AbstractID: 9069 Title: Evaluation of a commercial semiconductor detector for patient
dosimetry
Measurement of the dose delivered to treatment fields during radiation therapy,
commonly referred to as in vivo dosimetry, is usually achieved by placing semiconductor
detectors on the treatment portal. Several factors may affect the accuracy of diode
measurements. Among them are the amount of inherent buildup in the diode leading to
variations of response with SSD, rotation of the diode with respect to the incident beam
because of inaccurate placement or body contour, and air gaps between the diode and the
skin due to inaccurate placement or the presence of immobilization devices (masks, etc.).
In this study, we have evaluated the EquiDose diode (CNMC, Nashville, TN) in terms of
its response variation with SSD, beam incidence direction, field size, and presence of air
gap. We have compared its response to these factors to that of other commercially
available diodes. We have also evaluated the diode’s response in the dynamic mode of
multileaf collimator operation utilized for IMRT treatments. The x-ray beams used for
this evaluation were of 6, 10, 18, and 25 MV energies.