Digital Radiography: Selected Topics

ISBN-13: 9781468450705 / Angielski / Miękka / 2012 / 208 str.

J. G. Kereiakes; C. G. Orton; S. R. Thomas

Opis

Digital radiography is a general term describing any projection radiological system in which the image exists in digital form at some stage between acquisition and viewing. In an earlier form, radiographic films were dig itized in an attempt to enhance and redisplay information of interest. The field has evolved to its current state, in which X-ray signals are detected electronically, converted to digital form, and processed prior to being recorded and displayed. A primary goal of digital radiography is the re moval of interfering effects from secondary structures in an image, so that clinically significant details can be displayed with enhanced visibility. The achievement of this goal involves many parameters, including con trast agents, subtraction techniques, processing techniques, filtering tech niques, system noise, and quantitative aspects. It is the purpose of this book to present material by noted individuals in the field covering several of the above topics. The authors acknowledge the secretarial and editorial assistance of Mrs. Helen Taylor and the editorial assistance of Mrs. Ruth McDevitt. James G. Kereiakes Stephen R. Thomas Cincinnati, Ohio Colin G. Orton Detroit, Michigan ix Contents 1. DIGITAL RADIOGRAPHY: OVERVIEW B. A. Arnold, 1. G. Kereiakes, and S. R. Thomas 1. Introduction . . . . . . . . . 1 2. Point-Scanned Detector Systems 3 3. Line-Scanned Detector Systems 4 4. Area Detector Systems 5 4.1. Stimulable Phosphors 5 4.2. Selenium Detectors ."

Spis treści

1. Digital Radiography: Overview.- 1. Introduction.- 2. Point-Scanned Detector Systems.- 3. Line-Scanned Detector Systems.- 4. Area Detector Systems.- 4.1. Stimulable Phosphors.- 4.2. Selenium Detectors.- 4.3. Digital Video Systems.- 5. Comparison of X-Ray Imaging Systems.- 6. Summary.- References.- 2. Image Processors for Digital Angiography: Algorithms and Architectures.- 1. Introduction.- 2. Algorithms for Handling and Processing of Digitized Angiograms.- 2.1. Image Data Compression.- 2.2. Image Enhancement by Digital Subtraction.- 2.3. Image Enhancement and Extraction by Digital Filtering of Pixeldensograms.- 2.4. Image Analysis.- 2.5. Algorithm Structures.- 2.5.1. Point Operations.- 2.5.2. Filtering of Pixeldensograms.- 2.5.3. Two-Dimensional Processing.- 2.6. Data Structure.- 3. Processor Architectures for Digital Angiography.- 3.1. General-Purpose Computer with Video Interface.- 3.2. Special-Purpose Processors for Real-Time Subtraction.- 3.3. Special Computer Systems for Digital Angiography.- 3.4. Experimental Systems for Digital Angiography.- 4. Conclusions and Discussion.- References.- 3. Temporal Integration Processing Techniques.- 1. Introduction.- 2. Theory.- 2.1. The Conventional DSA Reference.- 2.2. Temporal Integration.- 2.3. Matched Filtering.- 3. Implementation.- 4. Applications.- 4.1. SNR Improvement.- 4.2. X-Ray Exposure Reduction.- 4.3. Contrast Dose Reduction.- 4.4. Hybrid Subtraction SNR Recovery.- 5. Discussion.- References.- 4. Noise Analysis in Digital Radiography.- 1. Introduction.- 2. Sources of Noise in Digital Systems.- 3. Conspicuity and Image Subtraction.- 4. Theoretical Analysis.- 4.1. Detail SNR.- 4.2. Detectability Threshold and Image Gray Levels.- 4.3. Contrast-Detail Relationship for Threshold Detectability.- 4.4. Detector Quantum Efficiency.- 4.5. Minimum Patient Exposure for Detection.- 4.6. Sample Calculations for Digital Angiography.- 4.7. Summary of Theoretical Analysis.- 5. Experimental Measurements of Noise.- 5.1. SNR.- 5.2. Scattered Radiation and Detail SNR.- 5.3. Wiener Power Spectra.- 5.4. Phantom Tests of Iodine Detectability.- 6. Summary.- References.- 5. Quantitative Aspects of Image Intensifier-Television-Based Digital X-Ray Imaging.- 1. Introduction.- 2. System Description.- 2.1. X-Ray Generator and Tube.- 2.2. Object.- 2.3. Image Intensifier.- 2.4. Television Camera.- 2.5. Analog-to-Digital Converter.- 2.6. Image Acquisition Memory.- 2.7. Measurement of System Response.- 2.7.1. TV Camera Response.- 2.7.2. II-TV Response.- 2.8. System Spatial Resolution.- 3. Characterization of Physical Degradation Factors.- 3.1. Beam Hardening.- 3.2. X-Ray Scatter.- 3.3. Veiling Glare.- 4. Effect of Degradation Factors on Videodensitometric Volume Measurements.- 4.1. Absolute Volume Measurements.- 4.2. Relative Volume Measurements.- 5. Techniques for Reduction of Degradation Factors.- 5.1. Veiling Glare.- 5.1.1. Deconvolution of Lead Disk Images.- 5.1.2. Effects of Glare Deconvolution on Volume Measurements.- 5.2. X-Ray Scatter.- 5.3. Beam Hardening.- 6. Applications.- 6.1. Relative Volume Measurements.- 6.1.1. Measurement of Ventricular Ejection Fraction.- 6.1.2. Stenosis Measurement.- 6.2. Absolute Volume Measurements.- 7. Summary.- References.- 6. Recursive Filtering Techniques Applied to Digital Subtraction Angiography.- 1. Introduction.- 2. Temporal Filtering Theory.- 3. Noncardiac Clinical Results Using Recursive Filtering.- 4. Cardiac Applications.- References.- 7. Energy-Selective Radiography: A Review.- 1. Introduction.- 2. Apparatus for Energy-Selective Imaging.- 3. Decomposition of the Attenuation Coefficient.- 3.1. Intuitive Limits to Dimensionality.- 3.2. The Singular Value Decomposition.- 4. Conditions for Calculating Complete Energy-Dependent Information.- 4.1. Vector Space Descriptions of Mixtures and Line Integrals.- 4.2. Calculation of Line Integrals in Conventional Radiographic Systems.- 4.3. Complete Information Extraction in Energy-Selective Systems.- 5. Applications of Energy-Selective Imaging.- 5.1. Synthesized Monoenergetic Images.- 5.2. Selective Material Images.- 5.3. Generalized Projection Signal Processing.- 5.4. Computation for Energy-Selective Imaging.- 6. Analysis of Conspicuity and Noise.- 6.1. Statistics of Basis Coefficient Estimation.- 6.2. Basis Noise and the System’s Physical Properties.- 6.3. Noise Optimal Generalized Projections.- 6.4. Comparison of Noise in Conventional and Energy-Selective Systems.- 6.5. Conspicuity Enhancement.- 7. Conclusion.- References.