Thorsten R.C. Johnson MD, Presenter: Speakers Bureau, Siemens AG Research grant, Bayer AG

Jan C Schenzle, Abstract Co-Author: Nothing to Disclose

Wieland H. Sommer MD, Abstract Co-Author: Nothing to Disclose

Gisela Michalski, Abstract Co-Author: Nothing to Disclose

Klement Neumaier, Abstract Co-Author: Nothing to Disclose

Hans-Christoph Richard F. Becker MD, Abstract Co-Author: Nothing to Disclose

Ursula Lechel, Abstract Co-Author: Nothing to Disclose

Konstantin Nikolaou MD, Abstract Co-Author: Nothing to Disclose

Maximilian F. Reiser MD, Abstract Co-Author: Nothing to Disclose

00030490-DMT et al, Abstract Co-Author: Nothing to Disclose

To assess dose and image noise of Dual Energy CT with reference to a standard chest scan and to compare contrast to noise ratios (CNR) of spectral information with different combinations of x-ray spectra.

An anthropomorphic Alderson phantom was assembled with thermoluminiscent detectors (TLD) and its chest was scanned on a Dual Source CT (Siemens Somatom Definition) in dual energy mode at 140 and 80 kVp with 14x1.2mm collimation. The same was performed on another Dual Source CT (Siemens Somatom Definition Flash) at 140kVp with 0.8 mm tin filter (Sn) and 100 kVp at 128x0.6 mm collimation. Reference scans were obtained at 120 kVp with 64x0.6mm collimation at equivalent CT dose index of 5.4 mGy*cm. Syringes filled with water and 10mg iodine/ml were scanned with the same settings. Dose was calculated from the TLD measurements and the dose length products of the scanner. Image noise was measured in the phantom scans and spectral contrast was determined in the iodine and water samples.

The effective dose measured with TLDs was 2.60, 2.67 and 2.64mSv for the 140/80kVp, the 140Sn/100kVp and the standard 120kVp scans. Respective calculated doses from the scanner protocols amounted to 2.43, 2.80 and 2.49mSv. Image noise measured in the average images of the phantom scans was 11.0, 9.7 and 9.0 HU, respectively. The CNR of iodine was 35.6 at 140Sn/100kVp and 34.3 at 140/80kVp.

Dual Energy CT is feasible without additional dose. The minimal increase in image noise is practically irrelevant. A restriction in collimation is required for dose-neutrality at 140/80kVp, while this is not necessary at 140Sn/100kVp. The CNR for iodine detection is similar at both combinations of spectra.

With 140Sn and 100kVp spectra, Dual Energy CT can be acquired without compromises in image quality or resolution and without additional dose. Thus, CT can be performed routinely in Dual Energy mode.

Johnson, T, Schenzle, J, Sommer, W, Michalski, G, Neumaier, K, Becker, H, Lechel, U, Nikolaou, K, Reiser, M, et al, 0, Dual-Energy CT: How about the Dose?.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8007828.html