Project purposes

Computed Tomography (CT) is certainly a fantastic tool that, unfortunately, runs the risk of becoming a victim of its own success because of the public health concerns it may generate. A few years ago, on Jan 23rd 2001, USA Today published a particularly alarming paper (titled: “Radiologists agree CT scans harm kids”) in which it was mentioned that 1,500 patients from the 1.6 million children (under the age of fifteen) scanned might eventually die from cancer caused by excess radiation; this, without any emphasis on the fact that CT actually saves lives. More recently, the June 19th, 2007 edition of The New York Times highlighted once again the impact of CT on the population’s exposure level. It mentioned in particular that the 62 million CT scans performed in the US in 2006 were responsible for more than half of the population’s total exposure from radiological investigations. Over the last one or two years, cardiac CT acquisition has become more and more popular. This might pose an additional problem with respect to the population’s exposure since relatively high doses (from 12 to 40 mSv per examination) are typically delivered to patients over 45 – 50 years old. If this situation is already problematic for an adult population, it is even more so for young children investigated for cardiac malformations which are then followed-up by many CTs over their entire life. Since children are particularly sensitive to ionizing radiation, it becomes an ethical imperative to make every effort to reduce their exposure as much as possible. At the moment, data acquisition protocols have not been optimized along the lines of a sound methodology. The aim of this project is to address this problem by answering the following questions:

• How to objectively balance patient dose and image quality of static and moving structures?
  • How valid is the CTDIvol (volume Computed Tomography Dose Index) concept in assessing patient dose?
  • What are the benefits and limits of the NEQ (Noise Equivalent Quanta) and DQE (Detective Quantum Efficiency) metrics when applied to CT?
  • What is the feasibility to apply model observers to CT?"
  • In the patient dose-image quality space (expressed in terms of CTDIvol or a more appropriate quantity and NEQ) how fast is image quality reduced when changing acquisition parameters such as kV, mAs, pitch values, X-ray tube rotation time,…?
  • Where is the present state-of-the-art of the practice located? Which parameters could be proposed to improve the situation?
  • What gain in dose can be expected from iterative image reconstruction algorithms recently introduced for CT?
• Are the optimal sets of parameters using the methodology adequate in clinical applications?
  • When dealing with very young children (up to 10 years old)?
  • When dealing with follow-up studies for young adults?

This project will assure that cardiac CT examinations performed on children and young adults in Switzerland are optimized using a state-of-the-art methodology. This project will also provide the scientific community with a methodology that allows an objective way to reconcile image quality and patient dose by means of the very latest concepts from a dose and image quality point of view (introduction of new dosimetric concepts such as equilibrium dose, dose line integral … and use of objective image quality descriptors such as NEQ and DQE, parameters that are being adapted for CT in particular). Finally, the development of scientific competences in this field in Switzerland will help future international collaborations.

Dernière modification le 27.01.2010