Andrew Chun-Che Yen MD, Presenter: Nothing to Disclose

Ann N. C. Leung MD, Abstract Co-Author: Consultant, Actelion, Ltd

Margaret Lin MD, Abstract Co-Author: Nothing to Disclose

Justus E. Roos MD, Abstract Co-Author: Nothing to Disclose

Jarrett Rosenberg PhD, Abstract Co-Author: Nothing to Disclose

Dominik Fleischmann MD, Abstract Co-Author: Speakers Bureau, Siemens AG Speakers Bureau, Bracco Group Research support, General Electric Company

Less cardiac-related lung motion artifacts have been reported with ECG synchronization on early generation CT scanners. With the advent of 64 slice CT, the acquisition time of a routine helical chest CT has decreased to the point where such artifacts appear negligible. At the same time, prospective ECG triggering (PT) can be employed in a single breath-hold and without increased radiation dose. We sought to compare these two techniques with respect to image quality and artifacts in thoracic 64 slice CT.

Fifty consecutive patients were randomized into either PT (n=24) or helical (n=26) scanning. All exams were acquired on a GE VCT with 40mm detector coverage. PT (Cardiac Snapshot) was acquired with a 0.35 sec rotation time. Helical scans were acquired with a pitch of 1.375 and a 0.5 sec rotation time. All patients received comparable doses of radiation. Contiguous 1.25 mm axial images were reconstructed and independently scored by 3 blinded readers for motion artifact in each slice using a 3-point scale. For analysis, the bilateral lungs were divided into 6 zones, 3 on each side, and compared between groups using ordinal logistic regression. Each reader then evaluated contiguous 2 mm coronal and sagittal images for the presence of 1) gross respiratory motion artifact, given longer breath holds with PT; 2) offset > 2mm to assess integrity of PT reconstruction; and 3) stitch artifact. Analysis was performed using the Chi-square test.

PT showed less motion artifact than helical technique in all lung zones, with the greatest effect seen in the right upper lung zone (p < .0001). The left mid and lower lung zones also showed significantly less artifacts (p < .0001). On coronal and sagittal images, stitch artifact was seen almost exclusively with PT (p << .0001). No significant differences were demonstrated with respiratory motion artifact or offset > 2mm (p = .67 and p = .11 respectively).

With 64 slice CT, PT remains superior in lung image quality compared to helical technique. Although stitch artifact is pervasive with PT in the non-axial planes, neither slab offset nor respiratory motion artifact is a dominant feature.

PT reduces but doesn’t eliminate cardiac-related lung motion artifact in thoracic CT. Helical scanning is comparable in image quality and obviates longer breath holds and resources associated with PT.

Yen, A, Leung, A, Lin, M, Roos, J, Rosenberg, J, Fleischmann, D, Prospectively ECG-triggered Axial versus Helical CT of the Thorax: Effect on Image Quality.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9014874.html