• 3D full-wave multi-scattering forward solver for coherent microscopes 

      Qin, Yingying; Butola, Ankit; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-21)
      A rigorous forward model solver for conventional coherent microscope is presented. The forward model is derived from Maxwell’s equations and models the wave behaviour of light matter interaction. Vectorial waves and multiple-scattering effect are considered in this model. Scattered field can be calculated with given distribution of the refractive index of the biological sample. Bright field images ...
    • 3D refractive index reconstruction from phaseless coherent optical microscopy data using multiple scattering-based inverse solvers - a study 

      Qin, Yingying; Butola, Ankit; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-27)
      Reconstructing 3D refractive index profile of scatterers using optical microscopy measurements presents several challenges over the conventional microwave and RF domain measurement scenario. These include phaseless and polarization-insensitive measurements, small numerical aperture, as well as a Green's function where spatial frequencies are integrated in a weighted manner such that far-field angular ...
    • Adaptive fluctuation imaging captures rapid subcellular dynamics 

      Opstad, Ida Sundvor; Ströhl, Florian; Birgisdottir, Åsa birna; Acuña Maldonado, Sebastian Andres; Kalstad, Trine; Myrmel, Truls; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel, 2019-07-22)
      In this work we have explored the live-cell friendly nanoscopy method Multiple Signal Classification Algorithm (MUSICAL) for multi-colour imaging of various organelles and sub-cellular structures in the cardiomyoblast cell line H2c9. We have tested MUSICAL for fast (up to 230Hz), multi-colour time-lapse sequences of various sub-cellular structures (mitochondria, endoplasmic reticulum, microtubules, ...
    • Adaptive fluctuation imaging captures rapid subcellular dynamics 

      Opstad, Ida Sundvor; Ströhl, Florian; Birgisdottir, Åsa birna; Maldonado, Sebastián Andrés Acuña; Kalstad, Trine; Myrmel, Truls; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-22)
      In this work we have explored the live-cell friendly nanoscopy method Multiple Signal Classification Algorithm (MUSICAL) for multi-colour imaging of various organelles and sub-cellular structures in the cardiomyoblast cell line H2c9. We have tested MUSICAL for fast (up to 230Hz), multi-colour time-lapse sequences of various sub-cellular structures (mitochondria, endoplasmic reticulum, microtubules, ...
    • Artefact removal in ground truth deficient fluctuations-based nanoscopy images using deep learning 

      Jadhav, Suyog; Acuña Maldonado, Sebastian Andres; Opstad, Ida Sundvor; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Prasad, Dilip K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-08)
      Image denoising or artefact removal using deep learning is possible in the availability of supervised training dataset acquired in real experiments or synthesized using known noise models. Neither of the conditions can be fulfilled for nanoscopy (super-resolution optical microscopy) images that are generated from microscopy videos through statistical analysis techniques. Due to several physical ...
    • Blind Super-Resolution Approach for Exploiting Illumination Variety in Optical-Lattice Illumination Microscopy 

      Samanta, Krishnendu; Sarkar, Swagato; Acuña, Sebastian; Joseph, Joby; Ahluwalia, Balpreet Singh; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-19)
      Optical-lattice illumination patterns help in pushing high spatial frequency components of the sample into the optical transfer function of a collection microscope. However, exploiting these high-frequency components require precise knowledge of illumination if reconstruction approaches similar to structured illumination microscopy are employed. Here, we present an alternate blind reconstruction ...
    • Chip-based multimodal super-resolution microscopy for histological investigations of cryopreserved tissue sections 

      Villegas, Luis; Dubey, Vishesh Kumar; Nystad, Mona; Tinguely, Jean-Claude; Coucheron, David Andre; Dullo, Firehun Tsige; Priyadarshi, Anish; Acuna Maldonado, Sebastian Andres; Ahmad, Azeem; Mateos, Jose M.; Barmettler, Gery; Ziegler, Urs; Birgisdottir, Åsa Birna; Hovd, Aud-Malin Karlsson; Fenton, Kristin Andreassen; Acharya, Ganesh; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-24)
      Histology involves the observation of structural features in tissues using a microscope. While diffraction-limited optical microscopes are commonly used in histological investigations, their resolving capabilities are insufficient to visualize details at subcellular level. Although a novel set of super-resolution optical microscopy techniques can fulfill the resolution demands in such cases, the ...
    • Classification of Micro-Damage in Piezoelectric Ceramics Using Machine Learning of Ultrasound Signals 

      Tripathi, Gaurav; Anowarul, Habib; Agarwal, Krishna; Prasad, Dilip K. (Journal article; Peer reviewed, 2019-09-28)
      Ultrasound based structural health monitoring of piezoelectric material is challenging if a damage changes at a microscale over time. Classifying geometrically similar damages with a difference in diameter as small as 100 m is difficult using conventional sensing and signal analysis approaches. Here, we use an unconventional ultrasound sensing approach that collects information of the entire ...
    • Deriving high contrast fluorescence microscopy images through low contrast noisy image stacks 

      Acuna Maldonado, Sebastian Andres; ROY, MAYANK; Villegas, Luis; Dubey, Vishesh Kumar; Ahluwalia, Balpreet Singh; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-11)
      Contrast in fluorescence microscopy images allows for the differentiation between different structures by their difference in intensities. However, factors such as point-spread function and noise may reduce it, affecting its interpretability. We identified that fluctuation of emitters in a stack of images can be exploited to achieve increased contrast when compared to the average and Richardson-Lucy ...
    • Eigen-analysis reveals components supporting super-resolution imaging of blinking fluorophores 

      Agarwal, Krishna; Prasad, Dilip Kumar (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-30)
      This paper presents eigen-analysis of image stack of blinking fluorophores to identify the components that enable super-resolved imaging of blinking fluorophores. Eigen-analysis reveals that the contributions of spatial distribution of fluorophores and their temporal photon emission characteristics can be completely separated. While cross-emitter cross-pixel information of spatial distribution ...
    • Fluorescence fluctuation-based super-resolution microscopy using multimodal waveguided illumination 

      Opstad, Ida Sundvor; Hansen, Daniel Henry; Acuña Maldonado, Sebastian Andres; Ströhl, Florian; Priyadarshi, Anish; Tinguely, Jean-Claude; Dullo, Firehun Tsige; Dalmo, Roy Ambli; Seternes, Tore; Ahluwalia, Balpreet Singh; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-19)
      Photonic chip-based total internal reflection fluorescence microscopy (c-TIRFM) is an emerging technology enabling a large TIRF excitation area decoupled from the detection objective. Additionally, due to the inherent multimodal nature of wide waveguides, it is a convenient platform for introducing temporal fluctuations in the illumination pattern. The fluorescence fluctuation-based nanoscopy technique ...
    • Image inpainting in acoustic microscopy 

      Habib, Anowarul; Banerjee, Pragyan; Mishra, Sibasish; Yadav, Nitin; Agarwal, Krishna; Melandsø, Frank; Prasad, Dilip K (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-27)
      Scanning acoustic microscopy (SAM) is a non-ionizing and label-free imaging modality used to visualize the surface and internal structures of industrial objects and biological specimens. The image of the sample under investigation is created using high-frequency acoustic waves. The frequency of the excitation signals, the signal-to-noise ratio, and the pixel size all play a role in acoustic image ...
    • Label-free imaging on waveguide platform with enhanced resolution and contrast 

      Jayakumar, Nikhil; Dullo, Firehun Tsige; Dubey, Vishesh Kumar; Ahmad, Azeem; Cauzzo, Jennifer; Mazagao Guerreiro, Eduarda; Snir, Omri; Skalko-Basnet, Natasa; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Conference object; Konferansebidrag, 2021)
      Chip-based Evanescent Light Scattering (cELS) utilizes the multiple modes of a high-index contrast optical waveguide for near-field illumination of unlabeled samples, thereby repositioning the highest spatial frequencies of the sample into the far-field. The multiple modes scattering off the sample with different phase differences is engineered to have random spatial distributions within the integration ...
    • Learning Nanoscale Motion Patterns of Vesicles in Living Cells 

      Sekh, Arif Ahmed; Opstad, Ida Sundvor; Birgisdottir, Åsa B.; Myrmel, Truls; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Prasad, Dilip K. (Conference object; Konferansebidrag, 2020-08-05)
      Detecting and analyzing nanoscale motion patterns of vesicles, smaller than the microscope resolution (~250 nm), inside living biological cells is a challenging problem. State-of-the-art CV approaches based on detection, tracking, optical flow or deep learning perform poorly for this problem. We propose an integrative approach, built upon physics based simulations, nanoscopy algorithms, and shallow ...
    • Learning nanoscale motion patterns of vesicles in living cells 

      Sekh, Arif Ahmed; Opstad, Ida Sundvor; Birgisdottir, Åsa Birna; Myrmel, Truls; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Prasad, Dilip K. (Chapter; Bokkapittel, 2020)
      Detecting and analyzing nanoscale motion patterns of vesicles, smaller than the microscope resolution (~250 nm), inside living biological cells is a challenging problem. State-of-the-art CV approaches based on detection, tracking, optical flow or deep learning perform poorly for this problem. We propose an integrative approach, built upon physics based simulations, nanoscopy algorithms, and shallow ...
    • Multi-moded high-index contrast optical waveguide for super-contrast high-resolution label-free microscopy 

      Jayakumar, Nikhil; Dullo, Firehun Tsige; Dubey, Vishesh Kumar; Ahmad, Azeem; Ströhl, Florian; Cauzzo, Jennifer; Mazagao Guerreiro, Eduarda; Snir, Omri; Skalko-Basnet, Natasa; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-20)
      The article elucidates the physical mechanism behind the generation of superior-contrast and highresolution label-free images using an optical waveguide. Imaging is realized by employing a high index contrast multi-moded waveguide as a partially coherent light source. The modes provide near-field illumination of unlabeled samples, thereby repositioning the higher spatial frequencies of the ...
    • Multimodal on-chip nanoscopy and quantitative phase imaging reveals the nanoscale morphology of liver sinusoidal endothelial cells 

      Butola, Ankit; Coucheron, David Andre; Szafranska, Karolina; Ahmad, Azeem; Mao, Hong; Tinguely, Jean-Claude; McCourt, Peter Anthony; Paramasivam, Senthilkumaran; Mehta, Dalip Singh; Agarwal, Krishna; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-23)
      Visualization of three-dimensional (3D) morphological changes in the subcellular structures of a biological specimen is a major challenge in life science. Here, we present an integrated chip-based optical nanoscopy combined with quantitative phase microscopy (QPM) to obtain 3D morphology of liver sinusoidal endothelial cells (LSEC). LSEC have unique morphology with small nanopores (50-300 nm in ...
    • MusiJ: an ImageJ plugin for video nanoscopy 

      Acuña Maldonado, Sebastian Andres; Ströhl, Florian; Opstad, Ida Sundvor; Ahluwalia, Balpreet S.; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-14)
      We present an open-source implementation of the fluctuation-based nanoscopy method MUSICAL for ImageJ. This implementation improves the algorithm’s computational efficiency and takes advantage of multi-threading to provide orders of magnitude faster reconstructions than the original MATLAB implementation. In addition, the plugin is capable of generating super-resolution videos from large stacks of ...
    • Non-heuristic automatic techniques for overcoming low signal-to-noise-ratio bias of localization microscopy and multiple signal classification algorithm 

      Agarwal, Krishna; Macháň, Radek; Prasad, Dilip Kumar (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-21)
      Localization microscopy and multiple signal classification algorithm use temporal stack of image frames of sparse emissions from fluorophores to provide super-resolution images. Localization microscopy localizes emissions in each image independently and later collates the localizations in all the frames, giving same weight to each frame irrespective of its signal-to-noise ratio. This results in a ...
    • Object detection neural network improves Fourier ptychography reconstruction 

      Ströhl, Florian; Jadhav, Suyog; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Prasad, Dilip K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-23)
      High resolution microscopy is heavily dependent on superb optical elements and superresolution microscopy even more so. Correcting unavoidable optical aberrations during post-processing is an elegant method to reduce the optical system’s complexity. A prime method that promises superresolution, aberration correction, and quantitative phase imaging is Fourier ptychography. This microscopy technique ...