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QA of imaging equipment: X-ray and CT


Introduction

A QA programme in diagnostic radiology serves to ensure that the diagnostic images produced are of sufficiently high quality so that they reliably provide adequate diagnostic information with both the lowest possible cost and the least possible exposure of the patient to radiation. A QA programme of imaging equipment used in radiotherapy should not only address image quality but also geometry, including laser/couch and other geometric alignment. Furthermore, if CT data are used for treatment planning, the consistency of the electron density values across the CT, treatment planning system (TPS), and digitally-reconstructed radiographs (DRRs) should be verified.

Important Principles

Imaging equipment used in radiotherapy is often shared between diagnostic radiology, nuclear medicine and radiotherapy departments. Depending on the local situation, QA tests will therefore also be performed by the medical physicist responsible for its main clinical use.

Introduction to References

The report of the Consultant's Meeting provides an overview of current use and future developments of imaging in radiotherapy, and provides a number of guidance documents for QA of imaging equipment. Comprehensive guidelines for the QA of CT simulators and the CT-simulation process are given in the AAPM Task Group Report 66. Further guidelines for QA of imaging equipment can be found in the IAEA Radiation Oncology Physics Handbook (particularly chapter 12), and in IPEM Report 81.