Houzhu Ding

Comparison of photometric stereo and spectral analysis for visualization and assessment of burn injury from hyperspectral imaging

Burn wounds resulting from thermal insult to the skin are typically classified according to varying depth and therefore require differential levels of medical intervention. In this paper, two methods are proposed for assessing burn injury. The two methods compared are photometric stereo (PS) and spectral analysis. Firstly, PS represents a robust topography recovery algorithm that is implemented to reconstruct the burn and normal skin tissue from multiple hyperspectral images under different illumination conditions. This enabled the visualization of a 3D skin depth map which is used to assess the burn degree. Next, the hyperspectral measurement data of the skin are analyzed to assess partial thickness thermal injury with functional correlation through hemodynamic parameters related to tissue perfusion and oxygen delivery. Two dimensional principle component analysis (2DPCA) is used for noise reduction towards extracting features from the hyperspectral images within the wavelength range from 375 nm to 1050 nm. This is followed by applying the spectral analysis algorithm to calculate oxygen saturation fraction and concentration of total hemoglobin, where each parameter provided a biomarker of injured tissue. The two methods yielded alternative indicators for burn assessment that could be correlated with each other. Specifically, the spectral measurement result could be used as a reference value for the physical skin site depth map.

A Novel Melt Electrospinning System for Studying Cell Substrate Interactions

Controlling cell behavior has generated immense attention in the fields of tissue engineering and regenerative medicine. Particular emphasis has been given to the creation of 3D biomimetic cellular microenvironments that replicate the complex nature of the extracellular matrix (ECM). A key factor that has not been rigorously deconstructed using scalable, layered manufacturing approaches is the structural dimension or scale aspect of in vitro culture models. Melt electrospinning represents a bio-additive manufacturing process that has been relatively under-reported. Although complex in nature, the melt electrospinning process can furnish a 3D cell delivery format with physiologically relevant 3D structural cues. In the present work, poly-e-caprolactone (PCL) has been chosen as the biomaterial substrate. Rheological studies that guide the design phase of the reported system have been performed for the entire PCL melt processing range, implicating the governing effect of the experimental melt temperature on the scale and the topography in the final processed material. Notable challenges that arise from the nature of the process with respect to the electrospun fiber stability and resolution have been overcome through the design of a novel heating element configuration. In this paper, a reliable biofabrication process with tunable processing of the fiber diameter and alignment is reported. Fundamental parametric studies utilizing the major processing parameters demonstrate the potential for the system to precisely fabricate 3D PCL scaffolds with microstructural features.Copyright

Design of a Personalized Skin Grafting Methodology Using an Additive Biomanufacturing System Guided by 3D Photogrammetry

In this paper, the authors propose a novel method whereby a prescribed simulated skin graft is 3D printed, followed by the realization of a 3D model representation using an open-source software AutoDesk 123D Catch to reconstruct the entire simulated skin area. The methodology is photogrammetry, which measures the 3D model of a real-word object. Specifically, the principal algorithm of the photogrammetry is structure from motion (SfM) which provides a technique to reconstruct a 3D scene from a set of images collected using a digital camera. This is an efficient approach to reconstruct the burn depth compared to other non-intrusive 3D optical imaging modalities (laser scanning, optical coherence tomography). Initially, an artificial human hand with representative dimensions is designed using a CAD design program. Grooves with a step-like depth pattern are then incorporated into the design in order to simulate a skin burn wound depth map. Then, the *.stl format file of the virtually wounded artificial hand is extruded as a thermoplastic material, acrylonitrile butadiene styrene (ABS), using a commercial 3D printer. Next, images of the grooves representing different extents of burned injury are acquired by a digital camera from different directions with respect to the artificial hand. The images stored in a computer are then imported into AutoDesk 123D Catch to process the images, thereby yielding the 3D surface model of the simulated hand with a burn wound depth map. The output of the image processing is a 3D model file that represents the groove on the plastic object and thus the burned tissue area. One dimensional sliced sections of the designed model and reconstructed model are compared to evaluate the accuracy of the reconstruction methodology. Finally, the 3D CAD model is designed with a prescribed internal tissue scaffold structure and sent to the dedicated software of the 3D printing system to print the design of the virtual skin graft with biocompatible material poly-e-caprolactone (PCL).Copyright