Atsushi Urikura MS, Presenter: Nothing to Disclose

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

Takanori Hara PhD, Abstract Co-Author: Nothing to Disclose

Eiji Nishimaru RT, Abstract Co-Author: Nothing to Disclose

Yoshihiro Nakaya, Abstract Co-Author: Nothing to Disclose

To investigate a new method utilizing a comb phantom and an image-addition technique for iterative reconstruction (IR).

We evaluated adaptive iterative dose reduction 3D (AIDR-3D) provided by Toshiba Medical Systems. The comb phantom made with acrylic (CT no. = 135HU), which was placed in a water phantom was used. Since we needed to make the contrast between combs and background a low-contrast of about 20 HU, we injected an Iodine contrast media into the water and the contrast was adjusted to 115 HU. The phantom was scanned at various scan conditions, and the images were reconstructed by filtered back-projection (FBP) and various strength of the AIDR-3D (Weak, Mild, Standard and Strong). Since the image noise was obstacle for the correct resolution measurement, we added many images obtained by multi scans. The numbers of addition images were adjusted so that standard deviation (SD) values became less than 2 HU. From the addition images, we calculated the contrast transfer functions (CTFs).

Due to the addition technique, the correctly CTF measurement was achieved. The CTFs of the  AIDR-3D images were decreased in proportion to the strength. The CTFs of the AIDR-3D (strong) images were decreased by up to 57% and 61% at 0.50 and 0.67 cycles/mm, compared to the FBP [Fig. 1]. Furthermore, CTFs of the AIDR-3D was decreased according to the amount of noise of the original image, and the effect of the AIDR-3D on spatial resolution was clarified.  

The addition technique we devised was effective to evaluate the resolution for low-contrast objects, and was consistent to evaluate the effect of the IR on clinical image quality.

Our new method is effective to evaluate the changes in the spatial resolution of iterative reconstructions in CT images.

Urikura, A, Ichikawa, K, Hara, T, Nishimaru, E, Nakaya, Y, The Image-addition Technique to Evaluate Low-contrast Spatial Resolution of Iterative Reconstruction Images in CT.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12037143.html