Negar Tavassolian

Pulse Transit Time Measurement Using Seismocardiogram, Photoplethysmogram, and Acoustic Recordings: Evaluation and Comparison

This work proposes a novel method of pulse transit time (PTT) measurement. The proximal arterial location data are collected from seismocardiogram (SCG) recordings by placing a micro-electromechanical accelerometer on the chest wall. The distal arterial location data are recorded using an acoustic sensor placed inside the ear. The performance of distal location recordings is evaluated by comparing SCG–acoustic and SCG–photoplethysmogram (PPG) measurements. PPG and acoustic performances under motion noise are also compared. Experimental results suggest comparable performances for the acoustic-based and PPG-based devices. The feasibility of each PTT measurement method is validated for blood pressure evaluations and its limitations are analyzed.

Motion Artifact Cancellation of Seismocardiographic Recording From Moving Subjects

This paper presents a novel method of extracting seismocardiographic (SCG) data from moving adult subjects recorded via micro-electromechanical (MEMS) accelerometers. A digital signal processing system based on the normalized least mean square (NLMS) adaptive filter design is developed in MATLAB to process the signals collected from the MEMS sensor node. Standardized experiments were performed on 40 moving adult subjects. False-positives were ruled out for a more precise detection rate. The research on sliding ensemble average was also conducted to find the minimum required window size. The results indicate a detection rate of 96% and a sliding window size of 32 intervals for robust continuous monitoring, showing that adaptive filtering could be a promising technique for the cancellation of motion noise artifacts from SCG recordings in moving subjects.

Utilizing Gyroscopes Towards the Automatic Annotation of Seismocardiograms

This paper reports on the use of the rotational component of chest vibrations for the automatic annotation of seismogram (SCG) recordings for the first time. An inertial measurement unit consisting of a three-axis MEMS accelerometer and a three-axis MEMS gyroscope is used for recording chest vibrations. The gyroscope signal acts as a reference for the detection of the isovolumic moment (IM) and aortic valve closure (AC) peaks on the SCG signal. Experimental results from ten subjects at rest indicate a close correlation between the timings of the P1 and P2 peaks of the gyroscope energy waveform and the accelerometer IM and AC peaks, and provide the capability for ECG-free annotation of the SCG signal using the energy peaks, which are simpler to detect. Furthermore, extended experiments from walking subjects reveal the feasibility of using the head-to-foot axis gyroscope recordings as an enhancement tool for the annotation of the SCG signal.

Optimization of Dielectric Material Stoichiometry for High-Reliability Capacitive MEMS Switches

This letter examines the effect of dielectric material stoichiometry and substrate temperature on the charging performance and reliability of capacitive MEMS switches with silicon nitride. Various dielectric stoichiometries were obtained by varying the deposition temperature and gas flow ratios during the PECVD deposition process. Results from both MIM capacitors and MEMS switches have shown that charging is mitigated in silicon nitride films deposited at 150 °C with a high ratio of nitrogen to silicon content (N/Si = 0.98).

Motion noise cancellation in seismocardiographic monitoring of moving subjects

This paper presents a novel method of extracting seismocardiographic data from moving adult subjects using chest-worn wireless MEMS accelerometers. A DSP system including a normalized LMS adaptive filter is designed and tested in MATLAB. Data results from 11 subjects indicate a detection rate of 97.33% and a high correlation between SCG and ECG signals simultaneously acquired. The results suggest that adaptive filtering could be a relevant technique for this purpose.

Ultra-Wideband Millimeter-Wave Dielectric Characteristics of Freshly Excised Normal and Malignant Human Skin Tissues

Millimeter waves have recently gained attention for the evaluation of skin lesions and the detection of skin tumors. Such evaluations heavily rely on the dielectric contrasts existing between normal and malignant skin tissues at millimeter-wave frequencies. However, current studies on the dielectric properties of normal and diseased skin tissues at these frequencies are limited and inconsistent. In this study, a comprehensive dielectric spectroscopy study is conducted for the first time to characterize the ultra-wideband dielectric properties of freshly excised normal and malignant skin tissues obtained from skin cancer patients having undergone Mohs micrographic surgeries at Hackensack University Medical Center. Measurements are conducted using a precision slim-form open-ended coaxial probe in conjunction with a millimeter-wave vector network analyzer over the frequency range of 0.5–50 GHz. A one-pole Cole–Cole model is fitted to the complex permittivity dataset of each sample. Statistically considerable contrasts are observed between the dielectric properties of malignant and normal skin tissues over the ultra-wideband millimeter-wave frequency range considered.

Annotation of seismocardiogram using gyroscopic recordings

This paper introduces a novel setup and algorithm for the automatic annotation of seismocardiographic (SCG) recordings from a MEMS accelerometer. The setup utilizes gyroscopic recordings as a reference for the detection of isovolumic moment (IM) and aortic valve closure (AC) peaks. A method for deriving the rotational kinetic energy waveform is proposed and the coefficients are generated using singular vector decomposition (SVD). Experimental results on 5 subjects at rest indicate an IM detection rate of 96.9% and AC detection rate of 95.6% without envelope filtering. It is suggested that this algorithm is feasible as an ECG-free automatic peak annotation method of SCG recordings from subjects at rest.

Three-dimensional super-wideband micro-antenna for high-resolution millimeter-wave medical imaging.

This paper reports on a novel super-wideband micro-hemispherical antenna with application in millimeter-wave medical imaging. The antenna is composed of a hemispherical shell suspended above a substrate and can be fabricated using a fabrication technology originally developed for micron-scale electromechanical resonators. The antenna exhibits a wide fractional bandwidth of more than 80% (from 64 GHz to 150 GHz) and a high gain of 8.6 dBi at its center frequency. Radiation parameters of the antenna are characterized and the effect of its super-wideband behavior on pulsed millimeter-wave imaging is demonstrated. Finally, a preliminary array configuration composed of two antennas placed side-by-side in the vicinity of a skin-mimicking target is evaluated and the ability to fully detect the target has been demonstrated.

A Y-slot wideband circularly polarized antenna for non-contact health monitoring applications

The primary object of this paper is to investigate the polarization mismatch effects between transmitter and receiver antennas in noncontact monitoring applications. It is shown that circularly-polarized antennas have better performance compared to similar linearly-polarized ones in the presence of the human body. A novel y-slot wideband CP antenna is proposed. The antenna consists of a u-shaped feed, a y-slot, and a parasitic stub. Simulation results show a bandwidth of 82% (3-7.2 GHz) for VSWR<;2:1 with a 3 dB axial ratio (AR) bandwidth of 33% (4.6-6.4 GHz). The proposed antenna has a low profile with an overall size of 28 mm×28 mm×1.6 mm.

Pulse transit time measurement using seismocardiogram and in-ear acoustic sensor

This paper presents a new setup and method of measuring pulse transit time (PTT) using seismocardiographic data from a MEMS accelerometer and acoustic recordings from a commercial microphone placed inside the ear. A DSP system is designed and implemented in MATLAB, and experimentally tested on 5 healthy adult subjects at rest. Failure conditions are also examined to evaluate the robustness of the system. Our results suggest that the proposed technique could be a highly-relevant method for PTT measurements, which could be further translated into blood pressure (BP) values.