Using an orbit shield during volume perfusion CT: is it useful protection or an obstacle?

Area of Science:

• Medical Imaging
• Radiology
• Computed Tomography

Background:

• Orbit shielding is used in computed tomography (CT) to reduce radiation dose.
• The impact of in-plane orbit shielding on CT perfusion image quality and artifact formation is not fully understood.

Purpose of the Study:

• To evaluate image quality and artifacts from in-plane orbit shielding during CT perfusion.
• To assess the effectiveness of the iterative metal artifact reduction (iMAR) algorithm in reducing these artifacts.

Main Methods:

• Retrospective analysis of 28 CT perfusion examinations from 20 patients using orbit shields.
• Categorization of artifact types and extent in source images and perfusion maps.
• Comparison of original images with those processed using the iMAR algorithm.

Main Results:

• All source images exhibited orbit shielding-related artifacts, with 85.7% extending to the posterior fossa.
• Perfusion maps showed artifacts in 92.8% of scans, primarily incorrect color coding, often reaching the posterior fossa.
• The iMAR algorithm increased artifact extent in 93% of perfusion maps without improving image quality.

Conclusions:

• In-plane orbit shielding during whole-brain CT perfusion generates significant artifacts, rendering shield-level areas undiagnosable.
• The use of orbit shields in this context is not recommended.
• Alternative methods for radiation dose reduction should be explored.