Acceptance testing and quality assurance of automated scanning film densitometers used in the dosimetry of electron and photon therapy beams.

Scanning film densitometry routinely used for obtaining dosimetric information about therapy treatment beams is subject to several sources of inaccuracies. The most significant of these are described and appropriate methods of testing are presented. This establishes the need for adequate acceptance testing followed by a quality assurance program if these devices are to be used to provide accurate relative dose information over extended periods of time.