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An epidural injection is one among many medical procedures used for a long time for anaesthesia and pain associated with radiculopathy. It is the most preferred method for drug delivery for sciatica patients and local anaesthesia. It is crucial to precisely assess the exact position of the needle while performing the procedure. There have been several cases of paralysis, mainly after transforaminal epidural injections. So, there is always a high scope for a device that can precisely measure the needle position in real-time during the epidural injection. Optical coherence tomography (OCT) has become an essential tool in bio-imaging. An OCT is a Michelson interferometer with one of the mirrors replaced by the sample that we want to image. The main attraction offered by the system is that it is non-invasive. We report using an OCT-based optical fibre catheter, which can be used to guide the epidural injections. The catheter is made of single-mode optical fibre, and for focusing the light beam, a ball lens is designed and fabricated on the tip of the fibre. The lens is designed to have a diameter of 250 µm and will be inserted into the needle. The fibre catheter will be connected to a custom-made SD-OCT system equipped with a high speed inhouse made spectrometer. By analysing the A-scan images from the system, we can precisely calculate the thickness of the surface in front of the catheter. This data will guide the clinician to assess the needle position precisely in real-time. © 2022 SPIE

The anatomical structures of the eye possessed by vertebrates and arthropods are of two major types when considering the natural image-forming systems. Study of these vision systems gives an opportunity to understand the solution to a specific problem developed by the Nature. Also, the understanding of the eye systems in the animal world is fascinating and important in the development of bioinspired manufacturing of dioptric systems for many advanced and sophisticated instruments. The techniques used to study anatomical features of a compound eye like electron microscopies (SEM, TEM), micro computed tomography (µCT), histology etc. have limitations, making them unsuitable for in vivo studies. In vivo imaging tools especially with high resolution imaging capability can provide an insight of visual ecology in greater detail. It also reduces the cost and the amount of time required to perform experiments. Full-field optical coherence tomography (FF-OCT) is an expansion of OCT technique that uses high numerical aperture microscope objective to get highly resolved en face tomographic image of a biological sample in the in vivo condition. We report the application of an in-house developed time domain full-field optical coherence tomography (TD FF-OCT) system for depth resolved en face and three dimensional, in vivo imaging of dragonfly's prominent compound eye. © 2022 SPIE

The assessment of mechanical stiffness is an essential diagnostic tool for investigating the biomechanical properties of biological tissues. Surface wave elastography (SWE) is an emerging technique to quantify elastic properties of tissues in clinical diagnosis. High-speed optical imaging combined with SWE has enormous potential in quantifying the elastic properties of tissues at microscale resolutions. In this study, we implement surface wave elastography using high-speed optical interferometry to characterize the elastic properties of tissue-mimicking phantoms and ex-vivo native caprine liver tissue by imaging the surface wave induced by an electromechanical actuator. The sinusoidal mechanical excitations ranging from 120 Hz to 1.2 kHz on the surface of tissues are captured using a high-speed camera with a frame rate of 4 kHz at micrometer resolutions. The surface wavefront reconstruction is performed using a phase-shifting algorithm and linear regression is used to calculate the surface wave velocity. The mechanical stiffness estimated from the optical system is compared with the results of mechanical compression testing measurements. The results from this multimodal platform combining optical interferometry and vibrational spectroscopy using SWE are highly promising towards a non-invasive or minimally invasive imaging for in-vivo and ex-vivo mechanical characterization of tissues with future clinical applications. © 2022 IOP Publishing Ltd.

Viscoelasticity is an important diagnostic parameter to investigate physiological dysfunctions in biological tissues. This Letter reports the quantification of viscoelastic parameters by Rayleigh wave tracing on the surface of tissue-mimicking phantoms using holographic imaging. The Rayleigh wave is induced by an electromechanical actuator on the surface of oil-in-gelatin phantoms and a biological tissue sample followed by holographic imaging and reconstruction of the wave. The frequency-dependent velocity dispersion is fitted to a Voigt model for the quantification of viscous and elastic moduli. The viscoelastic parameters calculated by the proposed method are validated by comparing the results from a conventional mechanical rheometer. © 2022 Optica Publishing Group

We have implemented an untrained deep neural network powered with explicit regularization by denoising for twin image-free reconstruction in inline lensless holographic microscopy. The performance of different denoisers in twin image elimination is discussed. © OSA 2021, © 2021 The Author(s)

High quality, real time imaging of coronary arteries in-vivo presents considerable challenges. We demonstrate the application of phase-retrieval algorithm on fluoroscopy-derived images of coronary arteries using transport of intensity equation. © 2021 The Author (s).

The quantitative and qualitative studies of biomechanical properties is an important diagnostic tool for investigating abnormal tissues. Elastography is an experimental technique that is used to characterize soft materials including tissues collagen and fat etc. The existing ultrasound and magnetic-based elastography methods are limited by low spatial resolution and small imaging depth. The optical methods have enormous potential to quantify the elastographic measurement with microscale resolution. So, digital holography can establish a new platform for measuring the bulkelastographic properties of the soft tissues. In this work, we calculate the phase map of the Surface Acoustic Wave (SAW) produced by piezo-transducer on the surface of the tissue phantom using the Digital Holography (DH) imaging method. The temporal phase-shifting algorithm is employed to reconstruct the phase map of the SAW for accurate quantification of surface wave velocity. The precise calculation of surface wave velocity gives the direct measurement of the mechanical parameter like elastic modulus and shear modulus. The preliminary results obtained from the proposed method can be used to facilitate non-invasive or minimally invasive imaging with in-vivo and ex-vivo applications.

Ectatic corneal diseases are a group of eye disorders characterized by progressive thinning and outward bulging of the cornea, resulting in vision impairment. A few attempts have been made to use cornea-derived extracellular matrix hydrogels for corneal tissue engineering; however, no studies have investigated its application in corneal ectasia. In this study, we have first developed an animal surgical model that mimics a few specific phenotypes of ectatic cornea. Later, we investigated the potential of decellularized cornea matrix hydrogels (dCMH) from both human and bovine sources in increasing the thickness of the cornea in the developed surgical model. Our data advocate that surgical stromal depletion can be followed to establish ectatic models and can also provide information on the biocompatibility of materials, its integration with native stroma, degradation over time, and tissue remodeling. We observed that dCMH from both sources could integrate with ectatic thin corneal stroma and helps in regaining the thickness by regenerating a reasonably functional and transparent stroma; however, no significant difference was spotted between the dCMH made from human and bovine corneal tissue sources. Hence, this study is a promising step toward developing a non-invasive technique for the treatment of corneal ectasia by using dCMH. © 2021 American Chemical Society.

Acne is one of the common dermatological skin inflammatory conditions. The current therapeutic modalities for the treatment of acne include the administration of antibiotics and anti-inflammatory agents. The rising instance of antibiotic resistance in acne strains has led to the exploration of alternative therapeutic modalities. In the current study, we have employed a liposomal gold nanoparticle entrapping curcumin (Au Lipos Cur NPs) for dual light-mediated therapy for the treatment of acne. These nanoparticles exerted a positive zeta potential that enabled their localized follicular delivery by iontophoresis. The localized deposition of Au Lipos NPs leads to photothermal transduction causing destruction of sebaceous glands. Furthermore, when the nanoparticles were assessed in vitro by sequential irradiation with NIR and blue light, it resulted in significant inhibition of bacterial growth. Thus the dual light-mediated therapy by Au Lipos Cur NPs can form a potential therapeutic modality for the efficient treatment of recurrent acne.