Thin-section CT of the lung: influence of 0.5-s gantry rotation and ECG triggering on image quality

The aim of this study was to determine if ECG triggering and a shorter acqu isition time of 0.5-s rotation decrease cardiac motion artifacts of thin-se ction CT of the lung. In 25 patients referred for thin-section thoracic CT, 1-mm thin-section slices were performed with a scanning time of 0.5 s with ECG gating, 0.5 s and 1 s during the diastolic phase of the heart at five identical anatomical levels from the aortic arch to lung basis. At each ana tomical level and for each lung, cardiac motion artifacts were graded indep endently on a four-point scale by three readers. Patients were divided into two groups according to their heart rate. A four-way analysis of variance was used to assess differences between the three modalities. Mean cardiac m otion artifacts scores were rated 1.23 +/- 0.02, 1.47 +/- 0.02, and 1.79 +/ - 0.02, at 0.5 s with ECG gating, 0.5 s without ECG gating, and 1 s, respec tively (F = 139, p < 0.0001). At the four anatomical levels below the aorti c arch, the left lung scores were greater than the right lung score for the three modalities. For the modality 0.5 s with ECG gating no difference of scores was found between patients grouped according to their cardiac freque ncy. The 0.5-s gantry rotation with or without ECG gating scans reduces car diac motion artifacts on pulmonary thin-section CT images and is mainly ben eficial for the lower part of the left lung.