Medical imaging, particularly ultrasound imaging, is undergoing a transformation. Historically, clinicians used cart-based high-performance ultrasound systems for diagnosis; now they can use handheld devices. Advances in semiconductor technology have reduced component size and enabled portable smart probes that can be used outside traditional clinical settings.
What is a smart probe
A smart ultrasound probe is essentially a portable ultrasound device with the entire front end and most of the back-end hardware integrated into the probe. Smart probes are low power and compact, able to process data while maintaining signal quality, and can display images on mobile devices via high-speed USB or wireless connections.
In the near future, most clinicians may be able to carry a smart probe in a pocket. Over the next decade, millions of such probes could appear on the global market, complementing standard ultrasound systems. Shrinking an ultrasound system to handheld size presents many challenges. Below are seven key design challenges faced by smart probe engineers.
Power
Designing the probe power supply requires minimizing both power consumption and electrical noise. Power-supply designers must work in a very small volume, targeting efficiencies above 90%, extremely low standby power, and, most importantly, low noise. Many manufacturers limit switching frequencies to below 500 kHz and synchronize them with an external clock to minimize harmonic interference across the 2–20 MHz ultrasound operating band. 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, connected to a backplane and a standard computer. Today, a complete 64-channel probe front end must be smaller than a credit card (85 mm x 54 mm). Even with advances in integration, achieving that level of miniaturization remains difficult.
Channel count
Handling more channels improves image quality. Most cart-based scanners have 128 or more channels. Early probes integrated 8 to 16 channels and relied on a larger system for processing. Manufacturers are now attempting to integrate up to 64 or 128 channels into the probe itself. To reach this channel density, they can use highly integrated commercial front-end devices from suppliers such as Texas Instruments. Using a TX7332 32-channel transmit analog front end together with an AFE5832LP 32-channel receive analog front end, designers can implement 64 channels with only two devices. These front ends provide transducer excitation, echo processing, and conversion to digital signals for imaging. Additional devices, such as processors or field-programmable gate arrays (FPGA), are still required to control the front ends and process the data. The challenge is to pack as many of these components as possible to increase channel count within the same power budget.
Per-channel power
A cart-based 128-channel ultrasound scanner typically consumes about 500 W to 1 kW. A handheld smart probe has a power budget of only 3–5 W so that the device does not overheat and can often be battery-powered. Low power eliminates active cooling such as fans, which introduce vibration and image blur. Designers must use various strategies to keep the probe within its power budget, including putting some components into deep sleep or powering them down when not in use.
Data processing
Data processing depends on channel count, the allowable power budget, and data transmission bandwidth. For example, a 64-channel front end sampled at 40 MHz can generate around 5.12 GB of raw data per second, which cannot be streamed directly to a tablet or mobile device for real-time processing. Therefore, raw data must be reduced to a manageable size before sending it to the display. The amount of on-probe processing is a trade-off among display power, bandwidth, and processing capability. Many designers use ultra-low-power FPGAs and processors to handle front-end control and data reduction.
Data transfer
For wired probes, USB Type-C with USB 3.1 or higher provides the necessary power delivery and high data throughput. For truly mobile probes, data must be transmitted wirelessly. Several wireless communication options are available, including Wi-Fi standards such as 802.11n, 802.11ac, 802.11ad, and 802.11ax. When multiple devices share the same band, these protocols are subject to interference and reduced effective bandwidth. Other standards like 802.11ah (Sub-1 GHz) exist, but they typically offer limited bandwidth.
Data interpretation
A major challenge for smart probes is fast, efficient interpretation of large data volumes. Accurate interpretation traditionally requires significant clinician time and expertise. High-speed connectivity enables sending data to remote servers for rapid analysis. With advances in big-data analytics, artificial intelligence, and image comparison, interpretation and diagnostic support can be performed in near real time.
Conclusion
The next wave in medical imaging will be driven by miniaturization. As probe designers resolve technical challenges and bring lower-cost, smaller, connected devices to market, smart probes are likely to be adopted more widely—from hospitals in developed regions to remote clinics and battlefield diagnostics—potentially improving access to medical imaging globally.
