An external dosimetry audit programme to credential static and rotational IMRT delivery for clinical trials quality assurance.

Purpose: External dosimetry audits give confidence in the safe and accurate delivery of radiotherapy. The RTTQA group have performed an on-site audit programme for trial recruiting centres, who have recently implemented static or rotational IMRT, and those with major changes to planning or delivery systems.

Methods: Measurements of reference beam output were performed by the host centre, and by the auditor using independent equipment.