This book addresses radiation protection of patients having digital radiography and computed tomography (CT) examinations. The literature on radiation doses to patients from these two modalities have reported that the doses to patients are high. As a result, the radiology community has focused on methods and procedures to keep these doses as low as reasonably achievable (ALARA) without compromising the diagnostic image quality. This book outlines the motivation for dose optimization in radiology, identifies and describes the ICRP principle of optimization, outlines the factors affecting the dose in digital radiography and in CT, and identifies and describes strategies used in digital radiography and in CT for dose optimization. This book is intended for all those working in digital radiography and CT environments including radiological technologists, and radiographers, radiologists, biomedical engineering technologists, and student medical physicists. It is best used as a supplement to radiologic science textbooks, and in particular, radiation protection textbooks. Furthermore, this book lays the foundations for students and practitioners engaged in research on dose reduction and dose optimization in radiology. · Provides practical and useful methods for optimization of doses from digital radiography and CT · Describes the International Commission on Radiological Protection (ICRP) principle of optimization · Outlines the factors affecting the dose in digital radiography and in computed tomography

Optimization of dose in radiographic examinations is essential since the utilization of x-radiation is related to increased cancer risk. The study’s objective was to guide radiographers in ensuring best practices for common radiographic examinations of acceptable image quality in digital radiography while minimizing radiation doses that could result in harmful effects. The study comprised of three phases. The first phase involved 90 respondents between 20 to 60 years of age and weighing between 60-80 kilograms for the following examinations: anterior-posterior (AP) abdomen, AP or lateral lumbar sacral spine and posterior-anterior (PA) chest examinations. During this phase, the radiographic examination’s technical parameters for 30 radiographs for each examination were at the radiographers’ discretion. Kerma X_plus, DAP (dose area product) meter was utilized to evaluate the entrance surface dose (ESD), while CALDose_X 5.0 Monte Carlo was used to estimate the effective dose. The experimental study utilized an anthropomorphic phantom (PBU-50) and Leeds test object to compare the image quality. The best parameters were adapted to the patient’s AP thickness for the optimization study from the different technical parameters used in the experimental phase.

Radiation protection is a core element of radiologic technology programmes and daily practice alike. Rad Tech's Guide to Radiation Protection is a comprehensive yet compact guide designed to illuminate the extensive field of radiation protection for technologists, trainees, and radiology students. Organised into ten digestible chapters, the second edition of this popular book provides new discussions of dose factors in computed tomography, the debate concerning the use of the LNT model, Diagnostic Reference Levels (DRLs), dose optimization, and more. Written by a recognised expert in medical radiation sciences, this valuable guide: Helps students and technologists acquire the skills required to protect patients, personnel, and members of the public in the radiology department Reflects the most current standards for radiation protection, with references to relevant organisations and resources Covers basic radiobiology, sources of radiation exposure, dose management regulations and optimization, and more Presents essential information in a bulleted, easy-to-reference format Rad Tech's Guide to Radiation Protection is a must-have resource for student radiographers and radiology technologists, particularly those preparing for the American Registry of Radiation Technologist (ARRT) exams.

Digital imaging has long been available in radiology in the form of computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound. Initially the transition to general radiography was slow and fragmented but in the last 10-15 years in particular, huge investment by the manufacturers, greater and cheaper computing power, inexpensive digital storage and high bandwidth data transfer networks have lead to an enormous increase in the number of digital radiography systems in the UK. There are a number of competing digital radiography (DR) technologies, the most common are computer radiography (CR) systems followed by indirect digital radiography (IDR) systems. To ensure and maintain diagnostic quality and effectiveness in the radiology department appropriate methods are required to evaluate and optimise the performance of DR systems. Current semi-quantitative test object based methods routinely used to examine DR performance suffer known short comings, mainly due to the subjective nature of the test results and difficulty in maintaining a constant decision threshold among observers with time. Objective image quality based measurements of noise power spectra (NPS) and modulation transfer function (MTF) are the 'gold standard' for assessing image quality. Advantages these metrics afford are due to their objective nature, the comprehensive noise analysis they permit and in the fact that they have been reported to be relatively more sensitive to changes in detector performance. The advent of DR systems and access to digital image data has opened up new opportunities in applying such measurements to routine quality control and this project initially focuses on obtaining NPS and MTF results for 12 IDR systems in routine clinical use. Appropriate automatic exposure control (AEC) device calibration and a reproducible measurement method are key to optimising X-ray equipment for digital radiography. The uses of various parameters to calibrate AEC devices specifically for DR were explored in the next part of the project and calibration methods recommended. Practical advice on dosemeter selection, measurement technique and phantoms were also given. A model was developed as part of the project to simulate CNR to optimise beam quality for chest radiography with an IDR system. The values were simulated for a chest phantom and adjusted to describe the performance of the system by inputting data on phosphor sensitivity, the signal transfer function (STF), the scatter removal method and the automatic exposure control (AEC) responses. The simulated values showed good agreement with empirical data measured from images of the phantom and so provide validation of the calculation methodology. It was then possible to apply the calculation technique to imaging of tissues to investigate optimisation of exposure parameters. The behaviour of a range of imaging phosphors in terms of energy response and variation in CNR with tube potential and various filtration options were investigated. Optimum exposure factors were presented in terms of kV-mAs regulation curves and the large dose savings achieved using additional metal filters were emphasised. Optimum tube potentials for imaging a simulated lesion in patient equivalent thicknesses of water ranging from 5-40 cm thick for example were: 90-110kVp for CsI (IDR); 80-100kVp for Gd2O2S (screen /film); and 65-85kVp for BaFBrI. Plots of CNR values allowed useful conclusions regarding the expected clinical operation of the various DR phosphors. For example 80-90 kVp was appropriate for maintaining image quality over an entire chest radiograph in CR whereas higher tube potentials of 100-110 kVp were indicated for the CsI IDR system. Better image quality is achievable for pelvic radiographs at lower tube potentials for the majority of detectors however, for gadolinium oxysulphide 70-80 kVp gives the best image quality. The relative phosphor sensitivity and energy response with tube potential were also calculated for a range of DR phosphors. Caesium iodide image receptors were significantly more sensitive than the other systems. The percentage relative sensitivities of the image receptors averaged over the diagnostic kV range were used to provide a method of indicating what the likely clinically operational dose levels would be, for example results suggested 1.8 μGy for CsI (IDR); 2.8 μGy for Gd2O2S (Screen/film); and 3.8 μGy for BaFBrI (CR). The efficiency of scatter reduction methods for DR using a range of grids and air gaps were also reviewed. The performance of various scatter reduction methods: 17/70; 15/80; 8/40 Pb grids and 15 cm and 20 cm air gaps were evaluated in terms of the improvement in CNR they afford, using two different models. The first, simpler model assumed quantum noise only and a photon counting detector. The second model incorporated quantum noise and system noise for a specific CsI detector and assumed the detector was energy integrating. Both models allowed the same general conclusions and suggest improved performance for air gaps over grids for medium to low scatter factors and both models suggest the best choice of grid for digital systems is the 15/80 grid, achieving comparable or better performance than air gaps for high scatter factors. The development, analysis and discussion of AEC calibration, CNR value, phosphor energy response, and scatter reduction methods are then brought together to form a practical step by step recipe that may be followed to optimise digital technology for clinical use. Finally, CNR results suggest the addition of 0.2 mm of copper filtration will have a negligible effect on image quality in DR. A comprehensive study examining the effect of copper filtration on image quality was performed using receiver operator characteristic (ROC) methodology to include observer performance in the analysis. A total of 3,600 observations from 80 radiographs and 3 observers were analysed to provide a confidence interval of 95% in detecting differences in image quality. There was no statistical difference found when 0.2 mm copper filtration was used and the benefit of the dose saving promote it as a valuable optimisation tool.