Sebastian Tobias Schindera MD, Presenter: Nothing to Disclose

Rendon Clive Nelson MD, Abstract Co-Author: Consultant, General Electric Healthcare, Inc Research support, Bracco Diagnostics, Inc Research support, E-Z-EM, Inc Research support, Valleylab, Inc

Keigo Kawaji BS, Abstract Co-Author: Nothing to Disclose

Carolyn R Lowry BS, Abstract Co-Author: Nothing to Disclose

Terry T. Yoshizumi PhD, Abstract Co-Author: Research support, General Electric Company

Greta Toncheva BS, Abstract Co-Author: Nothing to Disclose

Giao Nguyen, Abstract Co-Author: Nothing to Disclose

Srinivasan Mukundan PhD, MD, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

To assess the effective dose, image noise, and attenuation values of iodinate solutions at different tube voltages on 64-slice multidetector computed tomography (MDCT).

Three phantoms were scanned on a 64-slice MDCT scanner (LightSpeed VCT, GE Healthcare) (64x0.625 mm, pitch 1.35) using four different pairs of tube voltage (kVp) and tube current-time product (mAs) to achieve similar noise: (A) 140/225, (B) 120/275, (C) 100/420, and (D) 80/675, respectively. Using an adult female anthropomorphic phantom, effective doses were acquired and the normalized effective doses per 100 mAs were calculated. Image noise was measured on the image uniformity module of a Catphan phantom (Phantom Laboratory). Four plastic vials filled with 14 mL of different concentrations of iodinated solution (5, 10, 15, and 20 mg I/mL) and one vial with distilled water were imaged in the center of the scanner. Attenuation measurements in Hounsfield units (HU) were obtained from each vial.

The mean effective dose for the four different pairs of tube voltage and current-time product measured: (A) 11.1±0.6mSv, (B) 8.7±0.8mSv, (C) 7.9±0.7mSv, and (D) 4.8±0.3mSv. The normalized effective dose per 100 mAs was: (A) 4.9±0.3mSv, (B) 3.2±0.3mSv, (C) 1.9±0.2mSv, and (D) 0.7±0.1mSv. By decreasing the tube voltage, image noise increased, with the mean gain as follows: (A) vs. (B) 4.2%, (A) vs. (C) 6.1%, and (A) vs. (D) 23.9%. For each constant tube voltage, the mean HU numbers of the four different iodine concentrations increased linearly (r = 0.998). The HU numbers for all vials were higher with decreasing tube voltage and the mean increase in HU numbers for the four different iodine concentrations were: (A) vs. (B) 12.9-15.5%, (A) vs. (C) 37.2-43.2%, and (A) vs. (D) 71.4-86.2%.

The use of a low kVp, high mAs technique for abdominal MDCT scans yields a reduction of the radiation dose while decreasing the contrast material consumption.

Besides abdominal MDCT angiography, a low kVp/high mAs technique might also result in an increased contrast-to-noise ratio of hypervascular liver lesion at the same contrast media dose.

Schindera, S, Nelson, R, Kawaji, K, Lowry, C, Yoshizumi, T, Toncheva, G, Nguyen, G, Mukundan, S, et al, , Multi-Energy 64-Slice Multidetector Abdominal CT: Effect on Radiation Dose, Image Noise, and Contrast Opacification.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4438755.html