Medical Physics and Biophysics

 

Background Computed tomography (CT) scan of the brain is a good method for investigating cranial lesions. Given that chronic accumulation of oxidative stress in the eyes induces carcinogenesis and cataract, we aimed to protect the eyes during CT scans by understanding the effects of non-latex barium sulfate shields on image quality and radiation dose to lens of the eye.

 

Materials & Methods: A human head phantom was scanned either by a 16-slice CT scanner at a fixed tube current of 300 mAs or by a 256-slice Dual-Source CT (DSCT) scanner with automatic tube current modulation. For the assessment of image quality

and radiation dose, various tube voltages were applied with or without eye shielding under clinical settings. Pencil-shaped ionization chambers were implemented for measuring air kerma close to the eye. CT images at slices that exibit zygomatic, orbital and nasal bones were used for the calculation of signal-to-noise and contrast-to-noise ratios.

 

Results: The signal-to-noise and contrast-to-noise ratios of DSCT images maintained relatively consistent with the increasing number of barium sulfate shield(s). On the contrary, the ratios of 16-slice CT images deviated or elevated along with the shield increment, leading to greater reduction in image quality upon the application of one shield. Similarly, radiation dose decreased with decreasing tube voltage and the increasing number of shields. The application of two shields on the 16-slice CT scan

reduced up to 52% of dose close to the eye.

 

Conclusion: Results of this study indicate that tube current modulation should be considered for acquiring better image quality with eye shielding