AbstractID: 8597 Title: In-Vivo dosimetry for IMRT using MOSFET dosimeter
Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeters have been
widely studied as a tool for patient dose verification. The major advantage of this
dosimeter is its ease of use and small size, closely approximating a point detector. In this
article, we report on the characterization of a prototype micro MOSFETs for clinical use.
The MOSFETs were characterized for reproducibility with accumulated dose, linearity,
energy dependence, angular dependence and effective depth of sensitive volumeThe
system was used for 2 different clinical applications. In the first application, the micro
MOSFET was used for IMRT prostate treatment verification. Fluence maps from a plan
developed under CadPlan/Helios were transferred to a flat phantom and a point dose was
calculated at a depth of 5cm for each field. The dose at the calculation point for each
field was measured at depth using the MOSFET system. In the second clinical
application, the MOSFETs were used for in-vivo dosimetry and verification of head and
neck treatments. The MOSFETS were calibrated and placed in polyethylene tubing for
HDR catheters. This MOSFET in the catheter was accurately positioned in the patient’s
oral cavity. Two additional MOSFETs were taped under the thermoplastic mask around
the patient’s eyes. Each point of measurement was selected within the region of uniform
dose. The measured doses were compared with the CadPlan calculated point doses.
Characterization of MOSFET showed it to be suitable for clinical studies. Initial results
on in-vivo dosimetry and IMRT QA showed good agreement.