Quality Assurance in Radiotherapy - Development and evaluation of new tools for improved patient safety

Sammanfattning: Preparation for radiotherapy is a complex procedure that involves many different technologies and groups of professionals. The rapid development and introduction of new technologies throughout the last decade have made it possible to deliver highly conformal, individually-shaped dose distributions with high accuracy. However, there is widespread concern that current quality assurance practices have not been updated at the pace necessary to provide adequate and cost-effective safeguards against treatment delivery errors. The overall aim of this thesis was to develop and evaluate new, efficient tools for patient-specific quality assurance of the radiotherapy process, including the following areas: transfer of information, independent monitor unit verification, pre-treatment measurements, in vivo dosimetry, and end-to-end tests. Within the framework of the thesis, a concept for ensuring data integrity was proposed and used to compare different combinations of treatment planning systems and record-and-verify systems with respect to data integrity. Because the concept is based on the Digital Imaging and Communications in Medicine (DICOM) global information standard, it is generally applicable to most radiotherapy computer systems. Additionally, a software for monitor unit verifications was developed, and the tools within Statistical Process Control were used to analyse calculation results from this software in a multicentre study. Time-resolved dosimetry systems were developed and applied to pre-treatment measurements and in vivo dosimetry, allowing rigorous analysis of the accuracy of the treatment planning and delivery systems and forming a basis for real-time in vivo dosimetry. Finally, gel dosimetry and anthropomorphic phantoms were demonstrated to provide important tools for complete end-to-end tests. The tools developed in this thesis have two important applications: routine use in daily clinical practice, and when introducing new technologies in the local clinical setting. The proposed methods and concepts can improve patient safety and reduce the resources required for a comprehensive quality assurance program.