The ambition of this review is
to provide an up-to-date synopsis of the state of 3D printing
technology for optical and photonic components, to gauge technological
advances, and to discuss future opportunities. While a range of
approaches have been developed and some have been commercialized, no
single approach can yet simultaneously achieve small detail and low
roughness at large print volumes and speed using multiple materials.
Instead, each approach occupies a niche where the
components/structures that can be created fit within a relatively
narrow range of geometries with limited material choices. For
instance, the common Fused Deposition Modeling (FDM) approach is
capable of large print volumes at relatively high speeds but lacks the
resolution needed for small detail (
>
100
µ
m
) with low roughness (
>
9
µ
m
). At the other end of the spectrum,
two-photon polymerization can achieve roughness (
<2018
Traumatic injury resulting in hemorrhage is a prevalent cause of death worldwide. The current standard of care for trauma patients is to restore hemostasis by controlling bleeding and administering intravenous volume resuscitation. Adequate resuscitation to restore tissue blood flow and oxygenation is critical within the first hours following admission to assess severity and avoid complications. However, current clinical methods for guiding resuscitation are not sensitive or specific enough to adequately understand the patient condition. To better address the shortcomings of the current methods, an approach to monitor intestinal perfusion and oxygenation using a multiwavelength (470, 560, and 630 nm) optical sensor has been developed based on photoplethysmography and reflectance spectroscopy. Specifically, two sensors were developed using three wavelengths to measure relative changes in the small intestine. Using vessel occlusion, systemic changes in oxygenation input, and induction of hemorrhagic shock, the capabilities and sensitivity of the sensor were explored in vivo. Pulsatile and nonpulsatile components of the red, blue, and green wavelength signals were analyzed for all three protocols (occlusion, systemic oxygenation changes, and shock) and were shown to differentiate perfusion and oxygenation changes in the jejunum. The blue and green signals produced better correlation to perfusion changes during occlusion and shock, while the red and blue signals, using a new correlation algorithm, produced better data for assessing changes in oxygenation induced both systemically and locally during shock. The conventional modulation ratio method was found to be an ineffective measure of oxygenation in the intestine due to noise and an algorithm was developed based on the Pearson correlation coefficient. The method utilized the difference in phase between two different wavelength signals to assess oxygen content. A combination of measures from the three wavelengths provided verification of oxygenation and perfusion states, and showed promise for the development of a clinical monitor.
Cross-sectional 4-D imaging of vocal fold morphology and function is desirable for accurate diagnosis of many vocal fold pathologies, which occur throughout the epithelial layer and alter the mucosal wave. Clinical videoendoscopy provides qualitative diagnostic information but remains limited to surface visualization of layered vocal fold structure and two-dimensional mucosal vibration. While OCT has been investigated to address the shortcomings of standard 2-D endoscopy, challenges remain in reconstruction of the 4-D mucosal wave over the entire vocal fold structure. To address these challenges, we have developed a fast-scanning OCT laryngoscope to enable asynchronous Nyquist sampling of the human voice fundamental frequency range (and its harmonics, up to 1 kHz). We present a new algorithm for reconstruction of the 4-D vocal fold dynamics during phonation using OCT volume data of the entire anterior-posterior vocal fold structure. Reconstruction of the vibration of a vocal fold phantom confirmed feasibility of the algorithm and preliminary reconstruction of the in vivo vocal fold glottal cycle is presented. This work represents the first cross-sectional Nyquist sampling of the in vivo human mucosal wave using an OCT system with hardware capable of encompassing the human fundamental frequency range (i.e., 90-260 Hz). The developed OCT laryngoscope and algorithm will enable volumetric representations of vocal fold dynamics in the clinic and development of quantitative metrics for diagnostic and interventional guidance.
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