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Magnetic detection electrical impedance tomography (MDEIT) is an imaging modality that aims to compute the cross-sectional distribution of the conductivity of a volume from the magnetic flux density surrounding the object. Owing to the Biot-Savart law, the MDEIT inverse problem is inherently ill-conditioned making image reconstruction highly susceptible to the effects of noise and numerical errors. Appropriate priors or penalties are needed to facilitate reconstruction and to restrict the search space to a specific solution set. The images have the sparsity property and sharp variations. Consequently, this paper presents an approach involving a combination of the L¹ and total variation norm penalties, the former to suppress spurious background signals and enforce sparsity and the latter to preserve local smoothness and piecewise constancy in the MDEIT reconstructed images. The primal dual-interior point method (PD-IPM) for minimizing the joint L¹--TV penalty was used in the paper. The method was validated by using MDEIT simulated data and experimental data in comparison with the performances of the L², L¹ and total variation norm penalty-based approaches. The results show that the joint L¹--TV regularized algorithm preserves sparsity property, local smoothness and piecewise constancy, leading to improvements in the localization of the reconstructed images in MDEIT. [ABSTRACT FROM AUTHOR]

Magnetic resonance electrical impedance tomography (MREIT) is a noninvasive modality to visualize the internal electrical conductivity distribution of an electrically conductive object using a magnetic resonance imaging (MRI) scanner. The impedance tomography step may provide valuable additional information that cannot be recovered from the MR reconstruction. Previous research has been mostly performed on the reconstruction algorithms and the measurement system. However, the anatomical information provided by the MR images is not in full use. This paper proposes an image reconstruction method based on anatomical information which provides the prior knowledge. The sensitivity algorithm with generalized minimum residual (GMRES) is proposed to reconstruct conductivity image. Simulations of a realistic geometry leg model are performed to show that our approach is not only capable of achieving high accuracy, but also able to improve the speed of the image reconstruction. At the end, a preliminary phantom experiment is presented, illustrating the feasibility of this proposed method. [ABSTRACT FROM AUTHOR]

In order to remotely monitor the activities of heartbeat, respiration and body movement, this article designed and implemented a single-channel nonorthogonal in-phase/quadrature (I/Q) RF sensor, which works at the central frequency of 2.4 GHz. The designed RF sensor is based on a printed circuit board (PCB) antenna. Taking into account low cost, simple structure and easy fabrication, the antenna is designed and implemented with a special broad-band microstrip-tocoplanar strip line Balun structure by combining the transmitter with the receiver on a PCB to form one single antenna system. The gain of the sensor is 7.7 dB. The return loss is -22.7 dB at 2.4 GHz and the directionality of the antenna is satisfactory for monitoring vital signs. It has been validated that the designed sensor can detect the respiration, heartbeat and body movement accurately in comparison with the signals acquired by respiration sensor and pulse sensor. [ABSTRACT FROM AUTHOR]

Non-contact method to monitor vital signs using radar-based sensor system is a more convenient way in comparison with the contact monitoring devices. Portable with a low profile and low-cost non-contact vital signs sensors system that are capable to monitor heart and respiration rates are presented and evaluated their performances. A printed 2x1 patch array antenna, Yagi-Uda antenna and dipole array antenna are designed and integrated with sensor system Tx/Rx module for their performances analysis. The gain of the designed antennas are 6.38 dBi, 7.7 dBi, and 10.5 dBi, VSWR are 1.1, 1.15, and 1.0, and return loss are -26.26 dB, -22.7 dB and -21.6 dB respectively at 2.4 GHz. The evaluations performances of these antennas were compared with a standard respiratory-rate measurement using a pulse sensor and respiratory sensor. The measurement results using the proposed non-contact sensor systems and the standard contact systems showed excellent performance with the printed dipole array antenna compared with other two antennas, the error between the average heart rate extracted by the non-contact systems and the reference systems are ±1.1 beat/min for dipole array antenna, ±1.5 beat/min for printed 2x1 patch array antenna and ±1.9 beat/min for Yagi-Uda antenna. [ABSTRACT FROM AUTHOR]