Bipolar-power-transistor-based limiter for high frequency ultrasound imaging systems

Choi, Hojong; Yang, Hao‐Chung; Shung, K. Kirk

doi:10.1016/j.ultras.2013.10.010

Cited by 8 publications

(7 citation statements)

References 10 publications

(16 reference statements)

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“…Many pre-clinical US imaging systems use high frequency transducers in the range 40 to 80 MHz (ref. [43][44][45][46] with recent advances to 100 MHz, 47,48 which may be indicative that the nanobubbles will show enhanced contrast and be useful as higher resolution image contrast agents for preclinical imaging and high frequency clinical imaging.…”

Section: Ultrasound Measurementsmentioning

confidence: 99%

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging

et al. 2016

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Micron-sized lipid-stabilised bubbles of heavy gas have been utilised as contrast agents for diagnostic ultrasound (US) imaging for many years. Typically bubbles between 1 and 8 μm in diameter are produced to enhance imaging in US by scattering sound waves more efficiently than surrounding tissue. A potential area of interest for Contrast Enhanced Ultrasound (CEUS) are bubbles with diameters <1 μm or 'nanobubbles.' As bubble diameter decreases, ultrasonic resonant frequency increases, which could lead to an improvement in resolution for high-frequency imaging applications when using nanobubbles. In addition, current US contrast agents are limited by their size to the vasculature in vivo. However, molecular-targeted nanobubbles could penetrate into the extra-vascular space of cancerous tissue providing contrast in regions inaccessible to traditional microbubbles. This paper reports a new microfluidic method for the generation of sub-micron sized lipid stabilised particles containing perfluorocarbon (PFC). The nanoparticles are produced in a unique atomisation-like flow regime at high production rates, in excess of 10(6) particles per s and at high concentration, typically >10(11) particles per mL. The average particle diameter appears to be around 100-200 nm. These particles, suspected of being a mix of liquid and gaseous C4F10 due to Laplace pressure, then phase convert into nanometer sized bubbles on the application of US. In vitro ultrasound characterisation from these nanoparticle populations showed strong backscattering compared to aqueous filled liposomes of a similar size. The nanoparticles were stable upon injection and gave excellent contrast enhancement when used for in vivo imaging, compared to microbubbles with an equivalent shell composition.

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Section: Ultrasound Measurementsmentioning

confidence: 99%

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging

et al. 2016

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“…For small apertures, higher frequency (> 15 MHz) transducers usually have lower sensitivity than that of lower-frequency transducers [19]. Since high-frequency transducer performance is highly dependent on the PA dynamic range, a linear PA is desirable for ultrasound electronics.…”

Section: Discussionmentioning

confidence: 99%

Power Amplifier Linearizer for High Frequency Medical Ultrasound Applications

2015

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Power amplifiers (PAs) are used to produce high-voltage excitation signals to drive ultrasonic transducers. A larger dynamic range of linear PAs allows higher contrast resolution, a highly desirable characteristic in ultrasonic imaging. The linearity of PAs can be improved by reducing the nonlinear harmonic distortion components of high-voltage output signals. In this paper, a linearizer circuit is proposed to reduce output signal harmonics when working in conjunction with a PA. The PA performance with and without the linearizer was measured by comparing the output power 1-dB compression point (OP1dB), and the second- and third-order harmonic distortions (HD2 and HD3, respectively). The results show that the PA with the linearizer circuit had higher OP1dB (31.7 dB) and lower HD2 (−61.0 dB) and HD3 (−42.7 dB) compared to those of the PA alone (OP1dB (27.1 dB), HD2 (−38.2 dB), and HD3 (−36.8 dB)) at 140 MHz. A pulse-echo measurement was also performed to further evaluate the capability of the linearizer circuit. The HD2 of the echo signal received by the transducer using a PA with the linearizer (−24.8 dB) was lower than that obtained for the PA alone (−16.6 dB). The linearizer circuit is capable of improving the linearity performance of PA by lowering harmonic distortions.

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“…IN 1 and IN 2 represent the signal inputs, and OUT 1 and OUT 2 represent the signal outputs of the two-stage class-B amplifier. Z IN1 and Z IN2 are the impedance values observed at the signal’s input, and Z OUT1 and Z OUT2 are the impedance values observed at the output of the signal [ 59 ]. C GS represent the transistor’s internal gate-source capacitances.…”

Section: Methodsmentioning

confidence: 99%

Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications

Kim

You

Choi

2020

Sensors

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Piezoelectric transducers are important devices that are triggered by amplifier circuits in mobile ultrasound systems. Therefore, amplifier performance is vital because it determines the acoustic piezoelectric transducer performances. Particularly, mobile ultrasound applications have strict battery performance and current consumption requirements; hence, amplifier devices should exhibit good efficiency because the direct current (DC) voltage in the battery are provided to the supply voltages of the amplifier, thus limiting the maximum DC drain voltages of the main transistors in the amplifier. The maximum DC drain voltages are related with maximum output power if the choke inductor in the amplifier is used. Therefore, a need to improve the amplifier performance of piezoelectric transducers exists for mobile ultrasound applications. In this study, a post-voltage-boost circuit-supported class-B amplifier used for mobile ultrasound applications was developed to increase the acoustic performance of piezoelectric transducers. The measured voltage of the post-voltage-boost circuit-supported class-B amplifier (62 VP-P) is higher than that of only a class-B amplifier (50 VP-P) at 15 MHz and 100 mVP-P input. By performing the pulse-echo measurement test, the echo signal with the post-voltage-boost circuit-supported class-B amplifier (10.39 mVP-P) was also noted to be higher than that with only a class-B amplifier (6.15 mVP-P). Therefore, this designed post-voltage-boost circuit can help improve the acoustic amplitude of piezoelectric transducers used for mobile ultrasound applications.

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Bipolar-power-transistor-based limiter for high frequency ultrasound imaging systems

Cited by 8 publications

References 10 publications

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging

Power Amplifier Linearizer for High Frequency Medical Ultrasound Applications

Post-Voltage-Boost Circuit-Supported Single-Ended Class-B Amplifier for Piezoelectric Transducer Applications

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