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Medical imaging, especially ultrasound imaging, is undergoing significant change. Historically, clinicians used trolley-based high-performance ultrasound systems for diagnosis; today, handheld devices can perform ultrasound imaging. Advances in semiconductor technology have reduced the size of ultrasound smart probes and made them portable, enabling healthcare delivery outside offices and hospitals.
An ultrasound smart probe is essentially a portable ultrasound device with the entire front end and most of the back-end hardware integrated into a single probe. These smart probes have low power consumption and compact size, can process data while maintaining signal quality, and can display images on mobile devices via high-speed USB or wireless connections.
In the not-too-distant future, most clinicians will be able to carry a smart probe in a pocket. Over the next decade, millions of such probes could appear in the global market, complementing standard ultrasound systems. Shrinking an ultrasound system to handheld size, however, is technically challenging. Below are seven major challenges faced by smart probe designers.
Power
The probe power supply must deliver low power while keeping noise to a minimum. Designers must work within very small volumes, target power efficiencies above 90 percent, and ensure low standby consumption. Crucially, the power supply must be quiet. Many manufacturers choose switching frequencies below 500 kHz and synchronize with an external clock to minimize harmonic interference in the 2 to 20 MHz ultrasound operating range. Balancing size and efficiency is a major challenge.
Size
Twenty years ago, a 64-channel ultrasound system consisted of multiple A4-sized boards for transmit, receive, ADC, beamforming, and processing, mounted on a backplane and connected to a standard computer. Today, the front-end board for a full 64-channel smart probe must be smaller than a credit card (85 mm x 54 mm). Even with integration advances, meeting that size constraint remains difficult.
Channel Count
Processing more channels improves image quality. Most trolley-based scanners have 128 or more channels. Early probes integrated 8 to 16 channels internally and relied on a larger system for processing. Manufacturers now aim to integrate up to 64 or 128 channels into the probe. To achieve this density, designers can use highly integrated commercial front-end devices from vendors such as Texas Instruments (TI). Using devices like the TX7332 32-channel transmit analog front end and the AFE5832LP 32-channel receive analog front end, designers can place 64 channels using just two devices. These front ends power sensors to generate ultrasonic pulses, process received echoes, and convert them to digital signals for image formation. They still require additional devices, such as processors or FPGAs, to control them and handle the generated data. The challenge is to fit as many of these components as possible to increase channel count within the same power budget and thereby improve image quality.
Per-Channel Power Consumption
A trolley-based 128-channel ultrasound scanner consumes roughly 500 W to 1 kW. A handheld smart probe typically has a power budget of only 3 to 5 W so the device does not overheat and can often operate from batteries. This low power budget removes the option of active cooling like fans, since fans introduce vibration that can blur images. Designers must combine strategies such as putting components into sleep modes or shutting them down when idle to keep the probe within its power budget.
Data Processing
Data processing depends on channel count, target power consumption, and data transfer bandwidth. In a 64-channel system sampling at 40 MHz, the front end can generate about 5.12 GB of raw data per second, which cannot be streamed directly to a tablet or mobile device. Even if transfer were possible, the display unit cannot process such a data rate in real time. Therefore, data must be reduced to a manageable size before transmission to the display. Processing trade-offs are based on the display unit's power, bandwidth, and processing capability. Many designers use ultra-low-power FPGAs and processors to handle front-end control and data reduction.
Data Transmission
For wired probes, USB Type-C with USB 3.1 or later interfaces is advantageous because it can supply power and provide high data bandwidth simultaneously. For truly mobile smart probes, however, data must be transmitted wirelessly. Several wireless communication protocols are available, such as Wi-Fi standards 802.11n, 802.11ac, 802.11ad, and 802.11ax. When multiple devices use the same band, available bandwidth is constrained by interference. Other standards, such as 802.11ah in the sub-1 GHz band, exist but typically offer limited bandwidth.
Data Interpretation
One of the largest challenges in smart probes is rapid, efficient interpretation of large data volumes. Accurate interpretation traditionally requires expert clinicians to analyze images, which places high demands on skill and time. High-speed connections enable sending data to remote servers for fast analysis. With the rise of big data analytics and artificial intelligence, image comparison and interpretation can be performed online in near real time, enabling quicker diagnosis.
Conclusion
The next major wave in medical imaging will be small form factors. As designers address the technical challenges and deliver smaller, better-connected probes at lower costs, adoption of smart probes will accelerate. From hospitals in developed countries to telemedicine centers in developing regions and to field diagnostics for injured personnel, rapid development of ultrasound smart probes is changing clinical practice and expanding access to medical imaging.
