Atherosclerosis (hardening of the arteries) of the arteries supplying blood to the brain is the greatest risk factor for stroke, the most common neurologic disease, the cause of lifelong disabilities and typically preventable with even simple treatment. Typically it is atherosclerosis that narrows arteries that reduces blood flow to the brain and risks a blood clotting crisis that results in stroke. An individual may not present any symptoms of reduced blood flow to the brain until the sudden onset of stroke when critical brain cells die.
The right and left carotid artery networks are mirrored in the right and left sides of the neck and head. The common carotid arteries are superficial in the right and left sides of the neck and their strong pulse can be felt there. These arteries branch near the ears into an external carotid that supplies most of the surface of the head and an internal carotid that supplies most of the needs of the brain. People may be screened for the risk of stroke by detecting the narrowing of the arteries that supply the vast majority of blood to the brain; the internal carotid arteries. Unfortunately, the most definitive means of evaluating any narrowing of the carotid arteries are also the most invasive and involve real risk of causing stroke, the very disease they seek to prevent. Several non-invasive tests are available that provide high correlations with the invasive studies. While Doppler ultrasound is the most common non-invasive means of evaluating narrowing of the carotid arteries, it is notoriously inconsistent and, typically, only evaluates only the first branch of the carotid arteries. Infrared imaging (thermology) is another non-invasive means of detecting narrowing in the carotid arteries. Thermology has the advantage over Doppler ultrasound of greater reliability, the ability to evaluate blood flow over greater lengths of the carotid artery and the ability to detect compensating blood flow from parallel arteries; natures bypasses.
Infrared cerebral-vascular studies, also known as carotid studies, use images from the front and the right and left sides of the face and neck with special attention given to the areas of the eyes and the forehead. This is to evaluate the delivery of warming blood from the major branches of the internal carotid artery, the ophthalmic arteries. The areas in the neck over the carotid arteries themselves are not used for the study. Infrared imaging is completely passive and non-contact and authorities studies have demonstrated it as 96% effective as the highly invasive arteriogram without any of the associated risks. Further, infrared cerebral-vascular studies are highly objective and quantitative; meaning that it is able to detect subtle changes with good reliability.