Influence of phantom design on evaluation metrics in photon counting spectral head CT: a simulation study

Area of Science:

• Medical Imaging
• Radiological Physics

Background:

• Accurate iodine quantification in head CT is vital for diagnosis and treatment.
• Traditional CT methods face limitations like radiation exposure and artifacts.
• Photon-counting detectors (PCDs) offer improved spectral resolution but require new evaluation methods.

Purpose of the Study:

• To assess the impact of phantom design on iodine quantification accuracy in spectral head CT.
• To compare conventional cylindrical phantoms with anatomically realistic elliptical phantoms.
• To evaluate the performance of different material decomposition methods.

Main Methods:

• Simulations of a photon-counting spectral CT system.
• Comparison of cylindrical and elliptical phantoms with skull simulants.
• Evaluation of image-based and projection-based material decomposition techniques.

Main Results:

• Image-based methods showed higher sensitivity to phantom design, with cylindrical phantoms overestimating performance.
• Projection-based material decomposition demonstrated greater consistency and accuracy across phantom designs.
• Anatomically realistic phantoms revealed performance differences not apparent with cylindrical phantoms.

Conclusions:

• Phantom design, particularly the inclusion of skull-mimicking materials, critically influences quantitative accuracy.
• Cylindrical phantoms may lead to an overestimation of spectral head CT system performance.
• Anatomically realistic phantoms are essential for clinically relevant evaluation of spectral photon-counting head CT.