Author: Stephen Araujo, Jing-Tzyh Alan Chiang, Cynthia E. Davis, Eri Haneda, Andrew Karellas, Thomas C Larsen, William Ross, Hsin Wu Tseng, Srinivasan Vedantham, Pengwei Wu 👨🔬
Affiliation: Department of Biomedical Engineering, The University of Arizona, GE Aerospace Research, Department of Medical Imaging, The University of Arizona, GE HealthCare Technology & Innovation Center 🌍
Purpose: To determine the system parameters and technique factors for image acquisition needed so that the mean glandular dose (MGD) of approximately 4.5 mGy is not exceeded for a recently developed, short-scan, upright-geometry, dedicated cone-beam breast CT (UBCT) system.
Methods: The UBCT system operates at 60 kV and provides flexible selection of angular range, number of projections, tube current, pulse-width, and changeable X-ray tube filtration. The X-ray tube filtration was varied (0.05–0.25 mm Cu + 1 mm Al) and measurements of half-value layer (HVL) and air kerma at isocenter were obtained. A semi-ellipsoidal phantom representative of an average breast was used to evaluate threshold size for lesion visibility. Images were reconstructed to 0.22 mm isotropic voxels using Feldkamp-Davis-Kress algorithm with Parker weights. For an average sized breast and for each spectrum, the normalized glandular dose coefficient (DgN) was determined from Monte Carlo simulations.
Results: Phantom studies indicate 210 projections over 210 degrees provided artifact-free reconstruction. This resulted in scan time of 16 seconds. MGD of 4.25 mGy was achieved using 0.25 mm Cu + 1 mm Al (HVL: 4.23 mm Al) at the midpoint of the mAs range. Phantom evaluation showed visualization of 1 mm mass-like lesion and 0.24-0.27 mm calcium carbonate specks at MGD of 4.25 mGy with this KV and beam quality.
Conclusion: This evaluation of the UBCT investigated system parameters and acquisition factors, and identified the appropriate settings needed to achieve a MGD that is comparable to standard two-view mammography. Phantom evaluations exceeded MQSA requirements indicating suitability for clinical trials.