Florian Dammann MD, Presenter: Nothing to Disclose

Martin Heuschmid MD, Abstract Co-Author: Nothing to Disclose

Assen Koitschev, Abstract Co-Author: Nothing to Disclose

Ingo Baumann, Abstract Co-Author: Nothing to Disclose

Claus Detlef Claussen MD, Abstract Co-Author: Nothing to Disclose

To develop a quality optimized low dose examination protocol for paranasal imaging using a 16-row spiral CT.

An Alderson-Rando phantom was scanned with a 16-row multislice CT (MSCT) applying a variety of settings for table feed, reconstruction increment, and kernel. The collimation was 0.75 mm, rotation time 0.5 s, and the effective mAs value was 20. Secondary coronary reformations were calculated from all datasets. The best protocol was selected to examine 50 patients who were routinely submitted to biplane paranasal CT. A transversal scan was performed on the MSCT, whereas a conventional single-row spiral CT was used for the complementary coronal scan. The image quality of direct coronals scans was compared with coronal reformations of the 16-row CT. The presence of artifacts (dental amalgam, stair step, sunburst artifacts) as well as the depiction of critical anatomical landmarks (cribroid plate, ethmoidal septae, orbital wall) and the overall subjective image impression was rated on a 5 point scale.

AA 16x0.75/12/0.4 mm setting for collimation, table feed and increment in combination with sharp kernels (H60s, B50f) provided the best image quality of 16-row CT datasets as the basis for coronary reformations. The reformations did not show any notable stair step artifacts. In 44% slight sunburst artifacts were visible but did not affect the diagnostic value. In contrast, clinically relevant impairment of the image quality was noted in 14% of the direct coronal scans due to the superposition of dental metal artifacts. The depiction of anatomic landmarks was rated significantly superior for 16-row CT coronary reformations (4.88) as compared with direct coronal scans (3.99). When directly comparing both modalities the image quality of 16-row CT reformations were judged superior in 48% of all patients including clinically additional information in 17%.

A low dose examination protocol for paranasal imaging with a 16-row multi-slice CT is proposed. The reduced slice thickeness of 0.75 mm enables secondary reformations without notable stair step artifacts. The image quality is superior when compared with conventional directly coronal paranasal CT scans.

Dammann, F, Heuschmid, M, Koitschev, A, Baumann, I, Claussen, C, 16-Row Spiral CT for Paranasal Sinus Imaging.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4406432.html