Eiji Nishimaru RT,PhD, Presenter: Nothing to Disclose

Katsuhiro Ichikawa PhD, Abstract Co-Author: Nothing to Disclose

Masao Kiguchi RT, Abstract Co-Author: Nothing to Disclose

Minoru Ishifuro, Abstract Co-Author: Nothing to Disclose

Yasushi Nagata MD, Abstract Co-Author: Nothing to Disclose

Kazuo Awai MD, Abstract Co-Author: Research grant, Toshiba Corporation Research grant, Hitachi, Ltd Research grant, Bayer AG

Kazushi Yokomachi RT, Abstract Co-Author: Nothing to Disclose

Chikako Fujioka RT, Abstract Co-Author: Nothing to Disclose

At helical- but not step-and-shoot scanning, axial images can be reconstructed in arbitrary position along the z-axis. Consequently, the quality of multi-planar reconstruction (MPR) images from step-and shoot- is inferior to helical CT data. The radiation dose is lower at step-and-shoot- than helical scanning. We devised a processing method to improve the quality of MPR images from step-and shoot scan data and validated the effectiveness of our method in a phantom study.

We devised an image processing method that adjusts the response factors of the modulation transfer function (MTF) on MPR images from step-and shoot scan data. We used 2D frequency processing based on the 2D fast Fourier transform (2D-FFT) and manually optimized the frequency processing functions. We obtained step-and-shoot scans of a slit phantom (0.9 cycles/mm) on a 64-detector CT (VCT, GE) and reconstructed MPR images on an Advantage workstation (GE). The scan parameters were 120 kVp, 400 mAs, display field of view 100 mm, slice thickness and interval 0.625 mm, detector configuration 16 x 0.625 mm, and standard and bone reconstruction kernels. We measured the standard deviation (SD) in regions of interest (ROI) and the plot profile value across the slit phantom on MPR images obtained with the conventional- and our new method.

The SD value of the conventional- and our method was 190- and 299 HU, respectively. Spatial resolution in the z-direction was better on MPR images of the slit phantom obtained with our method because the SD values were higher. Plot profile curves confirmed that the spatial resolution of the slit phantom along the z-axis was effectively improved by our method.

Our new reconstruction method improved the quality of MPR images made from step-and-shoot scanning CT data.

Our method may improve the reconstruction of MPR images of the temporal bones where field axial CT images are often obtained by step-and-shoot scanning.

Nishimaru, E, Ichikawa, K, Kiguchi, M, Ishifuro, M, Nagata, Y, Awai, K, Yokomachi, K, Fujioka, C, A Novel Processing Method to Improve the Quality of Multiplanar Reconstruction Images Obtained with Step-and-Shoot CT Scanning.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004157.html