An implantable wireless microdosimeter for radiation oncology

Radiation therapy is, alongside surgery and chemotherapy, the core therapeutic modality to combat malignant tumors. The ultimate goal in radiation therapy is to maximize the delivered dose to the tumor while minimizing the exposure of the healthy surrounding tissues. Accurate knowledge of the delivered radiation dosage to the tumors and sensitive organs is critical for optimal outcomes. A combination of modeling, numerical simulations, and measurements on tissue phantoms is commonly used to estimate the spatial dose distribution. For verification and quality control assurance, this is usually augmented by radiation measurement on the patient. Dose distribution verification has become a more complicated problem with advancements in treatment techniques as more precise information for such treatments is required. A wireless miniature, implantable dosimeter will be of great benefit in this respect. In this thesis, a micromachined passive transponder for in-situ measurement of ionizing radiation is designed, fabricated, and tested. γ-ray dose is remotely measured by monitoring the resonance frequency change correlated with a change in the surface charge of an electret. This is achieved through a micromachined capacitor with a movable plate that is partiallyfilled with a Teflon® electret and connected in parallel with an inductor, forming a passive LC tank