Selective laser sintering (SLS) is an efficient process in additive manufacturing that enables rapid part production from computer-based designs. However, SLS is limited by its notable lack of in situ process monitoring when compared with other manufacturing processes. We report the incorporation of optical coherence tomography (OCT) into an SLS system in detail and demonstrate access to surface and subsurface features. Video frame rate cross-sectional imaging reveals areas of sintering uniformity and areas of excessive heat error with high temporal resolution. We propose a set of image processing techniques for SLS process monitoring with OCT and report the limitations and obstacles for further OCT integration with SLS systems.
State-of-the-art treatment for joint diseases like osteoarthritis focus on articular cartilage repair/regeneration by stem cell implantation therapy. However, the technique is limited by a lack of precision in the physician’s imaging and cell deposition toolkit. We describe a novel combination of high-resolution, rapid scan-rate optical coherence tomography (OCT) alongside a short-pulsed nanosecond thulium (Tm) laser for precise cell seeding in cartilage. The superior beam quality of thulium lasers and wavelength of operation 1940 nm offers high volumetric tissue removal rates and minimizes the residual thermal footprint. OCT imaging enables targeted micro-well placement, precise cell deposition, and feature contrast. A bench-top system is constructed using a 15 W, 1940 nm, nanosecond-pulsed Tm fiber laser (500 μJ pulse energy, 100 ns pulse duration, 30kHz repetition rate) for removing tissue, and a swept source laser (1310 ± 70 nm, 100 kHz sweep rate) for OCT imaging, forming a combined Tm/OCT system – a “smart laser knife”. OCT assists the smart laser knife user in characterizing cartilage to inform micro-well placement. The Tm laser creates micro-wells (2.35 mm diameter length, 1.5 mm width, 300 μm deep) and micro-incisions (1 mm wide, 200 μm deep) while OCT image-guidance assists and demonstrates this precision cutting and cell deposition with real-time feedback. To test micro-well creation and cell deposition protocol, gelatin phantoms are constructed mimicking cartilage optical properties and physiological structure. Cell viability is then assessed to illustrate the efficacy of the hydrogel deposition. Automated OCT feedback is demonstrated for cutting procedures to avoid important surface/subsurface structures. This bench-top smart laser knife system described here offers a new image-guided approach to precise stem cell seeding that can enhance the efficacy of articular cartilage repair.
Optical coherence tomography (OCT) retinal imaging contributes to understanding central nervous system (CNS)
diseases because the eye is an anatomical “window to the brain” with direct optical access to nonmylenated retinal
ganglion cells. However, many CNS diseases are associated with neuronal changes beyond the resolution of standard
OCT retinal imaging systems. Though studies have shown the utility of scattering angle resolved (SAR) OCT for particle
sizing and detecting disease states ex vivo, a compact SAR-OCT system for in vivo rodent retinal imaging has not
previously been reported. We report a fiber-based SAR-OCT system (swept source at 1310 nm ± 65 nm, 100 kHz scan
rate) for mouse retinal imaging with a partial glass window (center aperture) for angular discrimination of backscattered
light. This design incorporates a dual-axis MEMS mirror conjugate to the ocular pupil plane and a high collection
efficiency objective. A muring retina is imaged during euthanasia, and the proposed SAR-index is examined versus time.
Results show a positive correlation between the SAR-index and the sub-cellular hypoxic response of neurons to
isoflurane overdose during euthanasia. The proposed SAR-OCT design and image process technique offer a contrast
mechanism able to detect sub-resolution neuronal changes for murine retinal imaging.
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