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To compare the dose and image quality of three methods for reducing the radiation dose to the eye at head computed tomography (CT): bismuth shielding, organ-based tube current modulation (TCM), and global reduction of the tube current.

An anthropomorphic head phantom was scanned under six conditions: (a) without any dose reduction techniques (reference scanning); (b) with one bismuth eye shield; (c) with organ-based TCM; (d) with reduced tube current to yield the same dose reduction as one bismuth shield; (e) with two layers of bismuth shields; and (f) with organ-based TCM and one bismuth shield. Dose to the eye, image noise, and CT numbers in the brain region were measured and compared. The effect of increasing distance between the bismuth shield and eye lens was also investigated.

Relative to the reference scan, the dose to the eye was reduced by 26.4 …