Digital techniques have the potential to improve the practice of radiology but they also risk the overuse of radiation. The main advantages of digital imaging, i.e. wide dynamic range, post processing, multiple viewing options, and electronic transfer and archiving possibilities, are clear but overexposures can occur without an adverse impact on image quality. In conventional radiography, excessive exposure produces a black film. In digital systems, good images are obtained for a large range of doses. It is very easy to obtain (and delete) images with digital fluoroscopy systems, and there may be a tendency to obtain more images than necessary. In digital radiology, higher patient dose usually means improved image quality, so a tendency to use higher patient doses than necessary could occur. Different medical imaging tasks require different levels of image quality, and doses that have no additional benefit for the clinical purpose should be avoided. Image quality can be compromised by inappropriate levels of data compression and/or post processing techniques. All these new challenges should be part of the optimisation process and should be included in clinical and technical protocols. Local diagnostic reference levels should be re-evaluated for digital imaging, and patient dose parameters should be displayed at the operator console. Frequent patient dose audits should occur when digital techniques are introduced. Training in the management of image quality and patient dose in digital radiology is necessary. Digital radiology will involve new regulations and invoke new challenges for practitioners. As digital images are easier to obtain and transmit, the justification criteria should be reinforced. Commissioning of digital systems should involve clinical specialists, medical physicists, and radiographers to ensure that imaging capability and radiation dose management are integrated. Quality control requires new procedures and protocols (visualisation, transmission, and archiving of the images).
1. INTRODUCTION 1. Purpose of this document 1.2. Introduction 1.3. History 1.4. What is digital radiology? 1.5. Differences between intrinsic digital modalities and digital radiology 1.6. Digitised conventional films 1.7. Plain radiography 1.8. Digital fluoroscopy 1.9. Comparison of digital and non-digital techniques 1.10. Image quality and exposure levels in digital radiology 1.11. Further aspects of digital radiology 2. PATIENT DOSE AND IMAGE QUALITY IN DIGITAL RADIOLOGY 2.1. Relationship between image quality (or diagnostic information) and patient dose in digital radiology 2.2. What image quality (or diagnostic information) is needed for a medical imaging task? 2.3. Actions that affect patient dose 2.4. Practical advice for managing patient dose and image quality 2.5. Training needs for radiologists and radiographers 3. REGULATORY ASPECTS AND QUALITY MANAGEMENT 3.1. Radiation protection principles 3.2. Quality control and image management 3.3. Electrical safety inspection 3.4. Diagnostic reference levels 3.5. Auditing dose levels in digital imaging 3.6. Deterministic injuries 3.7. The DICOM standard 4. ICRP RECOMMENDATIONS FOR DIGITAL RADIOLOGY APPENDIX A. THE FUNDAMENTALS AND ADVANTAGES OF DIGITAL SYSTEMS A.1. Introduction A.2. Basic terminology A.3. Imaging chain of digital x-ray systems A.4. Image processing A.5. Image quality and imaging performance A.6. Integrated dosimetry tools APPENDIX B. PATIENT DOSIMETRY: QUANTITIES AND UNITS B.1. Absorbed dose B.2. Kerma B.3. Mean organ dose B.4. Equivalent dose B.5. Effective dose B.6. Dose-area product B.7. Backscatter factor B.8. Skin dose APPENDIX C. OUTLINE FOR GENERAL EDUCATION AND TRAINING ASPECTS IN DIGITAL RADIOLOGY 5. REFERENCES