and to keep exposures according to the ALARA philosophy. Technologists must refer to the safety codes of their respective countries for more detailed information. Two such examples of these guidelines on radiography and fluoroscopy state that selection and use of the best possible exposure technique factors should keep the dose ALARA without compromising image quality. Additionally, high‐kVp techniques reduce the dose to the patient.
Procedural factors for minimizing dose to personnel are wide and varied and technologists must work within the ALARA philosophy to accomplish this task. Two such examples of recommendations to ensure personnel dose reduction are that (i) only essential personnel must be present in an x‐ray room during the exposure and (ii) technologists must remain in the control booth during radiographic exposures and must wear protective aprons when the situation makes this impossible. Another significant recommendation relates to shielding, a radiation protection action and design criterion that is intended to protect patients, personnel, and members of the public. Shielding includes specific area shielding (protecting radiosensitive organs) and protective barriers (walls) positioned between the source of radiation and the individual. This type of shielding, for example, is specifically intended to protect personnel and members of the public from unnecessary radiation.
Optimization of radiation protection
The ICRP optimization framework refers to optimization as keeping the dose ALARA and not compromise the diagnostic quality of the image. Therefore, optimization includes image quality and radiation dose.
The journal Radiation Protection Dosimetry dedicated a special issue to optimization strategies in medical imaging for fluoroscopy, radiography, mammography, and CT. Several studies identified at least four important requirements for dose and image‐quality optimization research. First, patient safety must be a priority in any study. Second, the level of image quality needed for a particular diagnostic task must be determined. The third requirement involves acquiring images at various exposure levels from high to low and in such a manner that accurate diagnosis can still be made, and finally, use reliable and valid methodologies for the dosimetry, image acquisition, and evaluation of image quality using human observers, keeping in mind the nature of the detection task.
An interesting study utilizing these elements of dose optimization is one by Seeram and colleagues published in Radiologic Technology in 2016. The purpose was to investigate a technique for optimizing radiation dose and image quality for a CR system. The researchers measure the entrance skin doses for phantom models of the pelvis and lumbar spine imaged using the vendor's recommended exposure settings (i.e. the reference doses) as well as doses above and below the vendor's recommended settings for both body parts. Images were assessed using visual grading analysis (VGA). The phantom dosimetry results revealed strong positive linear relationships between dose and milliampere seconds (mAs), mAs and inverse EI, and dose and inverse EI for both body parts. The VGA showed that optimized values of 16 mAs/EI = 136 for the anteroposterior (AP) pelvis and 32 mAs/EI = 139 for the AP lumbar spine did not compromise image quality. Selecting optimized mAs reduced dose by 36% compared with the vendor's recommended mAs (dose) values. The study concluded that optimizing the mAs and associated EIs can be an ED management strategy.
Bibliography
1 1. American Society of Radiologic Technologists (2016). Radiography Curriculum. Albuquerque, NM: American Society of Radiologic Technologists.
2 2. Bushong, S. (2017). Radiologic Science for Technologists. St Louis, MO: Elsevier.
3 3. Bushberg, J.T., Seibert, J.A., Leidholdt, E.M. Jr., and Boone, J.M. (2012). The Essential Physics of Medical Imaging, 3e. Philadelphia, PA: Wolters Kluwer/Lippincott Williams & Wilkins.
4 4. Seeram, E. and Brennan, P. (2017). Radiation Protection in Diagnostic X‐Ray Imaging. Burlington, MA: Jones and Bartlett Learning.
5 5. Seeram, E. (2016). Computed Tomography: Physical Principles, Clinical Applications, and Quality Control. St Louis, MO: Elsevier.
6 6. Wolbarst, A.B., Capasso, P., and Wyant, A. (2013). Medical Imaging: Essentials for Physicians. Hoboken, NJ: Wiley.
7 7. Seeram, E. (2020). Rad Tech's Guide to Radiation Protection, 2e. Hoboken, NJ: Wiley.
8 8. Seeram, E. (2019). Digital Radiography: Physical Principles and Quality Control. Singapore: Springer.
2 Digital radiographic imaging systems: major components
FILM‐SCREEN RADIOGRAPHY: A SHORT REVIEW OF PRINCIPLES
DIGITAL RADIOGRAPHY MODALITIES: MAJOR SYSTEM COMPONENTS
Flat‐panel digital radiography
Picture archiving and communication system
The purpose of this chapter is to present a general overview of the digital radiographic imaging systems used in diagnostic radiology, by describing briefly, the general system components of each of the modalities in an effort to lay the foundations needed for a good understanding of how each component works to create images and protect not only patients but technologists as well. The more technical details will be reviewed in later chapters on each of the modalities. First, it is important to review the essential principles of film‐screen radiography (FSR) in order to fully understand the rationale for the emergence of digital imaging modalities.
FILM‐SCREEN RADIOGRAPHY: A SHORT REVIEW OF PRINCIPLES
The overall system components of FSR are shown in Figure 2.1. These include the x‐ray generator, the x‐ray tube, a radiographic table, the image receptor, a chemical processing unit, and a light view‐box. A film‐based image is created as follows:
