighting (CFW) have been used to improve the lateral resolution of ultrasound images. Although the two methods are effective for array-based ultrasound imaging, many researchers have also employed the methods for single-element-based imaging including intravascular ultrasound (IVUS) imaging. For single-element-based imaging, CFW is generally calculated from the scanlines obtained by SAF and applied to the scanline obtained after coherent summation of the SAF delayed scanlines, which is called a SAF-CFW method. In the paper, a theoretical model was derived to explore the effectiveness of SAF and CFW for single-element-based imaging, and the model was used to explain that SAF is not effective for IVUS imaging in terms of enhancing the spatial resolution, although it has the advantage of improving a contrast-to-noise ratio (CNR). This means that the SAF-CFW method is not optimal for improving the spatial resolution of IVUS imaging. In contrast, it was found in simulations and experiments that applying CFW to the target scanline itself is beneficial for the spatial resolution rather than a coherent summed scanline for IVUS SAF imaging, but CNR was not as good as SAF and SAF-CFW. As a result of both simulation and experimentation, it could be concluded that focused IVUS transducers without the application of those methods may be more advantageous to improve the spatial and contrast resolution simultaneously, considering the system complexity in the implementation of such imaging methods.
Collapse
Affiliation(s)
- Sungwoo Kang
- Department of Electronic Engineering, Sogang University, Seoul, South Korea
| | - Junsu Lee
- Department of Electronic Engineering, Sogang University, Seoul, South Korea
| | - Jin Ho Chang
- Department of Information and Communication Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea.
| |
Collapse
|
10
|
Zhu P, Peng H, Mao L, Tian J. Piezoelectric Single Crystal Ultrasonic Transducer for Endoscopic Drug Release in Gastric Mucosa. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:952-960. [PMID: 32970594 DOI: 10.1109/tuffc.2020.3026320] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Modern advanced minimally invasive surgery has been implemented for most of the significant gastrointestinal diseases. However, patients with coagulopathy or unresectable tumors cannot be cured by current treatment methods. Moreover, other existing medical devices for targeted drug release are too large to be applied in gastric endoscope because the diameter of the biopsy channel is smaller than 3 mm. To address it, in this work, we developed a piezoelectric single crystal ultrasonic transducer (the diameter was only 2.2 mm and the mass was 0.076 g) to produce acoustic waves, which could promote the drug release in the designed position of the digestive tract through an endoscope. It exhibited the electromechanical coupling coefficient of 0.36 and the center frequency of 6.9 MHz with the -6-dB bandwidth of 23%. In in vitro sonophoresis experiment, the gastric mucosa permeability to Bovine Serum Albumin increased about 5.6 times when the ultrasonic transducer was activated at 40 [Formula: see text] and 60% duty ratio, proving that employment of this transducer could facilitate drug penetration in the gastric mucosa. Meanwhile, the permeability could be adjusted by tuning the duty ratio of the ultrasonic transducer. The corresponding sonophoresis mechanism was related to the acoustic streaming and the thermal effect produced by the transducer. In addition, the measured maximum power density was 128 mW/cm2 and the mechanical index of the ultrasonic transducer was 0.02. The results held a great implication for applications of the transducer for targeted drug release in the gastrointestinal tract.
Collapse
|
11
|
Collins GC, Jing B, Lindsey BD. High contrast power Doppler imaging in side-viewing intravascular ultrasound imaging via angular compounding. ULTRASONICS 2020; 108:106200. [PMID: 32521337 PMCID: PMC7502537 DOI: 10.1016/j.ultras.2020.106200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 05/26/2020] [Accepted: 05/28/2020] [Indexed: 05/11/2023]
Abstract
The ability to assess likelihood of plaque rupture can determine the course of treatment in coronary artery disease. One indicator of plaque vulnerability is the development of blood vessels within the plaque, or intraplaque neovascularization. In order to visualize these vessels with increased sensitivity in the cardiac catheterization lab, a new approach for imaging blood flow in small vessels using side-viewing intravascular ultrasound (IVUS) is proposed. This approach based on compounding adjacent angular acquisitions was evaluated in tissue mimicking phantoms and ex vivo vessels. In phantom studies, the Doppler CNR increased from 3.3 ± 1.0 to 13 ± 2.6 (conventional clutter filtering) and from 1.9 ± 0.15 to 7.5 ± 1.1 (SVD filtering) as a result of applying angular compounding. When imaging flow at a rate of 5.6 mm/s in 200 µm tubes adjacent to the lumen of ex vivo porcine arteries, the Doppler CNR increased from 5.3 ± 0.95 to 7.2 ± 1.3 (conventional filtering) and from 23 ± 3.3 to 32 ± 6.7 (SVD filtering). Applying these strategies could allow increased sensitivity to slow flow in side-viewing intravascular ultrasound imaging.
Collapse
Affiliation(s)
- Graham C Collins
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA 30332, United States.
| | - Bowen Jing
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA 30332, United States
| | - Brooks D Lindsey
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA 30332, United States
| |
Collapse
|
12
|
Sung JH, Jeong EY, Jeong JS. Intravascular Ultrasound Transducer by Using Polarization Inversion Technique for Tissue Harmonic Imaging: Modeling and Experiments. IEEE Trans Biomed Eng 2020; 67:3380-3391. [PMID: 32286955 DOI: 10.1109/tbme.2020.2986284] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Intravascular ultrasound (IVUS) tissue harmonic imaging (THI) is a useful vessel imaging technique that can provide deep penetration depth as well as high spatial and contrast resolution. Typically, a high-frequency IVUS transducer for THI requires a broad bandwidth or dual-frequency bandwidth. However, it is very difficult to make an IVUS transducer with a frequency bandwidth covering from the fundamental frequency to the second harmonic or a dual-peak at the desired frequency. To solve this problem, in this study, we applied the polarization inversion technique (PIT) to the IVUS transducer for THI. The PIT makes it relatively easy to design IVUS transducers with suitable frequency characteristics for THI depending on the inversion ratio of the piezoelectric layer and specifications of the passive materials. In this study, two types of IVUS transducers based on the PIT were developed for THI. One is a front-side inversion layer (FSIL) transducer with a broad bandwidth, and the other is a back-side inversion layer (BSIL) transducer with a dual-frequency bandwidth. These transducers were designed using finite element analysis (FEA)-based simulation, and the prototype transducers were fabricated. Subsequently, the performance was evaluated by not only electrical impedance and pulse-echo response tests but also B-mode imaging tests with a 25 μm tungsten wire and tissue-mimicking gelatin phantoms. The FEA simulation and experimental results show that the proposed scheme can successfully implement the tissue harmonic IVUS image, and thus it can be one of the promising techniques for developing IVUS transducers for THI.
Collapse
|
13
|
Abstract
Abstract
Purpose
Photoacoustic (PA) microscopy has emerged as a useful tool in biomedical imaging applications such as visualization of microvasculature and hemoglobin oxygen saturation, single-cell, and label-free imaging of organs including cancer. Since the ultrasound transducers used for PA signal detection are not optically transparent, the integration of optical and acoustic modules for coaxial alignment of laser and acoustic beam fields in PA microscopy is complex and costly.
Methods
Here, we report a recently developed optically transparent focused transducer for combined PA and ultrasound (US) microscopy. All the acoustic layers including the acoustic lens are optically transparent, enabling simple integration of optical and acoustic modules for both imaging modalities.
Results
The mean light transmittance of the transducer’s backing layer and acoustic lens and of the transducer itself were measured at 92%, 83%, and 66%, respectively. Results from in vitro and in vivo experiments demonstrated the transducer to be suitable for both US and PA imaging.
Conclusions
The results of this study represent a step toward efficient construction of probes for combined PA and US microscopy.
Collapse
|
14
|
Park J, Lee C, Lee J, Ha JI, Choi H, Chang JH. Magnetically Actuated Forward-Looking Interventional Ultrasound Imaging: Feasibility Studies. IEEE Trans Biomed Eng 2019; 67:1797-1805. [PMID: 31634823 DOI: 10.1109/tbme.2019.2948391] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Interventional ultrasound imaging is a prerequisite for guiding implants and treatment within the hearts and blood vessels. Due to limitations on the catheter's diameter, interventional ultrasonic transducers have side-looking structures although forward-looking imaging may provide more intuitive and real time guidance in treating diseased sites ahead of catheters. To address the issue, a magnetically actuated forward-looking interventional ultrasound imaging device is implemented for the first time. METHODS A forward-looking catheter containing a 1 mm ring type focused 35 MHz ultrasound transducer and a micro magnet, was fabricated. For imaging, the transducer was placed at the center of four electromagnetic coils positioned on four sides of a squared acrylic housing. By modifying the magnetic field, the catheter tip could be remotely translated for sector scanning. RESULTS The scanning angle could reach up to 3° in 1 Hz with 15 mT, while wider angles of 5° could be achieved with a higher magnetic field of 25 mT for ex-vivo imaging. The position of the transducer could be detected by monitoring the motion with a CCD camera, mimicking clinical X-ray imaging. In the wire target and tissue mimicking phantom studies, the measured hole size, spatial resolution and distance between wires by the proposed system were comparable with the values from a linear scanner. Multi-frame real time data acquisition was demonstrated via ex-vivo imaging on a pig's coronary artery. CONCLUSION/SIGNIFICANCE The feasibility of magnetically actuated forward-looking interventional ultrasound imaging was demonstrated. The remote-controlled scanning method may allow to simplify the structures of forward-looking interventional ultrasound imaging catheters.
Collapse
|