Author: Ahad Ollah Ezzati, Xiaoyu Hu, Xun Jia, Youfang Lai, Kai Yang, Yuncheng Zhong 👨🔬
Affiliation: Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Massachusetts General Hospital, Johns Hopkins University 🌍
Purpose: Contrast-enhanced breast cone-beam computed tomography (bCBCT) provides high-resolution, 3D imaging of breast tissues with improved differentiation between normal and abnormal tissues. Current bCBCTs with energy integrating detectors (EID) suffers from electronic noise, especially given the strict dose limit for breast imaging. This ultimately limits the minimum contrast agent concentration that can be detected in lesions. bCBCT with a photon counting detector (PCD) can potentially offer better resolution and low noise. This study performs a comprehensive Monte Carlo (MC) simulation of bCBCT imaging process and a head-to-head comparison of bCBCTs with the two detectors.
Methods: We employed VICTRE toolkit to generate a realistic breast phantom within a 14 cm-diameter breast with 0.25mm3 voxel size and 80% fat fraction. Spiculated lesions with 2-6 mm mean diameters were inserted in the breast phantom. Each lesion was inserted in 3 different locations with 0.25-6 mg/ml of iodine concentration. At 60 kVp, 360 projections were simulated with a total number of 3.2×1012 photons, corresponding to ~4 mGy mean glandular dose, comparable to a two-view mammography. For EID-bCBCT, electronic noise was added to the projections. bCBCT images were reconstructed with FDK algorithm. Overall image quality and contrast enhanced lesion detection performance were evaluated.
Results: EID-bCBCT images had higher noise due to electronic noise. Both imaging methods showed cupping artifacts resulting from X-ray scatter and beam hardening, with EID-bCBCT displaying slightly more pronounced artifacts, attributed to more severe beam hardening. Image noise standard deviation was 0.057 for EID-bCBCT and 0.04 cm-1 for PCD-bCBCT. PCD-bCBCT improves the contrast to noise ratio of enhanced tumor by factor of 1.5-4 with respect to EID-bCBCT, depending on the contrast concentration.
Conclusion: PCD-bCBCT improves the detection of contrast enhanced lesions with respect to conventional EID-bCBCT.