RSNA 2012 

Abstract Archives of the RSNA, 2012


LL-PHS-MO5D

How Does Tube Voltage Affect Beam-hardening Reduction by Model-based Iterative Reconstruction with Variable Diameters of Enhanced Structures in Contrast-enhanced CT? A Phantom Experiment

Scientific Informal (Poster) Presentations

Presented on November 26, 2012
Presented as part of LL-PHS-MOPM: Physics Afternoon CME Posters

Participants

Isao Tanaka, Presenter: Nothing to Disclose
Rika Fukui, Abstract Co-Author: Nothing to Disclose
Haruhiko Machida MD, Abstract Co-Author: Nothing to Disclose
Tubasa Iwasaki, Abstract Co-Author: Nothing to Disclose
Xiao Zhu Lin MD, Abstract Co-Author: Nothing to Disclose
Eiko Ueno MD, Abstract Co-Author: Nothing to Disclose
Yun Shen PhD, Abstract Co-Author: Employee, General Electric Company Researcher, General Electric Company

PURPOSE

To assess by phantom experiment how tube voltage affects beam-hardening reduction by model-based iterative reconstruction (MBIR) with variable diameters of enhanced structures in contrast-enhanced (CE) CT.

METHOD AND MATERIALS

At isocenter, we placed a cylindrical phantom (QSP-1, FUYO) containing an 18-mm-diameter cylindrical tube filled with 100.0 mg/mL of iodine contrast medium at its center and 8 tubes of 4- to 18-mm (2-mm step) diameter filled with 10.0 mg/mL of medium located symmetrically in its periphery, all 9 parallel to the z-axis. With a 64-detector CT scanner (Discovery CT750 HD, GE), we scanned the phantom (tube current, 4.5-HU noise index with 1.25-mm slice thickness using auto mA, 1.0-sec rotation speed, 1.375 helical pitch, various tube voltages, 80, 100, 120, and 140 kVp) and reconstructed 0.625-mm-thick axial images by MBIR and filtered back projection (FBP). On 5 different slices of each image, we placed circular regions of interest of the same area to measure the standard deviation of CT attenuation at the midpoint between the phantom’s center and each tube (SDa) and at each remote site of minimal artifact as background (SDb). We calculated artifact index (AI) as ([SDa]2 - [SDb]2)1/2 and compared AI for each iodine density between MBIR and FBP using paired t-test.

RESULTS

As diameter increased from 4 to 18 mm, the mean AI at 80 kVp increased: 5.5 ± 0.4, 7.8 ± 0.5, 10.1 ± 0.3, 12.8 ± 0.6, 16.1 ± 0.5, 19.1 ± 0.6, 21.1 ± 0.5, and 22.9 ± 0.5 HU by MBIR and 9.1 ± 0.8, 11.2 ± 0.4, 14.2 ± 0.8, 18.1 ± 0.9, 19.2 ± 0.8, 21.8 ± 0.4, 24.3 ± 1.4, and 27.3 ± 1.1 HU by FBP. The mean AI of all diameters by MBIR was 14.4 ± 6.4 HU (80 kVp), 11.5 ± 5.1 HU (100), 10.3 ± 4.2 HU (120), and 9.3 ± 3.8 HU (140), and that by FBP was 18.2 ± 6.4 HU at 80 kVp, 14.0 ± 4.9 HU (100), 12.6 ± 4.1 HU (120), and 9.8 ± 3.5 HU (140). At all tube voltages, the mean AI was significantly lower by MBIR than by FBP (P < 0.05) and reduced with MBIR by 20.5% at 80 kVp, 18.3% (100), 18.3% (120), and 5.6% (140).

CONCLUSION

In CECT, MBIR is more useful than FBP in reducing beam-hardening artifact, most effectively at lower kVp.

CLINICAL RELEVANCE/APPLICATION

MBIR is clinically useful for reducing beam-hardening artifact and improving diagnostic accuracy in contrast-enhanced CT, especially at low kVp.

Cite This Abstract

Tanaka, I, Fukui, R, Machida, H, Iwasaki, T, Lin, X, Ueno, E, Shen, Y, How Does Tube Voltage Affect Beam-hardening Reduction by Model-based Iterative Reconstruction with Variable Diameters of Enhanced Structures in Contrast-enhanced CT? A Phantom Experiment.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043923.html