Cochlear implant is by far the most successful treatment for sensorineural hearing loss (SNHL) - the most common sensory deficit in the world. Although it was generally prescribed, the understanding of the etiology and the cellular structural abnormalities of SNHL is still limited due to the lack of direct imaging of the interior of the inner ear of living human patients. We have developed a micro-OCT probe that can serve as the stylet of a cochlear implant, which can perform cellular-level imaging through the cochlear implant during the surgery, providing diagnostic information and guidance to the surgeons.
Micro-optical coherence tomography (µOCT), is an emerging optical imaging approach enabling visualization of tissue microstructures at near cellular level. Small form-factor fiber-optic probes are needed to enable uOCT devices for minimally invasive diagnostic procedures such as coronary catheterization for atherosclerosis evaluation. Manufacturing complexities associated with miniaturizing current fiber-optic probes limit their optical and mechanical performance. We will present details of the design and construction of these miniaturized µOCT probes comprising TPL-based 3D printed optics, along with pre-clinical imaging results from an animal model. This probe is capable of lateral resolution of 5 µm and EDOF exceeding 850 µm in tissue.
We have previously demonstrated a miniaturized transnasal introduction tube (TNIT) for transnasal endomicroscopy (TNEM) with optical coherence tomography (OCT) for clinical imaging of the small intestine of infants and adults in vivo. Although the TNIT is a convenient and effective way to implement TNEM, OCT probes for imaging through the TNIT had long manufacturing times and low yields, and its multiple cylindrical surfaces caused severe optical aberrations, degrading OCT image quality. Here we introduce a new optical design for 3D-printed microoptics that correct TNIT-induced astigmatism. Preliminary results show that the lens improves resolution and can be reliably manufactured.
Endoscopic biopsies play a vital role in the diagnosis of many diseases of the gastrointestinal (GI) tract. The standard means of biopsy capture using forceps presents challenges in obtaining adequate tissue samples, especially for unsedated transnasal endoscopy (uTNE). Cryobiopsy is an emerging minimally-invasive alternative where the distal tip of a dual-lumen uTNE probe is cooled momentarily, freezing and adhering the tissue in contact, which is collected for histology. OCT image guidance during cryobiopsy can enable pre-biopsy lesion examination; however, dimensional constraints make this challenging. Here, we demonstrate a microscale 3D-printed device capable of minimally-invasive side-viewing OCT image-guided cryobiopsy though uTNE scopes.
With intravascular Optical Coherence Tomography (IVOCT), phantom models are invaluable for system characterization and clinical training. However, accurately simulating 3D tissue geometries and heterogeneous optical properties has been challenging with phantom fabrication methods used to date. Anatomical phantom models typically require mesoscale structures integrated with heterogenous materials to simulate optical scattering and absorption by vascular tissue. In this study, we showed that two photon polymerisation (2PP) 3D printing offers the potential to generate complex tissue phantom scaffolds with sub-micron resolution (<200 nm), and that microinjection of tissue mimicking materials into these scaffolds allows for creation of realistic mesoscale anatomical phantom models of both healthy and diseased tissues. We developed three types of IVOCT phantom models: a free-standing wire model, a vessel side-branch model and an arterial plaque model. The free-standing wires ranged in diameter from 5 to 34 microns. Integration of tissue mimicking materials was performed using micropipettes with a tip diameter of 50 to 60 microns. Healthy vascular tissue was simulated using a mixture of PDMS, silicone oil and TiO2. Coconut oil was used to simulate a pathological lipid inclusion. All models were examined using optical microscopy and scanning electron microscopy, prior to imaging with a commercial IVOCT system. To our knowledge, this is the first phantom study to use 2PP 3D printing for OCT phantoms. The combination of optically-generated 3D scaffolds and microinjection of tissue mimicking materials will enable complex imaging phantoms for a wide range of microscopic and mesoscale optical imaging techniques.
Microscopic and mesoscale optical imaging techniques allow for three-dimensional (3-D) imaging of biological tissue across millimeter-scale regions, and imaging phantom models are invaluable for system characterization and clinical training. Phantom models that replicate complex 3-D geometries with both structural and molecular contrast, with resolution and lateral dimensions equivalent to those of imaging techniques (<20 μm), have proven elusive. We present a method for fabricating phantom models using a combination of two-photon polymerization (2PP) to print scaffolds, and microinjection of tailored tissue-mimicking materials to simulate healthy and diseased tissue. We provide a first demonstration of the capabilities of this method with intravascular optical coherence tomography, an imaging technique widely used in clinical practice. We describe the design, fabrication, and validation of three types of phantom models: a first with subresolution wires (5- to 34-μm diameter) arranged circumferentially, a second with a vessel side-branch, and a third containing a lipid inclusion within a vessel. Silicone hybrid materials and lipids, microinjected within a resin framework created with 2PP, served as tissue-mimicking materials that provided realistic optical scattering and absorption. We demonstrate that optical phantom models made with 2PP and microinjected tissue-mimicking materials can simulate complex anatomy and pathology with exquisite detail.
Small form-factor invasive pressure sensors are widely used in minimally invasive surgery, for example to guide decision making in coronary stenting procedures. Current fiber-optic sensors can have high manufacturing complexities and costs, which severely constrains their adoption outside of niche fields. A particular challenge is the ability to rapidly prototype and iterate upon sensor designs to optimize performance for different applications and medical devices. Here, we present a new sensor fabrication method, which involves two-photon polymerization printing and integration of the printed structure onto the end-face of a single-mode optical fiber. The active elements of the sensor were a pressure-sensitive diaphragm and an intermediate temperature-sensitive spacer that was insensitive to changes in external pressure. Deflection of the diaphragm and thermal expansion the spacer relative to the fiber end-face were monitored using phase-resolved low coherence interferometry. A pressure sensitivity of 0.031 rad/mmHg across the range of 760 to 1060 mmHg (absolute pressure), and a temperature sensitivity of 1.2 mrad/°C across the range 20 to 45°C were observed. This method will enable the fabrication of a wide range of fiber-optic sensors with pressure and temperature sensitivities suitable for guiding minimally invasive surgery.
We report an optical fiber ultrasound transmitter with electrospun MWCNT-polymer composite, generating high-amplitude broadband ultrasound. They produced pressures in the range of conventional intravascular imaging transducers, and can be incorporated into catheters/needles for keyhole surgery
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