Rationale and Objectives
The treatment of nonmelanoma skin cancer (NMSC) is usually by surgical excision or Mohs micrographic surgery and alternatively may include photodynamic therapy (PDT). To guide surgery and to optimize PDT, information about the tumor structure, optical parameters, and vasculature is desired.
Materials and Methods
Spatial frequency domain imaging (SFDI) can map optical absorption, scattering, and fluorescence parameters that can enhance tumor contrast and quantify light and photosensitizer dose. High frequency ultrasound (HFUS) imaging can provide high-resolution tumor structure and depth, which is useful for both surgery and PDT planning.
Results
Here, we present preliminary results from our recently developed clinical instrument for patients with NMSC. We quantified optical absorption and scattering, blood oxygen saturation (StO2), and total hemoglobin concentration (THC) with SFDI and lesion thickness with ultrasound. These results were compared to histological thickness of excised tumor sections.
Conclusions
SFDI quantified optical parameters with high precision, and multiwavelength analysis enabled 2D mappings of tissue StO2 and THC. HFUS quantified tumor thickness that correlated well with histology. The results demonstrate the feasibility of the instrument for noninvasive mapping of optical, physiological, and ultrasound contrasts in human skin tumors for surgery guidance and therapy planning.
The dielectric breakdown strength of the elastomer films used in dielectric elastomer actuators and generators (DEA & DEG) limits the peak actuation strains and maximum efficiency that can be achieved by these electromechanical transducers. In order to reduce the likelihood of failure during their operation, the factors that lead to breakdown should be well understood. Recent efforts in this area have focused on electromechanical and thermal effects that lead to breakdown, however degradation and ultimately breakdown caused by partial discharge activity represent another key way an insulating material can fail. This work presents partial discharge data collected from the VHB4910 (3M) acrylic elastomer, tested using solid stainless steel electrodes, solid graphite electrodes, and powdered carbon electrodes. It is found that degradation due to partial discharge activity does play a role in the breakdown of the samples tested using solid electrodes, and that their detection could provide an indication of the degradation that leads to breakdown. However when powdered carbon electrodes are used, significantly more partial discharge activity occurs between the carbon particles of the electrode on the surface of the dielectric. This obscures the detection of the partial discharges occurring due to internal defects that cause damage to the dielectric.
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