Vitals such as blood pressure (BP) serve as an imperative role in physician decisions. Not only does blood pressure indicate the cardiac function, but it also indicates possible dysfunctions in other organs. Although the current use of sphygmomanometer

proves its functionality, its circulation-inhibiting high pressure and insensitivity often render discomfort. There are several other innovations that measure BP on the wrist or finger, but they fail to take account for motion and pressure drop from the heart. Therefore, a novel BP measurement device is proposed to accurately measure BP, pulse rate, and oxygen saturation without stopping the flow in the brachial artery as the conventional sphygmomanometer would.

This technology includes th

e use of wearable non-enhanced Time-of-Flight MRI (TOF-MRI) and label-free near infrared (NIR) light mounted on a snap-on band that can be worn on any upper arm size to maintain the same elevation as the heart. Since blood travels in convective flow in arteries, a mathematical model calculating the blood pressure can be derived as followed. Convective flux is moles/(time*area). Pressure is force/area and can be simplified down further. A final equation of pressure can be arrived as pressure=convective flux*distance/time in Pascal.

Unenhanced MRI technique has been developed to distinguish blood vessels from static tissues without the use of contrast agent, such as the TOF-MRI. The use of parallel imaging technique and multi-coil system allows a decrease in imaging time. To identify arteries and veins, inflow direction can be distinguished. (Morita,”Time-of-Flight”) In addition, cheap and wearable MRIs with motion correction ability have been developed to reduce production cost and increase accuracy. (Dalton, Prussmann, Jepsen) With the cross-sectional images obtained from MRI, ImageJ can be used to identify the average diameter of the arteries and arterioles and thus the average area. TOF-MRI also allows the detection of plaque build-up on vessel walls with morphology analysis. (Blum, Tarkin)

To obtain the red blood cell (RBC) flux, multiple 15 kHz NIR imaging beams are placed against the skin, and split-detector imaging configuration is used to detect the differential scatter of the RBC. Cell counter from ImageJ can then be used to obtain the cells/time. In this process, convective principle of Navier-Stokes momentum equation and Continuity Equation can be considered for assumptions. Since the variable moles is required for the equation, the number of RBC can be converted into amount of irons in grams and moles (blood consists of 2.64E13 RBC with a total of 2.90 grams of iron) (York). NIR light also allows the detection of blood

oxygen saturation based on red blood cell absorbance differences, and the light fluctuation recorded by the detector can be transformed into a waveform that indicates pulse rate.

After acquiring the values, pressure in Pascal can be calculated. This pressure will be adjusted to account for plasma pressure with machine learning, which then can be converted to mmHg. This non-invasive wearable technology prevents fluid build-up in elderlies and pain in children. With the increase in computing power, this innovation will be affordable and accessible in many settings.


Author: Jerry Chen

Status: Project Concept