A recent study published in the journal Sensors introduces an innovative approach to monitoring this condition. Researchers from Ireland have developed wireless implantable sensors (WIS) that offer a promising method for long-term monitoring of aneurysm growth.
An illustration of the experimental evaluation of the reading system and the evaluated sensors, according to the spacing between the transmitter and repeater inductors (s) and the distance between the reading system and the sensor (d). The evaluation of the variability between the transmitter and repeater inductors is represented in (a). In (b,c), the evaluation of the medium and large sensors align at 0° with the reading system for distances between 1 and 10 cm, respectively, while (d) represents the same evaluation but with the sensor aligned at 90°. Image Credit: https://www.mdpi.com/1424-8220/24/10/3195
Background
An abdominal aortic aneurysm (AAA) is a critical condition marked by the abnormal enlargement of the aortic artery, potentially leading to life-threatening complications if it ruptures.
Current clinical practices to treat AAA predominantly rely on endovascular aneurysm repair (EVAR) as a treatment option, necessitating regular follow-ups through medical imaging to monitor aneurysm progression. However, this approach necessitates frequent follow-ups with medical imaging, posing challenges in terms of cost and resource allocation. Furthermore, it may not provide continuous real-time monitoring.
In response to these challenges, the development of wireless implantable medical sensors offers a promising alternative for longitudinal monitoring of AAA size changes post-EVAR. By enabling continuous monitoring without the need for frequent imaging procedures, wireless implantable medical sensor technology has the potential to enhance patient care and improve treatment outcomes. These sensors can provide valuable data on aneurysm growth, allowing healthcare providers to intervene promptly when necessary.
Previous studies have explored the use of wireless inductive coupling systems to power and communicate with implantable sensors, demonstrating the feasibility of remote monitoring for various medical conditions. Optimizing inductor configurations and integrating repeater inductors have also proven to enhance the efficiency of energy transfer and data communication between external and implantable inductors.
The Current Study
The methodology used in this study to develop and characterize a read-out system for detecting the size of an AAA via wireless implantable medical sensors involved a systematic and detailed approach. The core component of the system, the inductor, was crucial for enabling communication with the sensors. The researchers innovated beyond traditional inductor designs, optimizing the geometry of the inductors to maximize the efficiency of data transmission between the external read-out inductor and the implantable sensor.
To achieve this optimization, a multi-coil inductive read-out system consisting of a transmitter and a repeater inductor was constructed. The spacing between these inductors was meticulously characterized to maximize the detection sensitivity of the Z-shaped sensor deployed in the aneurysmal sac. By varying the alignment angles between the Z-shaped inductor and the external read-out system, the impact of orientation on detection performance was thoroughly analyzed.
In addition to the conventional two-coil link methodology, the study explored the use of repeater inductors to amplify the signal received from the wireless implantable medical sensors, thereby enhancing the overall power efficiency of the read-out system. Experimental evaluations were conducted to assess the system's performance under different conditions, including variations in transmitter coil orientations relative to the wireless implantable medical sensors.
Additionally, the selection of FDA-approved nitinol material for developing wireless implantable medical sensors, as well as transmitter and repeater inductors, served as a proof of concept for future research. Experimental results from characterizing the system in an air medium demonstrated its ability to detect the sensors up to a distance of 5 cm, regardless of the orientation of the Z-shaped sensor. Significantly, the detection range improved as the sensor's orientation neared 0°, highlighting the system's potential for effective monitoring of AAA expansion over time.
Results and Discussion
The study underscores the critical role of inductor alignment and spacing in optimizing power transfer efficiency and enhancing component interaction in wireless implantable medical sensors. Experimental data demonstrated that precise alignment between the read-out system and the sensor is essential for maximizing detection sensitivity. The research also highlights the importance of maintaining accurate alignment, particularly in anatomical placements within the body, to ensure reliable and accurate monitoring of AAA size changes over time.
Moreover, the addition of repeater inductors within the read-out system proved advantageous, significantly amplifying signal power and improving communication efficiency between the external and implantable inductors. This enhancement in signal strength is crucial for effectively detecting changes in the resonance frequency of the Z-shaped sensor embedded within the AAA sac.
Conclusion
The development and characterization of the three-coil inductive read-out system mark a substantial advancement in the field of wireless monitoring for AAA. By focusing on optimizing the interaction between external read-out inductors and implantable sensors, this study sets the groundwork for more effective and dependable monitoring of AAA progression.
The system introduced offers a non-invasive, continuous monitoring solution, poised to transform post-EVAR patient care significantly. Looking ahead, future efforts may include further refinement of the read-out system design and its integration with advanced monitoring technologies to boost the overall performance of wireless implantable medical sensors in managing AAA.
Journal Reference
Silva, N.P., Elahi, A., et al. (2024). Design and Characterisation of a Read-Out System for Wireless Monitoring of a Novel Implantable Sensor for Abdominal Aortic Aneurysm Monitoring. Sensors, 24, 3195. https://doi.org/10.3390/s24103195, https://www.mdpi.com/1424-8220/24/10/3195