Sebastian Faby DIPLPHYS, Abstract Co-Author: Nothing to Disclose

Stefan Kuchenbecker MENG, Abstract Co-Author: Nothing to Disclose

David Simons MD, Abstract Co-Author: Nothing to Disclose

Heinz-Peter Schlemmer MD, Abstract Co-Author: Nothing to Disclose

Michael Marcus Lell MD, Abstract Co-Author: Research Grant, Siemens AG Speakers Bureau, Siemens AG Research Grant, Bayer AG Speakers Bureau, Bayer AG Research Consultant, Bracco Group

Marc Kachelriess PhD, Presenter: Nothing to Disclose

To compare the performance of different state-of-the-art dual energy CT (DECT) techniques with novel photon counting (PC) multi energy CT (MECT) with respect to dose efficiency in contrast-enhanced imaging.

A typical spectral CT application is the decomposition of CT data into virtual non-contrast (VNC) and iodine overlay images. We study its dose efficiency given that a number of spectral CT implementations are available and that others may become available. Different clinical DECT implementations were simulated: dual source, rapid kV switching and sandwich detector DECT. We further simulated promising types of realistic PC detectors with a variable number of energy bins. We also simulated dual source systems with one or two detectors being PC. For our simulation patient data were decomposed and a polychromatic forward projection yields the corresponding rawdata. Statistically optimal material decomposition [Faby et al., SPIE 2014] was employed to guarantee a fair comparison of all modalities. Dose, spatial resolution and contrast were the same among the modalities and thus it is sufficient to compare image noise which can then be converted into dose reduction values.

Results are expressed with dual source DECT at 100 kV/140 kV Sn (tin prefilter) being the reference. Using dual source settings of 90 kV/150 kV Sn led to a dose reduction of -39% VNC/-45% iodine. This is comparable to the performance of an ideal PC detector with two energy bins. Using eight energy bins results in -48%/-75%. Sandwich detector DECT at 140 kV is showing a dose increase +56%/+92%. A realistic PC detector with two energy bins performs as the sandwich detector for the VNC image but much better for the iodine image (+58%/+11%). Rapid kV switching with 80 kV/140 kV evaluated to +73%/-15%. Due to a lack of space we will present results for other spectral CT implementations at the meeting.

The results indicate significant patient dose saving possibilities for dual source CT settings of 90 kV/150 kV Sn (-39%/-45%) and an ideal PC detector with two energy bins (-29%/-59%). Using more than two energy bins improves the results further. Degrading effects in the PC detector set this technology back to the level of today’s DECT.

Dose saving possibilities for the patient in the context of contrast agent enhanced imaging are evaluated based on different dual and multi energy techniques.

Faby, S, Kuchenbecker, S, Simons, D, Schlemmer, H, Lell, M, Kachelriess, M, Performance of Today’s Dual Energy CT and Future Multi Energy CT in Virtual Non Contrast Imaging and in Iodine Quantification  .  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006645.html