Satoru Takahashi MD, Abstract Co-Author: Nothing to Disclose

Emi Murakami, Presenter: Nothing to Disclose

Toshihide Itoh, Abstract Co-Author: Employee, Siemens AG

Hidekazu Niikawa, Abstract Co-Author: Nothing to Disclose

Atsushi Shikata, Abstract Co-Author: Nothing to Disclose

Hiroshi Tsunoda, Abstract Co-Author: Nothing to Disclose

Hiroshi Yamamoto MD, Abstract Co-Author: Nothing to Disclose

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

3-material decomposition analysis with dual-energy CT can generate “iodine map” of tissue. Although the “iodine map” is applicable for lung perfusion study, it is potentially vulnerable to image noise. The purpose of the study was to evaluate if the “iodine map” was reliable in demonstrating low concentration of iodine in tissue under substantial image noise.

A phantom with various concentration of diluted iodine contrast medium (1 to 75 HU at 120kVp) was placed in a water bath and scanned with dual-energy CT scanner (Somatom Definition, Siemens) using 1) low-noise protocol of dual energy acquisition (140kV, 80mAs; 80kV, 425mAs), slice thickness of 5-mm, and 2) high-noise protocol of (140kV, 20mAs; 80kV, 85mAs), slice thickness of 0.75-mm. The images were analyzed on “virtual non-contrast analysis” to extract iodine concentration on images. The CT values on “iodine map” were compared to those on “mixed” image representing CNR at 120kVp. The trend of ratio between CT value of “iodine map” and “mixed image” was evaluated both for low and high-noise protocol.

The standardized ratio between CT value of “iodine map” and “mixed image” were constant for 7.5HU or higher concentration of diluted contrast medium both low and high-noise protocol. “Iodine map” overestimated the concentration of iodine of <7.5HU.

“Iodine map” with dual-energy CT could detect minimum concentration of iodine of 7.5HU reliably. “Iodine map” was robust to image noise.

useful to optimise scanning protocols for lung perfusion study; such as injection rate and amount of contrast medium, scan timing, as well as to evaluate “iodine map” appropriately

Takahashi, S, Murakami, E, Itoh, T, Niikawa, H, Shikata, A, Tsunoda, H, Yamamoto, H, et al, 0, Dose Image Noise Affect Reliability of Minimum Iodine Detection with Dual-Energy CT? A Phantom Study.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8016466.html