Akihisa Yamazaki RT, Presenter: Nothing to Disclose

Koichi Sugisawa, Abstract Co-Author: Nothing to Disclose

Yoshiyuki Okano, Abstract Co-Author: Nothing to Disclose

Yutaka Tanami MD, Abstract Co-Author: Nothing to Disclose

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

Sachio Kuribayashi MD, Abstract Co-Author: Research grant, General Electric Company

Yasuhiro Imai MS, Abstract Co-Author: Employee, General Electric Company

Kosuke Sasaki MS, Abstract Co-Author: Employee, General Electric Company

Koji Segawa RT, Abstract Co-Author: Employee, General Electric Company

00030490-DMT et al, Abstract Co-Author: Nothing to Disclose

A state-of-the-art multislice CT (Discovery CT750 HD, GE Healthcare) enables a high-resolution acquisition mode to improve spatial resolution. The purpose of this study was to evaluate spatial resolution improvement by this mode using quality assessment phantoms.

The high-resolution acquisition mode (HiRes mode) enabled more than 2.5 times view sampling per gantry rotation (2496 views) compared with the normal mode on the multislice CT. We scanned a 0.05-mm-thin-tungsten-wire for MTF measurements, and the high-resolution insert of the Catphan phantom at the iso-center and 15 cm off-center in the scan plane for visual evaluations. We also acquired a 20-cm-water phantom to evaluate image noise. The MTF values were calculated by the 2-D Fourier transform in the scan plane. Image noises were measured by using the region-of-interest in the Axial images reconstructed by both the current filtered back-projection algorithm (FBP) and a new iterative reconstruction algorithm (Adaptive Statistical Iterative Reconstruction: ASIR).

The 50%-MTF, 10%-MTF values at the iso- and off-center were 4.22, 6.97 and 3.34, 5.82 with the normal mode, 4.64, 8.53 (10% and 22% were improved) and 4.03, 7.15 (21% and 23% were improved) with the HiRes mode in the standard reconstruction kernel. The 50%-MTF, 10%-MTF values at the iso- and off-center were 10.78, 14.05 and 5.10, 9.02 with the normal mode, 14.43, 18.64 (34% and 33% were improved) and 6.46, 10.76 (27% and 31% were improved) with the HiRes mode in the high-resolution reconstruction kernel. The detectable slits were 7 lp/cm at the iso-center, 6 lp/cm at the off-center with the normal mode, 9 lp/cm at the iso-center, 7 lp/cm at the off-center with the HiRes mode in the standard reconstruction kernel. Image noises in 5 mm slice thickness were 6.4 HU with the HiRes mode and 5.0 HU with normal mode by the FBP, however image noise of HiRes mode was improved to 5.0 HU by using the ASIR.

The HiRes mode improved around 20% in the standard reconstruction kernel and 30% in the high-resolution reconstruction kernel from physical analysis, and 1 to 2 lp/cm from visual assessments. Image noise increase by the HiRes mode was compensated for the ASIR.

Spatial resolution improvement by the high-resolution acquisition mode brings detailed visualization without image noise or radiation dose penalty by using the new iterative reconstruction algorithm. 

Yamazaki, A, Sugisawa, K, Okano, Y, Tanami, Y, Jinzaki, M, Kuribayashi, S, Imai, Y, Sasaki, K, Segawa, K, et al, 0, Spatial Resolution Improvement Using a Novel High Resolution Acquisition Mode on Multislice CT.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8013221.html