Analytical Study of Radiation Dose to the Eye Lens in CT Brain Protocols and the Impact of Optimised Scanning Techniques at Teaching Hospitals in Kaduna State

The crystalline lens is highly radiosensitive and subject to a substantially reduced dose threshold for cataract induction following ICRP 2011 recommendations, making eye lens dose monitoring and optimisation in CT brain scanning clinically relevant for frequent CT recipients in North West Nigerian teaching hospitals. This study analytically evaluates eye lens radiation doses in routine CT brain protocols and measures the impact of optimised scanning techniques at teaching hospitals in Kaduna State. A phantom-based comparative study uses an anthropomorphic head phantom with Gafchromic film and OSLD dosimeters placed at the lens position to measure eye lens doses under standard and optimised CT brain protocol conditions (gantry tilt, z-axis restriction, tube current modulation, kVp reduction) at Ahmadu Bello University Teaching Hospital and Barau Dikko Teaching Hospital. Eye lens dose values under standard and optimised protocols are compared using paired t-tests in SPSS, with image quality assessed using automated noise and resolution metrics. Available CT eye lens dose literature from North West Nigeria identifies absence of gantry angulation practice as the primary avoidable eye lens dose contributor, with estimated dose reductions of 30 to 50 percent achievable through simple tilt optimisation. The ICRP 2011 revised eye lens dose limit and European Society of Radiology eye lens dose reduction guidance provide the analytical reference. Findings are expected to confirm significant eye lens dose reduction achievable with optimised techniques without diagnostic image quality compromise. Recommendations address mandatory gantry tilt protocols and routine eye lens dose monitoring at Kaduna State CT brain departments. Keywords: eye lens dose, CT brain, dose optimisation, Kaduna State, North West Nigeria.