Evaluation of the variable depth resolution of active dynamic thermography on human skin

Abstract

Active dynamic thermography (ADT) is an imaging technique capable of characterizing the non-homogenous thermal conductance of damaged tissues. The purpose of this study was to determine optimal stimulation parameters and quantify the optical resolution of ADT through various depths of human skin. Excised tissue from plastic surgery operations was collected immediately following excision. A total of 12 thin to thick split-thickness grafts were harvested from 3 patients. Grafts were placed on top of a 3D printed resolution chart and thermal stimulation was applied from a 300W halogen lamp array for between 0.5-10 seconds to determine optimal parameters. Video was captured with a thermal camera, and analysis was performed by reconstructing an image from thermal gradients. In this study ADT resolved 0.445±0 lp/mm at a depth of 0.010", 0.356±0.048 lp/mm at a depth of 0.015", 0.334±0.027 lp/mm at a depth of 0.020" and 0.265±0.022 lp/mm at a depth of 0.025". The stimulus energy required for maximum resolution at each depth was 3-4s, 8s, 12s and 12s respectively. ADT is a sensitive technique for imaging dermal structure, capable of resolving detail as fine as 1124 μm, 1427 μm, 1502 μm and 1893 μm in thin to thick split-thickness skin grafts respectively. This study has characterized a correlation between stimulus input and maximal resolution at differing depths of skin. It has also defined the functional imaging depth of ADT to below the sub-cutis, well below conventional spectrophotometric techniques.

3D bioprinting of skin: a state-of-the-art review on modelling, materials, and processes

“…Synthetic biopolymers are man-made polymers which includes polylactic acid (PLA), polyglycolic acid (PGA), poly(ε-caprolactone) (PCL), poly(lactic-co-glycolic acid) (PLGA), poly(propylene fumarate), polyanhydrides, polycarbonates, polyorthoesters, polyurethanes, and polyphosphazenes. Synthetic Active dynamic thermography (ADT) Accurate measurement of tissue/burn depths, High resolution Necessity of using proper thermal models of living tissues, controlled experimental conditions required [135][136][137][138][139] biopolymers are known for their excellent mechanical properties, which are important for a scaffold material. Key advantage is the ability to tailor the mechanical properties and degradation kinetics, by altering the polymer structure, to suit various biomedical applications, for example, bone graft or skin graft [146].…”

“…Many parameters including the healing time within three weeks are also assessed previously using this technique [136,138]. Pirindeze et al [139] examined the optical resolution of ADT, to define the resolution limits of this system and to establish a set of parameters for thermal simulation using this system. In fact, they used human skin of varying thicknesses for this resolution study and have successfully demonstrated the A typical process for bioprinting 3D tissues involving six steps namely Imaging (imaging the injured site/tissue), design approach (image converted to 3D models; approach can be either printing the biomimetic structure along with cells, self-assembly of cells or constructing mini-tissues to be assembled later), material selection (based on the intended application, can be natural or synthetic polymers, ECM or combinations of them), cell selection (based on the intended application, can be stem cells or differentiated cells), bioprinting (using commercial or custom-made bioprinters) and application (post-processing in a bioreactor for maturation, grafting or implantation at the injury site).…”