Takanori Masuda, Presenter: Nothing to Disclose

Yoshinori Funama PhD, Abstract Co-Author: Nothing to Disclose

Naoyuki Imada, Abstract Co-Author: Nothing to Disclose

Takayuki Oku, Abstract Co-Author: Nothing to Disclose

Satoshi Inada, Abstract Co-Author: Nothing to Disclose

Kazuo Awai MD, Abstract Co-Author: Research Grant, Toshiba Medical Sysmtes Research Grant, Hitachi Medical Corporation Research Grant, Bayer AG Research Consultant, DAIICHI SANKYO Group Research Grant, Eizai Ltd

As children are more susceptible to radiation-induced damage than adults it is necessary to use a lower radiation dose at pediatric CT. An  effective reduction methods is the selection of large beam-shaping filters. We compared the radiation dose with small and large beam-shaping filters at different tube voltages and document  the usefulness of large beam-shaping filters at pediatric CT.

We used a 15-cm diameter cylindrical water phantom and inserted a 10-cm long pencil ionization chamber into the phantom center. Helical CT acquisitions were on a 64-detector CT scanner (VCT, GE Healthcare). The tube voltage was 80-, 100-, or 120 kVp; the beam pitch and gantry rotation time were 1.375 and 0.4 sec. The tube current was automatically set with automatic exposure control (noise index: 10 HU). The field-of-view (FOV) was 15- and 50 cm with small and large beam-shaping filters, respectively. Scans with a 50-cm  FOV were reconstructed at a 15-cm display FOV. The radiation dose and image noise (SD of the CT number) were compared on all reconstructed images.  

The radiation dose with the small beam-shaping filter was 2.08 mGy at 80-, 2.07 mGy at 100-, and 2.24 mGy at 120 kVp, respectively. With the large filter it was decreased to1.9, 1.94, and 1.77 mGy at 80-, 100-, and 120 kVp. At each tube voltage the radiation dose was lower with the large- than the small filter. The image noise was 8.42 HU at 80-, 8.34 HU at 100-, and 8.26 HU at 120 kVp with the small filter, respectively; with the large filter it was 8.52, 8.23, and 8.45 HU. There was no significant difference in image noise between small and large beam-shaping filters at all tube voltages (p>0.05).

The use of a large beam-shaping filter facilitates, radiation dose reductionsns by 10-20% without image quality degradation at pediatric CT.

Large beam-shaping filters help to reduce the radiation dose at 64-detector CT, eliminating the need for investments in new technology.

Masuda, T, Funama, Y, Imada, N, Oku, T, Inada, S, Awai, K, Usefulness of Large Beam-shaping Filters at Different Tube Voltages of Pediatric CT.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13016499.html