Repair of soft tissue defects of the lips as seen in complex maxillofacial injuries, requires pre-vascularized multi-tissue
composite grafts. Protocols for fabrication of human ex-vivo produced oral mucosal equivalents (EVPOME) composed
of epithelial cells and a dermal equivalent are available to create prelaminated flaps for grafting in patients. However, invivo
assessment of neovascularization of the buried prelaminated flaps remains clinically challenging. Here, we use
diffuse reflectance spectroscopy (DRS) and diffuse correlation spectroscopy (DCS) to non-invasively quantify
longitudinal changes in the vessel density and blood-flow within EVPOME grafts implanted in the backs of SCID mice
and subsequently to determine the utility of these optical techniques for assessing vascularization of implanted grafts. 20
animals were implanted with EVPOME grafts (1x1x0.05 cm<sup>3</sup>) in their backs. DRS and DCS measurements were
obtained from each animal both atop the graft site and far away from the graft site, at one week post-implantation, each
week, for four consecutive weeks. DRS spectra were analyzed using an inverse Monte Carlo model to extract tissue
absorption and scattering coefficients, which were then used to extract blood flow information by fitting the
experimental DCS traces. There were clear differences in the mean optical parameters (averaged across all mice) at the
graft site vs. the off-site measurements. Both the total hemoglobin concentration (from DRS) and the relative blood flow
(from DCS) peaked at week 3 at the graft site and declined to the off-site values by week 4. The optical parameters
remained relatively constant throughout 4 weeks for the off-site measurements.
There is a critical unmet clinical need for a device that can monitor and predict the onset of shock: hemorrhagic shock or bleeding to death, septic shock or systemic infection, and cardiogenic shock or blood flow and tissue oxygenation impairment due to heart attack. Together these represent 141 M patients per year. We have developed a monitor for shock based on measuring blood flow in peripheral (skin) capillary beds using diffuse correlation spectroscopy, a form of dynamic light scattering, and have demonstrated proof-of-principle both in pigs and humans. Our results show that skin blood flow measurement, either alone or in conjunction with other hemodynamic properties such as heart rate variability, pulse pressure variability, and tissue oxygenation, can meet this unmet need in a small self-contained patch-like device in conjunction with a hand-held processing unit. In this paper we describe and discuss the experimental work and the multivariate statistical analysis performed to demonstrate proof-of-principle of the concept.
Silicon avalanche photodiodes (APDs) fabricated through a deep diffusion process underwent a modified surface treatment in an attempt to improve their response in the ultraviolet region of the optical spectrum. After adjusting the doping profile in the near-surface region of the detectors, APDs were fabricated and tested at several wavelengths from ultraviolet to the near-infrared. At the target wavelength of 355 nm, the detector bandwidth was increased by a factor of 20 over devices fabricated without the modified surface treatment. Modest improvements in the internal quantum efficiency were also measured. Most importantly, the modified detectors maintained the high gain and low noise performance specifications that are hallmarks of traditional deep diffusion APDs.