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Biomedical Radars for Monitoring and Diagnosis of Respiratory and Cardiovascular Diseases
The “Doppler CardioGram” (DCG), which can be remotely measured by Doppler radar, describes the combined atrial and ventricular motions conducted to the skin. All the timing information of the P-wave, QRS complex, and the T-wave in ECGs can be derived from fine-grained DCG waveforms with high accuracy, which can be used to calculate the reliable cardiac timings like R-R intervals. Moreover, in physiology, DCG actually reflects human heart’s mechanical activities in terms of velocity and acceleration information that cardiac motions “project” on the skin, which can directly provide the relevant motion information of the cardiac contractions and relaxations of chambers in heart. This means DCGs might provide diagnostic information for heart diseases with abnormal mechanical activities such as Atrial Fibrillation (AF) and Premature HeartBeat (PHB). Extensive practical experiments in both normal office environment and clinical environment have been carried out. The experimental results demonstrated that the DCGs obtained by the proposed technique were aligned well with ECG waveform, and the R-R intervals obtained by differential DCG (D-DCG) exhibited high accuracy both in the short-term (10 s) and long-term experiments (10 min). It even showed enhanced accuracy than that in breath-hold condition of healthy people, which provides reliable data for HRV analysis. Furthermore, the D-DCG waveforms of patients with heart diseases (AF and PHB) obtained in this work exhibited similar disease symptom characteristics compared to ECGs. These results show promising potentials in applying DCGs in wide applications such as home healthcare, sleep monitoring, clinical heart monitoring, and heart disease auxiliary diagnosis.