Baojun Li PhD, Presenter: Nothing to Disclose

Junjun Deng, Abstract Co-Author: Nothing to Disclose

Albert Lonn, Abstract Co-Author: Employee, General Electric Company

Jiang Hsieh PhD, Abstract Co-Author: Employee, General Electric Company

To further improve the image quality and accuracy of treatment planning for obese patients, in particularly, to suppress the boundary artifacts, in the extended scan field-of-view (SFOV) reconstruction for wide-bore CT simulator.

During treatment planning, often time portions of patient anatomies can extend outside the 50cm scan field-of-view (SFOV). To combat projection truncation artifacts and to restore truncated objects outside the SFOV, an algorithm has previously been proposed based on fitting a partial water cylinder at the site of the truncation. Previous studies have shown this algorithm can simultaneously eliminate the truncation artifacts inside the SFOV and preserve the total amount of attenuation, owing to its emphasis on consistency conditions of the total attenuation in the parallel sampling geometry. Unfortunately, the water cylinder fitting parameters of this 2-D algorithm are inclining to high noise fluctuation in the projection samples from image to image, causing anatomy boundaries artifacts, especially during helical scans with higher pitch (≥ 1.0). To suppress the boundary artifacts and further improve the image quality, we propose to use a roughness penalty function, based on the Huber regularization function, to reinforce the z-dimensional boundary consistency. Extensive phantom and clinical tests have been conducted to test the accuracy and robustness of the enhanced algorithm.

Significant reduction in the boundary artifacts is observed in both phantom and clinical cases with the enhanced algorithm. The proposed algorithm also reduces the percent difference error between the horizontal and vertical diameters to well below 1%. It is also noticeable that the algorithm has improved CT number uniformity outside the SFOV compared to the original WF algorithm.

The proposed algorithm is capable of suppressing boundary artifacts and improving the CT number uniformity outside the 50cm SFOV.

The proposed algorithm improves image quality and accuracy of radiation treatment planning for obese patients on wide-bore CT simulator.

Li, B, Deng, J, Lonn, A, Hsieh, J, An Enhanced Reconstruction Algorithm to Extend CT Scan Field-of-view with Z-Axis Consistency Constraint  .  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12023049.html