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Digital Radiography
1
Robert Cole and Adrien-Maxence Hespel 2
1 Department of Clinical Sciences, College of Veterinary Medicine, Auburn, AL, USA
2 College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA

1.1 Introduction to Digital not follow proper radiation safety protocols. Human hands
Radiography should never be in the primary beam even when lead
gloves are worn. Personnel should not crop hands out of an
Digital radiography (DR) involves the electronic measure- image prior to sending it to a viewing station. Care should
ment of the pattern of X‐ray transmission through the be taken to correctly position patients to avoid excessive
patient with subsequent conversion of this electronic retakes and unnecessary exposure to radiation.
transmission into a digital file that is viewed on a computer The following sections will give a brief overview of DR.
workstation. The term DR is often applied incorrectly to This will include the components of the digital file, digital
any image that is generated electronically. Although the radiographic hardware, comparisons of digital versus
process is similar to a digital photograph, obtaining a digi- analog imaging, and image storage.
tal photograph of radiographic film is not DR. DR involves
the use of two major types of technology: computed radiog-
raphy (CR) and DR. 1.2 Digital Image File
The advantages of DR over conventional film radiogra-
phy include financial, image quality, and technical bene- The digital radiographic image is a computer file that con-
fits. In general, there is a large capital expense when tains the pattern of X‐ray transmission from the patient. This
making the transition to DR. However, there will be subse- file is commonly stored in a DICOM format. DICOM is an
quent financial savings on films and processing equip- acronym for Digital Imaging and Communications in
ment/maintenance. Less physical space is required for Medicine. This format was derived for consistency and to
archiving stored images and there is no requirement for a ensure connectivity between imaging devices [1,2], and con-
dark room resulting in square footage savings in the hospi- tains embedded information, including the manufacturer of
tal. Digital images are capable of displaying a wide range of the device, date, and time of image acquisition, patient
attenuation of tissues on the same image. This will trans- demographics, acquisition parameters, operator identifiers,
late into fewer images needed compared to analog (conven- and various other image information needed for medicole-
tional) film. In addition, DR has greater tolerance to gal reasons [2,3]. This added information is referred to as the
exposure factors, resulting in fewer retakes due to subopti- DICOM header (Figure 1.1) and helps to ensure security and
mal technique. prevent fraud. Some less expensive digital equipment may
Patient throughput is often increased with DR compared produce images in other formats, but these are typically infe-
to analog systems. The digital radiograph can be manipu- rior for viewing and their use is discouraged for diagnostic
lated (post processing, e.g. zooming, gray‐scale adjust- interpretation due to liability concerns.
ments) with the viewing software to maximize diagnostic A digital image is composed of picture elements, termed
quality. Lastly, digital images can be viewed at any location pixels. Pixels are arranged in rows and columns into a geo-
in the hospital or transmitted off‐site for rapid interpreta- metric matrix (Figure 1.2). Each pixel has a specified
tion or referral. The main disadvantage with direct digital shade of gray. The more pixels in a digital file, the larger
format is the tendency of personnel holding the patient to the matrix size and ultimately the larger the file size [4].

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.