Eye-Lens Dose Reduction using Region of Interest (ROI) Attenuators in Neuroimaging

Area of Science:

• Medical Physics
• Radiology
• Ophthalmology

Background:

• Neuro-interventional procedures carry a high risk of lens dose, potentially leading to cataractogenesis.
• Standard beam collimation reduces lens dose but also limits the field of view (FOV).

Purpose of the Study:

• To investigate the potential for lens-dose reduction using Region of Interest (ROI) imaging.
• To quantify the magnitude of dose reduction achievable with ROI techniques.

Main Methods:

• EGSnrc Monte Carlo simulations were performed using the Zubal head phantom.
• Lens dose was calculated for varying gantry angulations and head shifts for both large and small FOVs.
• ROI imaging was simulated using attenuators with varying transmission to assess dose reduction.

Main Results:

• Lens dose reduction with ROI imaging increases with Lateral Angulation (LAO), being highest for lateral and lowest for posterior-anterior projections.
• An ROI attenuator with a 5x5 cm field and 20% transmission reduced lens dose by ~75% for lateral projections compared to a full 10x10 cm FOV.
• Reductions of 30-40% were observed for posterior-anterior projections under similar conditions.

Conclusions:

• ROI imaging with attenuators substantially reduces ocular lens dose across various procedural angles and patient positions.
• This technique allows for peripheral visualization within a larger FOV while effectively lowering radiation exposure to the lens.