Srinivasan Mukundan, Presenter: Nothing to Disclose

Donald Paul Frush MD, Abstract Co-Author: Nothing to Disclose

Terry T. Yoshizumi PhD, Abstract Co-Author: Nothing to Disclose

Greta Toncheva, Abstract Co-Author: Nothing to Disclose

Giao Nguyen, Abstract Co-Author: Nothing to Disclose

Jeffrey Marcus, Abstract Co-Author: Nothing to Disclose

Carolyn R. Lowry, Abstract Co-Author: Nothing to Disclose

Kenny C Lai MD, Abstract Co-Author: Nothing to Disclose

Jesse Riley, Abstract Co-Author: Nothing to Disclose

Meredith Moore, Abstract Co-Author: Nothing to Disclose

Emily Kloeblen, Abstract Co-Author: Nothing to Disclose

Herbert Fuchs, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

To measure radiation dose reduction to the eye as a result of a bismuth shield.

Using a 16-slice scanner (GE Healthcare) both axial brain (5.0 mm thick slices; 140 kVp, 14 mAs) and helical craniofacial (2.5 mm thick slices; 170 mAs: 140, 120, and 100 kVp) pediatric protocols were performed. Eye shields were fabricated using a 1 cm thick foam covered double layer of bismuth impregnated latex (1.7 g of bismuth/cm2; F & L Products). Only the region medial to the orbital rims were shielded. Radiation doses were measured in a 5 year-old anthropomorphic phantom (CIRS Inc, Norfolk, VA) containing 25 metal oxide semiconductor field effect transistor (MOSFET) detectors. Each mAs/kVp combination was imaged 3 times and averaged with and without the eye shield. Each MOSFET detector had been individually calibrated at each CT energy with an ionization chamber. A linearity test was performed to verify actual dose response to prescribed instrument mA setting for the range 80 to 300 mA on the scanner used for this study.

The mAs linearity test demonstrated less than 1% variation from predicted values (r2=0.995) for the MDCT scanner. Reduction in dose as a percentage of the unshielded dose for the helical craniofacial acquisitions at 100, 120 and 140 kVp was 41%, 42% and 39%, respectively. The decrease in dose for the axial acquisition was 39% at 140 kVp. At this kVp the eye dose was 4.6 cGy without shields and 2.7 cGy with shielding. Although image quality was not evaluated in this study, no obvious change in image quality was observed.

There is up to 42% reduction in eye dose with the use of the bismuth eye shield. Absence of perceptible loss of image quality is similar to our prior experience with breast shields for pediatric patients undergoing chest CT. Continued development of size-based eye shields for the pediatric patient population is warranted based on our results.

Mukundan, S, Frush, D, Yoshizumi, T, Toncheva, G, Nguyen, G, Marcus, J, Lowry, C, Lai, K, Riley, J, Moore, M, Kloeblen, E, Fuchs, H, et al, , The Use of a Bismuth Shield to Decrease Radiation Dose to the Eye in Children: An Anthropomorphic Phantom Study.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4414700.html