How scanners work

When designing the AngioCode trackers, AlmaCode specialists leaned on the clinical trials and previous developments in the field of clinical and personal diagnostics devices for assessing the cardiovascular system state. At the heart of the tracker is the method for noninvasive research and assessment of arterial function and endothelial cell condition invented by Professor A.S. Parfyonov.

Noninvasive angioscanning: physical fundamentals

The angioscan uses optical sensors operating in the near-infrared region to reliably record the pulse wave. The user's finger is placed in the special clip on the device, and then exposed to the infrared light-emitting diode. Coming through the entire mass of the finger, the radiation is registered on the opposite side by an optical sensor—thus forming the input signal for further processing. This signal, a photoplethysmogram (PPG), is measured based on changes in blood volume in the limb during the heartbeat; it correlates with the signal that can be obtained with venous occlusion plethysmography (when the sensor is placed directly in the arterial lumen).

It's also possible to register the signal as it passes through the tissues or in the reflection mode (usually employed in wearable fitness trackers and similar devices). AngioCode uses the passing mode because it allows getting more accurate readings. And since the test takes 2 to 5 minutes, comfortable wearing is not a significant factor here, for the testing method requires the patient to be at complete rest.

Optical sensor on the finger

Scheme of the optical sensor installed on the terminal phalanx of the finger. Infrared radiation passes through the finger and is registered by the photo detector, which converts the light into either a voltage (light/voltage converter) or a frequency (light/frequency converter)

Blood pressure and Photoplethysmogram

Simultaneous registration of the arterial pressure curve and signal PPG. In the bottom part of the figure is an example of curves that illustrate how breathing affects both the pressure curve and the PPG.

The PPG looks very similar to the pressure pulse wave. Unlike the pressure pulse wave, which can only be registered invasively (in cardiological examination with the placement of the pressure sensor directly in the lumen of the artery), the PPG allows getting information using the tracker placed on the patient's skin. The signal is registered either by means of photons passing through the tissue from the light source to the photodetector, or in the reflection mode—where the light is reflected from the tissue back to the photodetector. In the first case, the sensor is installed on the terminal phalanx of a finger or earlobe; in the second case, it's placed on any area of the skin surface with an adhesive layer. A light penetration sensor offers a better signal-to-noise ratio and is more often used in pulse oximeters. A reflection sensor has two main advantages: it can be installed anywhere and exerts almost no pressure on the tissue. When it's necessary to monitor the signal for a long time (e.g., monitoring an intensive care patient), the reflection sensor comes in much more effective, since the location of the "clothespin" sensors needs to be changed every few hours of their operation. For short-term measurements (up to a few minutes long), light penetration sensors are the most optimal solution.

Example of an optical signal recording

Example of recording a signal registered from the terminal phalanx of the index finger. The box shows the optical sensor and a microphotograph of the vessels in the signal registration area.

Our methodology allows the sensor to identify the problems at the endothelial dysfunction phase—long before the clinical symptoms express themselves. At that time already, arteries become much stiffer—and this deviation can be registered.

Development of atherosclerotic lesions of the arteries

Development of atherosclerotic lesions of the arteries. Endothelial dysfunction is identified before the arterial wall experiences any structural transformations.

Many people are familiar with this diagram illustrating over-time deterioration of the arterial condition:

over-time deterioration of the arterial condition

The arterial system takes blood from the left ventricle, then delivers and distributes it through the capillaries. Highly important is the arteries' ability to smoothen arterial pressure pulsations.

The aorta receives and dampens a load of pulsation. Here's the work load calculation for an average pulse rate: 60 bpm * 60 min * 24 hours * 365 days, totaling over 31 million systolic discharges yearly. It's elastin fibers who take the most load—over time, they are partly substituted by stiffer collagen fibers; at the same time, the lumen of the proximal aorta dilates.

A young person's arterial system is a perfectly arranged apparatus that receives blood from the left ventricle (acting as a second heart) and further distributes it to the regions and delivers blood to the capillaries. Arteries dampen the arterial pressure pulsations generated by the heart's activity. In the left ventricle the range of pressure oscillations is 120 mmHg in systole and falls almost to zero in diastole, whereas the range of pressure oscillations in large muscular arteries is significantly smaller.

Pulse wave generation for normal aorta elasticity.

Pulse wave generation for normal aorta elasticity.

Increased stiffness of large conducting arteries, primarily the aorta, accelerates the pulse wave passage.

Reflected from the distal muscular arteries and arterioles, the pulse wave spreads faster and returns to the the heart earlier than needed—at the middle or even beginning of systole (when the left ventricle is still in contraction), not in diastole. Not only does this add to the heart burden but also myocardial perfusion occurs, since the supply of blood to the heart occurs in the diastole phase.

Pulse wave generation diagram

Pulse wave generation diagram.

If the heart is in non-optimal operation mode, pulse pressure grows and thus negatively affects the capillaries (brain and kidneys are exposed first)...

Pulse wave generation as aorta elasticity decreases.

Pulse wave generation as aorta elasticity decreases.

Pulse waves in different parts of the arterial bed

Pulse waves in different parts of the arterial bed (left — elastic arteries, right — rigid arteries).

Vascular wall condition data can be used to detect the cardiovascular risk in people suffering from:

  • Arterial hypertension
  • Hypertension
  • Atherosclerosis
  • Heart failure
  • Coronary heart disease
  • Diabetes and insulin resistance
  • Vascular stenosis of the brain and lower extremities
  • Organic erectile dysfunction caused by endothelial dysfunction

AngioCode carries out integrated analysis of pulse waves, their intervals and amplitudes. heart operation phases, and other parameters.

The core task of monitoring with the help of AngioCode trackers is identifying patients with a high risk of cardiovascular diseases, heart attack, and stroke—to make a decision on preventive drug therapy and change the behavioral habits toward a healthy lifestyle.

AngioCode trackers are intended both for non-specialists in the field of cardiovascular diagnostics (ordinary users) using AngioCode devices at home to monitor their parameters and parameters of family members, and professional users who are specialists in related fields (e.g., private practitioners, sports coaches, fitness center professionals, dietary supplement retailers, etc.). For their case, heart and vascular monitoring can show how a given external factor affects the body.

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