Research Project: Evaluation of Potential Optical Safety Hazards
As optical diagnostic device technology evolves and new applications for light-emitting devices are developed, new safety issues can arise. The Optical Diagnostic Devices laboratory performs research to elucidate and quantify new potential optical hazards raised by scientific publications, premarket device reviews and postmarket adverse event reports. Recent efforts to elucidate two potential optical safety hazards are described below.
Photothermal Assessment of Cutaneous Transilluminators
In a recent study, we analyzed the optical and thermal outputs of cutaneous transiluminators used to locate blood vessels for injections and catheterization in adults and neonates. Direct measurements of transilluminator optical output and temperature rise were made, as were measurements during transilluminator irradiation of tissue. The results were compared with safe limits in the standards and analyzed with an Arrhenius rate process analysis. Devices with higher irradiance levels based on novel white light LEDs were found to generate significant temperatures that approach, but do not exceed the safe limits for standard short-duration use. The research was published in a recent journal article (Pfefer TJ, Mehrabi A, James R, Landry R, Weininger S, Chang I, Kaufman D, Miller S. Optical-thermal characterization of cutaneous transilluminators. Phys Med Biol 54:6867-6880, 2009).
Spectral irradiance measurements of three battery powered transilluminators (BPTs).
Ultraviolet radiation damage assessment
In collaboration with OSEL’s Division of Biology, we performed initial measurements to assess the relative levels of damage produced by ultraviolet radiation in skin and mucosal tissues. The methods involved irradiating engineered tissue samples and quantifying immediate damage as well as repair after 24 hours using novel immunohistochemistry multi-labeling techniques. The pictures below were taken under a microscope with 40X objective and show the red fluorescent label for cyclobutane pyrimidine dimers (CPDs), a major type of UV-induced DNA damage, inside skin cells’ nuclei. Early results indicate that more DNA damage accumulates in mucosal tissues compared to skin, as evidenced by the slopes in the graph below.
Fluorescence microscopy images of the CPD-labeled nuclei in skin tissue after low (top) and high (bottom) UV doses