This study evaluates the impact of charge summing correction (CSC) on a Cadmium Telluride (CdTe) Photon Counting Detector in breast CT. A laboratory benchtop system that consists of a 0.1mm pixel pitch CdTe detector and a tungsten anode x-ray source. Images were acquired at 55kVp with 2mm Al external filtration under three different tube currents: 25, 100, and 200mA. Performance was assessed using contrast to noise ratio (CNR), modulation transfer function (MTF), noise power spectrum (NPS), and iodine quantification. Anticoincidence (AC) and single pixel (SP) modes were compared, both with signal-to-thickness calibration and FDK reconstruction. AC mode showed enhanced low-energy contrast and accurate iodine quantification, while SP mode had better CNR at low-energy. High x-ray fluence reduced AC mode uniformity, but not SP. Results suggest that CSC in breast CT improves iodine quantification but at the cost of increased noise in low-energy images. These effects are dependent on the studied system and operational parameters.
This study assesses the impact of charge summing correction (CSC) on a Cadmium Telluride (CdTe) Photon Counting Detector in breast CT. A laboratory benchtop system that consists of a 0.1 mm pixel pitch CdTe detector and a tungsten anode X-ray source. Images were acquired at 55 kVp with 2 mm Al external filtration under three different tube currents of 25, 100, and 200 mA at high and low energy thresholds. Performance was evaluated using contrast to noise ratio (CNR), modulation transfer function (MTF), noise power spectrum (NPS), and iodine quantification. Anticoincidence (AC) and single pixel (SP) modes were compared, both with signal-to-thickness calibration and FDK reconstruction. AC mode displayed enhanced low-energy contrast and accurate iodine quantification, while SP mode had better CNR at low-energy. High fluence reduced AC mode uniformity, but not SP. Results indicate that CSC in breast CT improves iodine quantification but with the tradeoff of increased noise in low-energy images. These effects are dependent on the studied system and operational parameters.
KEYWORDS: Bone, Radiomics, Data modeling, 3D microstructuring, 3D modeling, Computed tomography, Random forests, Modeling, Mahalanobis distance, Image resolution
We present a method to generate random synthetic trabecular bone microstructures sufficiently diverse for modeling a dataset of human femur bones. We further demonstrate that using a random forest regressor, we can also generate synthetic bones with prespecified microstructure metric values. This tunability allows for the user to generate synthetic datasets with arbitrary distributions of microstructure metrics that can be useful for modeling trabecular bone in other anatomical sites or disease states. Virtual imaging studies can be applied to simulate high resolution CT image data and used for developing new texture-based models for the evaluation of bone health.
Evaluation of bone fracture risk is important for the diagnosis and treatment of osteoporosis. Bone stiffness is a major factor in determining overall bone strength and fracture risk. With recent improvements in the spatial resolution of CT systems, it is possible to visualize bone microstructure and extract texture features. It is hypothesized that bone texture can be used to improve the assessment of bone strength compared to using bone mineral density (BMD) alone. In this work, we develop image analysis models for bone stiffness estimation utilizing deep learning (DL) features, radiomics features, and gradient structure tensors (GSTs) to estimate trabecular bone stiffness for high-resolution CT. We base our analysis on a dataset containing micro-CT images of 70 individual lumbar vertebrae. Ten trabecular bone ROIs were extracted from each vertebral body and their bone structure was segmented. The mechanical stiffness of each ROI was estimated using micro-finite element (μFE) analysis. Blur and correlated noise derived from clinical high-resolution CT systems were then added to the trabecular bone ROIs to generate simulated high-resolution CT images. A 3D residual network (ResNet) was trained to extract DL features to predict μFE-derived bone stiffness from the simulated CT images. Radiomics and GST features of bone ROIs were also computed for the same task. The prediction results for DL, radiomics, and GST features combined showed the best performance with a root mean square error (RMSE) of 2.646 N/μm and an R2 of 0.881. The performance of DL features alone was better than using BMD alone or using radiomic features alone. Additionally, incorporating orientation information from GST into the models resulted in improved accuracy. We demonstrate that μFEestimated mechanical properties of lumbar vertebral trabecular bone can be inferred from high-resolution CT images and that a combination of DL, radiomic, and GST features provides the highest prediction performance.
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