CHARACTERIZATION AND USE OF A COMMERCIAL N-TYPE DIODE SYSTEM

The characteristics of n-type diodes (linearity, temperature, dose rat e, radiation damage response, directional dependence, output factors, wedge factors and percentage depth dose determinations) were investiga ted. Subsequently, the diodes were used clinically for in vitro dose v erification during external megavoltage photon beam therapy. It has be en shown that n-type diodes are easy to use and the results obtained a re comparable to those reported for p-type diodes. On most occasions, n-type diodes can be used without any additional correction factors ap art from regular monthly calibration. There is good agreement between the uncertainty limits estimated from the diodes' characteristics and those obtained on the basis of 2261 patient measurements.