Radiation Exposure and Image Quality in X-Ray Diagnostic Radiology

Transcription

1 Horst Aichinger Joachim Dierker Sigrid Joite-Barfuß Manfred Säbel Radiation Exposure and Image Quality in X-Ray Diagnostic Radiology Physical Principles and Clinical Applications Second Edition Springer

2 Contents Part I Introduction 1 Principles of X-Ray Imaging Projection Radiography and Fluoroscopy Computed Tomography 5 References 7 2 Structure of the Book Part II: Physical Principles Part III: Clinical Applications Part IV: Supplement CD-ROM 10 References 10 Part II Physical Principles 3 Production and Measurement of X-Rays Production Measuring Photon Spectra of Diagnostic X-Rays X-Ray Spectrometer Measuring Corrections for Detector Influences Preparing for Calculations with X-Ray Spectra 19 References 19 4 Interaction of Photons with Matter Exponential Law of Attenuation Interaction Processes Compton Effect Photoelectric Effect Rayleigh Scattering Total Coefficients for Attenuation, Energy Transfer and Energy Absorption 25 References 31 5 Radiation Field and Dosimetric Quantities General Radiation Field Characteristics Characteristics of the Radiation Field in Projection Radiography and Fluoroscopy Characteristics of the Radiation Field in Computed Tomography 35 xi

3 xii Contents 5.4 Dosimetric Quantities for the Description of Radiation Exposure Effect of Filtration 37 References 39 6 Penetration of X-Rays Attenuation by the Patient Simulation of Attenuation by the Patient Basis of Exposure Tables Attenuation by the Patient Support and the Components of the Imaging Device Patient Support Anti-scatter Grid Ionisation Chamber Geometry Important Differences Between Over-Table and Under-Table X-Ray Units Characteristics of Computed Tomography 51 References 51 7 Scattered Radiation Measurement of Scattered Radiation Properties of Scattered Radiation Radiography and Fluoroscopy Mammography Computed Tomography Techniques in Radiography and Fluoroscopy to Reduce Scattered Radiation at the Image Receptor Air-Gap Technique Slot Technique Anti-scatter Grid Quantities for the Description of the Characteristics of Grids Derived Quantities for the Description of the Efficiency of Anti-scatter Grids Application Limits for Focused Grids 63 References 65 8 Image Receptors Characteristics of Phosphor Screens Digital Image Receptors and CT Receptors Automatic Exposure Control Direct Technique (in Connection with Film-Screen Systems) Fluoroscopy and Indirect Technique (in Connection with an Image Intensifier) Digital Imaging (Using Flat Panel Detectors) Computed Tomography Image Receptor Dose/Dose Rate (System Dose/Dose Rate) Analogue Image Receptors Digital Image Receptors 8 I References 82 9 Image Quality and Dose Characteristics of Image Receptors Contrast Sharpness Noise 92

4 XIII 9.5 Signal-to-Noise Ratio Detective Quantum Efficiency Other Image-Quality Figures Dependence of Image Quality on Exposure Parameters Detection of Covered Structures in the X-Ray Image 99 References 99 Part III Clinical Applications 10 Evaluation of Dose to the Patient Specific Dosimetric Quantities Used for Patient-Dose Evaluation Quantities Influencing Patient Dose Initial Dosimetric Quantities for the Estimation of Organ Doses Determination of the Initial Dosimetric Quantities Radiography Fluoroscopy Mammography Computed Tomography Estimation of Organ Doses from the Initial Dosimetric Quantities Estimation of Organ Doses H T by the Use of Conversion Factors Estimation of the Absorbed Dose to an Organ Dorg by the Use of Tissue-Air Ratios or Relative Depth Doses Estimation of Effective Dose Uncertainties in Patient-Dose Estimation 117 References Scattered Radiation Influence on Image Quality and Dose The Various Types of Anti-scatter Grids Employment of Grids in Paediatrics Employment of Grids in Mammography Employment of Grids in Digital Radiography Cone-Beam Computed Tomography (CBCT) 129 References Optimisation of Image Quality and Dose General X-Ray Diagnostics Angiography Mammography Computed Tomography 142 References 143 Part IV Supplement 13 X-Ray Spectra General X-Ray Diagnostics Mammography Interaction Coefficients Elements Compounds and Mixtures 188

5 xiv Conte nts 15 Characteristics of the Primary Radiation Beam General X-Ray Diagnostics Mammography Characteristics of the Imaging Radiation Field General X-Ray Diagnostics Mammography Miscellaneous Penetration and Absorption of X-rays X-ray Detectors Image Quality Figures Patient Dose Estimation General X-Ray Diagnostics Mammography 298 Index 301