Yoshonori Funama PhD, Presenter: Nothing to Disclose

Kazuo Awai MD, Abstract Co-Author: Nothing to Disclose

Nozomu Nagasue, Abstract Co-Author: Nothing to Disclose

Yasuyuki Yamashita MD, Abstract Co-Author: Nothing to Disclose

Optimal Combination of the Scan Parameters at Cone Beam C-arm CT for Abdominal Imaging

For abdominal 3D C-arm imaging, the AAPM CT performance phantom was scanned with the AXIOM Artis dBA C-arm system (Siemens); 240,419, 274 projections were acquired at 6-, 8-, and 10 s (protocols A, B, and C). Pixel depth was 14- (protocols A, B) and 12 bits (protocol C). We filled the 3.2-25.4-mm cavities in the phantom with a sodium chloride solution. The per-view-settings of tube voltage and time product (mAs) were automatically regulated from 80- to 90 kVp according to the object size at each rotational angle. Five radiologists visually evaluated noise, signal conspicuity, and overall image quality at the 3 protocols using paired comparisons based on Thurstone’s law. We calculated the contrast-to-noise ratio for the signal from the objects and background in the same phantom. We also measured the radiation dose for the 3 protocols using an ionization chamber inserted in the center of a 14-cm acrylic phantom.

The comparative scale for noise was 1.37, 3.77, and 0.0 at protocols A, B, and C, respectively; for signal conspicuity it was 2.64, 3.54, and 0.0. The contrast-to-noise ratio was 2.89, 3.49, and 2.75, in line with our results for noise and signal conspicuity. For overall image quality, the scale was 1.30, 3.63, and 0.0 and the relative radiation dose at protocols A and B was 0.76 and 0.8, respectively, when the mean radiation dose per view was 1.0 at protocol C.

At abdominal 3D C-arm imaging, the image quality acquired with protocol B (419 combined projections, pixel depth 14 bits) is superior to protocols A and C.

At abdominal 3D C-arm imaging, image quality is influenced by the number of projections and pixel depth. In clinical practice, the most appropriate combination of projections and pixel depth shoul

Funama, Y, Awai, K, Nagasue, N, Yamashita, Y, Optimal Combination of the Scan Parameters at Cone Beam C-arm CT for Abdominal Imaging.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6008547.html