Volume-of-interest imaging with dynamic fluence modulation using multiple aperture devices

Area of Science:

• Medical Imaging
• Radiological Physics

Background:

• Volume-of-interest (VOI) imaging in computed tomography (CT) aims to reduce radiation dose by limiting x-ray exposure to specific anatomical regions.
• Current VOI-CT implementation faces challenges in hardware for tailored fluence delivery and reconstruction of truncated projection data.

Purpose of the Study:

• To propose a general VOI-CT imaging framework utilizing multiple aperture devices (MADs) for improved dose efficiency and image quality.
• To address the interior tomography problem with truncated data using a modified penalized-likelihood reconstruction method.

Main Methods:

• A novel VOI-CT framework employing MADs, a beam filtration scheme with two binary x-ray filters.
• VOI localization via anterior-posterior (AP) and lateral scout views, with MAD motion trajectories optimized for fluence maximization within the VOI.
• Modified penalized-likelihood reconstruction for heavily truncated data using full-field scout views.

Main Results:

• Demonstrated feasibility of non-centered and elliptical VOI imaging in spine and lung applications.
• Achieved improved dose utilization and retained image quality compared to standard full-field CT protocols.
• Observed a 40% higher contrast-to-noise ratio (CNR) at the same dose compared to low-dose full-field scans, with 50% total dose reduction for equivalent CNR.

Conclusions:

• The proposed MAD-based VOI-CT framework offers a viable solution for dose reduction in CT.
• This approach effectively maintains or enhances image quality within the region of interest while significantly lowering radiation exposure.
• The method shows promise for clinical applications requiring targeted imaging, such as spine and lung examinations.