Sixteen-slice multidetector computed tomography pulmonary angiography: evaluation of cardiogenic motion artifacts and influence of rotation time on image quality.

OBJECTIVE: To describe the site and severity of cardiogenic motion artifacts on 16-slice multidetector computed tomography (CT) angiograms of the pulmonary circulation and to determine the impact of the gantry rotation time on image quality. METHODS: Sixty-nine patients underwent nonelectrocardiographically gated 16-slice multidetector CT angiography of the pulmonary circulation with a rotation time of 0.5 second (group 1, n = 37) or 0.375 second (group 2, n = 32). All scans were prospectively analyzed for the presence of cardiogenic motion artifacts in the pulmonary arteries, defined as a blurring of the edges of the pulmonary arteries on lung window settings with or without an artifactual loss of enhancement in the arterial lumen on soft tissue windows ("pseudofilling defect"). In addition, the severity of pulmonary arterial blurring was recorded using a 4-point scale. RESULTS: Fifty-six patients (81%) had at least 1 pulmonary artery affected by cardiogenic motion artifacts. At the level of the central pulmonary arteries, movement artifacts responsible for a blurring of the arterial wall were present in 35 patients (51%), mainly observed at the level of the pulmonary trunk (n = 28, 41% of patients) and right main pulmonary artery (n = 23, 33% of patients); in 2 patients, motion artifact was responsible for a pseudoflap appearance within the arterial lumen (n = 2, 4% of patients). Motion artifacts at the level of lobar pulmonary arteries were noted only in the lower divisions of the lingula (n = 1, 1.5% of patients) and in the left lower lobe (n = 2, 3% of patients). At the level of the segmental pulmonary arteries, motion artifacts were most frequently found in the lower divisions of the left upper lobe (lingula) (n = 19, 27.5% of patients) and left lower lobe (n = 29, 42% of patients). At the subsegmental level, motion artifacts were most common in the lower divisions of the left upper lobe (lingula) (n = 30, 43.5% of patients) and left lower lobe (n = 35, 51% of patients). Pseudofilling defects were depicted at the segmental and subsegmental levels in 28 patients (41% of the study group), almost exclusively located in the lingula and left lower lobe. Cardiogenic motion artifacts were observed with a significantly lower frequency in group 2 (22 of 32 patients, 69%) than in group 1 (34 of 37 patients, 92%) (P = 0.0142), with a concurrent reduction in the frequency of pseudofilling defects identified in 20 patients (54%) in group 1 and in 8 patients (25%) in group 2 (P = 0.0142). CONCLUSION: The use of a 0.375-second rotation time enables significant reduction in the frequency of cardiogenic motion artifacts on 16-slice multidetector CT angiograms of the pulmonary circulation.

Coronary arteries: assessment of image quality and optimal reconstruction window in retrospective ECG-gated multislice CT at 375-ms gantry rotation time.

Our objective was to evaluate the image quality of a 16-slice CT system with a rotation time of 375 ms in the assessment of coronary arteries. One hundred patients underwent iodine-enhanced CT coronary angiography within a single breath hold. Images were reconstructed in diastole, 300, 350, 400, 450, 500 and 550 ms prior to the onset of the next R-wave using absolute reverse retrospective ECG gating. The 15 coronary segments of the AHA classification were consensually reviewed by two radiologists. On the whole, best quality imaging was obtained with reconstruction intervals of -350 ms and -400 ms in high percentages of each segment (P<0.0001). Only 6.2% of the arteries with a diameter greater than or equal to 1.5 mm were not assessable because of extensive calcifications (3.9%), cardiac motion artifacts (1.9%), lack of enhancement (0.2%) and stent artifacts (0.3%). In patients with a heart rate above 70 beats per minute, the percentage of assessable segments decreased to 88%, while at a lower heart rate it increased to 95%. In 61% of the patients, all segments were assessable. In conclusion, this generation of CT technique may allow visualization of coronary arteries with a low percentage of non-assessable segments.