Radiation Protection of the Eye Lens During Brain CT Imaging Using a Barium Sulphate Vinyl Shield

Head CT examinations may result in significant and unnecessary exposure to the lens of the eye. The International Commission of Radiological Protection (ICRP) has estimated the threshold for detectable opacities in the lens from a single brief exposure to be 0.5 2Gy and the threshold for visual impairment (cataract) to be 5Gy. The lens dose for sequential CT scanning of the brain with the orbit in the primary beam has been reported to be approximately 50mGy which is significantly lower than these dose thresholds. However, the ICRP have recently suggested that the lens of the eye may be more radiosensitive than previously considered and that, because of the uncertainty concerning this risk, recommend particular emphasis on optimisation. Optimisation of lens exposure through the use of bismuth and lead shielding materials has been widely investigated. The aim of this study was to investigate the use of a new shielding material, barium sulphate vinyl (Kemmetech Ltd, Kent, UK), with respect to eye lens dose reduction and significance of generated image artefacts during computed tomography (CT) of the brain. The vinyl is stated to be an inexpensive, latex free and inert material. These properties enable the shield to be totally disposable and avoid the need for decontamination between patients.