High-resolution Biomedical Imaging Research Articles

Multifractality in Surface Potential for Cancer Diagnosis.

Recent advances in high-resolution biomedical imaging have improved cancer diagnosis, focusing on morphological, electrical, and biochemical properties of cells and tissues, scaling from cell clusters down to the molecular level. Multiscale imaging revealed high complexity that requires advanced data processing methods of multifractal analysis. We performed label-free multiscale imaging of surface potential variations in human ovarian cancer cells using Kelvin probe force microscopy (KPFM). An improvement in the differentiation between nonmalignant and cancerous cells by multifractal analysis using adaptive versus median threshold for image binarization was demonstrated. The results reveal the multifractality of cancer cells as a new biomarker for cancer diagnosis.

Preface

International School of Photonics (ISP) was established in 1995 as a separate school under Cochin University of Science and Technology (CUSAT) with objectives of developing and establishing research activities in photonics and related fields. ISP offers a two-year MTech Programme in Optoelectronics and Laser Technology and Five-year Integrated Masters Programme in Photonics. Equiped with sophisticated research facilities, ISP also offers PhD in Photonics and related area.As a part of academic activities, ISP has been conducting a national level annual photonics workshop since its inception. This workshop gradually developed in to National Photonics Symposium (NPS) since 2017. NPS brings together leading scientists, academicians, industrialists and young researchers in India and aborad for fruitful interactions and active discussions on various aspects of photonics. Permanent venue of the conference is ISP, CUSAT, Cochin. In 2022, NPS was conducted as an International Conference on Recent Trends in Photonics (NPS 2022) in online mode during 27 February to 01 March. Virtual mode was preferred due to government restrictions in place due to COVID-19. NPS 2022 brought 12 invited speakers from India and abroad including one key note speaker and three plenary speakers. In addition to this, 21 contributed talks and 34 posters were also included for presentations. All invited talks were scheduled for one hour duration including the time for discussion. Contributed speakers were allotted 12 minutes for presentation and discussions. ZOOM Webinar was used for delivering the talks and Breakout Room facility in ZOOM Meetings was used for poster presentations. Dedicated sessions were arranged for industrial collaborators to present and discuss their latest research tools and equipment.The opening of NPS 2022 was marked by the keynote address of Prof. Franz X. Kärtner from the University of Hamburg, Germany. Prof. Kärtner talked about the latest experimental results and the implementation of electron and X-ray sources at DESY, Germany. There were three plenary talks covering various diverse areas of photonics research. Dr. Kazuhiko Maeda, an expert in the field of photocatalysis and energy, from the Tokyo Institute of Technology, Japan, talked bout artificial photosynthetic assemblies using layered materials. He also gave a general outlook on artificial photosynthesis, solar water splitting with recent developments, challenges and opportunities in the field. Another plenary speaker was Dr. Pablo Albella, from the University of Cantabria, Santander, Spain. Dr. Albella gave an elaborate account of the research activities in his research group in the area of dielectric nanoantennas for guiding light and heat at the nanoscale. The third plenary talk was delivered by Dr. V. M. Murukeshan, Director, Centre for Optical and Laser Engineering (COLE) at Nanyang Technological University, Singapore. Prof. Murugeshan’s talk focused at the research activities in his group on high resolution biomedical optical imaging of various tissues in human body.The invited speakers also included experts from various field of optics and photonics, Dr. Tatyana Sizyuk (Argonne National Laboratory, USA), Dr. Radhakrishna Prabhu (Robert Gordon University, Aberdeen, UK), Dr. Sonia Mary (The Jackson Laboratory, USA), Dr. Madhu V. (Technical University of Denmark, Denmark) and Dr. Swapna Nair (Central University of Kerala, India).Industrial sessions in NPS 2022 included two invited speakers and various contributed presentations from industries. Dr. Renilkumar Mudachathi, Chief Scientist at Motion Imager, Twente, The Netherlands gave an invited talk focused on various fabrication techniques for photonic and optoelectronic research and industry. Industry session was also marked by the interaction with Dr. Suresh Nair, IEEE India Council Chair, on the activities of IEEE and the industrial research related to optics and photonics. NPS 2022 also marked the celebration of National Science Day on 28 February, with a special lecture from Prof. G. Ravindra Kumar, TIFR, Mumbai. The lecture delivered on the development of ultraintense lasers and their application in research, was also open to the public.List of Committee members, NPS 2022 is available in this Pdf.

Application and Performance Discussion of Fiber-Reinforced Composite Materials in Sports Equipment Based on Image Processing Technology

Fiber reinforced composites can meet the needs of lightweight, heavy load, long-span, high strength, and modern structures and work under strict conditions. Therefore, it is widely used in various fields. Sports equipment generally cannot meet the requirements of high-strength use, so there is an urgent need for new fiber materials to make these instruments. Aiming at improving the efficiency of measurement and the reliability of measurement results, this paper studies the quantitative characterization method of the microstructure of short fiber reinforced composites. The swept-frequency OCT system is a newly developed high-resolution biomedical imaging system. The method of this paper is to study the performance parameters of swept frequency OCT system, deduce the application of image processing technology in fiber material detection, and then study the detection of residual strength and residual stiffness of composites, so as to obtain a composite material detection method that can be popularized. On this basis, image processing and performance analysis of the composites were carried out, and the composites were tested. And the prospect of application in this field has been analyzed. The experimental results show that better fiber length can be obtained by this method, and the maximum relative error is only 4.5%, thus ensuring the accurate determination of fiber length. Calculations were carried out using the experimental data, and the results showed that the performance of the sports product increased from 15.4% to 48.6% with the graphite-rubber composite. Using this material can improve the comprehensive performance of sports equipment by 2.1%∼4.5%.

Progress towards wafer-scale fabrication based on gel casting technique for 1–3 randomised piezocomposite μUS linear array

Microultrasound (μUS) linear arrays operating at frequencies over 25 MHz have applications in high resolution biomedical imaging. 1–3 connectively piezoceramic – polymer composite (“piezocomposite”) material is attractive for fabrication of these devices due to its high effective electromechanical coupling coefficient and low acoustic impedance for better acoustic matching between transducer and tissue. However, a major concern with this type of material comes from interference between the fundamental thickness-mode resonance and spurious modes, which is usually generated by wave propagation and reflection within the repetitive and symmetrical structure of classical piezocomposite. In general, a fine spatial scale is required of the material structure to suppress the spurious modes; however, the fabrication process is challenging using standard dice-and-fill methods at the fine scales required for high frequencies. A promising way to overcome this challenge is to manipulate the lateral geometry and spacing of the piezoceramic pillars with a random distribution. In this work, gel casting in association with a micromoulding technique has been developed for manufacturing 1–3 randomised piezocomposite active material for μUS linear arrays. 48 vol% solid loading of piezoceramic powder with 30 wt% Hydantoin resin content was employed to prepare a low viscosity aqueous suspension. Through varying powder size, it was found that the suspension with 1.22 µm powder had the highest viscosity, ~ 0.47 Pa.s, and a short gelation time, ~ 10 mins. However, all suspensions had viscosities less than 1 Pa.s at a shear rate of 100 s−1, indicating that they had good flowability. The green body samples showed mean flexural strength 49.7 ± 2.49 MPa. After piezocomposite fabrication with randomised pillars, surface planarisation was used to obtain reliable edge definition of photolithographically-defined electrodes. 20-element arrays with 50-μm element pitch were configured using a bilayer lift-off process. The 1–3 randomised piezocomposite demonstrated its capability to minimise the effects of spurious modes in the thickness mode frequency range, while the thickness resonances provided k33 = 0.67. Without a matching layer, the array produced a − 6 dB bandwidth of 38.4%- and − 20-dB pulse length of 0.26 μs. These results show that 1–3 randomised piezocomposite fabricated from gel-casting associated with a micromoulding technique is feasible for fabrication of μUS linear arrays and may offer a route to small wafer-scale production.

Laboratory Soft X-Ray Microscopy with an Integrated Visible-Light Microscope-Correlative Workflow for Faster 3D Cell Imaging.

Laboratory transmission soft X-ray microscopy (L-TXM) has emerged as a complementary tool to synchrotron-based TXM and high-resolution biomedical 3D imaging in general in recent years. However, two major operational challenges in L-TXM still need to be addressed: a small field of view and a potentially misaligned rotation stage. As it is not possible to alter the magnification during operation, the field of view in L-TXM is usually limited to a few tens of micrometers. This complicates locating areas and objects of interest in the sample. Additionally, if the rotation axis of the sample stage cannot be adjusted prior to the experiments, an efficient workflow for tomographic imaging cannot be established, as refocusing and sample repositioning will become necessary after each recorded projection. Both these limitations have been overcome with the integration of a visible-light microscope (VLM) into the L-TXM system. Here, we describe the calibration procedure of the goniometer sample stage and the integrated VLM and present the resulting 3D imaging of a test sample. In addition, utilizing this newly integrated VLM, the extracellular matrix of cryofixed THP-1 cells (human acute monocytic leukemia cells) was visualized by L-TXM for the first time in the context of an ongoing biomedical research project.

Flame-made Y2O3:Yb3+/Er3+ upconversion nanoparticles: Mass production synthesis, multicolor tuning and thermal sensing studies

Developing a rapid and continuous synthesis method for scalable production of upconversion nanoparticles (UCNPs) plays an important role in the applications of advanced color display, high-resolution biomedical imaging and precise optical thermometry. Here, for the first time, we report the multicolor tunable upconversion luminescence (UCL) in Y2O3:Yb3+/Er3+ (x/1 mol%) UCNPs with the average size of ∼14 nm, which were successfully fabricated by liquid-fed flame aerosol synthesis with a high production rate of ∼40 g h−1. Under the excitation of 980 nm continuous-wave (CW) laser, the UCL color can be efficiently modulated from green to red and the red-to-green (R/G) UCL intensity ratio is enhanced dramatically as the doping concentration of Yb3+ ions increases from 1 to 15 mol%. The UCL color manipulation can be ascribed to the cross-relaxation (CR) and the energy back transfer (EBT) processes between Yb3+ and Er3+ ions, and it was proved by investigating the dependence of UCL on the pump power and the decay lifetimes of 4S3/2 and 4F9/2 states. Moreover, the coefficients of CR and EBT processes were also calculated by a rate equation model, and the results suggest that they are efficient in Y2O3 host. In addition, the optical thermal sensing performance was also evaluated by analyzing fluorescence intensity ratio (FIR) of the thermally coupled levels (2H11/2, 4S3/2) of Er3+ ions in Y2O3:Yb3+/Er3+ (1/1 mol%) UCNPs, achieving an excellent thermal sensitivity of 0.0196 K−1 at 543 K.

Subwavelength resolution Fourier ptychography with hemispherical digital condensers.

Fourier ptychography (FP) is a promising computational imaging technique that overcomes the physical space-bandwidth product (SBP) limit of a conventional microscope by applying angular-varied illuminations. However, to date, the effective imaging numerical aperture (NA) achievable with a commercial LED board is still limited to the range of 0.3-0.7 with a 4 × /0.1NA objective due to the geometric constraint with the declined illumination intensities and attenuated signal-to-noise ratio (SNR). Thus the highest achievable half-pitch resolution is usually constrained between 500-1000 nm, which cannot meet the requirements of high-resolution biomedical imaging applications. Although it is possible to improve the resolution by using a high-NA objective lens, the FP approach is less appealing as the decrease of field-of-view (FOV) will far exceed the improvement of spatial resolution in this case. In this paper, we initially present a subwavelength resolution Fourier ptychography (SRFP) platform with a hemispherical digital condenser to provide high-angle programmable plane-wave illuminations of 0.95NA, attaining a 4 × /0.1NA objective with the final effective imaging performance of 1.05NA at a half-pitch resolution of 244 nm with the incident wavelength of 465 nm across a wide FOV of 14.60 mm2, corresponding to a SBP of 245 megapixels. Our work provides an essential step of FP towards high-throughput imaging applications.

Speckle noise reduction for optical coherence tomography based on adaptive 2D dictionary

As a high-resolution biomedical imaging modality, optical coherence tomography (OCT) is widely used in medical sciences. However, OCT images often suffer from speckle noise, which can mask some important image information, and thus reduce the accuracy of clinical diagnosis. Taking full advantage of nonlocal self-similarity and adaptive 2D-dictionary-based sparse representation, in this work, a speckle noise reduction algorithm is proposed for despeckling OCT images. To reduce speckle noise while preserving local image features, similar nonlocal patches are first extracted from the noisy image and put into groups using a gamma- distribution-based block matching method. An adaptive 2D dictionary is then learned for each patch group. Unlike traditional vector-based sparse coding, we express each image patch by the linear combination of a few matrices. This image-to-matrix method can exploit the local correlation between pixels. Since each image patch might belong to several groups, the despeckled OCT image is finally obtained by aggregating all filtered image patches. The experimental results demonstrate the superior performance of the proposed method over other state-of-the-art despeckling methods, in terms of objective metrics and visual inspection.

Two-photon laser scanning microscopy with electrowetting-based prism scanning.

Laser scanners are an integral part of high resolution biomedical imaging systems such as confocal or 2-photon excitation (2PE) microscopes. In this work, we demonstrate the utility of electrowetting on dielectric (EWOD) prisms as a lateral laser-scanning element integrated in a conventional 2PE microscope. To the best of our knowledge, this is the first such demonstration for EWOD prisms. EWOD devices provide a transmissive, low power consuming, and compact alternative to conventional adaptive optics, and hence this technology has tremendous potential. We demonstrate 2PE microscope imaging of cultured mouse hippocampal neurons with a FOV of 130 × 130 μm2 using EWOD prism scanning. In addition, we show simulations of the optical system with the EWOD prism, to evaluate the effect of propagating a Gaussian beam through the EWOD prism on the imaging quality. Based on the simulation results a beam size of 0.91 mm full width half max was chosen to conduct the imaging experiments, resulting in a numerical aperture of 0.17 of the imaging system.

Light Based Techniques for Improving Health Care: Studies at RRCAT

The invention of Lasers in 1960, the phenomenal advances in photonics as well as the information processing capability of the computers has given a major boost to the R&D activity on the use of light for high resolution biomedical imaging, sensitive, non-invasive diagnosis and precision therapy. The effort has resulted in remarkable progress and it is widely believed that light based techniques hold great potential to offer simpler, portable systems which can help provide diagnostics and therapy in a low resource setting. At Raja Ramanna Centre for Advanced Technology (RRCAT) extensive studies have been carried out on fluorescence spectroscopy of native tissue. This work led to two important outcomes. First, a better understanding of tissue fluorescence and insights on the possible use of fluorescence spectroscopy for screening of cancer and second development of diagnostic systems that can serve as standalone tool for non-invasive screening of the cancer of oral cavity. The optical coherence tomography setups and their functional extensions (polarization sensitive, Doppler) have also been developed and used for high resolution (~10 µm) biomedical imaging applications, in particular for non-invasive monitoring of the healing of wounds. Chlorophyll based photo-sensitisers and their derivatives have been synthesized in house and used for photodynamic therapy of tumors in animal models and for antimicrobial applications. Various variants of optical tweezers (holographic, Raman etc.) have also been developed and utilised for different applications notably Raman spectroscopy of optically trapped red blood cells. An overview of these activities carried out at RRCAT is presented in this article.

3D Tissue-Engineered Construct Analysis via Conventional High-Resolution Microcomputed Tomography Without X-Ray Contrast

As the field of tissue engineering develops, researchers are faced with a large number of degrees of freedom regarding the choice of material, architecture, seeding, and culturing. To evaluate the effectiveness of a tissue-engineered strategy, histology is typically done by physically slicing and staining a construct (crude, time-consuming, and unreliable). However, due to recent advances in high-resolution biomedical imaging, microcomputed tomography (μCT) has arisen as a quick and effective way to evaluate samples, while preserving their structure in the original state. However, a major barrier for using μCT to do histology has been its inability to differentiate between materials with similar X-ray attenuation. Various contrasting strategies (hardware and chemical staining agents) have been proposed to address this problem, but at a cost of additional complexity and limited access. Instead, here we suggest a strategy for how virtual 3D histology in silico can be conducted using conventional μCT, and we provide an illustrative example from bone tissue engineering. The key to our methodology is an implementation of scaffold surface architecture that is ordered in relation to cells and tissue, in concert with straightforward image-processing techniques, to minimize the reliance on contrasting for material segmentation. In the case study reported, μCT was used to image and segment porous poly(lactic acid) nonwoven fiber mesh scaffolds that were seeded dynamically with mesenchymal stem cells and cultured to produce soft tissue and mineralized tissue in a flow perfusion bioreactor using an osteogenic medium. The methodology presented herein paves a new way for tissue engineers to identify and distinguish components of cell/tissue/scaffold constructs to easily and effectively evaluate the tissue-engineering strategies that generate them.

High resolution biomedical imaging—multimodal ultrasound microscope and combination with optics

High frequency ultrasound imaging has evolved from classical acoustic microscopy to the multimodal ultrasound microscope which is available for quantitative C-mode, surface acoustic impedance mode and 3D-mode imaging. The evolution has realized both quantitative parametric imaging and easier observation. Quantitative C-mode representing two-dimensional distribution of attenuation or sound speed is realized by frequency-domain analysis of a single pulse by a high speed digitizer. Because the square of sound speed is proportional to the tissue elasticity, sound speed imaging provides biomechanical information of the tissues which is especially important in cardiology and orthopedic surgery. The data also help understanding clinical echo features, especially important in grading of liver fibrosis. Surface acoustic impedance mode without thin-slicing has been applied for imaging of fresh brain tissues and real time observation of high-intensity focused ultrasound procedures. High frequency 3D-mode imaging has visualized 3D structure of sebaceous gland in dermis. Compared with optical coherence tomography which provides higher resolution imaging, ultrasound is superior in the penetration depth and assessment of tissue elasticity. Photoacoustic imaging provides not only morphology but also small blood flow distribution. Both ultrasound and optical methods should develop together to realize high resolution and “gentle” biomedical imaging.

High Resolution and High Contrast Bio-Medical X-ray Imaging Technique Using Synchrotron Radiation in PLS

High Resolution and High Contrast Bio-Medical X-ray Imaging Technique Using Synchrotron Radiation in PLS

2D imaging of ultrasound fields using CCD array to map output of Fabry-Perot polymer film sensor

A 2D ultrasound field imaging system that uses a CCD array to map the optical output of a planar Fabry-Perot polymer film sensing interferometer is described. This system enables ultrasound fields to be rapidly mapped over a 6.6×4.7 mm aperture with spatial and temporal resolutions of the order of 10 µm and 10 ns, respectively. The concept was successfully demonstrated by imaging the acoustic field at the focus of a pulsed 5 MHz PZT ultrasound transducer. The technique offers an alternative to piezoelectric-based methods for high-resolution biomedical and industrial ultrasonic imaging and field characterisation applications.

Optical coherence tomography: feasibility for basic research and image-guided surgery of breast cancer.

Diagnostic trends in medicine are being directed toward cellular and molecular processes, where treatment regimens are more amenable for cure. Optical imaging is capable of performing cellular and molecular imaging using the short wavelengths and spectroscopic properties of light. Diffuse optical tomography is an optical imaging technique that has been pursued as an alternative to X-ray mammography. While this technique permits non-invasive optical imaging of the whole breast, to date it is incapable of resolving features at the cellular level. Optical coherence tomography (OCT) is an emerging high-resolution biomedical imaging technology that for larger and undifferentiated cells can perform cellular-level imaging at the expense of imaging depth. OCT performs optical ranging in tissue and is analogous to ultrasound except reflections of near-infrared light are detected rather than sound. In this paper, an overview of the OCT technology is provided, followed by images demonstrating the feasibility of using OCT to image cellular features indicative of breast cancer. OCT images of a well-established carcinogen-induced rat mammary tumor model were acquired. Images from this common experimental model show strong correlation with corresponding histopathology. These results illustrate the potential of OCT for a wide range of basic research studies and for intra-operative image-guidance to identify foci of tumor cells within surgical margins during the surgical treatment of breast cancer.

Ultrasound induced improvement in optical coherence tomography (OCT) resolution.

Optical coherence tomography (OCT) is a rapidly emerging technology for high-resolution biomedical imaging. The axial resolution of this technology is determined by the bandwidth of the source. Commercial sources generally provide resolutions of 10-20 microm whereas laboratory-based solid state lasers have resolutions of approximately 4 microm. The resolution in tissue depends almost exclusively on detecting single scattered events. However, the phenomenon known as multiple scattering results in a deterioration of resolution as a function of depth. In this study, OCT was combined with ultrasound in an attempt to reduce the effect of multiple scattering. The theory is that, with parallel ultrasound and OCT beams, multiply scattered light with a momentum component significantly perpendicular to the OCT beam will be reduced because the light is Doppler shifted outside the bandpass filter of the OCT detection electronics. A 7.5-MHz ultrasound transducer was used to introduce the photon/phonon interaction. A reflecting metal plate was placed within biological tissue, and the point spread function (PSF) was assessed off the reflector. The PSF was determined in the presence of no ultrasound, pulsed ultrasound, and continuous-wave (CW) ultrasound. CW ultrasound resulted in a 17% improvement (P < 0.001) in resolution and pulsed ultrasound resulted in 8% (P < 0.01). Image noise reduction could also be noted. Combining OCT with a parallel ultrasound beam results in an improvement in resolution through a reduced effect of multiple scattering due to photon/phonon interaction. With higher frequencies, better control of the acoustical beam, and tests in media with higher rates of multiple scattering, improved results are anticipated.