0.2 Design of an in-vivo radiation measurement scheme using a  (Page 8/2)

The purpose of this project is to develop a method for monitoring, evaluating the status of a tumor undergoing radiation treatment and transmit the radiation dose received by the tumor in real-time to an external data acquisition unit and evaluate the treatment strategy. The target system to be designed would consist of a miniature wireless sensor module which would be implanted in the region of interest and this unit transmits the data to an external receiver wirelessly. The Modern fabrication process allows us to fabricate CMOS circuits in nanometer range which is highly desirable when used in radiation sensing scheme where size is the main constraint. The heart of the sensing system is a MOS transistor device. The electrical properties of the MOS device (drain to source resistance, threshold voltage) change when exposed to gamma radiation. The objective of this project is to evaluate the MOS transistor parameters change with radiation dose, study the effects with varying transistor widths, lengths and propose the ideal characteristics of the CMOS device. The scheme of the radiation measurement is presented. Some of the questions that will be addressed in this report are – The effect of radiation on channel resistance during&after radiation, temperature dependency of the radiation effects. The complete characterization of the sensor is performed and the results are produced and cross checked with device physics. The characterized CMOS transistor is exposed to radiation and the radiation dosage received by the transistor is sent to a RFID receiver using radio frequency communication. The signal at the RFID receiver is filtered and the actual radiation dosage was determined from the filtered output’s duty cycle. A novel approach is used in determining the radiation measurement in this study.