Global, regional, and national prevalence of hearing loss from 1990 to 2019: A trend and health inequality analyses based on the Global Burden of Disease Study 2019.

As a severe public health issue, hearing loss has caused an increasingly disease burden, especially in the elderly population. Hearing loss may inevitably induce asymmetric hearing, which makes it difficult for elderly individuals to locate sound sources, therefore resulting in increased postural instability and falling risk. To emphasize the public health emergence of hearing loss, we investigated the temporal trend of prevalence of hearing loss over the last 30 years and further predicted its changes in the next 20 years, decomposed the trend according to demographic factors and epidemiological changes, and quantified the cross-country healthy inequalities, using the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019. In 2019, there were more than 140 million cases of hearing loss worldwide, a 93.89% increase from 70 million cases in 1990. The age-standardized rate (ASR) also increased with an estimated annual percentage change of 0.08% per year. Population growth and aging are the major drivers contributing to the changes, accounting for 60.83% and 35.35%. Of note, the contribution of aging varies showing a gradual increasing trend with sociodemographic index (SDI) elevating. Also notable, there were significant health inequalities across 204 countries and territories, with slope index of inequality rising over time. Projection of the global burden of hearing loss from 2020 to 2040 indicated progressive increases in both case number and ASR. These reflect the heavy disease burden of hearing loss that needed more targeted and efficient strategies in its prevention and management.

Golay-encoded excitation for dual-frequency harmonic detection of ultrasonic contrast agents.

Golay-encoded excitation in combination with the third harmonic (3f0) transmit phasing is examined for both signal-to-noise ratio (SNR) and contrast-to-tissue ratio (CTR) improvements in harmonic imaging of contrast microbubbles. To produce the cancellation pair of tissue harmonic signal in 3f0 transmit phasing, the phase of the bit waveform is properly designed for both the fundamental and the 3f0 transmit signals to provide the Golay encoding of the received harmonic responses. Results indicate that the proposed Golay excitation can effectively suppress the tissue harmonic amplitude to increase CTR. Meanwhile, the SNR of the contrast harmonic signal also improves because of the elongated waveform of Golay excitation. Nevertheless, the generation of marked range side-lobes of the bubble region would degrade the achievable SNR improvement and the image contrast, especially when the bit of Golay excitation increases. The range side-lobes could result from the nonlinear resonance of the microbubbles that interferes with the phase modulation of the Golay encoding.

Third harmonic transmit phasing for SNR improvement in tissue harmonic imaging with Golay-encoded excitation.

BACKGROUND: Ultrasound tissue harmonic signal generally provides superior image quality as compared to the linear signal. However, since the generation of the tissue harmonic signal is based on finite amplitude distortion of the propagating waveform, the penetration and the sensitivity in tissue harmonic imaging are markedly limited because of the low signal-to-noise ratio (SNR). METHODS: The method of third harmonic (3f(0)) transmit phasing can improve the tissue harmonic SNR by transmitting at both the fundamental (2.25MHz) and the 3f(0) (6.75MHz) frequencies to achieve mutual enhancement between the frequency-sum and the frequency-difference components of the second harmonic signal. To further increase the SNR without excessive transmit pressure, coded excitation can be incorporated in 3f(0) transmit phasing to boost the tissue harmonic generation. RESULTS: Our analyses indicate that the phase-encoded Golay excitation is suitable in 3f(0) transmit phasing due to its superior transmit bandwidth efficiency. The resultant frequency-sum and frequency-difference components of tissue harmonic signal can be simultaneously Golay-encoded for SNR improvement. The increase of the main-lobe signal with the Golay excitation in 3f(0) transmit phasing are consistent between the tissue harmonic measurements and the simulations. B-mode images of the speckle generating phantom also demonstrate the increases of tissue harmonic SNR for about 11dB without noticeable compression artifacts. CONCLUSION: For tissue harmonic imaging in combination with the 3f(0) transmit phasing method, the Golay excitation can provide further SNR improvement. Meanwhile, the axial resolution can be effectively restored by pulse compression while the lateral resolution remains unchanged.