[Protection of eye lens in computed tomography--dose evaluation on an anthropomorphic phantom using...

The lens of an eye is a particularly radiosensitive organ. This study investigates two different materials for eye shielding during CT scanning, i. e. a commercially available bismuth protector and a newly developed material for eye shielding, comprised of an alloy of Bi/Sb/Gd/W.

The radiation dose during head CT scanning was measured using thermoluminescence dosimeters and an anthropomorphic Alderson-RANDO phantom. A radiation dose reduction was compared to two shielding materials and to the condition without any eye shielding. The effect of gantry angulation that excludes the eyes from beam path was also investigated. Radiation dose measurements were validated using a Monte-Carlo simulation. For this simulation we used the EGSsnr code system, and a new application CTDOSPP was developed for simulation of the computed tomography examination. Eight radiologists evaluated the diagnostic quality of the images.

Dose measurements and Monte-Carlo simulations are in good agreement. If the eye shields are placed in the primary beam path, bismuth eye shielding and the new material reduce the dose by up to 38 % and 48 %, respectively. Angling the gantry causes an 88 % reduction in radiation dose. All shielding materials generate beam hardening artifacts located close to the protector, but the artifacts do not spread into the brain.

The application of eye shields during CT examination of a head causes a significant reduction in radiation dose. The new protector material shows a significantly higher dose reduction in contrast to the commercially available bismuth shield. The best protection from radiation dose can be attained using gantry angulation.