| dc.description.abstract | This thesis explores ultra-low-power wireless communication methods for biomedical implants. Leadless heart pacemaker (PM) and wireless capsule endoscopy are the two biomedical devices that have been used for prototyping and experimentation purpose.
For patients with heart arrhythmias, PM technology is an important treatment option. Conventional PMs, which are based on multiple leads, are dominant in the current treatment methods. They have one or more sensing and pacing leads connected to a subcutaneous device placed under the skin. The leads are placed in the right atrium (RA) and right ventricle (RV) through the veins or in the coronary sinus. Transvenous PMs have several short-term and long-term problems. Lead placement and lead dislodgement are the most frequent problems. Dual-chamber and multi-chamber leadless PMs are emerging solutions for reducing the limitations of conventional lead-based PMs.
A commonly used method for diagnosing the digestive system is using a leadbased endoscopy video, which can be an unpleasant experience. In addition, the presence of the medical experts during the diagnosing process is essential. Wireless capsule endoscopy (WCE) is an approach to eliminate the mentioned problems.
In order to migrate from lead-based medical devices to leadless versions, it is necessary to have a power-efficient, reliable wireless communication method. Wireless communication technology is well-developed and established, primarily for free-space applications. However, the communication methods used in free space are not power-efficient for lossy communication mediums like the human body.
In this thesis, three wireless communication methods have been proposed for power constrained medical devices that are deeply implanted in the body. For dualchamber leadless heart pacemakers, two methods are proposed. First, a conductive impulse scheme is proposed to support low data-rate wireless communication between the heart chambers. The conductive nature of the heart muscles and blood is used for electrical signal transmission between two pacemaker capsules that are placed in the right atrium and right ventricle chambers. The communication link utilizes the frequency range from 1 MHz to 10 MHz for conductive signal transmission.
A one-way backscatter communication based on the conductive coupling is proposed for data transmission from two pacemaker implants to a subcutaneous or on-body device. The implant capsules can communicate with an on-body device without having any active transmitter. Dual-chamber PM communication is enabled by using the subcarrier technique for discriminating the devices in the frequency domain. A low data rate of 11 kb/s is assigned to each PM capsule to communicate their vital information to the reader.
For the WCE system, a modified backscatter technique is used to transmit an analog video signal from the implant capsule to the on-body reader device. The video transmission system is fully passive and removes the battery for the video transmission in the WCE.
The proposed methods are designed and realized using off-the-shelf electronic components. The prototype systems are evaluated in in-vitro and in-vivo experiments. The results indicate that the proposed methods can provide ultra-low-power solutions for biomedical implants communication. | en_US |
