Dr Amit Kumar
DGCN COVAS, Palampur
In order that changes in outline, position,
and opacity be appreciated, it is essential
that the radiologist be familiar with the
radiologic appearance of normal structures
that is, radiologic anatomy.
If one is unfamiliar with the normal
appearance, one cannot appreciate
aberrations from it.
Because almost any structure can be rotated
through 360°, it would be virtually
impossible to become familiar with all the
possible projections that could be produced
from any given organ.
Consequently, standard projections of each
part of the body are used. These usually
consist of two projections made at right
angles to one another so that a three
dimensional impression is gained of the
structure under study. Agreed terms are
used to describe the standard projections.
The terminology used here is that
suggested by the Nomenclature Committee
of the American College of Veterinary
The committee recommended that
veterinary anatomic directional terms
should be those listed in the Nomina
Radiographic projections are described by
the direction in which the central ray of the
primary beam penetrates the body part of
interest-from the point of entrance to the
point of exit.
The meanings to be ascribed to the different terms are
Dorsal: The upper aspect of the head, neck, trunk,
tail, and cranial (anterior) aspects of the limbs from
the antebrachiocarpal (radiocarpal) and tarsocrural
articulations distally (downward). Dorsal also means
toward the back or vertebrae.
Ventral: The lower aspect of the head, neck, trunk,
and tail. Ventral also means toward the lower aspect
of the animal.
Cranial: A directional term that describes parts of the
neck, trunk, and tail positioned toward the head from
any given point. Cranial also describes those aspects
of the limb above the antebrachiocarpal and
tarsocrural joints that face toward the head.
Rostral. Describes parts of the head positioned
toward the nares from any given point on the head.
Caudal: A directional term that describes parts of the head,
neck, and trunk positioned toward the tail from any given
point. Caudal also describes those aspects of the limbs
above the antebrachiocarpal and tarsocrural articulations
that face toward the tail.
Palmar: This term is used instead of caudal when describing
the forelimb from the antebrachiocarpal articulation distally.
Plantar: This term is used instead of caudal when describing
the hindlimb from the tarsocrural articulation distally.
Proximal: Describes nearness to the point of origin of a
Distal: Describes remoteness (farther away) from the point
of origin of a structure.
Superior and Inferior: These terms are used to describe the
upper and lower dental arcades.
Recumbent: The animal is lying down when the radiograph
is made. Most radiographs of the dog and cat are made with
the animal in the recumbent position, and this position
should be presumed unless the contrary is stated. The term
decubitus is used when a horizontal beam is employed.
The direction of the x-ray beam is described from its
point of entry into the body to its point of exit.
For example, a right-left lateral recumbent projection
means that the animal is lying on its left side, and the
x-ray beam enters the body through the right side and
exits through the left side.
A ventrodorsal (VD) projection means that the x-ray
beam enters the body ventrally and exits dorsally to
reach the film. A dorsoventral (DV) projection indicates
Mediolateral means the x-ray beam enters a limb from
the medial side and exits on the lateral side. Most so-
called lateral radiographs of the limbs are taken in a
mediolateral direction. In a lateromedial projection, the
x-ray beam enters a limb from the lateral side and
exits on the medial side.
Appropriate safety measures should be adopted
irrespective of beam direction, and special care is
needed when horizontal beams are in use.
Standard projections are taken at right angles to one
another and usually are made in the routine
examination of a part of the body. The most common
are the dorsoventral, ventrodorsal, lateral,
mediolateral, craniocaudal, dorsopalmar, and
dorsoplantar. An oblique projection is made at an
angle, somewhere between the standard projections.
In the case of oblique projections, in addition to
stating the anatomic points of entry and exit of the
x-ray beam, the angle of obliquity may be given. This
information enables studies to be repeated with
accuracy. Thus, L50D-RVO is read as left 50° dorsal-
right ventral oblique. It means that an oblique study
was made with the beam entering the body on the
left side dorsally at an angle of 50° toward the back
and exiting on the right side ventrally.
Lesion-orientated studies are sometimes employed
using tangential (skyline) or nonstandard projections.
A lesion-orientated oblique projection is one that
profiles a lesion.
LLR Left Lateral
RLR Right Lateral