External audits of electron beams using mailed TLD dosimetry: preliminary results.

Aim: A feasibility study has been performed to investigate the possibility of using mailed thermoluminescence dosimetry (TLD) for external audits of clinical electron beams in Europe.

Methods: In the frame of the EC Network Project for Quality Assurance in Radiotherapy, instruction sheets and mailing procedures have been defined for mailed TLD dosimetry using the dedicated holder developed by a panel of experts of the International Atomic Energy Agency (IAEA). Three hundred and thirty electron beam set-ups have been checked in the reference centres and some local centres of the EC Network Project and in addition through the centres participating to the EORTC Radiotherapy Group trial 22922.

A method to estimate the transit dose on the beam axis for verification of dose delivery with portal images.

Purpose And Background: A feasibility study is performed to evaluate the possibility of using the transit dose of portal images on the beam axis to measure the accuracy in dose delivery. The algorithm and the method are tested on a breast phantom and on patients with a breast disease.

Materials And Methods: To estimate the transit dose at various air gaps behind the patient, a method is proposed which applies, for a given air gap, the inverse square law to the primary component of the exit dose and an experimentally determined function for the scatter component of the exit dose.

Evaluation of an electronic portal imaging device for transit dosimetry.

The possibility of using a commercially available electronic portal imaging device for transit dosimetry was investigated. The detection unit of the device comprises a metal plate/fluorescence screen and a camera. Basic parameters of this system were investigated: stability, detector uniformity, dose-response curve, field-size dependence and phantom-thickness dependence.