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Development of an automated processing method to detect still timing of cardiac motion for coronary magnetic resonance angiography

Whole-heart coronary magnetic resonance angiography (WH-MRA) is useful noninvasive examination. Its signal acquisition is performed during very short still timing in each cardiac motion cycle, and therefore the adequate still timing selection is important to obtain the better image quality. However, since the current available selection method is only manual one using visual comparison of cine MRI images with different phases, the selected timings are often incorrect and their reproducibility is not sufficient. We developed an automated selection method to detect the best still timing for the WH-MRA and compared the automated method with conventional manual one. Cine MRI images were used for the analysis. In order to extract the high-speed cardiac cine image, each phase directional pixel set at each pixel position in all cine images were processed by a high-pass filtering using the Fourie transform. After this process, the cine images with low speed timing became dark, and the optimal timing could be determined by a threshold processing. We took ten volunteers' WH-MRA with the manually and automatically selected timings, and visually assessed image quality of each image on a 5-point scale (1=excellent, 2=very good, 3=good, 4=fair, 5=poor). The mean scores of the manual and automatic methods for right coronary arteries (RCA), LDA left anterior descending arteries (LAD) and LCX left circumflex arteries (LCX) were 4.2±0.38, 4.1±0.44, 3.9±0.52 and 4.1±0.42, 4.1±0.24, 3.2±0.35 respectively. The score were increased by our method in the RCA and LCX, and the LCX was significant (p<0.05). As the results, it was indicated that our automated method could determine the optimal cardiac phase more accurately than or equally to the conventional manual method.