A flexible annular-array imaging platform for micro-ultrasound

2020

In ultrasonic systems, power amplifiers are one of the most important electronic components used to supply output voltages to ultrasonic devices. If ultrasonic devices have low sensitivity and limited maximum allowable voltages, it can be quite challenging to detect the echo signal in the ultrasonic system itself. Therefore, the class-J power amplifier, which can generate high output power with high efficiency, is proposed for such ultrasonic device applications. The class-J power amplifier developed has a power efficiency of 63.91% and a gain of 28.16 dB at 25 MHz and 13.52 dBm input. The pulse-echo measurement method was used to verify the performance of the electronic components used in the ultrasonic system. The echo signal appearing with the discharged high voltage signal was measured. The amplitude of the first echo signal in the measured echo signal spectrum was 4.4 V and the total-harmonic-distortion (THD), including the fundamental signal and the second harmonic, was 22.35%. The amplitude of the second echo signal was 1.08 V, and the THD, including the fundamental signal and the second harmonic, was 12.45%. These results confirm that a class-J power amplifier can supply a very high output echo signal to an ultrasonic device.

Section: Analysis Of the Class-j Power Amplifiermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Class-J Power Amplifier Implementation for Ultrasound Device Applications

You

Kim²,

2020

“…Recently, optoacoustic systems have been introduced because the low contrast of traditional ultrasound methods are unable to provide high enough resolution for soft tissues such as blood vessel and hemoglobin [10,11]. The optoacoustic systems can achieve a high optical contrast at ultrasound penetration depth and spatial resolution which are essential characteristics to differentiate soft tissue properties [12,13].…”

Section: Introductionmentioning

confidence: 99%

Development of a Double-Gauss Lens Based Setup for Optoacoustic Applications

Ryu

Yeom

2017

In optoacoustic (photoacoustic) systems, different echo signal intensities such as amplitudes, center frequencies, and bandwidths need to be compensated by utilizing variable gain or time-gain compensation amplifiers. However, such electronic components can increase system complexities and signal noise levels. In this paper, we introduce a double-Gauss lens to generate a large field of view with uniform light intensity due to the low chromatic aberrations of the lens, thus obtaining uniform echo signal intensities across the field of view of the optoacoustic system. In order to validate the uniformity of the echo signal intensities in the system, an in-house transducer was placed at various positions above a tissue sample and echo signals were measured and compared with each other. The custom designed double-Gauss lens demonstrated negligible light intensity variation (±1.5%) across the illumination field of view (~2 cm diameter). When the transducer was used to measure echo signal from an eye of a bigeye tuna within a range of ±1 cm, the peak-to-peak amplitude, center frequency, and their −6 dB bandwidth variations were less than 2 mV, 1 MHz, and 6%, respectively. The custom designed double-Gauss lens can provide uniform light beam across a wide area while generating insignificant echo signal variations, and thus can lower the burden of the receiving electronics or signal processing in the optoacoustic system.

“…Using an x-y galvanometer scanner to scan the focused light beam could avoid the adverse effects of mechanical scanning but would reduce the field of view and cause optical lens aberrations [7]. Therefore, these PA methods are used to obtain target information by employing mechanical motors to cover wide areas [9,10]. However, a motor typically generates mechanical noise, which directly decreases the echo signal quality [6,10,11].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, these PA methods are used to obtain target information by employing mechanical motors to cover wide areas [9,10]. However, a motor typically generates mechanical noise, which directly decreases the echo signal quality [6,10,11]. It is thus imperative to be able to obtain information from wide areas without using motors.…”

Section: Introductionmentioning

confidence: 99%

A Novel Fisheye-Lens-Based Photoacoustic System

Ryu

Kim

2016

This paper presents a novel fisheye-lens-based photoacoustic (PA) system. In conventional PA systems, mechanical motors are utilized to obtain the target information due to the small fields of view of such systems. The use of such motors introduces mechanical noise, which is difficult to remove when processing the echo signals. A fisheye lens system offering a wide field of view would effectively reduce the motor effects (i.e., the noise) and enable the system to have a wide field of view. Therefore, in this work, we propose a novel fisheye lens scheme and describe a PA system based on the developed lens scheme. In addition, to confirm the feasibility of the fisheye-lens-based PA system, we present the typical pulse-echo responses obtained using a 20 MHz single element immersion transducer and the echo signals measured from bull’s eye tissue samples separated by approximately 4, 6, 8, and 10 cm diagonally and 2 cm vertically from the fisheye lens. The experimental results demonstrate that the echo signal amplitudes, their center frequencies, and the −6 dB bandwidths obtained using red, green, and blue lights and a fisheye lens are acceptable when the fisheye lens is separated from a sample both diagonally and vertically. Therefore, fisheye-lens-based PA systems could be a potential method of achieving wide fields of view while reducing the mechanical motor effects.