System Optimization of Spectral Breast CT Based On An Energy-Resolved Photon-Counting Si Strip Detector: A Simulation Study
H Cho1*, h ding1, F Masaki1, W Barber2, J Iwanczyk2, S Molloi1, (1) Department of Radiological Sciences, Unviersity of California, Irvine, CA,(2) Dx-ray Inc., Northridge, CATH-A-103-8 Thursday 8:00AM - 9:55AM Room: 103
Purpose: To determine the optimal design parameters for a high resolution spectral breast CT system based on an energy-resolved photon counting Si strip detector for breast imaging.
Methods:A simulation package was developed for a spectral breast CT system. The focal spot size (100 to 300 μm), magnification (1.1 to 1.4), motion blurring and detector pixel size (intrinsic pixel pitch and 4 x 4 pixel binning) were considered to optimize the system design. Simulations were conducted using single slice fan beam geometry at 60 kVp with 2 mm Al filter. The system modulation transfer functions (MTFs) were calculated from reconstructed image of a 10 μm diameter tungsten wire. The performance of the system with optimal design parameters was evaluated with a simulated breast phantom. A 14 cm diameter cylindrical phantom made of breast tissue with 20% glandularity was used to simulate an average-sized breast. The soft tissue lesions and microcalcifications were simulated with spheres of glandular tissues (1, 2, and 4 mm in diameter) and hydroxyapatite (100 to 250 μm in diameter), respectively.
Results:The spatial frequencies at 10 % of the maximum MTF was calculated to be 1.6 lp/mm and 6.4 lp/mm with and without a 4 x 4 pixel binning, respectively. The optimal system magnification was estimated to be 1.2. There was minimal improvement in system MTF when the x-ray tube focal spot size was changed from 300 to 100 μm. In the simulated breast phantom image, 100 μm microcalcifications can be clearly identified and the soft tissue contrast-to-noise ratio was improved with separate image processing, where 4 x 4 pixel binning was used at a dose level of 6 mGy.
Conclusion:The simulation results show that the proposed system can potentially detect micro-calcifications and soft tissue lesions with a dose level equivalent to that of a standard two-view mammography.