Design, analysis, and fabrication of a prototype non-invasive system for assessment of biological and synthetic tissues

Abstract

A new instrument system for the non-invasive assessment of biological systems has been designed, built and validated. This system utilizes the optical characteristics of a biological system to assess both its static and dynamic response over time. The changes in the optical properties can then be used to quantify the response of the biological system to external or internal stimuli. This new system incorporates an efficient light delivery system, as well as a novel light collection system to provide high repeatability, reproducibility, sensitivity, and detection thresholds. The system incorporates simultaneous measurement of transmitted light, forward scattered light, specularly reflected light, and non-specularly reflected light in across the visible spectrum, to provide flexibility in the biological systems that can be measured. It is shown that typical values are 0.02% for repeatability and 0.15% for reproducibility. Sensitivity in transmission and backscatter measurements was improved by a factor of 20 compared to a previously built instrument, which was the basis for the new design. The system is capable of detecting light attenuated down to 0.0063% of the maximum intensity, resulting in a superior threshold. The system was then validated by measuring the optical properties of various biological samples, both natural and engineered. These samples include bovine, porcine, and human corneas and lenses, as well as synthetic materials. Biological sample testing were consistent with published results on the back vertex distance (BVD) test (bovine lenses), the bovine corneal opacity test (BCOP, bovine corneas), and published results obtained with the precursor to the new device.