Dose reduction for CT coronary calcium scoring with a calcium-aware image reconstruction technique: a phantom study

Area of Science:

• Medical Imaging
• Radiology
• Image Reconstruction

Background:

• Computed tomography (CT) imaging is crucial for cardiovascular assessment, but accurate calcium quantification can be challenging due to variations in imaging parameters.
• Standard CT reconstruction techniques may yield inconsistent CT numbers for calcifications when tube voltage is altered, impacting diagnostic accuracy.
• A calcium-aware reconstruction technique has been developed to address tube voltage-dependent CT numbers for calcium.

Purpose of the Study:

• To evaluate the dose reduction potential of a calcium-aware reconstruction technique.
• To assess the consistency of CT numbers and Agatston scores for calcium using this novel technique across different patient sizes and tube voltages.
• To determine the impact of automatic tube voltage selection on radiation dose and image quality.

Main Methods:

• A cardiothoracic phantom simulating three patient sizes was scanned with calcium inserts of varying density and size.
• Tube voltage was manipulated manually and automatically, with tube current adapted to maintain image quality.
• Data were reconstructed using standard (Qr36) and calcium-aware (Sa36) techniques, analyzing CTDIvol, noise, CT numbers, and Agatston scores.

Main Results:

• Automatic tube voltage selection led to CTDIvol reductions of 12-22% across phantom sizes.
• The calcium-aware technique demonstrated significantly more consistent CT numbers (up to 11% difference) compared to the standard technique (up to 64% difference) across varying tube voltages.
• Agatston scores showed improved consistency with the calcium-aware technique (up to 8% deviation) versus the standard technique (up to 40% deviation).

Conclusions:

• The calcium-aware reconstruction technique ensures stable CT numbers and comparable calcium scores when tube voltage varies.
• Automatic tube voltage optimization offers a substantial radiation dose reduction of up to 22%.
• The study highlights the limitations of the current Agatston scoring method, particularly for small, low-density calcifications.