Development Trend and Application of Ultrasound Technology in Medical Field

Ultrasound (Ultrasound) is a sound wave with a frequency higher than 20,000Hz, which has specific applications in industry, medical and other fields. With the advancement of medical technology and the continuous updating of equipment, ultrasound has become an indispensable application technology in the medical field. Medical ultrasound equipment mainly uses signals or energy attributes generated by ultrasonic feedback to different parts of the human body to diagnose or treat abnormal states or diseases of the human body.

At present, the most widely used field of medical ultrasound is the use of ultrasound technology for diagnosis, mainly through ultrasound beam scanning human body parts imaging, that is, through the reception of reflected signals, processing, in order to obtain images of internal organs. With the real-time movement of the probe of medical ultrasound equipment to obtain specific images of the patient's internal organs, it can provide comprehensive scanning of superficial, abdominal, heart, obstetrics and gynecology, urinary, musculoskeletal, etc. It is a common diagnostic method for soft tissue examination.

Technology Trends in Ultrasound

Digitalization and miniaturization is one of the main trends in medical ultrasound. The traditional cart-type, large probe ultrasonic equipment is huge and expensive, and now the miniaturized ultrasonic equipment in the market has been updated and developed, while ensuring clear images and high resolution, it not only has more complete functions, but also more diversified probes. These new small equipment can better meet the needs of various scenarios such as hospital clinical departments, primary medical market, and disaster first aid outside the hospital, and reduce the difficulty of medical workers.

Many manufacturers at home and abroad are promoting the above trend, and some of the technologies are generally perceived in the industry, such as sub-beam formers (Sub Beamformer) that can be placed in equipment probes, ultra-low power consumption (Ultralow Power) that is sensitive to temperature and requires extremely low power consumption, and wireless connections (Wireless Connection) that are currently of general interest in the industry.

In addition, another development direction of medical ultrasound is high performance, which is also the common direction of global medical ultrasound. On a large scale, in recent years, domestic manufacturers are gradually in line with international manufacturers in this direction, but there is still a gap between major key areas such as cardiology and top international applications, such as higher image quality, more comprehensive functions and better processes.

From a technical point of view, higher image quality means lower noise and higher signal-to-noise ratio (SNR), and higher signal-to-noise ratio puts forward higher requirements on the number of channels, from the previous 32, 64 channels to the current 128 or even 256 channels. In the past ten years, the analog performance of the entire receiving end has not been greatly improved. Although linear transmission and increasing the number of channels can bring certain effects, at the same time, the multi-wave number also means that the amount of data of the beamformer is increasing. Therefore, Software Beamformer is also a trend in pursuit of high performance.

ADI's Medical Ultrasound Solutions

In the entire medical ultrasound industry, ADI can provide low-noise, low-power analog front-end, precision amplifier, converter and power supply solutions, and has a high reputation in the industry. As can be seen from the following architecture diagram of the overall ultrasound solution, ADI's products almost cover the entire ultrasound system including the transmit link, the receive link, etc., excluding such non-chip vendor products as probes (Transducer) and FPGA beamformers (Beamformer). The following will introduce ADI's related representative products and solutions from the aspects of transmit link, receive link, clock and power management. There are two methods for the aa127b26-93cd-11ee-9788-92fbcf53809c.png launch part currently on the market: the first is the Pulser Beamformer method, and the second is the linear launch mentioned above. The two architectures are different. The former is mainly used to generate a high-voltage pulse to drive the probe, while the latter is based on the DAC Beamforme and adds a high-voltage amplifier.

Excelpoint Shijian, a technology-based authorized agent who has cooperated with ADI for more than 30 years, has built a number of solutions close to customers' application needs based on ADI's product and solution portfolio and has been recognized by the market. For the two ways of transmitting links, Shijian focuses on recommend MAX14815 and AD9106 in combination with the current market.

The MAX14815 is a highly integrated eight-channel 5-stage high-voltage ultrasonic transmitter (pulser). The pulse generator generates high-frequency high-voltage bipolar pulses for driving piezoelectric transducers in an ultrasound system via two separate pairs of high-voltage power supplies. Each channel can transmit up to 200Vpp, has up to 2A current capability, and integrates 2A active clamp (return to zero). Programmable current capability as low as 0.4A.

The embedded digital resources (SRAM and state machine) that the transmitter can use to control the pulse generator support transmit beamforming, significantly reducing the number of interconnects and FPGA I/O. The embedded digital resource is programmed over a high-speed serial interface and supports sophisticated transmit techniques such as PWM techniques for burst shaping and apodization techniques for beam shaping.

The MAX14815 also integrates eight independent low-noise, low-impedance active T/R switches. The T/R switch can be externally configured to support receive multiplexing, where the number of receive channels used is less than the number of transmit channels. The device can also be controlled by an external digital source (FPGA) via traditional dedicated CMOS logic inputs. In addition to ultrasound medical imaging, the product is also used in high-pressure sensor MEMS drivers, ultrasound industrial applications (NDT), etc., which can simplify the design of portable ultrasound systems and save power consumption. The aa2804fa-93cd-11ee-9788-92fbcf53809c.pngAD9106 TxDAC and waveform generator is a high-performance four-channel digital-to-analog converter (DAC). It is a 12-bit output, up to 180 MHz host clock sine wave generator with 24-bit tuning word, supports 10.8Hz/LSB frequency resolution, integrated on-chip mode memory, used for complex waveform generation, and has a direct digital frequency synthesizer (DDS).

The waveform generator has a single frequency output for all four DACs, and a built-in mode control state machine allows the user to program the mode period for all four DACs and the in-cycle start delay for each DAC channel signal output. The SRAM data may include directly generated stored waveforms, amplitude modulation patterns applied to the DDS output or DDS frequency tuning words.

The AD9106 provides excellent AC and DC performance and supports DAC sampling rates up to 180 MSPS. Its SPI interface is used to configure the digital waveform generator and load the pattern into the SRAM to adjust the gain and offset of the signal as the digital signal is sent to the four DACs. The device has a flexible operating power supply range (1.8V to 3.3V) and low power consumption, making it ideal for portable and low power applications. aa38f53a-93cd-11ee-9788-92fbcf53809c.png For ADI receive link products, Shijian recommend the AD9671 designed to support medical ultrasound applications with current market focus, designed for low cost, low power consumption, small size and ease of use. It includes an 8-channel variable gain amplifier (VGA), a low-noise preamplifier (LNA), a CW harmonic rejection I/Q demodulator with programmable phase rotation, an anti-aliasing filter (AAF), an analog-to-digital converter (ADC), and a digital demodulator and decimator for processing data and reducing bandwidth.

Each channel of the integrated digital demodulator has a maximum gain of 52 dB, a fully differential signal path, and an active input preamplifier termination. The channels are optimized for high dynamic range and low power consumption, and are suitable for applications requiring small packages. In addition, the LNA has a single-ended to differential gain, which can be selected by SPI. In CW Doppler mode, each LNA output drives an I/Q demodulator with independently programmable phase rotation and 16 phase settings.

Each channel of the AD9671 can enter the power saving mode independently, thus extending the battery life of portable applications. The standby mode can be quickly powered on for power-on restart. When operating in CW Doppler mode, the VGA, AAF, and ADC all enter power-save mode. ADC built-in features, such as programmable clock, data alignment, generating programmable digital test code, etc., can make the device flexibility to achieve better, lower system costs. aa499c1e-93cd-11ee-9788-92fbcf53809c.pngAD9528 is the ADI clock product recommend by Shijian in combination with the current market focus. It is a two-stage PLL, JESD204B/JESD204C integrated SYSREF generator for multi-device synchronization. The first stage phase-locked loop (PLL) (PLL1) enables input reference voltage conditioning by reducing system clock jitter. The second stage PLL(PLL2) provides a high frequency clock with lower integration jitter from the clock output driver and lower wideband noise.

An external VCXO provides the low-noise reference voltage required by the PLL2 to meet demanding phase noise and jitter requirements for acceptable performance. The tuning frequency range of the on-chip VCO is 3.450 GHz to 4.025 GHz. The integrated SYSREF generator outputs a single, N or continuous signal and is synchronized with the PLL1 and PLL2 outputs to align the time of multiple devices.

The AD9528 produces six and eight outputs with the highest frequencies of 1.25 GHz and 1 GHz respectively. Each output can be configured to output directly from PLL1, PLL2 or an internal SYSREF generator. Each of the 14 output channels includes a frequency divider with digital phase coarse adjustment function and an analog fine adjustment phase delay module, allowing all 14 outputs to have high flexibility in timing alignment. It can also be used as a flexible dual-channel input buffer for 14-way device clock and SYSREF signal distribution. aa5d7374-93cd-11ee-9788-92fbcf53809c.png finally, regarding power management, Shijian recommend a four-channel 40VIN, 3A step-down Silent Switcher μModule regulator LTM8060. The Silent Switcher architecture minimizes EMI while achieving high efficiency operation at frequencies up to 3MHz. The controller, power switch, inductor and other related components are built into the package.

The LTM8060 supports a wide input voltage range, an output voltage range of 0.8V to 8V, and a switching frequency range of 200kHz to 3MHz, each set by a single resistor. The design can be completed using only the input and output filter body capacitors; the output array can also be configured to achieve up to 12A current capability through the parallel output of the array. aa6be620-93cd-11ee-9788-92fbcf53809c.png sum up, Shijian believes that ADI's innovative technology and system expertise are helping to shape the future of the medical and health industry. While grasping the development trend of miniaturization, digitization and high performance in the field of medical ultrasound, its products and solutions also provide a basis for future technological innovation in the market, which can help the market better meet various challenges.