An implantable wireless microdosimeter for radiation oncology

Wireless measurement of ionizing radiation in close proximity or within an irradiated solid tumor is extremely valuable for dose verification and quality control in radiation oncology. For such applications, it is preferable to manufacture such sensors using passive components since high levels of ionizing radiation can damage active electronics. This paper reports on the development of an implantable micromachined passive LC transponder (2.5 mm in diameter and 2.8 cm in length.) Dose measurement is performed by monitoring the resonance frequency change associated with the decay of surface change of an electret upon exposure to radiation. The test results show that a dose of 30 Gy can produce 1.46 MHz frequency shift resulting in a sensitivity of 49 kHz/Gy.