DOSE MEASUREMENTS IN THE STRAY FIELD OF A GE OPTIMA CT660

Statistics show how important computed tomography (CT) dosimetry has become. In order to estimate the dose distribution in the CT scan room during an examination, measurements of the ambient dose equivalent H*(10) have been performed. The primary aim of this study is the radiation protection of the staff and not the determination of the dose to the patient or in the primary beam. Therefore, the dose outside the primary beam, i.e. in the scattered field of the Physikalisch-Technische Bundesanstalt's GE Optima CT660, is of importance. The results of the dose measurements are analysed in dependence on the settings of the X-ray tube voltage, the collimator width and (with and without) the bow-tie filter of the CT scanner. For the radiation protection measurements, ionisation chambers have been used. Additionally, the influence of the patient on the radiation field and, therefore, on the dose is simulated by using an Alderson body phantom.