Optimizing iterative reconstruction for quantification of calcium hydroxyapatite with photon counting flat-detector...

Area of Science:

• Medical Imaging
• Radiology
• Cardiovascular Imaging

Background:

• Coronary artery calcium (CAC) scoring using computed tomography (CT) is a screening tool for coronary artery disease.
• Concerns exist regarding the radiation dose associated with CT CAC scoring.
• Photon counting detectors and iterative reconstruction (IR) offer potential for dose reduction.

Purpose of the Study:

• To evaluate the applicability of IR for CAC quantification using a photon counting flat-detector.
• To assess if IR preserves CAC scoring accuracy compared to traditional methods.

Main Methods:

• A cardiac phantom with calcium hydroxyapatite inserts was imaged using a photon counting flat-detector CT.
• Filtered back projection (FBP) and two IR algorithms with varying regularization strengths were applied.
• Air kerma, image quality parameters, and CAC quantification accuracy were compared.

Main Results:

• IR regularization strength significantly impacted CAC scores.
• CAC volumes and scores were most similar between FBP and IR when IR's spatial resolution matched FBP's.
• At the lowest radiation dose, FBP yielded more accurate CAC volumes and scores than IR.

Conclusions:

• IR can achieve comparable CAC scores and volumes to FBP if regularization is optimized for spatial resolution.
• IR did not demonstrate improved CAC scoring accuracy at low radiation doses in this study.
• Further research is needed to optimize IR for low-dose CAC scoring.