Publications
377 results found
Elson D, Tincknell L, Avila Rencoret F, et al., Intraoperative hyperspectral circumferential resection margin assessment for gastrointestinal cancer surgery (second prize), Career in Surgery
Singh M, Nabavi E, Zhou Y, et al., Fluorescence image-guided photothermal therapy: Diagnosis and treatment of upper gastrointestinal cancer and beyond (prize winner), Global Surgery
Ong ZY, Chen S, Nabavi E, et al., 2017, Multibranched Gold Nanoparticles with Intrinsic LAT-1 Targeting Capabilities for Selective Photothermal Therapy of Breast Cancer., ACS Applied Materials and Interfaces, Vol: 9, Pages: 39259-39270, ISSN: 1944-8244
Because of the critical role of the large neutral amino acid transporter-1 (LAT-1) in promoting tumor growth and proliferation, it is fast emerging as a highly attractive biomarker for the imaging and treatment of human malignancies, including breast cancer. While multibranched gold nanoparticles (AuNPs) have emerged as a promising modality in the photothermal therapy (PTT) of cancers, some of the key challenges limiting their clinical translation lie in the need to develop reproducible and cost-effective synthetic methods as well as the selective accumulation of sufficient AuNPs at tumor sites. In this study, we report a simple and direct seed-mediated synthesis of monodispersed multibranched AuNPs using the catechol-containing LAT-1 ligands, L- and D-dopa, to confer active cancer targeting. This route obviates the need for additional conjugation with targeting moieties such as peptides or antibodies. Nanoflower-like AuNPs (AuNF) with diameters of approximately 46, 70, and 90 nm were obtained and were found to possess excellent colloidal stability and biocompatibility. A significantly higher intracellular accumulation of the L- and D-dopa functionalized AuNFs was observed in a panel of breast cancer cell lines (MCF-7, MDA-MB-231, MDA-MB-468, and MDA-MB-453) when compared to the nontargeting control AuNFs synthesized with dopamine and 4-ethylcatechol. Importantly, no significant difference in uptake between the targeting and nontargeting AuNFs was observed in a non-tumorigenic MCF-10A breast epithelial cell line, hence demonstrating tumor selectivity. For PTT of breast cancer, Ag(+) was introduced during synthesis to obtain L-dopa functionalized nanourchin-like AuNPs (AuNUs) with strong near-infrared (NIR) absorbance. The L-dopa functionalized AuNUs mediated selective photothermal ablation of the triple negative MDA-MB-231 breast cancer cell line and sensitized the cells to the anticancer drugs cisplatin and docetaxel. This work brings forward an effective strategy
Qi J, He H, Lin J, et al., 2017, Assessment of tissue polarimetric properties using Stokes polarimetric imaging with circularly polarized illumination, Journal of Biophotonics, Vol: 11, ISSN: 1864-063X
Tissue depolarization and linear retardance are the main polarization characteristics of interest for bulk tissue characterization, and are normally interpreted from Mueller polarimetry. Stokes polarimetry can be conducted using simpler instrumentation and in a shorter time. Here we use Stokes polarimetric imaging with circularly polarized illumination to assess the circular depolarization and linear retardance properties of tissue. Results obtained were compared with Mueller polarimetry in transmission and reflection geometry respectively. It is found that circular depolarization obtained from these two methods is very similar in both geometries, and that linear retardance is highly quantitatively similar for transmission geometry and qualitatively similar for reflection geometry. The majority of tissue circular depolarization and linear retardance image information (represented by local image contrast features) obtained from Mueller polarimetry is well preserved from Stokes polarimetry in both geometries. These findings can be referred to for further understanding tissue Stokes polarimetric data, and for further application of Stokes polarimetry under the circumstances where short acquisition time or low optical system complexity is a priority, such as polarimetric endoscopy and microscopy.
Harris-Birtill D, Singh M, Zhou Y, et al., 2017, Gold nanorod reshaping in vitro and in vivo using a continuous wave laser., PLoS ONE, Vol: 12, ISSN: 1932-6203
Gold nanorods (GNRs) are increasingly being investigated for cancer theranostics as they possess features which lend themselves in equal measures as contrast agents and catalysts for photothermal therapy. Their optical absorption spectral peak wavelength is determined by their size and shape. Photothermal therapy using GNRs is typically established using near infrared light as this allows sufficient penetration into the tumour matrix. Continuous wave (CW) lasers are the most commonly applied source of near infrared irradiation on GNRs for tumour photothermal therapy. It is perceived that large tumours may require fractionated or prolonged irradiation. However the true efficacy of repeated or protracted CW irradiation on tumour sites using the original sample of GNRs remains unclear. In this study spectroscopy and transmission electron microscopy are used to demonstrate that GNRs reshape both in vitro and in vivo after CW irradiation, which reduces their absorption efficiency. These changes were sustained throughout and beyond the initial period of irradiation, resulting from a spectral blue-shift and a considerable diminution in the absorption peak of GNRs. Solid subcutaneous tumours in immunodeficient BALB/c mice were subjected to GNRs and analysed with electron microscopy pre- and post-CW laser irradiation. This phenomenon of thermally induced GNR reshaping can occur at relatively low bulk temperatures, well below the bulk melting point of gold. Photoacoustic monitoring of GNR reshaping is also evaluated as a potential clinical aid to determine GNR absorption and reshaping during photothermal therapy. Aggregation of particles was coincidentally observed following CW irradiation, which would further diminish the subsequent optical absorption capacity of irradiated GNRs. It is thus established that sequential or prolonged applications of CW laser will not confer any additional photothermal effect on tumours due to significant attenuations in the peak optical absorpt
Qi J, He H, Ma H, et al., 2017, Extended polar decomposition method of Mueller matrices for turbid media in reflection geometry, OPTICS LETTERS, Vol: 42, Pages: 4048-4051, ISSN: 0146-9592
The polar decomposition method for Mueller matrices proposed by Lu–Chipman has been demonstrated and validated for many applications. However, in some situations, e.g., when analyzing the Mueller matrix of birefringent turbid media with Mie-sized scatterers acquired in reflection geometry, the method may suffer from limitations due to the assumptions required by this method. Here we extend the Lu–Chipman method and show that it can provide more reasonable results for these situations. The method has been validated experimentally with turbid phantoms. Thus, this Letter may prove useful in tissue polarimetry.
Qi J, He C, Elson DS, 2017, Real time complete Stokes polarimetric imager based on a linear polarizer array camera for tissue polarimetric imaging, Biomedical Optics Express, Vol: 8, Pages: 4933-4949, ISSN: 2156-7085
Tissue polarimetric imaging measures Mueller matrices of tissues or Stokes vectors of the emergent light from tissues (normally using incidence with a fixed polarization state) over a field of view, and has demonstrated utility in a number of surgical and diagnostic applications. Here we introduce a compact complete Stokes polarimetric imager that can work for multiple wavelength bands with a frame-rate suitable for real-time applications. The imager was validated with standard polarizing components, and then employed as a polarization state analyzer of a Mueller imaging polarimeter and a standalone Stokes imaging polarimeter respectively to image the process of dehydration of bovine tendon tissue. The results obtained in this work suggested that the polarization properties of the samples rich of collagen fibres can change with the degree of dehydration, and therefore, dehydration of the samples prepared for polarimetric imaging (e.g. polarimetric microscopy) should be carefully controlled.
Jones G, Clancy NT, Du X, et al., 2017, Fast estimation of haemoglobin concentration in tissue via wavelet decomposition, International Conference on Medical Image Computing and Computer-Assisted Intervention, Publisher: Springer, Pages: 100-108, ISSN: 0302-9743
Tissue oxygenation and perfusion can be an indicator for organ viability during minimally invasive surgery, for example allowing real-time assessment of tissue perfusion and oxygen saturation. Multispectral imaging is an optical modality that can inspect tissue perfusion in wide field images without contact. In this paper, we present a novel, fast method for using RGB images for MSI, which while limiting the spectral resolution of the modality allows normal laparoscopic systems to be used. We exploit the discrete Haar decomposition to separate individual video frames into low pass and directional coefficients and we utilise a different multispectral estimation technique on each. The increase in speed is achieved by using fast Tikhonov regularisation on the directional coefficients and more accurate Bayesian estimation on the low pass component. The pipeline is implemented using a graphics processing unit (GPU) architecture and achieves a frame rate of approximately 15 Hz. We validate the method on animal models and on human data captured using a da Vinci stereo laparoscope.
Wirkert SJ, Vemuri AS, Kenngott HG, et al., 2017, Physiological parameter estimation from multispectral images unleashed, Medical Image Computing and Computer-Assisted Intervention − MICCAI 2017, Publisher: Springer International Publishing AG, Pages: 134-141, ISSN: 0302-9743
© Springer International Publishing AG 2017. Multispectral imaging in laparoscopy can provide tissue reflectance measurements for each point in the image at multiple wavelengths of light. These reflectances encode information on important physiological parameters not visible to the naked eye. Fast decoding of the data during surgery, however, remains challenging. While model-based methods suffer from inaccurate base assumptions, a major bottleneck related to competing machine learning-based solutions is the lack of labelled training data. In this paper, we address this issue with the first transfer learning-based method to physiological parameter estimation from multispectral images. It relies on a highly generic tissue model that aims to capture the full range of optical tissue parameters that can potentially be observed in vivo. Adaptation of the model to a specific clinical application based on unlabelled in vivo data is achieved using a new concept of domain adaptation that explicitly addresses the high variance often introduced by conventional covariance-shift correction methods. According to comprehensive in silico and in vivo experiments our approach enables accurate parameter estimation for various tissue types without the need for incorporating specific prior knowledge on optical properties and could thus pave the way for many exciting applications in multispectral laparoscopy.
Lin J, Clancy NT, Hu Y, et al., 2017, Endoscopic depth measurement and super-spectral-resolution imaging, Medical Image Computing and Computer-Assisted Intervention − MICCAI 2017, Publisher: Springer Nature Switzerland AG, Pages: 39-47, ISSN: 0302-9743
Intra-operative measurements of tissue shape and multi/hyperspectral information have the potential to provide surgical guidance and decision making support. We report an optical probe based system to combine sparse hyperspectral measurements and spectrally-encoded structured lighting (SL) for surface measurements. The system provides informative signals for navigation with a surgical interface. By rapidly switching between SL and white light (WL) modes, SL information is combined with structure-from-motion (SfM) from white light images, based on SURF feature detection and Lucas-Kanade (LK) optical flow to provide quasi-dense surface shape reconstruction with known scale in real-time. Furthermore, “super-spectral-resolution” was realized, whereby the RGB images and sparse hyperspectral data were integrated to recover dense pixel-level hyperspectral stacks, by using convolutional neural networks to upscale the wavelength dimension. Validation and demonstration of this system is reported on ex vivo/in vivo animal/human experiments.
Qi J, Nabavi E, Hu Y, et al., 2017, A light-weight near infrared fluorescence endoscope based on a single color camera: a proof-of-concept study, Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR), Publisher: IEEE
Dong Y, Qi J, He H, et al., 2017, Quantitatively characterizing the microstructural features of breast ductal carcinoma tissues in different progression stages by Mueller matrix microscope, BIOMEDICAL OPTICS EXPRESS, Vol: 8, Pages: 3643-3655, ISSN: 2156-7085
Polarization imaging has been recognized as a potentially powerful technique for probing the microstructural information and optical properties of complex biological specimens. Recently, we have reported a Mueller matrix microscope by adding the polarization state generator and analyzer (PSG and PSA) to a commercial transmission-light microscope, and applied it to differentiate human liver and cervical cancerous tissues with fibrosis. In this paper, we apply the Mueller matrix microscope for quantitative detection of human breast ductal carcinoma samples at different stages. The Mueller matrix polar decomposition and transformation parameters of the breast ductal tissues in different regions and at different stages are calculated and analyzed. For more quantitative comparisons, several widely-used image texture feature parameters are also calculated to characterize the difference in the polarimetric images. The experimental results indicate that the Mueller matrix microscope and the polarization parameters can facilitate the quantitative detection of breast ductal carcinoma tissues at different stages.
Qi J, Elson D, Mueller polarimetric imaging for surgical and diagnostic applications: a review, Journal of Biophotonics, Vol: 10, Pages: 950-982, ISSN: 1864-0648
Polarization is a fundamental property of light anda powerful sensing tool that has been applied to many areas. A Mueller matrix is a complete mathematical description of the polarization characteristics of objects that interact with light, and is known as a transfer function of Stokes vectors which characterise the state of polarization of light. Mueller polarimetric imaging measures Mueller matrices over a field of view and thus allows for visualising the polarization characteristics of the objects. It has emerged as a promising technique in recent years for tissue imaging, improving image contrastand providinga unique perspective to reveal additional information that cannot be resolved by other optical imaging modalities. This review introduces the basis of the Stokes-Mueller formulism, interpretation methods of Mueller matrices into fundamental polarization properties, polarization properties of biological tissues, and considerations in the construction of Mueller polarimetric imaging devices for surgical and diagnostic applications, including primary configurations, optimization procedures, calibration methods as well as the instrument polarization properties of several widely-used biomedical optical devices. The paper also reviews recent progress in Mueller polarimetric endoscopes and fibre Mueller polarimeters, followed by the future outlook in applying the technique to surgery and diagnostics.
Janatka M, Ramdoo KS, Tatla T, et al., 2017, Examining in vivo tympanic membrane mobility using smart phone video-otoscopy and phase-based eulerian video magnification, Conference on Medical Imaging - Computer-Aided Diagnosis, Publisher: SPIE- Society of Photo-optical Instrumentation Engineers, ISSN: 0277-786X
The tympanic membrane (TM) is the bridging element between the pressure waves of sound in air and the ossicular chain. It allows for sound to be conducted into the inner ear, achieving the human sense of hearing. Otitis media with effusion (OME, commonly referred to as ‘glue ear’) is a typical condition in infants that prevents the vibration of the TM and causes conductive hearing loss, this can lead to stunting early stage development if undiagnosed. Furthermore, OME is hard to identify in this age group; as they cannot respond to typical audiometry tests. Tympanometry allows for the mobility of the TM to be examined without patient response, but requires expensive apparatus and specialist training. By combining a smartphone equipped with a 240 frames per second video recording capability with an otoscopic clip-on accessory, this paper presents a novel application of Eulerian Video Magnification (EVM) to video-otology, that could provide assistance in diagnosing OME. We present preliminary results showing a spatio-temporal slice taken from an exaggerated video visualization of the TM being excited in vivo on a healthy ear. Our preliminary results demonstrate the potential for using such an approach for diagnosing OME under visual inspection as alternative to tympanometry, which could be used remotely and hence help diagnosis in a wider population pool.
Jones G, Clancy NT, Helo Y, et al., 2017, Bayesian estimation of intrinsic tissue oxygenation and perfusion from RGB images, IEEE Transactions on Medical Imaging, Vol: 36, Pages: 1491-1501, ISSN: 0278-0062
Multispectral imaging (MSI) can potentially assist the intra-operative assessment of tissue structure, function and viability, by providing information about oxygenation. In this paper, we present a novel technique for recovering intrinsic MSI measurements from endoscopic RGB images without custom hardware adaptations. The advantage of this approach is that it requires no modification to existing surgical and diagnostic endoscopic imaging systems. Our method uses a radiometric color calibration of the endoscopic camera's sensor in conjunction with a Bayesian framework to recover a per-pixel measurement of the total blood volume (THb) and oxygen saturation (SO2) in the observed tissue. The sensor's pixel measurements are modeled as weighted sums over a mixture of Poisson distributions and we optimize the variables SO2 and THb to maximize the likelihood of the observations. To validate our technique, we use synthetic images generated from Monte Carlo physics simulation of light transport through soft tissue containing sub-surface blood vessels. We also validate our method on in vivo data by comparing it to a MSI dataset acquired with a hardware system that sequentially images multiple spectral bands without overlap. Our results are promising and show that we are able to provide surgeons with additional relevant information by processing endoscopic images with our modeling and inference framework.
Elson D, Surgical Imaging and Biophotonics, EPSRC Image Guided Therapies Network Meeting
Elson D, Polarization-resolved Endoscopy for Image-guided Surgery (invited), OSA Optical Molecular Probes, Imaging and Drug Delivery 2017
Elson D, Lin J, An endoscopic system enabling tissue surface depth measurement and hyperspectral imaging, EPSRC Image Guided Therapies Network Meeting
Lin J, Clancy N, Hu Y, et al., Endoscopic Depth Measurement and Super-Spectral-Resolution Imaging, Medical Image Computing and Computer Aided Intervention
Qi J, Nabavi E, Hu Y, et al., A Light‐weight Near Infrared Fluorescence Endoscope Based On A Single Color Camera: A Proof‐of‐concept Study, CLEO Pacific Rim
Schams S, Nabavi E, Singh M, et al., Development And Evaluation Of LED Light Source For Contrast Enhancement In Minimally‐invasive Procedures, CLEO Pacific Rim
Elson D, Polarization- And Wavelength-resolved Endoscopy - Practical Approaches for In Vivo Imaging (invited), CLEO Pacific Rim
Nabavi E, Qi J, Leiloglou M, et al., Preliminary Studies Of Simultaneous RGB And NIR Fluorescence Imaging Of Ex Vivo Human Breast Tissue Using Indocyanine Green (ICG), CLEO Pacific Rim
Elson D, Lin J, Clancy N, Recovering Dense Tissue Multispectral Signal from in vivo RGB Images, Hamlyn Symposium on Medical Robotics
Tincknell L, Avila Rencoret F, Murphy J, et al., Intraoperative hyperspectral circumferential resection margin assessment for gastrointestinal cancer surgery, London Surgery Symposium
Zhang Y, Wirkert SJ, Iszatt J, et al., 2017, Tissue classification for laparoscopic image understanding based on multispectral texture analysis., Journal of Medical Imaging, Vol: 4, ISSN: 2329-4310
Intraoperative tissue classification is one of the prerequisites for providing context-aware visualization in computer-assisted minimally invasive surgeries. As many anatomical structures are difficult to differentiate in conventional RGB medical images, we propose a classification method based on multispectral image patches. In a comprehensive ex vivo study through statistical analysis, we show that (1) multispectral imaging data are superior to RGB data for organ tissue classification when used in conjunction with widely applied feature descriptors and (2) combining the tissue texture with the reflectance spectrum improves the classification performance. The classifier reaches an accuracy of 98.4% on our dataset. Multispectral tissue analysis could thus evolve as a key enabling technique in computer-assisted laparoscopy.
Qi J, Nabavi E, Hu Y, et al., 2017, A light-weight near infrared fluorescence endoscope based on a single color camera: A proof-of-concept study
© 2018 Optics InfoBase Conference Papers. All rights reserved. Here we demonstrated a light-weight near infrared fluorescence endoscope based on a low-cost single color camera to perform real time white light and fluorescence imaging, thanks to advances in image sensors and electronically controllable LED light sources. We further explored frame interpolation to facilitate the reduction of frame rate of this endoscope system, compared to a typical dual camera based NIRF endoscope system.
Clancy NT, Elson DS, Teare J, 2017, Hyperspectral imaging of colonic polyps in vivo (Conference Presentation), Conference on Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XV, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Tonutti M, Elson DS, Yang GZ, et al., 2016, The role of technology in minimally invasive surgery: state of the art, recent developments and future directions, Postgraduate Medical Journal, Vol: 93, Pages: 159-167, ISSN: 1469-0756
The diffusion of minimally invasive surgery has thrived in recent years, providing substantial benefits over traditional techniques for a number of surgical interventions. This rapid growth has been possible due to significant advancements in medical technology, which partly solved some of the technical and clinical challenges associated with minimally invasive techniques. The issues that still limit its widespread adoption for some applications include the limited field of view; reduced manoeuvrability of the tools; lack of haptic feedback; loss of depth perception; extended learning curve; prolonged operative times and higher financial costs. The present review discusses some of the main recent technological advancements that fuelled the uptake of minimally invasive surgery, focussing especially on the areas of imaging, instrumentation, cameras and robotics. The current limitations of state-of-the-art technology are identified and addressed, proposing future research directions necessary to overcome them.
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