PART I Spectral, Dual-Energy CT: Clinical Perspective and Applications. Chapter 1 Spectral Imaging Technologies and Apps and Dual-Layer Detector Solution. Chapter 2 Clinical Applications of Dual Energy CT in Neuroradiology. Chapter 3 Clinical Perspective on Dual Energy Computed Tomography. PART II Spectral, Photon-Counting CT: Clinical Perspective and Applications. Chapter 4 Imaging of the Breast with Photon- Counting Detectors. Chapter 5 Clinical Applications of Photon-Counting Detector Computed Tomography. Chapter 6 Clinical Perspectives of Spectral Photon-Counting CT. Chapter 7 Spectral CT imaging using MARS Scanners. Chapter 8 Advances in and Uses of Contrast Agents for Spectral Photon Counting Computed Tomography. Chapter 9 Clinical Applications of Spectral Computed Tomography: Enabling Technique for Novel Contrast Developments and Targeting Imaging?. PART III Photon-Counting Detectors for Spectral CT. Chapter 10 X-ray Detectors for Spectral Photon Counting CT. Chapter 11 Spectral Performance of Photon-Counting X-Ray Detectors: How Well Can We Capture the Rainbow?. Chapter 12 Photon Counting Detectors Viewed as Non-Linear, Shift-Variant Systems. Chapter 13 Signal Generation in Semiconductor Detectors for Photon-Counting CT. Chapter 14 Application Specific Integrated Circuits (ASICs) for Spectral Photon Counting. Chapter 15 ChromAIX: Energy-Resolving Photon Counting Electronics for High-Flux Spectral CT. Chapter 16 Modelling the Imaging Performance of Photon Counting X-Ray Detectors. Chapter 17 Design Considerations for Photon Counting Detectors: Connecting Detector Characteristics to System Performance. Chapter 18 Photon Counting Detector Simulator: Photon Counting Toolkit (PcTK). PART IV Image Reconstruction for Spectral CT. Chapter 19 Image Formation in Spectral Computed Tomography. Chapter 20 Spectral Distortion Compensation for Spectral CT. Chapter 21 Novel Regularization Method with Knowledge of Region Types and Boundaries.