Research On Fabrication And Characterization Of Hemoglobin Microcapsule Phantoms For Oximeter Calibration

Blood oxygen saturation,defined as the proportion of oxyhemoglobin in all kinds of hemoglobin in the blood,is an important indicator to assess the oxygen transport capacity of blood and has been widely used to assist disease diagnosis and patients'physiological health level assessment and monitoring.Based on the unique light absorption characteristics of hemoglobin,non-invasive and real-time measurement of blood oxygen saturation can be achieved by optical method,and the instruments developed based on this principle have been widely used.However,there are some differences between the measuring basis of different manufacturers' instruments,so a simple and reliable method is necessary to calibrate them.The conventional method is to calibrate the instrument by human test,but the individual differences and the ethical problems in this method affect the calibration.In recent decades,great progress has made in bio-optical phantoms that simulate the optical properties of biological tissues.Therefore,bio-optical phantoms that simulate the optical properties of blood are proposed to provide the basis for the instrument calibration.In order to achieve the simple and rapid calibration of blood oxygen monitors,we developed a manufacture method for heterogeneous solid bio-optical phantoms that can simulate specific oxygen saturation of tissues.First,hemoglobin microcapsules,also called "artificial red blood cells",were prepared by the liquid-driven coaxial flow focusing method and used as an absorbent for the phantom.Subsequently,the prepared microcapsules were mixed with UV-curing resin,RESIN-A.And homogeneous phantoms with different oxygen saturation were prepared by spin coating using this mixture.Finally,the mixture of microcapsules and UV-curing resin was used as the printing material to prepare non-homogeneous vessel phantoms with different oxygen saturation with the help of a modified UV 3D printer.The test spectra measured from an integrating sphere system showed that the proportion of oxyhemoglobin was 92.9%/2.4%in the oxygenated/deoxygenated non-homogeneous phantoms,while the proportion of methemoglobin was 7.1%/3.1%,which proved that these phantoms could simulate the blood oxygen characteristics of human body.The stability of the homogeneous phantoms during long-term preservation was further evaluated by analyzing the absorption spectra within 7 days.In the end,a multispectral imaging system was used to evaluate the performance of non-homogeneous phantoms in simulating blood vessels with different oxygen saturation.The analysis results of multispectral image system about proportion of components in the homogeneous phantoms was basically consistent with that of integrating sphere system,which showed that the blood vessel phantoms could simulate the oxygenated/deoxygenated state of blood vessels.A series of characterization results showed that our printed phantoms have the potential to be used in the calibration of blood oxygen monitors,and can promote the further development of these techniques.