An Experimental Double-Integrating Sphere Spectrophotometer for In Vitro Optical Analysis of Blood and Tissue Samples, Including Examples of Analyte Measurement Results

Data-driven science requires data to drive it. Being able to make accurate and precise measurement of biomaterials in the body means that medical assessments can be more accurate. There are differences between how blood absorbs and how it reflects light. The Mayo Clinic's Double-Integrating Sphere Spectrophotometer (MDISS) is an automated measurement device that detects both scattered and direct energy as it passes through a sample in a holder. It can make over 1,200 evenly spaced color measurements from the very deep purple (300-nm) through the visible light spectrum into the near infrared (2800-nm). The MDISS samples measured have been also measured by commercial laboratory equipment. The MDISS measurements are as accurate and more precise than those devices now in use. With so many measurements to be made during the time that the sample remains undegraded, mechanical and data collection automation was required. The MDISS sample holders include different thicknesses, versions that can operate at high pressure (such as divers may experience), and versions that can pump and rotate the measured material to maintain consistency of measurement. Although the data obtained are preliminary, they have potential to guide the design of new devices for more accurate assessments. There is an extensive "lessons learned" section. Please also see the companion report arXiv:2301.00938