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CHAPTER

Diagnostic Imaging

RADIOGRAPHY

Myra Barrett and elizaBeth acutt

Radiography is the most frequently used imaging EQUIPMENT
modality in the equine patient, and even with the growth
of advanced imaging technologies, radiography remains Knowledge of radiography equipment including X‐ray
a first‐line screening tool for equine musculoskeletal machines, detector systems, film processing equipment,
disease. image viewing devices, and accessory equipment is neces­
Advances in technology have made digital radiogra­ sary for obtaining good‐quality diagnostic radiographs
phy mainstream and accessible to most practitioners. safely. The reader should also be aware of the advantages
While the many developments in technology have and disadvantages of the different equipment options
resulted in more accessible and easily shared, high‐ that are available for veterinary practice.
quality images, the fundamental principles of radiology
remain the same as the days of screen‐film radiography. X‐ray Machines
The veterinarian must be familiar with the basic instru­
mentation of an X‐ray machine and the radiation safety The basic control settings of an X‐ray machine, the
techniques commonly practiced in radiography. An milliamperage (mA), exposure time, and kilovoltage
understanding of the normal equine radiographic anat­ potential (kVp) are located on the control panel and
omy, basic radiographic interpretation principles, exam­ may be changed to vary the exposure (Figure 3.1).
ination techniques, and post‐capture image processing is Milliamperage is the tube current and refers to the quan­
essential to perform diagnostic radiographic studies. tity of electrons flowing per second in the X‐ray tube.
Too often, knowledge of these basic concepts is Ultimately, it determines the quantity of X‐rays emitted
overlooked, resulting in inferior radiographic examina­ from the X‐ray tube.
tions. Poor‐quality radiographs may result in erroneous Exposure time is an important variable in equine radi­
diagnoses and conclusions. ology. Because of problems related to patient and detector
This section is not intended to comprehensively cover movement, exposure time should be 0.1 second or less, if
the physics behind the different radiographic systems; possible, for equine limb examinations. The use of elec­
however, a review of the various technologies available in tronic timers is recommended for accurate timing when
veterinary medicine including types of digital imaging the exposure is less than 0.1 second. For equine radiology,
systems and image display and storage is included. More an electronic timer with two‐step exposure button is
detailed information is available elsewhere. 22,29,31,49,50,56,63 desirable. The first step warms the X‐ray tube filament;
48
The normal equine radiographic anatomy with standard the exposure is made in the second step. The two‐step
projections used in the diagnosis of lameness in addition exposure button prolongs the X‐ray tube life. Because
to the common radiographic signs of bone and soft tissue exposure time (in seconds) multiplied by the milliamper­
response to different pathologic processes are also age equals milliamperage‐seconds (mAs), radiation
discussed. exposure is directly related to milliamperage‐seconds.

Adams and Stashak’s Lameness in Horses, Seventh Edition. Edited by Gary M. Baxter.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/baxter/lameness
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