Topogram-based tube current modulation of head computed tomography for optimizing image quality while protecting the...

Area of Science:

• Radiology
• Medical Physics
• Radiation Protection

Background:

• Repeated head CT scans elevate the risk of radiation-induced lens opacification.
• Ocular radiation exposure is a concern in head and neck CT imaging.

Purpose of the Study:

• To evaluate the impact of CT eye shielding and topogram-based tube current modulation (TCM) on lens radiation dose.
• To assess the effect of these techniques on the image quality of nasal and periorbital regions.

Main Methods:

• An anthropomorphic phantom underwent CT scans with fixed or automatic tube current modulation.
• Lens radiation dose was measured using Gafchromic films with and without orbital shielding.
• Image quality was assessed via signal-to-noise ratio (SNR) and contrast-noise ratio (CNR), with artifact evaluation by CT specialists.

Main Results:

• Barium sulfate and bismuth-antimony shields with fixed tube current reduced lens radiation dose by 22.0% and 35.6%, respectively.
• Topogram-based TCM reduced artifacts from shields and improved SNR (21.6%) and CNR (7.2%).
• Combined TCM and shielding reduced lens doses by 12.2% (barium sulfate) and 27.2% (bismuth-antimony).

Conclusions:

• Topogram-based TCM effectively mitigates artifacts from bismuth-antimony shields used for lens radioprotection.
• This combination enhances SNR in periorbital tissues and nasal bone imaging.
• CT eye shielding and TCM offer a dual benefit of reduced lens dose and maintained/improved image quality.