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Radiation Units: Better, Safer CT Scans

Computed Tomography (CT) has recently undergone a revival as a diagnostic technique, due to the advent of new imaging systems and methodologies. CT is a relatively 'high-dose' diagnostic technique and the interaction between patient dose and optimisation of image quality is a critical parameter and the main focus of this project.

Optimised image quality and patient dose

RAD UNITS aims to produce a report on three important issues for CT, in particular, modern CT procedures. These issues are the dose to the patient, image quality and the interaction between these two factors. CT has undergone a technological revolution in recent years with the advent of first single-spiral and then multi-slice spiral systems, which have an intrinsically higher patient irradiation than in conventional CT.

In 1999, the European Commission published the 'European Guidelines on Quality Criteria for Computed Tomography', but since then the performances of CT equipment and its use has changed dramatically. This project will assist in updating these guidelines.

ICRU CT Committee will seek to convert subjective measurements of image quality into an objective analytical and quantitative assessment © Courtesy of J. Boone
ICRU CT Committee will seek to convert subjective measurements of image quality into an objective analytical and quantitative assessment
© Courtesy of J. Boone

Assessing interacting factors

New CT technologies (for example, multi-slice spiral systems) are associated with intrinsically higher patient irradiation than conventional CT. More significantly, the enormous power, speed and versatility of the new scanners have led to their wider use, often replacing traditional medical techniques. The increasing number and complexity of CT studies is a matter of considerable concern for patients and health authorities. Therefore, the regulatory authorities are taking an increased interest in more accurate and objective information on patient exposure.

Numerous interacting factors contribute to image quality in CT, including the radiation dose used. There is a need for a critical review of the available data in this field (dose and image quality) to guide CT users, radiologists, technologists and medical physicists involved with CT. An important part of this project will deal with the compromise between patient dose and image quality, implying objective and subjective measures of image quality and the clinical information that it contains. The different factors influencing image quality will be systematically analysed. As a general rule, for any application in radiological imaging, the dose to the patient should be as low as possible. However, a compromise needs to be made which should be based, on the one hand, on objective, quantitative and reliable criteria on image quality and diagnostic information and, on the other hand, on accurate and reliable dosimetry. Another related issue for CT is how to handle the enormous amounts of data derived from the new techniques.

Reporting results for international action

The project will produce a report on CT, including dose determination, image quality and interaction between these two factors, which will be prepared by the Catholic University of Louvain (BE) and submitted to the European Commission during 2007. Most parts of the report will be ready and available for consultation and discussion one year earlier and this information will be widely disseminated, including via the German National Research Centre for the Environment and Health in Neuherberg near Munich.

Based on the EC report, an 'International Commission on Radiation Units' report will be published by Oxford University Press; a subsequent publication in electronic format is also planned. In addition, parts of the report will be published in the open literature and presented at international meetings where appropriate.

Better medical diagnostics at reduced risk

The direct benefits of the efforts described in the present project for patients in general are obvious: improving the diagnostic power of the CT techniques while, at the same time, reducing the radiation exposure levels experienced.

In addition, the documents and information produced by the project will trigger increased awareness in the radiological and medical-physicists community, the medical community in general and lastly, through them, the general public. In particular, it is important that the public becomes aware of the efforts being undertaken to improve the efficacy of the CT procedures and, simultaneously, to reduce the radiation exposure so that they can have confidence in the new techniques and be able to make appropriate informed choices about their own medical care.