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Wireless power charging for implantable biomedical electronics (IBEs) can potentially eliminate the need for frequent battery-replacement surgeries, ultimately improving patients' quality of life. Ultrasound wireless power transfer (US-WPT) based on piezoelectric receivers has demonstrated significant potential, particularly for deep-seated IBEs. However, most studies on US-WPT have overlooked the optimization of piezoelectric receiver dimensions relative to transmitted ultrasound beam profiles for maximizing battery-charging efficiency for IBEs. This study revealed that a piezoelectric receiver should have dimensions corresponding to the main lobe width of the transmit beam profile within a focal area. Moreover, its output power should be proportional to the cube of the receiver area. Considering these findings, an oblong-shaped ultrasound transmitter and receiver (OsUTR) was developed for efficient WPT, capable of fully charging commercial batteries. In water, the OsUTR produced an output power per unit area of 246.93 mW/cm2, which is 6.588 times higher than that achieved by previously reported methods. This resulted in an average charging rate of 1.64 mC/s, enabling the fully charging of a 30 mAh commercial battery in 1.33 h. Experiments with a 50 mm thick porcine tissue demonstrated that the OsUTR provided an output voltage and current of 38.4 V p-p and 103.4 mA p-p , respectively. Consequently, full charging of the battery was successfully achieved in 1.80 h. This high-performance OsUTR can enable long-term use of IBEs. This innovation reduces the burden of battery replacement and expands the applicability of implantable devices, driving significant advancements in the IBEs industry. [Display omitted] • This study investigates optimal conditions for piezoelectric receivers to achieve high efficient wireless power charging for implantable biomedical electronics (IBEs). • One condition is maximizing the size of the piezoelectric receivers because its output power is proportional to the cube of the receiver area. • Another condition is that the dimensions of P-receivers should be aligned with the main lobe of the transmitted ultrasound beam profile. • As a viable solution to satisfy the requirements, a oblong-shaped ultrasound transitter and receiver (OsUTR) was designed and fabricated. • The OsUTR could fully charge a 30 mAh lithium polymer battery at 50 mm in water and porcine tissue. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new frequency compounding is proposed to enhance ultrasound image quality. [•] Optimal weighting factors are estimated for the compounding along imaging depth. [•] The performances were verified through phantom and in vivo experiments. [•] SNR was improved by maximally 4.8dB compared to the conventional method. [ABSTRACT FROM AUTHOR]

Abstract: In medical ultrasound imaging, the frequency-dependent attenuation causes a downshift of the center frequency of transmitted ultrasound as it propagates through the body. The downshifting results in a considerable loss of signal-to-noise ratio (SNR) after quadrature demodulation (QDM) in which down-mixing and low pass filtering are involved. To overcome the problem, dynamic QDMs have been proposed, in which the change in the center frequency along the axial direction is obtained using autocorrelation-based spectral estimation and compensated in the QDM block. As an alternative, this paper proposes an adaptive dynamic QDM using the 2nd-order autoregressive model. The main advantage over the conventional dynamic QDMs is to use real radio-frequency (RF) data in the spectral estimation, while its counterparts require additional steps to obtain either complex RF signals or complex baseband signals. This allows the proposed method to be used with a minimal modification of signal processing blocks. The performances of the proposed method were evaluated through in vitro and in vivo experiments. The performances were also compared with those of the conventional dynamic QDM. From the experiments, it was learned that the proposed method improved SNR by maximally 7.8dB in the near field compared with the conventional dynamic QDM. In the far field, however, its SNR improvement is similar to its counterpart. This may be explained by the fact that the signal loss mainly results from the amplitude attenuation and the diffraction rather than the frequency downshift in the far field. In addition, the proposed method improved contrast resolution (CR) by at least 6.8%, compared with that of the conventional dynamic QDM. The experimental results demonstrated that the proposed method can be used to improve SNR and CR of ultrasound images in an effective manner. [Copyright &y& Elsevier]

Abstract: Background context: In pedicle screw fixation surgery, rigid instruments are inserted into a vertebral body. When the instruments are misdirected within the pedicle or advanced too far beyond it, perforations of the inner or outer cortex can cause damage to the spinal nerve roots and spinal cord. These complications can occur despite the use of imaging modalities, such as radiographs, fluoroscopy, and computerized axial tomography (CAT) scans. A-Mode ultrasound (US), a nonionizing modality, merits study for its possible use in such a type of surgery. Purpose: The purpose of the study was to determine the utility of A-mode US during pedicle screw placement, to characterize the approach to the marrow-cortex interface, and to obtain the signature profiles of cortex perforations. Study design: A-Mode data were generated on insertion of a forward-viewing transducer (FVT) and a side-viewing transducer (SVT) to successively greater drilled depths along the insertion pathway. A-Mode broadband US backscatter (BUB) pedicle screw emulation experiments were conducted with transducers inserted into drilled sheep vertebral bodies. BUB amplitude patterns were observed and analyzed. Descriptive statistics were used. Methods: In vitro acoustic experiments on vertebral bodies in a water bath were performed with two 1-MHz unfocused transducers to measure sound speed, broadband US attenuation, and backscatter coefficients. Micro-CAT scan three-dimensional (3-D) images of 10 disarticulated vertebral bodies were obtained pre- and postdrilling done in 5-mm depth increments with a flat-bottom drill. BUB patterns were noted of transducers inserted through rostral outer cortex, through the pedicle, and advanced to the ventral marrow-cortex interface. 2.5-MHz FVT and SVT were co-advanced in successive 5-mm increments along the insertion pathway, with BUBs measured at each point and the echoes composited into a single figure. Deliberate perforations of ventral cortex were made. Results: Evident patterns or measures indicating the proximity of the ventral marrow-cortex interface were: 1) marrow BUB values increasing in amplitude over three distal peaks in most FVT cases (7 out of 10) and SVT cases (9 out of 10); 2) BUB ratio of marrow-cortex interface to the smallest marrow value greater than 2, in all FVT cases (10 out of 10) with FVT mean of 4.00±1.82 (2.25–8.33); and 3) a ratio of distal BUB value to starting cortex BUB in the 0. 82 to 1.62 range (mean, 0.98±0.30) in 80% of FVT cases. Ventral FVT perforations resulted in a major drop in the BUB value. Conclusions: The increase in the BUB amplitudes in the distal insertion pathway suggests that, at least with a 2.5-MHz transducer, an approximate 1.5-cm US window exists in most cases, by which close approach of the ventral marrow-cortex interface could be anticipated. Other ratios may serve as stop criteria to prevent further drilling. A precipitous drop in BUB amplitude may be an indication of a cortex perforation. [Copyright &y& Elsevier]

An electrical impedance matching (EIM) network is proposed to achieve the broad bandwidth of a high frequency ultrasound transducer and to improve the signal-to-noise ratio (SNR) of an ultrasound image. The proposed EIM network is based on a general filter structure, i.e., either low-pass filter (LPF) or high-pass filter (HPF) structure composing a capacitor and an inductor. Either filter type can be selected depending on the spectral characteristics of a transducer. The prominent advantage of the proposed method is the capability to broaden the spectrum of a transducer by means of modifying its original spectrum. The values of the electronic components are computed with the measured electrical impedances of a transducer and an imaging system. In this paper, the EIM between a custom-made 50 MHz ultrasound needle transducer and a commercial pulser/receiver system was conducted to verify the characteristics and performance of the proposed method. The experimental results demonstrated that the proposed EIM network is capable of achieving the best performance of the transducer, i.e., broad bandwidth and high SNR that are desirable for the high quality of high frequency ultrasound images. [ABSTRACT FROM AUTHOR]

Accumulation of surficial tidal mud was observed in Muan Bay, Korea, to examine seasonal sedimentary cycles typical of semienclosed bays in contrast with open coast in the southeastern Yellow Sea. One-year monitoring of accumulation rates on the tidal flats indicates that patterns of deposition/erosion can be diverse according to both physiographic setting and seasons. During winter, tidal flats undergo slight deposition to moderate erosion depending on localities. In summer, however, the tidal flats are all consistently subject to stronger erosion. Meteorological data suggest that the erosional effect on the tidal flat might come from heavy rainfall during flooding seasons and possibly typhoon. The enduring rainfall could cause the exposed surface of the tidal flat to be sufficiently weakened for tidal currents alone to strip surficial mud off. [Copyright &y& Elsevier]