Tzu Hao Chow - Academia.edu (2024)

The application of gold nanoparticles as a contrast agent in optical bioimaging is well appreciat... more The application of gold nanoparticles as a contrast agent in optical bioimaging is well appreciated, but limited to a narrow excitation range due to its rather invariable optical resonance typically at 520 nm. Compared to gold nanoparticles, the optical response of gold nanoshells can be tuned to match the higher excitation wavelength of many promising clinical reflectance-based imaging modalities such as the optical coherence tomography (OCT). In this study, we demonstrate the tunability of gold nanoshells to improve the optical contrast of backscattering signal under confocal reflectance microscopy and OCT. The gold nanoshells were synthesized and conjugated to antibodies for in vitro demonstration of their selective optical contrast in cancer cells over normal cells under the confocal reflectance microscopy. The OCT signals from these gold nanoshells were compared to that from bare silica cores and intrinsic tissue scattering using 1% Intralipid. We have shown that gold nanoshells are able to elicit an optical contrast to discriminate between cancerous and normal cells under the confocal reflectance microscopy based on differences in molecular markers expression. Compared to bare silica core, the presence of the gold shell is able to effect a higher backscattered OCT signal with an apparent contrast over 1% Intralipid. This contrast can be made to be dependent on the molecular marker expression with antibody specificity.

The material behaviour of sutured tendons is important in healing models as mechanical trauma to ... more The material behaviour of sutured tendons is important in healing models as mechanical trauma to the tendon during surgery can compromise the healing process. This work demonstrates the use of spectral domain optical coherence tomography (SD-OCT) for the monitoring of normal and injured, and subsequently repaired flexor tendons and their behaviour under load. Vertical crimp patterns in normal tendons were observed to be replaced by uniform scattering as the load increases, but the crimp periods in sutured tendons were constrained at the suture site, with gap separation at the suture joint tapering off at high loads. This information could be useful for surgeons who need to balance gap separation in healing tendons and sustainable load.

Biophotonics 2007: Optics in Life Science, 2007

Biophotonics 2007: Optics in Life Science, 2007

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XIV, 2010

The material behaviour of sutured tendons is important in healing models as mechanical trauma to ... more The material behaviour of sutured tendons is important in healing models as mechanical trauma to the tendon during surgery can compromise the healing process. This work demonstrates the use of spectral domain optical coherence tomography (SD-OCT) for the monitoring of ...

Optics in the Life Sciences, 2011

Applied optics, 2009

Journal of biomedical optics

IEEE transactions on bio-medical engineering, 2012

This study investigates the autocorrelation bandwidths of dual-window (DW) optical coherence tomo... more This study investigates the autocorrelation bandwidths of dual-window (DW) optical coherence tomography (OCT) k-space scattering profile of different-sized microspheres and their correlation to scatterer size. A dual-bandwidth spectroscopic metric defined as the ratio of the 10% to 90% autocorrelation bandwidths is found to change monotonically with microsphere size and gives the best contrast enhancement for scatterer size differentiation in the resulting spectroscopic image. A simulation model supports the experimental results and revealed a tradeoff between the smallest detectable scatterer size and the maximum scatterer size in the linear range of the dual-window dual-bandwidth (DWDB) metric, which depends on the choice of the light source optical bandwidth. Spectroscopic OCT (SOCT) images of microspheres and tonsil tissue samples based on the proposed DWDB metric showed clear differentiation between different-sized scatterers as compared to those derived from conventional short-time Fourier transform metrics. The DWDB metric significantly improves the contrast in SOCT imaging and can aid the visualization and identification of dissimilar scatterer size in a sample. Potential applications include the early detection of cell nuclear changes in tissue carcinogenesis, the monitoring of healing tendons, and cell proliferation in tissue scaffolds.

Proceedings of SPIE - The International Society for Optical Engineering

Microwave and Optical Technology Letters, 2013

ABSTRACT Optical coherence tomography (OCT) was used to monitor various flexor tendon states incl... more ABSTRACT Optical coherence tomography (OCT) was used to monitor various flexor tendon states including tendon at rest, normal tendons during loading, tendon microstructural damage post loading, and healing tendons at 0, 3, and 8 weeks time points.Potential uses include assessing microstructural damage, monitoring the quality of suture repair, and tendon healing. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:990–995, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27514

Biomedical Optics, 2008

... James CY Kah1, Rachel CY Wan2, Tzu-Hao Chow3, Malini C. Olivo4, Subodh G. Mhaisalkar2, Colin ... more ... James CY Kah1, Rachel CY Wan2, Tzu-Hao Chow3, Malini C. Olivo4, Subodh G. Mhaisalkar2, Colin JR Sheppard1 1Division of Bioengineering, National University of Singapore, Singapore 2School of ... [2] SJ Oldenburg, RD Averitt, SL Westcott, NJ Halas, “Nanoengineering of ...

Journal of Biomedical Optics, 2009

This work investigates the use of optical coherence tomography (OCT) to identify virus infection ... more This work investigates the use of optical coherence tomography (OCT) to identify virus infection in orchid plants. Besides revealing the cross-sectional structure of orchid leaves, highly scattering upper leaf epidermides are detected with OCT for virus-infected plants. This distinct feature is not observable under histological examination of the leaf samples. Furthermore, the leaf epidermides of stressed but healthy plants, which exhibit similar visual symptoms as virus-infected plants, are not highly scattering and are similar to those of healthy plants. The results suggest that virus-infected orchid plants can be accurately identified by imaging the epidermal layers of their leaves with OCT. The OCT modality is suitable for fast, nondestructive diagnosis of orchid virus infection, which may potentially lead to significant cost savings and better control of the spread of viruses in the orchid industry.

Journal of Biomedical Optics, 2009

Abstract Optical coherence tomography (OCT) is an optical imaging technique that allows the visua... more Abstract Optical coherence tomography (OCT) is an optical imaging technique that allows the visualization of living tissues in vivo. However, the speckle noise affects their diagnostic accuracy by degrading the quality of OCT images. Wavelet based denoising methods have been successful in reducing the speckle noise in past but they require a manual selection of few parameters for optimum denoising. We propose a computerized method to select these parameters by using an evolutionary technique called differential evolution (DE). The ...

The application of gold nanoparticles as a contrast agent in optical bioimaging is well appreciat... more The application of gold nanoparticles as a contrast agent in optical bioimaging is well appreciated, but limited to a narrow excitation range due to its rather invariable optical resonance typically at 520 nm. Compared to gold nanoparticles, the optical response of gold nanoshells can be tuned to match the higher excitation wavelength of many promising clinical reflectance-based imaging modalities such as the optical coherence tomography (OCT). In this study, we demonstrate the tunability of gold nanoshells to improve the optical contrast of backscattering signal under confocal reflectance microscopy and OCT. The gold nanoshells were synthesized and conjugated to antibodies for in vitro demonstration of their selective optical contrast in cancer cells over normal cells under the confocal reflectance microscopy. The OCT signals from these gold nanoshells were compared to that from bare silica cores and intrinsic tissue scattering using 1% Intralipid. We have shown that gold nanoshells are able to elicit an optical contrast to discriminate between cancerous and normal cells under the confocal reflectance microscopy based on differences in molecular markers expression. Compared to bare silica core, the presence of the gold shell is able to effect a higher backscattered OCT signal with an apparent contrast over 1% Intralipid. This contrast can be made to be dependent on the molecular marker expression with antibody specificity.

The material behaviour of sutured tendons is important in healing models as mechanical trauma to ... more The material behaviour of sutured tendons is important in healing models as mechanical trauma to the tendon during surgery can compromise the healing process. This work demonstrates the use of spectral domain optical coherence tomography (SD-OCT) for the monitoring of normal and injured, and subsequently repaired flexor tendons and their behaviour under load. Vertical crimp patterns in normal tendons were observed to be replaced by uniform scattering as the load increases, but the crimp periods in sutured tendons were constrained at the suture site, with gap separation at the suture joint tapering off at high loads. This information could be useful for surgeons who need to balance gap separation in healing tendons and sustainable load.

Biophotonics 2007: Optics in Life Science, 2007

Biophotonics 2007: Optics in Life Science, 2007

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XIV, 2010

The material behaviour of sutured tendons is important in healing models as mechanical trauma to ... more The material behaviour of sutured tendons is important in healing models as mechanical trauma to the tendon during surgery can compromise the healing process. This work demonstrates the use of spectral domain optical coherence tomography (SD-OCT) for the monitoring of ...

Optics in the Life Sciences, 2011

Applied optics, 2009

Journal of biomedical optics

IEEE transactions on bio-medical engineering, 2012

This study investigates the autocorrelation bandwidths of dual-window (DW) optical coherence tomo... more This study investigates the autocorrelation bandwidths of dual-window (DW) optical coherence tomography (OCT) k-space scattering profile of different-sized microspheres and their correlation to scatterer size. A dual-bandwidth spectroscopic metric defined as the ratio of the 10% to 90% autocorrelation bandwidths is found to change monotonically with microsphere size and gives the best contrast enhancement for scatterer size differentiation in the resulting spectroscopic image. A simulation model supports the experimental results and revealed a tradeoff between the smallest detectable scatterer size and the maximum scatterer size in the linear range of the dual-window dual-bandwidth (DWDB) metric, which depends on the choice of the light source optical bandwidth. Spectroscopic OCT (SOCT) images of microspheres and tonsil tissue samples based on the proposed DWDB metric showed clear differentiation between different-sized scatterers as compared to those derived from conventional short-time Fourier transform metrics. The DWDB metric significantly improves the contrast in SOCT imaging and can aid the visualization and identification of dissimilar scatterer size in a sample. Potential applications include the early detection of cell nuclear changes in tissue carcinogenesis, the monitoring of healing tendons, and cell proliferation in tissue scaffolds.

Proceedings of SPIE - The International Society for Optical Engineering

Microwave and Optical Technology Letters, 2013

ABSTRACT Optical coherence tomography (OCT) was used to monitor various flexor tendon states incl... more ABSTRACT Optical coherence tomography (OCT) was used to monitor various flexor tendon states including tendon at rest, normal tendons during loading, tendon microstructural damage post loading, and healing tendons at 0, 3, and 8 weeks time points.Potential uses include assessing microstructural damage, monitoring the quality of suture repair, and tendon healing. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:990–995, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27514

Biomedical Optics, 2008

... James CY Kah1, Rachel CY Wan2, Tzu-Hao Chow3, Malini C. Olivo4, Subodh G. Mhaisalkar2, Colin ... more ... James CY Kah1, Rachel CY Wan2, Tzu-Hao Chow3, Malini C. Olivo4, Subodh G. Mhaisalkar2, Colin JR Sheppard1 1Division of Bioengineering, National University of Singapore, Singapore 2School of ... [2] SJ Oldenburg, RD Averitt, SL Westcott, NJ Halas, “Nanoengineering of ...

Journal of Biomedical Optics, 2009

This work investigates the use of optical coherence tomography (OCT) to identify virus infection ... more This work investigates the use of optical coherence tomography (OCT) to identify virus infection in orchid plants. Besides revealing the cross-sectional structure of orchid leaves, highly scattering upper leaf epidermides are detected with OCT for virus-infected plants. This distinct feature is not observable under histological examination of the leaf samples. Furthermore, the leaf epidermides of stressed but healthy plants, which exhibit similar visual symptoms as virus-infected plants, are not highly scattering and are similar to those of healthy plants. The results suggest that virus-infected orchid plants can be accurately identified by imaging the epidermal layers of their leaves with OCT. The OCT modality is suitable for fast, nondestructive diagnosis of orchid virus infection, which may potentially lead to significant cost savings and better control of the spread of viruses in the orchid industry.

Journal of Biomedical Optics, 2009

Abstract Optical coherence tomography (OCT) is an optical imaging technique that allows the visua... more Abstract Optical coherence tomography (OCT) is an optical imaging technique that allows the visualization of living tissues in vivo. However, the speckle noise affects their diagnostic accuracy by degrading the quality of OCT images. Wavelet based denoising methods have been successful in reducing the speckle noise in past but they require a manual selection of few parameters for optimum denoising. We propose a computerized method to select these parameters by using an evolutionary technique called differential evolution (DE). The ...