Cone-beam breast computed tomography with a displaced flat panel detector array.

Area of Science:

• Medical Imaging
• Radiological Physics
• Cone-Beam Computed Tomography

Background:

• Cone-beam computed tomography (CBCT), especially for breast imaging (CBBCT), faces challenges with image artifacts from photon scatter and high patient radiation dose.
• Reducing scatter and dose is crucial for improving CBBCT efficacy and safety.

Purpose of the Study:

• To investigate the detector displacement technique (asymmetric detector or "extended view" geometry) for reducing scatter artifacts and patient dose in CBBCT.
• To evaluate the impact of this technique on image quality metrics, including contrast-to-noise ratio (CNR) and contrast-to-noise ratio per unit of dose (CNRD).

Main Methods:

• Utilized Monte Carlo simulations and experimental measurements on a CBBCT laboratory scanner with PMMA phantoms simulating breast tissue.
• Acquired projection data using an asymmetrically positioned detector covering half the field of view, combined with a half beam collimator.
• Assessed image quality by analyzing contrast, noise, CNR, CNRD, and spatial resolution.

Main Results:

• The asymmetric detector technique reduced scatter-to-primary ratio by approximately 50% and mitigated cupping artifacts.
• A maximum 50% reduction in absorbed dose was observed, with CNR potentially decreasing but CNRD remaining comparable or higher due to reduced scatter.
• An estimated 12% average dose reduction for CBBCT at constant CNR was calculated for average uncompressed breasts.

Conclusions:

• CBCT reconstructions using the displaced detector technique and half beam collimation effectively reduce scatter artifacts and patient dose.
• While noise may increase and CNR decrease, the CNRD values are maintained or improved, indicating a favorable trade-off.
• The technique also presents potential benefits in reduced apparatus cost and improved data transfer speed.