Beshan S Chiang PhD, Abstract Co-Author: Nothing to Disclose

Katsuyuki Taguchi PhD, Presenter: Nothing to Disclose

Ilmar Hein PhD, Abstract Co-Author: Nothing to Disclose

Multi-slice helical CT is a promising noninvasive technique for coronary artery imaging. One of the challenges in cardiac CT is the robustness: In order to obtain the good image quality (IQ) in a robust manner, one has to reduce the heart rate variation (HRV) during the scan. Even with the administration of the beta blocker, the HRV can not be eliminated, which causes the horizontal, discontinuous banding artifact shown in MPR or 3D images. Thus, we propose an algorithm to reduce the effect of the heart rate variation.

The proposed algorithm consists of the following two parts: 1) an ECG-correlated cardiac banding artifact correction (CBC) technique and 2) cone-beam reconstruction (DIRECT) algorithm. CBC reduces the effect of the HRV by smoothly changing the contribution of each heart cycle along the z-axis. DIRECT applies weights to projection data to compensate the redundancy, followed by a cone-beam filtered backprojection. The weights considered the complementary rays, and thus, the cardiac time window width can be minimized, leading to the best temporal resolution possible. We evaluated the performance of the algorithm by using computer simulated moving phantoms, with and without changing frequency of the motion. Several clinical cardiac data sets obtained with Aquilion 64 (Toshiba America Medical Systems, Tustin, CA) were used for validating the proposed method.

DIRECT improved the temporal resolution and/or the image noise: the temporal resolution can be improved by 50%; the noise can be reduced by 27%. DIRECT also provides a robust temporal resolution over wide range of heart rate, reducing the effect of the HRV on the IQ. The effect of the irregularity of the motion pattern caused discontinuous banding artifact, which was significantly reduced by CBC. Contrast enhanced coronary images showed the banding artifact even if the heart rate is low (~60 bpm); some coronaries were even abruptly disappeared in 3D images. CBC improves the banding artifact making such coronaries smooth and continuous.

The proposed algorithm significantly improves the banding artifact with good temporal resolution. (KT is an employee of Toshiba America Medical Systems, Tustin, CA)

K.T.: KT was an employee of Toshiba America Medical Systems, Inc. when the work was carried out.B.S.C.,I.H.: The work was funded by Toshiba Medical Systems Corporation (Tochigi, Japan)

Chiang, B, Taguchi, K, Hein, I, Cone-beam Cardiac Reconstruction with a Cardiac Banding Artifact Correction.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4411168.html