Daniela Muenzel, Presenter: Nothing to Disclose

Peter B. Noel MS, Abstract Co-Author: Nothing to Disclose

Franziska Dorn, Abstract Co-Author: Nothing to Disclose

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

Ernst J. Rummeny MD, Abstract Co-Author: Nothing to Disclose

Armin Michael Huber MD, Abstract Co-Author: Nothing to Disclose

To evaluate the effect of a small field of view for step-and-shoot coronary computed tomography angiography (CCTA) with a wide detector on craniocaudal z-coverage per scan step, image quality and individual radiation exposure.

53 consecutive patients underwent prospectively ECG-gated CCTA at a 256-slice CT scanner (Brilliance iCT, Philips) using a standard step-and-shoot protocol with a mean transverse FOV > 250 mm (large wedge filter) and an alternative step-and-shoot-protocol with a mean FOV < 250 mm (medium wedge filter). Craniocaudal z-coverage was determined on coronal multiplanar reformations (MPR) of source images. Image noise, signal-to-noise ratio and qualitative image parameters were assessed on transverse slices. Individual radiation dose exposure was estimated from the dose length product.

Overall contrast opacification of the coronary arteries was considered to be excellent without significant differences between the large and small FOV protocol. Mean SNR was 28.4 and 24.6 and mean CNR was 18.9 and 19.7 in both groups, respectively. Diagnostic image quality was achieved with both protocols in 91.3 % (large FOV) and 89.9 % (small FOV) of coronary segments. A smaller FOV leads to an increase of craniocaudal coverage of a single CT scan step with reduction of the overlapping volume (r=–0.88; p<0.0001). Radiation dose was significantly lower (p<0.05) using a small FOV instead of a large FOV protocol with a DLP of 229 vs. 285 mGy*cm, respectively.

The use of a small FOV for step-and-shoot technique CCTA with a wide detector CT scanner leads to an increased z-coverage due to reduced overlap between single adjacent scan volumes. Radiation dose is decreased without negative impact on image quality.

The use of a small FOV for step-and-shoot coronary CTA increases z-coverage per scan volume and decreases radiation dose without negative impact on image quality.

Muenzel, D, Noel, P, Dorn, F, Dobritz, M, Rummeny, E, Huber, A, Coronary CT Angiography in Step-and-Shoot Technique with 256-slice CT: Impact of Field of View on Image Quality, Craniocaudal Coverage, and Radiation Exposure.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9003727.html