Masayuki Kudo PhD, RT, Presenter: Employee, General Electric Company

Tomoko Hyodo MD, Abstract Co-Author: Nothing to Disclose

Koji Yamada RT, Abstract Co-Author: Nothing to Disclose

Souma Sengupta MS, Abstract Co-Author: Employee, General Electric Company

Takamichi Murakami MD, PhD, Abstract Co-Author: Consultant, DAIICHI SANKYO Group

CT value (HU) of objects with single-energy CT (SECT) is influenced by patient body size due to beam hardening (BH) effect. Thus we have to increase the volume of contrast medicine for large patients. The purpose of this study is to assess whether virtual monochromatic image (VMI) with dual-energy CT (DECT) can reduce BH effect and maintain the CT value of large objects.

We made cylindrical phantoms having soft tissue-equivalent materials (density 1.018g/cm3, effective atomic number 7.444) to simulate X-ray attenuation coefficient of human body. A diameter of each phantom was 10cm, 20cm, 30cm. Five vials filled with degrees diluted solutions (0, 3, 6, 9,12mgI/cc) of iodine were inserted into center of cylindrical phantoms. Each vials with/without phantom were scanned with SECT mode (120kVp) and DECT mode using DECT (Discovery CT750 HD, GE Healthcare), respectively. SECT images and VMI (60keV-80keV, interval of 5keV) were reconstructed and CT value was measured by using the average measurement in three regions-of-interest (ROI). CT value of each vial was compared SECT images as basis with VMI about amount of change of CT value.

As size of phantom became large, CT value decreased in average as follows; 69.9% in SECT, 88.5% in 60keV, 90.7% in 65keV, 93.2% in 70keV, 96.2% in 75keV and 99.8% in 80keV. The change of the maximum CT value in each VMI compared on the basis of the maximum CT value of SECT image without cylindrical phantom was as follows; 119.7% in 60kev, 98.0% in 65keV, 80.9% in 70keV, 67.1% in 75keV and 56.0% in 80keV. CT value did not decrease due to increase of phantom size in use of higher keV VMI. On the other hand, overall CT value decreased in use of high keV VMI. 65keV VMI showed the same maximum CT value approximately as CT value of SECT without phantom, and there was little degradation of CT value due to increase of phantom size. BH effect can be effectively reduced by 65keV VMI.

VMI with DECT has the ability to reduce BH effect in contrast-enhance study. VMI with appropriate energy (keV) can maintain CT value of contrast medicine without increasing amount of contrast medicine with large patients.

Use of VMI at appropriate energy (keV) with DECT in contrast-enhanced study, it is possible to reduce BH effect. It may be possible not to increase amount of contrast medicine with larger patients.

Kudo, M, Hyodo, T, Yamada, K, Sengupta, S, Murakami, T, Can Virtual Monochromatic Image with Dual-Energy CT Correct Beam Hardening Effect and Reduce Contrast Agent? Phantom Experiment.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12029758.html