Non-Planar Narrow-Beam CT: Near Scatter-Free, High-Resolution Breast Imaging at Screening Mammography Doses. 📝

Author: Peymon Ghazi 👨‍🔬

Affiliation: MALCOVA Inc. 🌍

Abstract:

Purpose: To develop a near scatter‐free breast CT imaging system that expands coverage of the posterior breast anatomy and enhances contrast resolution for solid masses and microcalcifications, while reducing radiation dose to a level comparable to screening mammography.

Methods: We present a new imaging geometry, Non‐Planar Narrow‐Beam CT. The system is composed of two primary assemblies: a dynamic Fluence Modulator (collimator) and a photon‐counting line detector. During each projection, these assemblies operate in lockstep, creating a moving narrow beam that sweeps across the entire fan angle. The source and detector are decoupled and mounted on independently movable structures, allowing the source to be elevated above the patient plane for enhanced posterior breast coverage. The line detector operates in Time‐Delay‐Integration (TDI) mode with a line rate of 21,000 lines/second and a 0.1 mm detector element size. Its rotation speed is synchronized to the TDI rate to prevent motion blur.

Results: Non‐Planar Narrow‐Beam CT minimizes scattered radiation acquisition, achieving a scatter‐to‐primary ratio below 0.05 for a medium‐sized breast phantom. At focal spot sizes of 0.1 mm and 0.3 mm, the system achieves spatial resolutions of 7.1 and 5.8 lp/mm at 10% of maximum MTF, and 5.8 and 4.1 lp/mm at 50% of maximum MTF, respectively, at the field‐of‐view center—with minimal degradation toward the corners. The mean glandular dose for an average‐sized, average‐density breast is 4.2 mGy. Depending on their location, the system provides an average SDNR improvement of 115% and 62% for 250 µm microcalcifications relative to cone‐beam and spiral CT, respectively. Additionally, the non‐planar geometry improves posterior coverage by 5.2 cm compared to a planar CT system.

Conclusion: This work demonstrates the development, implementation, and characterization of a physical non‐planar narrow‐beam CT prototype that achieves high spatial resolution and minimizes scatter contamination, while operating at mandated radiation dose caps.