Design techniques for low-power magnetic-tracking biomedical circuits and systems

Wing Fai Loke, Purdue University

Abstract

Intensity-modulated radiation therapy (IMRT) requires real-time tumor tracking to allow precise delivery of the prescribed dose of radiation to the tumor and reduce damage to the surrounding tissue. A small size and low power wireless active transponder implanted in the vicinity of the tumor with a magnetic tracking system placed outside the patient's body can be used to locate the position of the tumor during the radiation therapy. The wireless active transponder uses a magnetic sensor to sense the magnetic field generated by the magnetic tracking system, and then transmits the magnetic field information back to the computer wirelessly using on/off keying (OOK) for tumor tracking. One of the challenges faced by an implantable device is that the device must consume as little power as possible for prolonged battery lifetime or battery-less remote-powered operations. To significantly reduce the power consumption of the wireless transponder, various low-voltage low-power design techniques are proposed in this dissertation. These techniques include low-voltage designs, time-division scheme, a low-power low-area-penalty sensor front-end topology, and low-power voltage-controlled oscillator (VCO). Using these low-power techniques, a wireless active transponder is implemented in 130-nm CMOS technology. The developed wireless active transponder consumes only 912 μW, and does not use any area-intensive integrated inductors. This ultra-low-power wireless inductorless active transponder only occupies an area of less than 4 mm2. Measurements show that the wireless transponder is able to provide tumor tracking with an error of less than 5 mm using the magnetic tracking system.

Degree

Ph.D.

Advisors

Jung, Purdue University.

Subject Area

Biomedical engineering|Electrical engineering

COinS