Microsystems technology in radiation therapy

In this paper, we present several implantable micro-devices targeted towards improving the efficacy of radiation therapy. Three micro-devices are discussed: a self-biased solid state dosimeter to be used for wireless monitoring of the delivered dose, an electromagnetic tracking system to locate the position of tumor in real-time, and a Guyton-chamber-embedded capacitive pressure sensor for wireless measurement of interstitial pressure inside a tumor. Dosimeter and tracking systems are developed to be integrated together to achieve a track-able radiation sensor. Guyton chamber of the pressure sensor will eliminate the sensor drift due to the interaction of cells and fibrous tissue with sensor´s membrane. The dosimeter has a sensitivity of up to 9 kΩ/Gy and a dynamic range of 10 Gy, when operating with a zero bias voltage. The tracking system is able to track a tumor that is 60 cm away with a resolution of 2 mm and a dynamic range of up to 5 cm. Finally, the capacitive pressure sensor has a sensitivity of 75 fF/kPa and a dynamic range of 60 mmHg.