Automatic detection of measurement points for non-contact vibrometer-based diagnosis of cardiac arrhythmias

Abstract

Monitoring of the heart rhythm is the cornerstone of the diagnosis of cardiac arrhythmias. It is done by means of electrocardiography which relies on electrodes attached to the skin of the patient. We present a new system approach based on the so-called vibrocardiogram that allows an automatic non-contact registration of the heart rhythm. Because of the contactless principle, the technique offers potential application advantages in medical fields like emergency medicine (burn patient) or premature baby care where adhesive electrodes are not easily applicable. A laser-based, mobile, contactless vibrometer for on-site diagnostics that works with the principle of laser Doppler vibrometry allows the acquisition of vital functions in form of a vibrocardiogram. Preliminary clinical studies at the Klinikum Karlsruhe have shown that the region around the carotid artery and the chest region are appropriate therefore. However, the challenge is to find a suitable measurement point in these parts of the body that differs from person to person due to e. g. physiological properties of the skin. Therefore, we propose a new Microsoft Kinect-based approach. When a suitable measurement area on the appropriate parts of the body are detected by processing the Kinect data, the vibrometer is automatically aligned on an initial location within this area. Then, vibrocardiograms on different locations within this area are successively acquired until a sufficient measuring quality is achieved. This optimal location is found by exploiting the autocorrelation function.

Recent Advances in Seismocardiography

“…SCG is used to estimate different cardiovascular parameters such as cardiac time intervals, pulse transit time, and blood pressure. For example, non-contact SCG was used at different body locations for estimating central arterial pressure and carotid arterial pressure waveforms [49,117,118]. Pulse transit time might be estimated from the time difference between AO point on the xiphoid SCG and AO point on the carotid SCG [119].…”

RF-Heartbeat: Robust and Contactless Heartbeat Monitoring Based on FMCW Radar

“…With the rapid evolution of the IOT and the ubiquitous deployment of wireless devices, wireless sensing has become a hot research issue. Recently, a number of research studies monitored heartbeat through wireless approaches including laser Doppler vibrometer (LDV) [11], [12], Wi-Fi [13], acoustics [14], [15], Doppler radar [16]- [19], FMCW radar [20]- [28], etc. Similar to SCG, these research studies recorded cardiogenic vibration through measuring displacement or velocity of specific body parts, for example, thoracic cavity and neck [12], [30].…”

“…Recently, a number of research studies monitored heartbeat through wireless approaches including laser Doppler vibrometer (LDV) [11], [12], Wi-Fi [13], acoustics [14], [15], Doppler radar [16]- [19], FMCW radar [20]- [28], etc. Similar to SCG, these research studies recorded cardiogenic vibration through measuring displacement or velocity of specific body parts, for example, thoracic cavity and neck [12], [30]. Due to the contactless nature of these devices, heartbeat can be monitored when users are unconscious.…”

“…Thus, LDV has been proved to be insensitive to noise from moving objects in other areas. However, once subjects change their posture or position, the measurement point need to be recalibrated manually or using auxiliary equipment [12]. Compared with the other wireless devices, the unique advantages of mmWave FMCW radar over others draw our attention: 1) Millimeterlevel wavelength makes it has a high sensitivity for detecting small displacements.…”

Forcecardiography: A Novel Technique to Measure Heart Mechanical Vibrations onto the Chest Wall

“…Hence, it is possible to estimate time intervals and velocities of physiological relevance, which give important insights into the mechanics of the beating heart (such as left ventricular ejection time, rapid diastolic filling time, isovolumic contraction and relaxation times [9,10], left ventricular lateral wall and septal wall contraction peak velocities, trans-aortic and trans-pulmonary peak flows [11]). The latest studies on methods for the detection of local heart mechanical vibrations of the chest wall have also used gyroscopes [19][20][21], laser Doppler vibrometers [22], microwave Doppler radars [23,24], airborne ultrasound surface motion cameras [25] and polyvinylidene fluoride (PVDF) piezoelectric sensors [26].…”