A simple model for predicting the signal for a head-mounted transmission chamber system, allowing IMRT in-vivo dosimetry without pretreatment linac time.

The DAVID is a transparent, multi-wire transmission-style detector that attaches to a linear accelerator (linac) collimator for use as an in vivo detector. Currently, the normal method for using the DAVID is to measure a signal at the time of phantom-based pretreatment verification and use that signal as a baseline to compare with in vivo measurements for subsequent treatment fractions. The device has previously been shown to be both stable and accurate.