Photo Acoustic Energy Applications for the Detection of Human Arterial Blockages via Multiple Skin/Bone Layers, a Non-Invasive Approach

The impact of arterial narrowing/blocking caused by plaque buildup in arteries leads to many life-threatening consequences. This is recognized as a cause in heart attacks and peripheral vascular disease. Diagnosing the illness is only feasible after symptoms have presented to the patient. Currently, the standard for visualizing coronary arteries is through angiography, which may have complications, and impact on the healthcare system. Furthermore, cardiac catheterization may also places high health risks, given its overall invasiveness. Cardiac arrhythmias, infection, and contrast dye nephrotoxicity are recognized complications within this process. Therefore, a noninvasive approach may have potentials to reduce patient complications, finances surrounding healthcare, and more efficient patient care through earlier screening and diagnosing. This research addresses a new approach using photoacoustic (PA) imaging. The transmission properties of atherosclerosis within walls of arteries, can be exploited using photo acoustics, to better visualize and characterize the degree and severity of atherosclerosis. The delivered energy is absorbed by components of the vascular tissue converted into heat, leading to transient thermos elastic expansion, which creates an acoustic emission. The thermal response was analyzed for its fall and recovery times that are attributed to the artery fat type. The control parameters, including the frequency, penetration depth, energy levels, and tissue layer sizes, for multilayered structures were considered. The structures investigated were fatty infiltrate within the artery, blood, bones, and skin, within frequency range from 1 MHz to 3 MHz, and typical tissue sizes in the milli to centimeter range. As high as 14 MPas in the acoustic pressure at 1 MHz, resulted in temperature difference of up to 3.4 K. When the operating frequency was altered to 2 MHz, the temperature changed to 23 K. Furthermore, when the frequency was changed to 3 MHz, the temperature moved to 43 K. The changes in temperatures were for nearly 1 second duration. The results obtained in this study suggest that there is high potential for practical models using flexible substrate with infra-red sensors and acoustic devices.

Electromagnetic Simulation for the Diagnosis of Lipoprotein Density in Human Blood, a Non-Invasive Approach

With the rise in prevalence of Type II diabetes throughout the world, an increasing need for a portable monitoring system for both blood glucose and lipoprotein concentrations is in demand. Recent work has led to non-invasive wearable devices for monitoring changes in blood glucose concentrations using electromagnetic (EM) waves. However, this still fall short as a means of monitoring cholesterol levels in diabetic patients. The EM study on human tissues emphasized here may also relate to the safety guidelines applied to cellular communications, power lines, and other EM applications. The specific absorption rate (SAR) for the power of the non-ionizing frequency must not exceed a threshold as it impacts DNA and can lead to cancerous tissues. In this study, we used COMSOL software for the investigation of the viability of using EM within the frequency range of 64 MHz-1 GHz as a means of monitoring the transmission properties of human blood and lipoprotein. In this approach, wave equations were solved within blood and lipoprotein boundaries. Research parameters, including frequency range, Power input (SAR), and lipoprotein densities, were investigated. The transmission properties, produced by the electrical and thermal characteristics of these physiological parameters, have led to proper diagnosis of lipoprotein density. Within the frequency range of 64 MHz to 1 GHz, and for a power range of 0.1 to 0.6 SAR, lipoprotein density from 1.00 g/mL to 1.20 g/mL was considered. A 2D model, with an antenna source that supplied the electromagnetic waves to human tissues, was created for the simulations. These were used for the study of the transmission properties of the EM energy into the blood and lipoprotein tissues. While the range of magnetic flux values between simulations varies only slightly or not at all, the distribution of these values is impacted by given parameters. As such, a device capable of comparing magnetic flux values and penetration depths could easily distinguish between samples of different lipoprotein densities. The results obtained in this study can be accommodated non-invasively by human tissues, and can be produced in a practical model using wearable devices. A practical model is proposed for future consideration.