Investigation of a Non-invasive/ Minimally Contact Based Method for Diagnosis of Cardiovascular Disease: Blockage(Stenosis) and Blood Flow

HYPOTHESIS AND OBJECTIVES In the proposed method of sensing the vital health sign related to Cardiovascular diseases, thermal heat transfer performance of the skin will be evaluated using a non-contact based Infrared temperature sensor. The temperature of the skin is significantly dependent upon the heat source as blood vessels (veins and capillaries) in the vicinity of the skin. However, there are several locations in the human body, where arteries are also at a relatively less depth from the outer skin surface (radial or ulnar arteries at the wrist and carotid artery in the neck). In any scenario, if it is possible to track the flow of blood from the thermal performance of the skin, then it could be useful in predicting various states of the human health related to cardiovascular activities.

• In the proposed hypothesis, a momentarily higher heat transfer window will be created using localized cooling of a small section of the skin over the superficial blood vessel (minimally contact) and hence, the warming process will be tracked using a non-contact and non-invasive Infrared temperature sensor. With the formation of plaques in the arteries at main aorta, carotid bifurcation or anywhere in the vessel, the flow turns into chaotic turbulent kind or in the case of blockage a very low or no blood flow, which impacts the heat transfer from the blood flow and can be easily detected from the heat transfer over the skin during that momentarily higher heaty transfer window.
• In order to apply this approach to Cardiovascular diseases diagnosis one of the probable method could be scanning temperature change at two locations of the body:

1. On both carotid artery on left and right of the neck.
2. On both superficial temporal artery on the left and right of the forehead.
3. It is expected that skin thermal variation at the forearm will always be in a relation to the blood flow in carotid artery for a healthy person that could be used as a signature marker for an individual to make comparison. Therefore, temperature mapping of the left forearm (upper limb).

This study involves 3 different techniques to be tested on 100 human subjects. Existing procedure to be used will be readily available Duplex Ultrasound that is considered as more reliable in clinical practice. Since the new technology involves temperature mapping, existing potential thermography technique (Passive Thermography) will be used to setup the baseline data. Other than this, currently under-development temperature mapping method (Active Thermography) that involves application of cooling (either pulsed or lock-in cooling) over the skin will be utilized. Accordingly, the whole study is divided into two parts: phase-1 and phase-2 as shown in Figure 2. By the time, the Active Thermography technique will be developed; data collection with the techniques mentioned in phase-1 will be completed.

Phase-1