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Lihong V Wang - One of the best experts on this subject based on the ideXlab platform.

  • correcting the limited view in optical resolution photoacoustic microscopy
    Journal of Biophotonics, 2018
    Co-Authors: Wei Liu, Lihong V Wang, Ruimin Chen, Qifa Zhou, Yuan Zhou, Mengran Wang, Emelina Vienneau, Jianwen Luo, Junjie Yao
    Abstract:

    Optical-resolution photoacoustic microscopy (OR-PAM) has proven useful for anatomical and functional imaging with high spatial resolutions. However, the coherent signal generation and the desired Reflection-Mode detection in OR-PAM can result in a limited detectability of features aligned with the acoustic axis (i.e., vertical structures). Here, we investigated the limited-view phenomenon in OR-PAM by simulating the generation and propagation of the acoustic pressure waves and determined the key optical parameters affecting the visibility of vertical structures. Proof-of-concept numerical experiments were performed with different illumination angles, optical foci, and numerical apertures (NA) of the objective lens. The results collectively show that an NA of 0.3 can readily improve the visibility of vertical structures in a typical Reflection-Mode OR-PAM system. This conclusion was confirmed by numerical simulations on the cortical blood vessels in a mouse brain, and by experiments in a suture-cross phantom and in a mouse brain in vivo.

  • continuous scanning of a time reversed ultrasonically encoded optical focus by Reflection Mode digital phase conjugation
    Optics Letters, 2014
    Co-Authors: Yuta Suzuki, Qiang Yang, Lihong V Wang
    Abstract:

    Time-reversed ultrasonically encoded (TRUE) optical focusing in turbid media was previously implemented using both analog and digital phase conjugation. The digital approach, in addition to its large energy gain, can improve the focal intensity and resolution by iterative focusing. However, performing iterative focusing at each focal position can be time-consuming. Here, we show that by gradually moving the focal position, the TRUE focal intensity is improved, as in iterative focusing at a fixed position, and can be continuously scanned to image fluorescent targets in a shorter time. In addition, our setup is, to the best of our knowledge, the first demonstration of TRUE focusing using a digital phase conjugate mirror in a Reflection Mode, which is more suitable for practical applications.

  • Reflection Mode submicron resolution in vivo photoacoustic microscopy
    Journal of Biomedical Optics, 2012
    Co-Authors: Chi Zhang, Kirk K. Shung, Konstantin Maslov, Ruimin Chen, Qifa Zhou, Lihong V Wang
    Abstract:

    Submicron-resolution photoacoustic microscopy (PAM) currently exists only in transmission Mode, due to the technical difficulties of combining high numerical-aperture (NA) optical illumination with high NA acoustic detection. The lateral resolution of Reflection-Mode PAM has not reached <2  μm in the visible light range. Here we develop the first Reflection-Mode submicron-resolution PAM system with a new compact design. By using a parabolic mirror to focus and reflect the photoacoustic waves, sufficient signals were collected for good sensitivity without distorting the optical focusing. By imaging nanospheres and a resolution test chart, the lateral resolution was measured to be ∼0.5  μm with an optical wavelength of 532 nm, an optical NA of 0.63. The axial resolution was measured at 15 μm. Here the axial resolution was measured by a different experiment with the lateral resolution measurement. But we didn’t describe the details of axial resolution measurement due to space limit. The maximum penetration was measured at ∼0.42  mm in optical-scattering soft tissue. As a comparison, both the submicron-resolution PAM and a 2.4 μm-resolution PAM were used to image a mouse ear in vivo with the same optical wavelength and similar pulse energy. Capillaries were resolved better by the submicron-resolution PAM. Therefore, the submicron-resolution PAM is suitable for in vivo high-resolution imaging, or even subcellular imaging, of optical absorption.

  • Fast 3-D dark-field Reflection-Mode photoacoustic microscopy in vivo with a 30-MHz ultrasound linear array
    Journal of Biomedical Optics, 2008
    Co-Authors: Liang Song, Rachel Bitton, Kirk K. Shung, Konstantin Maslov, Lihong V Wang
    Abstract:

    We present an in vivo dark-field Reflection-Mode photoacoustic microscopy system that performs cross-sectional (B-scan) imaging at 50Hz with real-time beamforming and 3-D imaging consisting of 166 B-scan frames at 1Hz with postbeamforming. To our knowledge, this speed is currently the fastest in photoacoustic imaging. A custom-designed light delivery system is integrated with a 30-MHz ultrasound linear array to realize dark-field Reflection-Mode imaging. Linear mechanical scanning of the array produces 3-D images. The system has axial, lateral, and elevational resolutions of 25, 70, and 200μm, respectively, and can image 3mm deep in scattering biological tissues. Volumetric images of subcutaneous vasculature in rats are demonstrated in vivo. Fast 3-D photoacoustic microscopy is anticipated to facilitate applications of photoacoustic imaging in biomedical studies that involve dynamics and clinical procedures that demand immediate diagnosis.

  • deep Reflection Mode photoacoustic imaging of biological tissue
    Journal of Biomedical Optics, 2007
    Co-Authors: Kwang Hyun Song, Lihong V Wang
    Abstract:

    A Reflection-Mode photoacoustic PA imaging system was designed and built to image deep structures in biological tissues. We chose near-infrared laser pulses of 804-nm wavelength for PA excitation to achieve deep penetration. To minimize unwanted surface signals, we adopted dark-field ring-shaped illumination. This imaging system employing a 5-MHz spherically focused ultrasonic transducer provides penetration up to 38 mm in chicken breast tissue. At the 19-mm depth, the axial resolution is 144 m and the transverse resolution is 560 m. Internal organs of small animals were imaged clearly. © 2007 Society

Konstantin Maslov - One of the best experts on this subject based on the ideXlab platform.

  • Reflection Mode submicron resolution in vivo photoacoustic microscopy
    Journal of Biomedical Optics, 2012
    Co-Authors: Chi Zhang, Kirk K. Shung, Konstantin Maslov, Ruimin Chen, Qifa Zhou, Lihong V Wang
    Abstract:

    Submicron-resolution photoacoustic microscopy (PAM) currently exists only in transmission Mode, due to the technical difficulties of combining high numerical-aperture (NA) optical illumination with high NA acoustic detection. The lateral resolution of Reflection-Mode PAM has not reached <2  μm in the visible light range. Here we develop the first Reflection-Mode submicron-resolution PAM system with a new compact design. By using a parabolic mirror to focus and reflect the photoacoustic waves, sufficient signals were collected for good sensitivity without distorting the optical focusing. By imaging nanospheres and a resolution test chart, the lateral resolution was measured to be ∼0.5  μm with an optical wavelength of 532 nm, an optical NA of 0.63. The axial resolution was measured at 15 μm. Here the axial resolution was measured by a different experiment with the lateral resolution measurement. But we didn’t describe the details of axial resolution measurement due to space limit. The maximum penetration was measured at ∼0.42  mm in optical-scattering soft tissue. As a comparison, both the submicron-resolution PAM and a 2.4 μm-resolution PAM were used to image a mouse ear in vivo with the same optical wavelength and similar pulse energy. Capillaries were resolved better by the submicron-resolution PAM. Therefore, the submicron-resolution PAM is suitable for in vivo high-resolution imaging, or even subcellular imaging, of optical absorption.

  • Fast 3-D dark-field Reflection-Mode photoacoustic microscopy in vivo with a 30-MHz ultrasound linear array
    Journal of Biomedical Optics, 2008
    Co-Authors: Liang Song, Rachel Bitton, Kirk K. Shung, Konstantin Maslov, Lihong V Wang
    Abstract:

    We present an in vivo dark-field Reflection-Mode photoacoustic microscopy system that performs cross-sectional (B-scan) imaging at 50Hz with real-time beamforming and 3-D imaging consisting of 166 B-scan frames at 1Hz with postbeamforming. To our knowledge, this speed is currently the fastest in photoacoustic imaging. A custom-designed light delivery system is integrated with a 30-MHz ultrasound linear array to realize dark-field Reflection-Mode imaging. Linear mechanical scanning of the array produces 3-D images. The system has axial, lateral, and elevational resolutions of 25, 70, and 200μm, respectively, and can image 3mm deep in scattering biological tissues. Volumetric images of subcutaneous vasculature in rats are demonstrated in vivo. Fast 3-D photoacoustic microscopy is anticipated to facilitate applications of photoacoustic imaging in biomedical studies that involve dynamics and clinical procedures that demand immediate diagnosis.

  • in vivo dark field Reflection Mode photoacoustic microscopy
    Optics Letters, 2005
    Co-Authors: Konstantin Maslov, Gheorghe Stoica, Lihong V Wang
    Abstract:

    Reflection-Mode photoacoustic microscopy with dark-field laser pulse illumination and high-numerical-aperture ultrasonic detection is designed and implemented in noninvasively imaged blood vessels in the skin in vivo. Dark-field optical illumination minimizes the interference caused by strong photoacoustic signals from superficial structures. A high-numerical-aperture acoustic lens provides high lateral resolution, 45–120μm in this system. A broadband ultrasonic detection system provides high axial resolution, estimated to be ∼15μm. The optical illumination and ultrasonic detection are in a coaxial confocal configuration for optimal image quality. The system is capable of imaging optical-absorption contrast as deep as 3mm in biological tissue.

Liang Song - One of the best experts on this subject based on the ideXlab platform.

  • Reflection Mode in vivo photoacoustic microscopy with subwavelength lateral resolution
    Biomedical Optics Express, 2014
    Co-Authors: Wei Song, Riqiang Lin, Wei Zheng, Ruimin Liu, Hongtao Huang, Xiaojing Gong, Shousheng Yang, Rui Zhang, Liang Song
    Abstract:

    We developed a Reflection-Mode subwavelength-resolution photoacoustic microscopy system capable of imaging optical absorption contrast in vivo. The simultaneous high-resolution and Reflection-Mode imaging capacity of the system was enabled by delicately configuring a miniature high-frequency ultrasonic transducer tightly under a water-immersion objective with numerical aperture of 1.0. At 532-nm laser illumination, the lateral resolution of the system was measured to be ~320 nm. With this system, subcellular structures of red blood cells and B16 melanoma cells were resolved ex vivo; microvessels, including individual capillaries, in a mouse ear were clearly imaged label-freely in vivo, using the intrinsic optical absorption from hemoglobin. The current study suggests that, the optical-absorption contrast, subwavelength resolution, and Reflection-Mode ability of the developed photoacoustic microscopy may empower a wide range of biomedical studies for visualizing cellular and/or subcellular structures.

  • Fast 3-D dark-field Reflection-Mode photoacoustic microscopy in vivo with a 30-MHz ultrasound linear array
    Journal of Biomedical Optics, 2008
    Co-Authors: Liang Song, Rachel Bitton, Kirk K. Shung, Konstantin Maslov, Lihong V Wang
    Abstract:

    We present an in vivo dark-field Reflection-Mode photoacoustic microscopy system that performs cross-sectional (B-scan) imaging at 50Hz with real-time beamforming and 3-D imaging consisting of 166 B-scan frames at 1Hz with postbeamforming. To our knowledge, this speed is currently the fastest in photoacoustic imaging. A custom-designed light delivery system is integrated with a 30-MHz ultrasound linear array to realize dark-field Reflection-Mode imaging. Linear mechanical scanning of the array produces 3-D images. The system has axial, lateral, and elevational resolutions of 25, 70, and 200μm, respectively, and can image 3mm deep in scattering biological tissues. Volumetric images of subcutaneous vasculature in rats are demonstrated in vivo. Fast 3-D photoacoustic microscopy is anticipated to facilitate applications of photoacoustic imaging in biomedical studies that involve dynamics and clinical procedures that demand immediate diagnosis.

F Lacroix - One of the best experts on this subject based on the ideXlab platform.

  • potential errors in optical density measurements due to scanning side in ebt and ebt2 gafchromic film dosimetry
    Medical Physics, 2010
    Co-Authors: Joannie Desroches, Hugo Bouchard, F Lacroix
    Abstract:

    PURPOSE The purpose of this study is to determine the effect on the measured optical density of scanning on either side of a Gafchromic EBT and EBT2 film using an Epson (Epson Canada Ltd., Toronto, Ontario) 10000XL flat bed scanner. METHODS Calibration curves were constructed using EBT2 film scanned in landscape orientation in both Reflection and transmission Mode on an Epson 10000XL scanner. Calibration curves were also constructed using EBT film. Potential errors due to an optical density difference from scanning the film on either side ("face up" or "face down") were simulated. RESULTS Scanning the film face up or face down on the scanner bed while keeping the film angular orientation constant affects the measured optical density when scanning in Reflection Mode. In contrast, no statistically significant effect was seen when scanning in transmission Mode. This effect can significantly affect relative and absolute dose measurements. As an application example, the authors demonstrate potential errors of 17.8% by inverting the film scanning side on the gamma index for 3%-3 mm criteria on a head and neck intensity modulated radiotherapy plan, and errors in absolute dose measurements ranging from 10% to 35% between 2 and 5 Gy. CONCLUSIONS Process consistency is the key to obtaining accurate and precise results in Gafchromic film dosimetry. When scanning in Reflection Mode, care must be taken to place the film consistently on the same side on the scanner bed.

  • technical note potential errors in optical density measurements due to scanning side in ebt and ebt2 gafchromic film dosimetry
    Medical Physics, 2010
    Co-Authors: Joannie Desroches, Hugo Bouchard, F Lacroix
    Abstract:

    Purpose: The purpose of this study is to determine the effect on the measured optical density of scanning on either side of a Gafchromic EBT and EBT2 film using an Epson (Epson Canada Ltd., Toronto, Ontario) 10000XL flat bed scanner. Methods: Calibration curves were constructed using EBT2 film scanned in landscape orientation in both Reflection and transmission Mode on an Epson 10000XL scanner.Calibration curves were also constructed using EBT film. Potential errors due to an optical density difference from scanning the film on either side (“face up” or “face down”) were simulated. Results: Scanning the film face up or face down on the scanner bed while keeping the film angular orientation constant affects the measured optical density when scanning in Reflection Mode. In contrast, no statistically significant effect was seen when scanning in transmission Mode. This effect can significantly affect relative and absolute dosemeasurements. As an application example, the authors demonstrate potential errors of 17.8% by inverting the film scanning side on the gamma index for 3%—3 mm criteria on a head and neck intensity modulated radiotherapy plan, and errors in absolute dosemeasurements ranging from 10% to 35% between 2 and 5 Gy. Conclusions: Process consistency is the key to obtaining accurate and precise results in Gafchromic film dosimetry. When scanning in Reflection Mode, care must be taken to place the film consistently on the same side on the scanner bed.

Roger J Zemp - One of the best experts on this subject based on the ideXlab platform.

  • ultraviolet photoacoustic remote sensing microscopy
    Optics Letters, 2019
    Co-Authors: Nathaniel J M Haven, Kevan Bell, Pradyumna Kedarisetti, John D Lewis, Roger J Zemp
    Abstract:

    Traditional histopathology involves fixing, sectioning, and staining protocols that are time consuming and subject to staining variability. In this Letter, we present ultraviolet photoacoustic remote sensing microscopy, capable of imaging cell nuclei without the need for exogenous stains or labelling. Our Reflection Mode approach is non-contact and has the potential to provide useful histological information without laborious sample preparation steps. Tumor cell cultures and excised tissue samples were imaged with the 0.7 μm resolution and signal-to-noise ratios as high as 53 dB, with close agreement to traditional hematoxylin and eosin staining.

  • in vivo optical resolution photoacoustic microscopy using glancing angle deposited nanostructured fabry perot etalons
    Optics Letters, 2015
    Co-Authors: Parsin Hajireza, Jason B Sorge, Michael J Brett, Roger J Zemp
    Abstract:

    In this Letter, Reflection-Mode optical resolution photoacoustic microscopy (OR-PAM) using glancing angle-deposited (GLAD) nanostructured Fabry–Perot interferometers (FPI) for in vivo applications is reported. GLAD is a single-step physical vapor deposition (PVD) technique used to fabricate porous nanostructured thin films. Using titanium dioxide, a transparent semiconductor with a high refractive index (n=2.4), the GLAD technique can be employed to fabricate samples with tailored nano-porosity, refractive index periodicities, and high Q-factor reflectance spectra. The OR-PAM in vivo images of chorioallantoic membrane (CAM) of 5-day chicken embryo Model are demonstrated. The phantom study shows lateral resolution and signal-to-noise ratio better than 7 μm and 35 dB, respectively. The sensitive GLAD FPI allows photoacoustic imaging down to a few-nJ pulse energy. To the best of our knowledge, this is the first time that a FPI-based Reflection Mode optical resolution photoacoustic imaging technique is demonstrated for in vivo applications.