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Ding Z, Gao Y, Hou C, Li S, Yu Y. Comparison of focusing property and radiation force between autofocusing Bessel beams and focused Gaussian beams. OPTICS EXPRESS 2024; 32:9982-9994. [PMID: 38571221 DOI: 10.1364/oe.516084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 02/15/2024] [Indexed: 04/05/2024]
Abstract
As abruptly autofocusing beams, autofocusing Bessel beams (ABBs) have been proven to be a class solution for the Helmholtz equation [Opt. Express31, 33228 (2023)10.1364/OE.500383]. In this paper, we use the Fresnel number as the basic parameter and accurately compare the focusing property and radiation force of ABBs versus focused Gaussian beams (FGBs) under the same Fresnel number. Unlike FGBs, ABBs can achieve autofocusing without the need for an initial focusing phase. Our analysis of the beam width defined by power in the bucket, revealed that FGBs exhibit uniform focusing along the straight line, whereas ABBs demonstrate accelerated focusing along the elliptic curve. At the same Fresnel number, FGBs exhibit a higher peak intensity in the focal plane, yet ABBs excel in gradient force on particles. In comparison to FGBs, ABBs exhibit smaller potential well widths, allowing for stable and precise trapping of high refractive index particles at the focal point. While FGBs are considered suitable for laser processing and ablation due to their high peak power density, ABBs possess significant advantages in optical manipulation due to their great gradient force. Furthermore, we conduct a comparative analysis between ABBs and circular Airy beams (CABs). The peak intensity and gradient force exhibited by CABs are slightly lesser than those of ABBs. CABs are appropriate for multi-point trapping along the axis, whereas ABBs are more suited for precise single-point trapping.
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Khattak S, Gupta N, Zhou X, Pires L, Wilson BC, Yucel YH. Non-invasive dynamic assessment of conjunctival melanomas by photoacoustic imaging. Exp Eye Res 2019; 179:157-167. [DOI: 10.1016/j.exer.2018.11.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 10/21/2018] [Accepted: 11/13/2018] [Indexed: 01/27/2023]
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Zafar H, Leahy M, Wijns W, Kolios M, Zafar J, Johnson N, Sharif F. Photoacoustic cardiovascular imaging: a new technique for imaging of atherosclerosis and vulnerable plaque detection. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aab640] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Hariri A, Wang J, Kim Y, Jhunjhunwala A, Chao DL, Jokerst JV. In vivo photoacoustic imaging of chorioretinal oxygen gradients. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-8. [PMID: 29524321 PMCID: PMC5844348 DOI: 10.1117/1.jbo.23.3.036005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 02/14/2018] [Indexed: 05/18/2023]
Abstract
Chorioretinal imaging has a crucial role for the patients with chorioretinal vascular diseases, such as neovascular age-related macular degeneration. Imaging oxygen gradients in the eye could better diagnose and treat ocular diseases. Here, we describe the use of photoacoustic ocular imaging (PAOI) in measuring chorioretinal oxygen saturation (CR - sO2) gradients in New Zealand white rabbits (n = 5) with ocular ischemia. We observed good correlation (R2 = 0.98) between pulse oximetry and PAOI as a function of different oxygen percentages in inhaled air. We then used an established ocular ischemia model in which intraocular pressure is elevated to constrict ocular blood flow, and notice a positive correlation (R2 = 0.92) between the injected volume of phosphate buffered saline (PBS) and intraocular pressure (IOP) as well as a negative correlation (R2 = 0.98) between CR - sO2 and injected volume of PBS. The CR - sO2 was measured before (baseline), during (ischemia), and after the infusion (600-μL PBS). The ischemia-reperfusion model did not affect the measurement of the sO2 using a pulse oximeter on the animal's paw, but the chorioretinal PAOI signal showed a nearly sixfold decrease in CR - sO2 (n = 5, p = 0.00001). We also observe a sixfold decrease in CR - sO2 after significant elevation of IOP during ischemia, with an increase close to baseline during reperfusion. These data suggest that PAOI can detect changes in chorioretinal oxygenation and may be useful for application to imaging oxygen gradients in ocular disease.
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Affiliation(s)
- Ali Hariri
- University of California-San Diego, Nanoengineering Department, La Jolla, California, United States
| | - Junxin Wang
- University of California-San Diego, Nanoengineering Department, La Jolla, California, United States
| | - Yeji Kim
- University of California-San Diego, School of Medicine, La Jolla, California, United States
| | - Anamik Jhunjhunwala
- University of California-San Diego, Bioengineering Department, La Jolla, California, United States
| | - Daniel L. Chao
- University of California-San Diego, Shiley Eye Institute, Department of Ophthalmology, La Jolla, California, United States
| | - Jesse V. Jokerst
- University of California-San Diego, Nanoengineering Department, La Jolla, California, United States
- University of California-San Diego, Material Science and Engineering Program, La Jolla, California, United States
- University of California-San Diego, Radiology Department, La Jolla, California, United States
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Abstract
OBJECTIVE Photoacoustic (PA) imaging emerges as a unique tool to study biological samples based on optical absorption contrast. In PA imaging, piezoelectric transducers are commonly used to detect laser-induced ultrasonic waves. However, they typically lack adequate broadband sensitivity at ultrasonic frequency higher than 100 MHz, whereas their bulky size and optically opaque nature cause technical difficulties in integrating PA imaging with conventional optical imaging modalities. To overcome these limitations, optical methods of ultrasound detection were developed and shown their unique applications in PA imaging. METHODS We provide an overview of recent technological advances in optical methods of ultrasound detection and their applications in PA imaging. A general theoretical framework describing sensitivity, bandwidth, and angular responses of optical ultrasound detection is also introduced. RESULTS Optical methods of ultrasound detection can provide improved detection angle and sensitivity over significantly extended bandwidth. In addition, its versatile variants also offer additional advantages, such as device miniaturization, optical transparency, mechanical flexibility, minimal electrical/mechanical crosstalk, and potential noncontact PA imaging. CONCLUSION The optical ultrasound detection methods discussed in this review and their future evolution may play an important role in PA imaging for biomedical study and clinical diagnosis.
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Hennen SN, Xing W, Shui YB, Zhou Y, Kalishman J, Andrews-Kaminsky LB, Kass MA, Beebe DC, Maslov KI, Wang LV. Photoacoustic tomography imaging and estimation of oxygen saturation of hemoglobin in ocular tissue of rabbits. Exp Eye Res 2015; 138:153-8. [PMID: 26048477 PMCID: PMC5821107 DOI: 10.1016/j.exer.2015.05.022] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 05/27/2015] [Accepted: 05/30/2015] [Indexed: 01/26/2023]
Abstract
This study evaluated in vivo imaging capabilities and safety of qualitative monitoring of oxygen saturation of hemoglobin (sO2) of rabbit ciliary body tissues obtained with acoustic resolution (AR) photoacoustic tomography (PAT). AR PAT was used to collect trans-scleral images from ciliary body vasculature of seven New Zealand White rabbits. The PAT sO2 measurements were obtained under the following conditions: when systemic sO2 as measured by pulse oximetry was between 100% and 99% (level 1); systemic sO2 as measured by pulse oximetry was between 98% and 90% (level 2); and systemic sO2 as measured by pulse oximetry was less than 90% (level 3). Following imaging, histological analysis of ocular tissue was conducted to evaluate for possible structural damage caused by the AR PAT imaging. AR PAT was able to resolve anatomical structures of the anterior segment of the eye, viewed through the cornea or anterior sclera. Histological studies revealed no ocular damage. On average, sO2 values (%) obtained with AR PAT were lower than sO2 values obtained with pulse oximetry (all p < 0.001): 86.28 ± 4.16 versus 99.25 ± 0.28, 84.09 ± 1.81 vs. 95.3 ± 2.6, and 64.49 ± 7.27 vs. 71.15 ± 10.21 for levels 1, 2 and 3 respectively. AR PAT imaging modality is capable of qualitative monitoring for deep tissue sO2 in rabbits. Further studies are needed to validate and modify the AR PAT modality specifically for use in human eyes. Having a safe, non-invasive method of in vivo imaging of sO2 in the anterior segment is important to studies evaluating the role of oxidative damage, hypoxia and ischemia in pathogenesis of ocular diseases.
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Affiliation(s)
- Stella N Hennen
- Solo Private Practice, Minneapolis, MN, USA; Department of Ophthalmology and Visual Sciences, School of Medicine, Washington University in St. Louis, St. Louis, MO, USA.
| | - Wenxin Xing
- Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, MO, USA; Optical Imaging Laboratory, Department of Biomedical Engineering, School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO, USA
| | - Ying-Bo Shui
- Department of Ophthalmology and Visual Sciences, School of Medicine, Washington University in St. Louis, St. Louis, MO, USA
| | - Yong Zhou
- Optical Imaging Laboratory, Department of Biomedical Engineering, School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO, USA
| | - Jennifer Kalishman
- Division of Comparative Medicine, School of Medicine, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Lisa B Andrews-Kaminsky
- Division of Comparative Medicine, School of Medicine, Washington University School of Medicine in St. Louis, St. Louis, MO, USA
| | - Michael A Kass
- Department of Ophthalmology and Visual Sciences, School of Medicine, Washington University in St. Louis, St. Louis, MO, USA
| | - David C Beebe
- Department of Ophthalmology and Visual Sciences, School of Medicine, Washington University in St. Louis, St. Louis, MO, USA
| | - Konstantin I Maslov
- Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, MO, USA; Optical Imaging Laboratory, Department of Biomedical Engineering, School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO, USA
| | - Lihong V Wang
- Department of Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, MO, USA; Optical Imaging Laboratory, Department of Biomedical Engineering, School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO, USA.
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Kim GR, Kang J, Kwak JY, Chang JH, Kim SI, Youk JH, Moon HJ, Kim MJ, Kim EK. Photoacoustic imaging of breast microcalcifications: a preliminary study with 8-gauge core-biopsied breast specimens. PLoS One 2014; 9:e105878. [PMID: 25153128 PMCID: PMC4143349 DOI: 10.1371/journal.pone.0105878] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 07/24/2014] [Indexed: 01/05/2023] Open
Abstract
Background We presented the photoacoustic imaging (PAI) tool and to evaluate whether microcalcifications in breast tissue can be detected on photoacoustic (PA) images. Methods We collected 21 cores containing microcalcifications (n = 11, microcalcification group) and none (n = 10, control group) in stereotactic or ultrasound (US) guided 8-gauge vacuum-assisted biopsies. Photoacoustic (PA) images were acquired through ex vivo experiments by transmitting laser pulses with two different wavelengths (700 nm and 800 nm). The presence of microcalcifications in PA images were blindly assessed by two radiologists and compared with specimen mammography. A ratio of the signal amplitude occurring at 700 nm to that occurring at 800 nm was calculated for each PA focus and was called the PAI ratio. Results Based on the change of PA signal amplitude between 700 nm and 800 nm, 10 out of 11 specimens containing microcalcifications and 8 out of 10 specimens without calcifications were correctly identified on blind review; the sensitivity, specificity, accuracy, positive predictive and negative predictive values of our blind review were 90.91%, 80.0%, 85.71%, 83.33% and 88.89%. The PAI ratio in the microcalcification group was significantly higher than that in the control group (the median PAI ratio, 2.46 versus 1.11, respectively, P = .001). On subgroup analysis in the microcalcification group, neither malignant diagnosis nor the number or size of calcification-foci was proven to contribute to PAI ratios. Conclusion Breast microcalcifications generated distinguishable PA signals unlike breast tissue without calcifications. So, PAI, a non-ionizing and non-invasive hybrid imaging technique, can be an alternative in overcoming the limitations of conventional US imaging.
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Affiliation(s)
- Ga Ram Kim
- Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jeeun Kang
- Sogang Institute of Advanced Technology, Sogang University, Seoul, Republic of Korea
- Interdisciplinary Program of Integrated Biotechnology, Seoul, Republic of Korea
| | - Jin Young Kwak
- Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jin Ho Chang
- Sogang Institute of Advanced Technology, Sogang University, Seoul, Republic of Korea
- Interdisciplinary Program of Integrated Biotechnology, Seoul, Republic of Korea
| | - Seung Il Kim
- Department of Surgery, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Ji Hyun Youk
- Department of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Hee Jung Moon
- Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Min Jung Kim
- Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Eun-Kyung Kim
- Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
- * E-mail:
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Chen R, Cabrera-Munoz NE, Lam KH, Hsu HS, Zheng F, Zhou Q, Shung KK. PMN-PT single-crystal high-frequency kerfless phased array. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2014; 61:1033-41. [PMID: 24859667 PMCID: PMC4477951 DOI: 10.1109/tuffc.2014.2999] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
This paper reports the design, fabrication, and characterization of a miniature high-frequency kerfless phased array prepared from a PMN-PT single crystal for forward-looking intravascular or endoscopic imaging applications. After lapping down to around 40 μm, the PMN-PT material was utilized to fabricate 32-element kerfless phased arrays using micromachining techniques. The aperture size of the active area was only 1.0 × 1.0 mm. The measured results showed that the array had a center frequency of 40 MHz, a bandwidth of 34% at -6 dB with a polymer matching layer, and an insertion loss of 20 dB at the center frequency. Phantom images were acquired and compared with simulated images. The results suggest that the feasibility of developing a phased array mounted at the tip of a forward-looking intravascular catheter or endoscope. The fabricated array exhibits much higher sensitivity than PZT ceramic-based arrays and demonstrates that PMN-PT is well suited for this application.
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Li H, Dong B, Zhang Z, Zhang HF, Sun C. A transparent broadband ultrasonic detector based on an optical micro-ring resonator for photoacoustic microscopy. Sci Rep 2014; 4:4496. [PMID: 24675547 PMCID: PMC3968454 DOI: 10.1038/srep04496] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 02/25/2014] [Indexed: 11/29/2022] Open
Abstract
Photoacoustic microscopy (PAM) does not rely on contrast agent to image the optical absorption contrast in biological tissue. It is uniquely suited for measuring several tissue physiological parameters, such as hemoglobin oxygen saturation, that would otherwise remain challenging. Researchers are designing new clinical diagnostic tools and multimodal microscopic systems around PAM to fully unleash its potential. However, the sizeable and opaque piezoelectric ultrasonic detectors commonly used in PAM impose a serious constraint. Our solution is a coverslip-style optically transparent ultrasound detector based on a polymeric optical micro-ring resonator (MRR) with a total thickness of 250 μm. It enables highly-sensitive ultrasound detection over a wide receiving angle with a bandwidth of 140 MHz, which corresponds to a photoacoustic saturation limit of 287 cm−1, at an estimated noise-equivalent pressure (NEP) of 6.8 Pa. We also established a theoretical framework for designing and optimizing the MRR for PAM.
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Affiliation(s)
- Hao Li
- 1] Department of Biomedical Engineering, Northwestern University, Evanston IL 60208 [2]
| | - Biqin Dong
- 1] Department of Biomedical Engineering, Northwestern University, Evanston IL 60208 [2] Department of Mechanical Engineering, Northwestern University, Evanston IL 60208 [3]
| | - Zhen Zhang
- Department of Mechanical Engineering, Northwestern University, Evanston IL 60208
| | - Hao F Zhang
- 1] Department of Biomedical Engineering, Northwestern University, Evanston IL 60208 [2] Department of Ophthalmology, Northwestern University, Chicago IL 60611
| | - Cheng Sun
- Department of Mechanical Engineering, Northwestern University, Evanston IL 60208
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Gould T, Wang Q, Pfefer TJ. Optical-thermal light-tissue interactions during photoacoustic breast imaging. BIOMEDICAL OPTICS EXPRESS 2014; 5:832-47. [PMID: 24688817 PMCID: PMC3959836 DOI: 10.1364/boe.5.000832] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 01/26/2014] [Accepted: 01/29/2014] [Indexed: 05/04/2023]
Abstract
Light-tissue interactions during photoacoustic imaging, including dynamic heat transfer processes in and around vascular structures, are not well established. A three-dimensional, transient, optical-thermal computational model was used to simulate energy deposition, temperature distributions and thermal damage in breast tissue during exposure to pulsed laser trains at 800 and 1064 nm. Rapid and repetitive temperature increases and thermal relaxation led to superpositioning effects that were highly dependent on vessel diameter and depth. For a ten second exposure at established safety limits, the maximum single-pulse and total temperature rise levels were 0.2°C and 5.8°C, respectively. No significant thermal damage was predicted. The impact of tissue optical properties, surface boundary condition and irradiation wavelength on peak temperature location and temperature evolution with time are discussed.
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Ofili EO, Fair A, Norris K, Verbalis JG, Poland R, Bernard G, Stephens DS, Dubinett SM, Imperato-McGinley J, Dottin RP, Pulley J, West A, Brown A, Mellman TA. Models of interinstitutional partnerships between research intensive universities and minority serving institutions (MSI) across the Clinical Translational Science Award (CTSA) consortium. Clin Transl Sci 2013; 6:435-43. [PMID: 24119157 DOI: 10.1111/cts.12118] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Health disparities are an immense challenge to American society. Clinical and Translational Science Awards (CTSAs) housed within the National Center for Advancing Translational Science (NCATS) are designed to accelerate the translation of experimental findings into clinically meaningful practices and bring new therapies to the doorsteps of all patients. Research Centers at Minority Institutions (RCMI) program at the National Institute on Minority Health and Health Disparities (NIMHD) are designed to build capacity for biomedical research and training at minority serving institutions. The CTSA created a mechanism fostering formal collaborations between research intensive universities and minority serving institutions (MSI) supported by the RCMI program. These consortium-level collaborations activate unique translational research approaches to reduce health disparities with credence to each academic institutions history and unique characteristics. Five formal partnerships between research intensive universities and MSI have formed as a result of the CTSA and RCMI programs. These partnerships present a multifocal approach; shifting cultural change and consciousness toward addressing health disparities, and training the next generation of minority scientists. This collaborative model is based on the respective strengths and contributions of the partnering institutions, allowing bidirectional interchange and leveraging NIH and institutional investments providing measurable benchmarks toward the elimination of health disparities.
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Affiliation(s)
- Elizabeth O Ofili
- Atlanta Clinical Translational Science Institute (ACTSI), RCMI Center of Excellence for Clinical and Translational Research, and Department of Medicine, Morehouse School of Medicine, Atlanta, Georgia, USA
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Kong F, Silverman RH, Liu L, Chitnis PV, Lee KK, Chen YC. Photoacoustic-guided convergence of light through optically diffusive media. OPTICS LETTERS 2011; 36:2053-5. [PMID: 21633446 PMCID: PMC3384991 DOI: 10.1364/ol.36.002053] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is proportional to the scattered light intensity at the light absorber.
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Affiliation(s)
- Fanting Kong
- Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
| | - Ronald H. Silverman
- Department of Ophthalmology, Columbia University Medical Center, New York, New York 10032, USA
- Riverside Research Institute, 156 William Street, New York, New York 10038, USA
| | - Liping Liu
- Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
| | - Parag V. Chitnis
- Riverside Research Institute, 156 William Street, New York, New York 10038, USA
| | - Kotik K. Lee
- Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
| | - Y. C. Chen
- Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
- Corresponding author:
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Silverman RH, Kong F, Chen YC, Lloyd HO, Kim HH, Cannata JM, Shung KK, Coleman DJ. High-resolution photoacoustic imaging of ocular tissues. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:733-42. [PMID: 20420969 PMCID: PMC2881573 DOI: 10.1016/j.ultrasmedbio.2010.02.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 01/28/2010] [Accepted: 02/11/2010] [Indexed: 05/04/2023]
Abstract
Optical coherence tomography (OCT) and ultrasound (US) are methods widely used for diagnostic imaging of the eye. These techniques detect discontinuities in optical refractive index and acoustic impedance, respectively. Because these both relate to variations in tissue density or composition, OCT and US images share a qualitatively similar appearance. In photoacoustic imaging (PAI), short light pulses are directed at tissues, pressure is generated due to a rapid energy deposition in the tissue volume and thermoelastic expansion results in generation of broadband US. PAI thus depicts optical absorption, which is independent of the tissue characteristics imaged by OCT or US. Our aim was to demonstrate the application of PAI in ocular tissues and to do so with lateral resolution comparable to OCT. We developed two PAI assemblies, both of which used single-element US transducers and lasers sharing a common focus. The first assembly had optical and 35-MHz US axes offset by a 30 degrees angle. The second assembly consisted of a 20-MHz ring transducer with a coaxial optics. The laser emitted 5-ns pulses at either 532 nm or 1064 nm, with spot sizes at the focus of 35 microm for the angled probe and 20 microm for the coaxial probe. We compared lateral resolution by scanning 12.5 microm diameter wire targets with pulse/echo US and PAI at each wavelength. We then imaged the anterior segment in whole ex vivo pig eyes and the choroid and ciliary body region in sectioned eyes. PAI data obtained at 1064 nm in the near infrared had higher penetration but reduced signal amplitude compared to that obtained using the 532 nm green wavelength. Images were obtained of the iris, choroid and ciliary processes. The zonules and anterior cornea and lens surfaces were seen at 532 nm. Because the laser spot size was significantly smaller than the US beamwidth at the focus, PAI images had superior resolution than those obtained using conventional US.
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Affiliation(s)
- Ronald H Silverman
- Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065, USA.
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Tao C, Liu X. Reconstruction of high quality photoacoustic tomography with a limited-view scanning. OPTICS EXPRESS 2010; 18:2760-2766. [PMID: 20174105 DOI: 10.1364/oe.18.002760] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The goal of this work is to resolve the limited-view problem of photoacoustic tomography (PAT). We report a two-loop iteration method to inverse the photoacoustic sources from the measured photoacoustic signals. PAT reconstruction with this method does not depend on the detection path. Therefore, the proposed method can provide recognizable image even when the detector only scans a small angle (about 20 degrees approximately 30 degrees). The comparison with the delay-and-sum method shows the advantage of the proposed method in reconstructing image from incomplete data.
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Affiliation(s)
- Chao Tao
- Key Lab of Modern Acoustics, Ministry of Education, Nanjing University, Nanjing 210093, People's Republic of China
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Hu S, Wang LV. Photoacoustic imaging and characterization of the microvasculature. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:011101. [PMID: 20210427 PMCID: PMC2821418 DOI: 10.1117/1.3281673] [Citation(s) in RCA: 205] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Revised: 09/15/2009] [Accepted: 09/21/2009] [Indexed: 05/06/2023]
Abstract
Photoacoustic (optoacoustic) tomography, combining optical absorption contrast and highly scalable spatial resolution (from micrometer optical resolution to millimeter acoustic resolution), has broken through the fundamental penetration limit of optical ballistic imaging modalities-including confocal microscopy, two-photon microscopy, and optical coherence tomography-and has achieved high spatial resolution at depths down to the diffusive regime. Optical absorption contrast is highly desirable for microvascular imaging and characterization because of the presence of endogenous strongly light-absorbing hemoglobin. We focus on the current state of microvascular imaging and characterization based on photoacoustics. We first review the three major embodiments of photoacoustic tomography: microscopy, computed tomography, and endoscopy. We then discuss the methods used to characterize important functional parameters, such as total hemoglobin concentration, hemoglobin oxygen saturation, and blood flow. Next, we highlight a few representative applications in microvascular-related physiological and pathophysiological research, including hemodynamic monitoring, chronic imaging, tumor-vascular interaction, and neurovascular coupling. Finally, several potential technical advances toward clinical applications are suggested, and a few technical challenges in contrast enhancement and fluence compensation are summarized.
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Affiliation(s)
- Song Hu
- Washington University in St. Louis, Department of Biomedical Engineering, St. Louis, Missouri 63130-4899, USA
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Abstract
Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This review provides a brief recap of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities, hybrid detection methods, photoacoustic contrast agents and the photoacoustic Doppler effect, as well as translational research topics.
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Affiliation(s)
- Changhui Li
- Optical Imaging Laboratory, Department of Biomedical Engineering Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Lihong V. Wang
- Optical Imaging Laboratory, Department of Biomedical Engineering Washington University in St. Louis, St. Louis, MO 63130, USA
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