Project

radiation exposure optimization; iterative reconstruction CT; image quality; pediatric CT; patient exposure

Lead
Lay summary
As in most Western countries,  CT is responsible for more than two third of the dose delivered to the population in Switzerland and this in spite of the fact that many efforts have been made by radiologists, medical physicists and manufacturers to optimize the examinations protocols.  Among the latest developments aiming at dose reductions one can mention the introduction of iterative image reconstructions, IR, and a better use of the X-ray beam energy.  The commercially available IRs (that tend to replace the standard filtered back projection, FBP) allow a modest dose reduction (about 30-40%) but require the acceptance of a change of the images’ texture.  More sophisticated IR’s are being developed where standard dose might be divided by factors as high as 8. Readable images are even obtained while reducing the dose by much higher factors.  In such a context it is essential to ensure that the diagnostic value of the examination remains sufficient. This project aims at determining up to what level patient dose can be reduced by taking FBP examinations as a gold standard and comparing them to follow up studies performed at very low dose levels together with IR.

Direct link to Lay Summary

Last update: 21.02.2013

Assessment of low contrast detection in CT using model observers: Developing a clinically-relevant tool for characterising adaptive statistical and model-based iterative reconstruction

Author	Ott, Julien G.; Ba, Alexandre; Racine, Damien; Viry, Anais; Bochud, François O.; Verdun, Francis R.
Publication date	01.06.2017
Persistent Identifier (PID)	27156923
Repository	Pubmed

Update on the non-prewhitening model observer in computed tomography for the assessment of the adaptive statistical and model-based iterative reconstruction algorithms

Author	Ott, Julien G; Becce, Fabio; Monnin, Pascal; Schmidt, Sabine; Bochud, François O; Verdun, Francis R
Publication date	07.08.2014
Persistent Identifier (PID)	24990844
Repository	Pubmed

Active participation

Number	Title	Start	Funding scheme

Scientific context:As in most Western countries, CT is responsible for more than two third of the dose delivered to the population in Switzerland and this in spite of the fact that many efforts have been made by radiologists, medical physicists and manufacturers to optimize the examinations protocols. Among the latest developments aiming at dose reductions one can mention the introduction of iterative image reconstructions, IR, and a better use of the X-ray beam energy. The commercially available IRs (that tend to replace the standard filtered back projection, FBP) allow a modest dose reduction (about 30-40%) but require the acceptance of a change of the images’ texture. More sophisticated IR’s are being developed where standard dose might be divided by factors as high as 8. Readable images are even obtained while reducing the dose by much higher factors. In such a context it is essential to ensure that the diagnostic value of the examination remains sufficient. Image quality should always be balanced with radiological risk which requires the assessment of organs dose. At the moment, only a few centers are able to accurately estimate individual patient doses in CT, but none are located in Switzerland. This requires Monte-Carlo simulations where programming in basic languages such as C++ represents a strong limitation in clinical routine. At the European level the “GATE” project aims to providing medical physicists with toolboxes to assess organ dose in radiology and nuclear medicine in a simpler and more efficient way. As CT protocols optimization needs to be done on the individual organ dose basis rather the on the effective dose basis, the use of GATE in CT dose estimation looks promising.Aims of the project:This project aims at investigating the balance between image quality and patient dose in CT. We first propose to assess the benefits and limits of IR’s with standardized phantoms by measuring image quality parameters (such as spatial resolution and image noise). We will also study the effect of the presence of movement during data acquisition since this might represent a challenge for IR’s. In parallel our goal is to characterize the changes of image texture IR’s might introduce and understand the potential effect this might have on clinical images. Different phantoms leading to images where various textures are produced will be studied with standard methodologies used to describe texture in objective ways. On a more clinical related level, we aim at determining up to what level patient dose can be reduced by taking FBP examinations as a gold standard and comparing them to follow up studies performed at very low dose levels together with IR. We also propose to investigate if the change of the reconstruction plan (sagittal or coronal instead of transverse) allows recovering more diagnostic information. In collaboration with a French laboratory we aim at developing the tools required by GATE to estimate patient dose at the organ level delivered by a state-of-the-art CT unit. Within this project we wish to assess the actual benefit tube voltage modulation during the acquisition might provide.Expected results:This project will concentrate on three common examinations (cardiac: follow up of congenital diseases; lung: follow up of patient suffering from cystic fibrosis (CF); abdomen: follow up of testicular tumors, sarcoma, lymphoma or Hodgkin’s disease) performed on children and young adults where it has been shown that 30% of that population might have at least 3 scans, 4% at least 9 scans. At the end of the project we would like to have a clear answer concerning the way CT protocols have to be modified to fully benefit from the IR approach for that particular population where dose reduction should have a full priority. Concerning the dose estimation aspect this project should demonstrate if for the population studied tube voltage modulation allows a further radiological risk reduction.Finally, this project aims to strengthen national and international scientific collaborations in the field of medical imaging.