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298 Tasks for the Veterinary Assistant

1. Manual dipping tank processing, or
2. Automatic processor, or
3. Digital processing
I. Maintain X‐ray log

Introduction to Diagnostic fairly expensive. The computed radiograph (CR)

Imaging system utilizes a reusable phosphor plate inside a cas-
sette that is sensitive to radiation but not to light. The
plates are positioned and imaged like the silver halide
Diagnostic imaging covers a broad range of tests used to cassettes, using the traditional radiography machine.
help a veterinarian determine an illness or condition: After exposure the plate is loaded into a laser scanner
radiography, ultrasound, computed tomography (CT), which projects the digital image to a computer and
magnetic resonance imaging (MRI), and positron resets the plate for the next image. The plates are
emission tomography (PET) scans. more sensitive than film which allows for a slightly
Radiology is the study of how radiographs are pro- lower radiation dose, reducing radiation exposure to
duced and used for diagnosing diseases or conditions staff and patient.
of the body. A radiograph is the “photographic” record Both systems project digital images on a computer
or image of a body part on film or in a digital format. monitor in about 30–90 seconds. If the radiograph
Radiograph is preferable to the term X‐ray; however, needs to be repeated because of movement or misalign-
they are used interchangeably. Radiography is the act ment it can be done immediately. The image can also
of exposing a film to radiation and a radiographic study be altered by increasing or decreasing the contrast and
is a series of radiographs consisting of two or more gray scale on the computer, which is called windowing.
views with or without contrast media. Contrast media is These radiographs can be sent via the internet to a spe-
used to show the presence of lesions or items that would cialist, which is an example of telemedicine, rather
normally not show up on a radiograph. A manual radio- than sending them in the mail. The digital images are
graph utilizes a silver halide film inside a cassette. It is stored in the patient’s medical record using the prac-
X‐ray and light sensitive and placed under a patient, tice’s management software whereas traditional films
exposed to radiation, and then developed using chemi- are stored in a filing cabinet so they can be retrieved as
cals to fix the image to the film. Digital radiography needed.
utilizes radiation, but the image is digitalized and sent
to a computer for viewing. More on this later in the
chapter. Advanced Imaging
The specialized equipment used in radiography
includes a view box which is a box with a light on the Technologies
inside and a white opaque surface on the outside. The
manual radiograph is placed in front of the light source In addition to radiography, there are advanced imaging
which illuminates the film for clearer viewing. Cassettes technologies that provide different visualizations of body
hold film for manual radiographs or have sensors built structures within a patient: diagnostic ultrasound, CT,
in that capture the digital image. Calipers are used to MRI, and PET scans. Ultrasonography produces sound
measure the body part of a patient; those measurements waves that interact with body tissues. The images pro-
are then used to set the settings on the radiography duced are echoes converted to electronic signals and
machine. processed by a computer. CT scans use X‐rays and yield
images along a single plane. MRI produces images along
three planes using strong magnetic and radio waves that
Digital Radiography are converted to images by a computer. Both CT and
MRI can use intravenous gadolinium‐based contrast
Radiation is utilized to produce an image; however, media that highlights specific structures. Each procedure
instead of film the image is changed to a digital requires anesthetizing or heavily tranquilizing the
format. There are two types of digital systems used to patient throughout as the patient must be absolutely still
produce a digital radiograph. Digital radiography for the duration of the procedure, which can be quite
(DR) uses a detector that transforms radiation into an lengthy. PET scans are rarely found in veterinary prac-
electrical charge which is sent to a unit that processes tices, primarily being used in teaching hospitals or
the image. DR requires specialized equipment that is research.