Powering the Future: The Journey to a Handheld Microwave Ablation System

Figure 1 SwiftPro microwave source module.

Figure 2 Qorvo QPA1010 application circuit and package.

Microwave ablation has emerged as a transformative technology in the medical field, particularly for the minimally invasive treatment of cancerous tumors. Traditional systems operating at 2.45 GHz have often been bulky, expensive and challenging to maneuver in clinical environments. Emblation® is addressing these challenges with the SwiftPro® device, the first commercially available FDA-cleared compact handheld microwave ablation system. At the heart of this solution is a highly integrated 8 GHz microwave source module, which is crucial for achieving the compact size, efficiency and performance required for a handheld device. This article explores the design and development challenges, with a special focus on the thermal management technology that makes compact microwave ablation possible.

Traditional microwave ablation systems rely on magnetron-based technology, known for its effectiveness but also its considerable drawbacks. The equipment is large, operates at high voltage and requires bulky cooling mechanisms, making it cumbersome and costly to operate. These limitations restrict the use of such systems to surgical operating environments, hindering the broader adoption of microwave ablation, especially in outpatient or resource-constrained settings.

Developing a handheld microwave ablation system presents a range of unique challenges. One of the primary hurdles is managing size and weight constraints. Unlike conventional systems, a handheld device must be both compact and lightweight, all while maintaining the performance standards required for effective ablation. Another critical consideration is power efficiency. Microwave ablation requires precise delivery of high frequency electromagnetic energy. In a handheld device, this requirement demands careful optimization of power consumption and advanced thermal management to ensure reliable operation without excessive heat generation. Integration of microwave components also poses significant challenges. Achieving miniaturization without compromising the performance or reliability of crucial components requires rethinking design approaches and engineering methods. Finally, user safety and ergonomics are essential factors. A handheld ablation device must be not only safe for the patient and user but also comfortable and easy to use for medical professionals during extended procedures, emphasizing the importance of ergonomic design and user-friendly controls.

To overcome key design challenges that include performance, weight, power efficiency and thermal management, Emblation developed the highly integrated microwave source module shown in Figure 1. The microwave source module, which is intentionally blurred, is mounted on a copper carrier. The printed circuit assembly is a six-layer, double-sided board combining microwave laminate/FR4 with embedded copper coins.

At the heart of this module is the Qorvo QPA1010 MMIC amplifier, shown in Figure 2. This device is an X-Band GaN-on-SiC amplifier operating from 7.9 to 11 GHz. The QPA1010 amplifier provides 15 W of saturated output power with 38 percent power-added efficiency and a large signal gain of 18 dB. This device is powered by a 24 V supply with IDQ = 600 mA and includes an integrated power detector in the 24-lead 4.5 × 5.0 × 1.72 mm air cavity laminate package. To achieve the desired linearity, R6, R17, C5 and C14 are required as extra bypassing components.

Figure 3 Compact size of microwave source module circuit assembly.

The QPA1010 incorporates multiple amplifier stages, bias circuits and control logic into a single MMIC chip. This integration significantly reduces the MMIC size, parasitic losses and overall size of the amplifier, which are all crucial factors when designing a portable device that operates at microwave frequencies. The QPA1010’s compact form factor allows it to be easily integrated with other components of the ablation device, such as power management and control systems while maintaining optimal performance.

Ensuring that the handheld ablation device could supply 10 W of operating power to the antenna and meet the performance requirements while operating at 8 GHz required extensive simulation and modeling. Circuit-level modeling techniques were used to optimize key performance metrics, including gain, output power, stability and efficiency. These simulations guided the integration of the QPA1010 amplifier with pre-amplifier gain stages to make sure that the complete amplifier met the performance specifications needed for effective ablation. This was particularly challenging given that the source module design had to meet a 60 mm × 25 mm footprint, as shown in Figure 3, which has also been intentionally blurred. With the limited space, the design and integration used very short transmission lines between components, which prevented the use of tapers or bends to adjust for variations in the dimensions of the component connection pads. In addition, the compact design and cascaded high-gain stages were prone to feedback and oscillations, which were overcome through careful filtering of device supply inputs.

The high power density of the handheld microwave ablation system necessitated advanced cooling techniques. These include selective heat-sinking strategies for specific areas of concentrated heat and specialized thermal interfacing to maintain the amplifier within safe operating temperatures. A key component of the thermal management strategy was the use of copper coin technology, a common practice in high-power electronic devices that enhances heat dissipation. The copper coin serves as an efficient thermal bridge embedded directly into the printed circuit board beneath the component, providing an efficient path for heat transfer to the thermal mass heat sink. With its high thermal conductivity, the integrated copper coin is placed in direct contact with the component’s base, where the most heat is generated, minimizing thermal resistance and allowing for rapid heat transfer. It is thermally connected to a compact thermal mass heat sink strategically positioned to dissipate the transferred heat from a number of specific circuit locations, maintaining a lightweight and compact design while ensuring efficient cooling.

Figure 4 Thermal camera images of the SwiftPro device during simulated prolonged usage.

Copper coin technology significantly enhances thermal performance by enabling rapid heat removal, maintaining optimal operating temperatures and helping maintain performance in concert with thermal compensation techniques. This efficient heat transfer also allows for a smaller heat sink, which helps keep the overall device size and weight to a minimum. Additionally, effective heat management ensures that the overall device remains cool to the touch, improving user comfort during extended procedures. This requirement was subsequently verified using FLIR measurements during prolonged use analysis testing, with results shown in Figure 4.

Once the microwave design was finalized, it was integrated into the overall ablation device. This required coordination between the microwave design team and other teams working on power management, control electronics, firmware, user interface (UI), product design and mechanical design. The amplifier’s power requirements had to be managed to ensure efficient operation while minimizing battery drain. A custom power distribution unit (PDU) was designed to provide stable power to the amplifier, even under varying load conditions. This PDU also had to power the higher voltage microwave circuitry and all other electronics from a low-voltage 3.7 V lithium cell-based battery supply or via an optional main-derived DC power input. Integrating an efficient power management system was crucial for the device, balancing the need for high performance with the goal of minimizing battery consumption.

This power management effort was another important challenge for the design. Traditional microwave power amplifier designs often maintain a constant quiescent bias, resulting in continuous power consumption even when the device is idle. This inefficiency can significantly impact battery life in a portable device, limiting the practicality of handheld devices in clinical environments where mobility and extended operation are essential. To address this challenge, the SwiftPro device implements a power management strategy centered around dynamic bias control. This approach dynamically adjusts the amplifier’s bias via firmware control to reduce power consumption during idle periods and between every energy treatment pause. Full bias is only engaged when active energy delivery is required at the point of treatment delivery.

The dynamic bias control mechanism of the ablation device allows the amplifier to rapidly ramp up bias during energy delivery and remove it when the device is not in use. This required coordination between the amplifier’s control circuitry, the PDU and the overall system logic to ensure smooth transitions without affecting the quality or precision of the ablation process. By minimizing power draw during idle periods, the device can operate for extended durations, delivering hundreds of treatment applications on a single battery charge. This feature makes the device attractive for multiple procedures in outpatient or remote settings since it does not require frequent recharging.

The custom-designed PDU plays a vital role in supporting the dynamic bias control strategy. Engineered to provide stable and efficient power across varying load conditions, the PDU delivers precise voltage and current to the amplifier during both active and idle states. The PDU incorporates adaptive power delivery techniques, managed in firmware, continuously adjusting output based on the amplifier’s current bias requirements to minimize wasted power and maximize overall energy efficiency. These adaptive power delivery techniques ensure that the amplifier receives the exact amount of power needed at any given moment, optimizing performance while conserving battery life.

In addition to managing power delivery, the PDU includes battery conservation features such as low-power “sleep” modes and rapid wake-up capabilities. These features enable the SwiftPro device to transition quickly between standby and active states, reducing power consumption during prolonged downtime without compromising the device’s readiness. This intelligent power management system is governed by software and firmware algorithms that monitor the device’s operational state, battery levels and usage patterns, making real-time adjustments to optimize power consumption. The integration of these algorithms with the UI provides healthcare professionals with real-time feedback on battery status and energy usage, allowing them to make informed decisions about device operation during procedures.

The UI was designed with the needs of medical professionals in mind, prioritizing ease of use and intuitive operation. The interface provides controls for adjusting ablation parameters of power level and time, allowing users to quickly adapt the device’s settings to suit specific clinical requirements. Custom software and firmware were developed to ensure seamless communication between the UI and the amplifier’s control logic. This UI was also specifically designed to maintain the ease of use and usability of the existing Swift® product from Emblation, coupled with the energy protocols that healthcare professionals were already familiar with. This user-centric approach allows the ablation device to be easily integrated into clinical workflows, even for practitioners who may be new to microwave ablation technology.

Following the initial design and simulation phase, prototypes were developed and tested under various use conditions to validate performance and identify areas for improvement. These prototypes were subjected to stringent performance requirements under the 60601 medical device standards, including the IEC 60601-2-6 standard specific to microwave medical equipment. Managing the heat generated by the amplifier during operation was a primary challenge due to the compact design and significant heat output of the high-power microwave amplifier.

The regulatory journey is as rigorous as its technical development. As a medical device intended for direct clinical use, ablation devices must meet stringent regulatory standards in multiple markets. The SwiftPro device achieved FDA 510(k) clearance (K222388, K240518) in the U.S. and CE marking in Europe is currently pending.

Figure 5 SwiftPro microwave ablation device and docking stand.

Manufacturing the SwiftPro involved scaling up production while maintaining strict quality control standards. The in-house production process was designed to ensure consistency and reliability, with each device undergoing comprehensive testing before shipping. Key components, particularly the GaN-based amplifier, were sourced from leading providers of semiconductor solutions with established reputations in the industry. This careful selection of suppliers helped to ensure a reliable supply chain, reducing the risk of component shortages or inconsistencies that could impact the device’s performance. The final SwiftPro device, along with its docking stand, is shown in Figure 5.

A pilot program involving key opinion leaders and leading clinicians supported the market introduction. These early adopters provided valuable feedback on the device’s performance, ergonomics and clinical utility, helping to refine the final product. The insights gained from these pilot programs were instrumental in optimizing the design and functionality, ensuring that the needs of healthcare professionals were met in real-world settings. A comprehensive training program was also developed to support clinicians in adopting the new technology, including detailed tutorials, in-person demonstrations and dedicated customer support.

CONCLUSION

The successful delivery of the SwiftPro device to the market represents a significant milestone in the evolution of microwave ablation technology. The performance and compact, portable design open new possibilities for microwave ablation procedures outside of traditional surgical suites. The device and the technology can be used in outpatient clinics, remote locations and potentially even home-based care environments in the future. This expanded accessibility has the potential to greatly enhance patient care by providing more treatment options in a broader range of settings.

Beyond its current use in tissue ablation, there is future potential for expanding the technology’s use in other medical applications such as dermatology and podiatry. These applications may include the treatment of benign and malignant skin conditions and a variety of other dermatological conditions. Future developments at Emblation may include software enhancements, expanded clinical applications and new treatment protocols to further increase the device’s versatility and clinical value.

ACKNOWLEDGMENT

Emblation received funding under the 1906 Eureka Singapore UKRI Grant number 105977.