Radiology
Certain radiographic features are
used to determine the nature of an object seen on the x-ray film. These
features are used to determines both normal anatomy as well as pathologic
alterations and should be evaluated for every structure examined on the
radiograph. These characteristics include size, shape, density, position, and
architecture.
Density is the mass of a structure
per unit volume. It is a major factor in determining the amount of radiation
that various object absorb.
- Objects that absorbs most or all the radiation impinging upon them are termed radiopaque. The photons do not pass through these object and therefore neither reach nor expose the x-ray film. These structures produce a clear area on the film, which appear white or light gray when viewed.
- Object that permit most of the radiation to pass through them are termed radiolucent and produce a black or dark gray image on the x-ray film.
In terms of radiographic density,
the animal may be considered as being composed of five components:
These elements can be ranked easily
in order of decreasing subject density when their composition is considered.
White
image on radiograph
Metallic object, the most dense,
have a high atomic number and absorb nearly all the x-ray photons; this prevents
the photons from reaching the film (or digital detector) and causes a white
image on the radiograph. Various metallic foreign objects produce this
radiographic density. They include surgical device as intramedullary pins,
metallic sutures or hemostatic clips, minerals such as uroliths, and
barium-containing compounds.
Dynamic cross pin repair of the
fracture in a rabbit.
Tibia/fibula fracture with external skeletal fixator in a chinchilla
Cystic calcium oxalate caculus. Calciuria in male drawf rabbit
Calciuria caused by hypercalcemia
from diet in male rabbit.
Nearly
white or light gray image
Bone, which is composed of elements
having a somewhat lower atomic number and an organic matrix that absorbs less
radiation, produced a nearly white or light gray white.
Whole body skeleton of ferret
Shade
of gray on film
Muscle, blood, and various organs,
which are composed predominately of water and absorb approximately equal
amounts of radiation, produce comparable shades of gray on film. Therefore,
these objects are described as fluid or soft-tissue dense. This shade of gray is darker than of the
bone.
Viscera of thorax and abdomen of
rabbit
Viscera of thorax and abdomen of
ferret
Viscera of thorax and abdomen of
ferret
Darker
image on the film
Fat and cartilage
absorb even less radiation than fluid or soft-tissue-dense elements and produce
a darker gray image on the film
Fat pads ventral, abdominal wall
(white arrows) of male Siamese cat.
Fat-dense structure (arrows)
between the gastrocnemius muscles and the deeper muscles of the tibia.
Black
image
Air or gas absorbs the least amount
of radiation and produce a black image.
The caecum is usually seen in the
right hemiabdomen and contains varying amounts of gas and ingesta.
Several small bowel segments of female ferret are abnormally dilated with gas and fluid
References:
Burk, R.L., and Daniel, A.F., 2003. Small Animal Radiology and Ultrasonography: A diagnostic Atlas and Text. Saunders.
Silverman, S., and Tell, L.A., 2005. Radiology of Rodents, rabbit, and Ferrets: An atlas of Normal Anatomy and Positioning. Elsevier, Saunders.
Quensenberry, K.E., and Carpenter, J.W., 2004. Ferrets, Rabbits, and Rodents Clinical Medicine and Surgery 2nd Eds. Saunders.
Komentar
Posting Komentar