Kazushi Yokomachi RT, Presenter: Nothing to Disclose

Chikako Fujioka RT, Abstract Co-Author: Nothing to Disclose

Eiji Nishimaru RT, Abstract Co-Author: Nothing to Disclose

Masao Kiguchi RT, Abstract Co-Author: Nothing to Disclose

Minoru Ishifuro, Abstract Co-Author: Nothing to Disclose

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

For emergency or pediatric head CT scans, a simplified- (pillow-type made of hard sponge) instead of a dedicated head holder may be used if it is difficult to fix the head. However, the radiation dose with the simplified head holder may be increased due to radiation absorption by the bed when the automatic exposure control (AEC) system is used. In this phantom study we compared the radiation dose delivered with the dedicated- and the simplified head holder.

We used a dedicated- and a pillow-type head holder made of hard sponge (simplified head holder). We set a 20-cm-diameter cylindrical phantom made of water-equivalent material and an anthropomorphic head phantom in the head holders and then scanned them five times with a 64-detector CT scanner (VCT, GE). We performed step-and-shoot and helical scanning with AEC; the noise index was set to 2.8. We measured the radiation dose with fluorescent glass dosimeters in the head phantom and the image noise at 5 sites in the cylindrical phantom; all values were averaged.

On step-and-shoot scans the mean image noise with the dedicated- and the simplified head holder was 3.30±0.05[SD] and 3.20±0.05, respectively. On helical scans they were 3.00±0.09 and 2.88±0.03, respectively. There was no statistically significant difference (p=0.02 and 0.04, Student’s t-test). The radiation dose with the dedicated- and the simplified head holder was 58.6 and 70.4 mGy, respectively, for step-and-shoot scanning and 41.8 and 49.0 mGy, respectively, for helical scanning. The doses were significantly higher with the simplified head holder at both step-and-shoot- and helical scanning (p<0.01 and <0.01).

We recommend the use of the dedicated head holder for head scanning with AEC because the radiation dose was lower than with the simplified head holder.

The image noise at head CT scanning with the simplified- and the dedicated head holder is comparable and the radiation dose is lower with the dedicated head holder.

Yokomachi, K, Fujioka, C, Nishimaru, E, Kiguchi, M, Ishifuro, M, Awai, K, Radiation Exposure at Head CT: Comparison of the Radiation Dose at Head CT with a Dedicated and a Simplified Head Holder.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12023315.html