Toru Higaki PhD, Presenter: Nothing to Disclose

Yoko Kaichi, Abstract Co-Author: Nothing to Disclose

Chikako Fujioka RT, Abstract Co-Author: Nothing to Disclose

Masao Kiguchi RT, Abstract Co-Author: Nothing to Disclose

So Tsushima, Abstract Co-Author: Employee, Toshiba Corporation

Kazuo Awai MD, Abstract Co-Author: Research Grant, Toshiba Corporation Research Grant, Hitachi Ltd Research Grant, Bayer AG Research Consultant, DAIICHI SANKYO Group Research Grant, Eisai Co, Ltd

Takuji Yamagami MD, Abstract Co-Author: Nothing to Disclose

Fuminari Tatsugami, Abstract Co-Author: Nothing to Disclose

Electron density images for radiotherapy planning are generally calculated from conventional CT images. However, electron density does not correlate accurately with the CT number. Novel analysis software that utilizes raw data-based dual-energy CT (rDECT) data was recently developed for 320-detector CT scanners. The purpose of this phantom study was to evaluate the accuracy of the electron density map generated from rDECT data.

We scanned a phantom with a 320 detector-row CT instrument (Aquilion ONE ViSION Edition, Toshiba Medical Systems, Tokyo, Japan). Scanning was at 80-135 kV, 800-140 mA, and 1.5 sec/rotation. The phantom was comprised of 27 cylinders filled with different solutions; 9 each contained various concentrations of iodine contrast media (iohexol, Omnipaque, Daiichi-Sankyo Seiyaku), calcium chloride, and mixtures of iodine contrast media and calcium chloride (see also Table 1 of attached image). Although the mix ratio differed among the solutions, it was adjusted so that the CT number in the different solution was similar. We used a CT scanner that featured the new software for data analysis and measurements.

In cylinders containing the calcium chloride solutions the CT number and electron density increased linearly in proportion to the concentration (row 3 in the attached Figure1 (a)(b)). In cylinders that contained the iodine solutions it also increased linearly in proportion to the concentration of the solutions but there was little change in the electron density (row 1). With respect to the mixed solutions, the CT number was almost the same in all cylinders, however, the electron density increased linearly in proportion to the weight of the calcium chloride (row 2). Quantitative results are shown in Chart 1 (a)(b)(c). Our findings indicate that the calculated theoretical values and the values based on solution concentrations tended to be similar.

rDECT yields a more accurate electron density map than the conventional method using the CT number.

http://abstract.rsna.org/uploads/2014/14003089/14003089_nhh3.jpg

Higaki, T, Kaichi, Y, Fujioka, C, Kiguchi, M, Tsushima, S, Awai, K, Yamagami, T, Tatsugami, F, Measurement of Electron Density Using Raw data-based Dual-energy Computed Tomography: Phantom Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14003089.html