Hiroto Takahashi, Presenter: Nothing to Disclose

Masahiro Okada MD, Abstract Co-Author: Nothing to Disclose

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

Yuki Kagawa MD, Abstract Co-Author: Nothing to Disclose

Masayuki Kudo PhD,RT, Abstract Co-Author: Employee, General Electric Company

Takamichi Murakami MD, PhD, Abstract Co-Author: Nothing to Disclose

To evaluate the enhancement of the liver, aorta, portal vein, IVC, image noise and radiation dose using low tube voltage scan condition.

Twenty patients underwent liver dynamic CT at 100 kVp with auto mA (Noise Index, NI=14.0) (as Group A) and other 20 patients received conventional dynamic CT at 120 kVp with auto mA (NI=11.0) (as Group B) for the detection and screening of hepatocellular carcinoma. Avarage CT dose index was 4.04 mGy and 6.38 mGy, dose length product was 124.57 mGy.cm and 194.54 mGy.cm for Group A and Group B, respectively on a 64ch MDCT (Discovery CT 750HD; GE Healthcare). Group A received 480mgI/kg of contrast agent in the setting of 40% of Adaptive Statistical Iterative Reconstruction (ASIR), whereas, Group B received 600mgI/kg of contrast agent in the setting of ASIR 0%. Display FOV and slice thickness were 35 cm and 5 mm, for both groups. Regions of interest (ROIs) of the vascular regions (0.5-1.0 cm2) and ROI of the liver (approximately 2 cm2) were placed on the aorta, portal vein, IVC and liver parenchyma of the unenhanced, arterial, portal venous and equilibrium phase images to analyze the enhancement values to measure CT numbers and image noise (standard deviation; SD). Mean vascular (aorta, portal vein, IVC) and hepatic enhancement values were compared between Group A and Group B. Statistical analysis was performed using Mann-Whitney’s U test.

The enhancement of aorta (in all phases) and IVC (in the portal venous and equilibrium phase) were significantly higher in Group A than Group B (p<0.05). Whereas, the enhancement of the liver showed no significant difference between Group A and Group B in all phases. Image noise for all vascular regions and liver showed no significant difference between Group A and Group B in all phases.

For liver dynamic CT examination, low tube voltage (100 kVp) technique CT with ASIR (lower radiation dose technique) increases vascular enhancement and image noise remains unchanged, in comparison with conventional (120 kVp) technique CT without ASIR. In addition, low tube voltage technique allows to decrease the amount of iodine contrast agent in the liver dynamic CT study.

Low tube voltage technique CT with iterative reconstruction can increase vascular enhancement and reduces both  radiation dose and the amount of iodine contrast agent in the liver dynamic study.

Takahashi, H, Okada, M, Hyodo, T, Kagawa, Y, Kudo, M, Murakami, T, Low Tube Voltage Technique CT with Iterative Reconstruction Increases Vascular Enhancement and Reduces Both Radiation Dose and the Amount of Iodine Contrast Agent in the Liver Dynamic Study.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004983.html