Study on motion artifacts in coronary arteries with an anthropomorphic moving heart phantom on an ECG-gated multidetector computed tomography unit

Abstract

Acquisition time plays a key role in the quality of cardiac multidetector computed tomography (MDCT) and is directly related to the rotation time of the scanner. The purpose of this study is to examine the influence of heart rate and a multisector reconstruction algorithm on the image quality of coronary arteries of an anthropomorphic adjustable moving heart phantom on an ECG-gated MDCT unit. The heart phantom and a coronary artery phantom were used on a MDCT unit with a rotation time of 500 ms. The movement of the heart was determined by analysis of the images taken at different phases. The results indicate that the movement of the coronary arteries on the heart phantom is comparable to that in a clinical setting. The influence of the heart rate on image quality and artifacts was determined by analysis of several heart rates between 40 and 80 bpm where the movement of the heart was synchronized using a retrospective ECG-gated acquisition protocol. The resulting reformatted volume rendering images of the moving heart and the coronary arteries were qualitatively compared as a result of the heart rate. The evaluation was performed on three independent series by two independent radiologists for the image quality of the coronary arteries and the presence of artifacts. The evaluation shows that at heart rates above 50 bpm the influence of motion artifacts in the coronary arteries becomes apparent. In addition the influence of a dedicated multisector reconstruction technique on image quality was determined. The results show that the image quality of the coronary arteries is not only related to the heart rate and that the influence of the multisector reconstruction technique becomes significant above 70 bpm. Therefore, this study proves that from the actual acquisition time per heart cycle one cannot determine an actual acquisition time, but only a mathematical acquisition time.

Visual and automatic grading of coronary artery stenoses with 64-slice CT angiography in reference to invasive angiography

“…Recent generations of computed tomography (CT) scanners with increasing numbers of detector rows and faster rotation speed [1] have greatly improved the robustness of coronary calcium scoring [2] and coronary CT angiography [3][4][5]. Even early studies in 4-and 16-slice multidetector CT (MDCT) showed a high negative predictive value for the method but mostly excluded the side branches of the coronary arteries [6].…”

Motion Calculations on Stent Grafts in AAA

“…ECG-gated CT is extensively used in cardiac exams (Albers et al, 2003;Manzke et al, 2004;Williamson et al, 2008), especially for the assessment of coronary arteries (Chartrand-Lefebvre et al, 2007;Dewey et al, 2008;Greuter et al, 2005). The goal in most of these studies is to limit the effect of motion rather than to examine the motion itself for which the technique can also be utilized.…”

Segmentation and motion estimation of stent grafts in abdominal aortic aneurysms

“…For parallel beam reconstruction, however, temporal resolution of half the rotation time can be achieved [96,94,45,86,1]. Multi segment reconstruction can result in an even higher temporal resolution for some heart rates by reconstructing a volume using the raw data from different heart cycles [46,1,32,37]. To be able to use an N-segment reconstruction, the spiral pitch factor (or pitch) has to be low enough and the heart rate high enough such that every z location is imaged during at least N heart beats.…”

“…This result strongly suggests that the scanner used a half scan reconstruction algorithm. However, above a certain heart rate some scanners might switch to multi segment reconstruction, which results in higher temporal resolution [46,37]. The number of phases to reconstruct should be chosen such that there is overlap between subsequent phases (T d < T w ) even for patients with low heart rates.…”

“…ECG gating is extensively used in cardiac exams [2,120,85], especially for the assessment of coronary arteries [32,18,46]. The goal in most of these studies is to limit the effect of motion rather than to examine the motion itself for which the technique can also be utilized.…”