Barbara Flach, Presenter: Nothing to Disclose

Jan Kuntz, Abstract Co-Author: Nothing to Disclose

Marcus Brehm, Abstract Co-Author: Nothing to Disclose

Soenke Heinrich Bartling MD, Abstract Co-Author: Nothing to Disclose

Marc Kachelriess PhD, Abstract Co-Author: Nothing to Disclose

To provide a continuously adaptive prior in 3D time-resolved interventional CT to correct for patient or organ motion during the intervention.

For 4D intervention guidance a permanent tomographic data acquisition during the whole intervention is necessary. To keep the dose level as low as in today’s 2D fluoroscopic guidance we limit ourselves to acquire as few as 15 projections per 180° per temporal update. The combination of this highly sparse information with a high quality prior aquired before intervention then allows to continuously provide high quality update volumes. To correct for patient motion we propose to continuously update this prior by transforming the high quality prior via registration to the Feldkamp-reconstructions of data from the last 4 rotations (120 projections). Since we only utilize those projections required for the temporal update and no additional projections need to be acquired to update our prior, patient dose is not increased by this new running prior technique. Since as of today no dedicated 3D+temporal interventional CT system exists we use a prototype CT scanner consisting of a flat detector mounted on a continuously rotating clinical CT gantry (volume CT system). The data are acquired by a standard protocol (120 projections per rotation). Therefrom we select every 4-th projection for our investigations. To validate the new technique we used the head scan of a pig in vivo.

Motion of the pig's head of up to 30 mm between the prior scan and the intervention was successfully corrected. The resulting running prior images show high image quality without introducing new artifacts compared to an initial static prior image obtained from a prior scan. In comparison to the static prior the running prior is able to correct for patient motion. The temporal updates show less inconsistency artifacts when using the new running prior technology.

The running prior technique is superior to the static prior in case of patient motion. The temporal updates then show less artifacts. Since no additional projections need to be acquired the running prior technique comes at no additional patient dose.

Improved visualization of the correct position of interventional material with respect to the surrounding patient tissue. No additional scan needed in case of patient motion.

Flach, B, Kuntz, J, Brehm, M, Bartling, S, Kachelriess, M, Running Prior for Patient Motion Correction in Low Dose 4D (3D+Time) Interventional Flat Detector CT.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12023019.html