CHAPTER 1
An Introduction to Radiographic Positioning and Terminology

This chapter will describe radiographic terminology in the following sections.

• Anatomical Terminology
• Positioning Terminology
• Projection Terminology
• Glossary of Terms

Anatomical Terminology

Diagnostic radiography uses a system of rules to describe the body and its movements. It is important to develop a good understanding of the terminology to be able to describe and understand the range of radiographic techniques outlined throughout this book. This terminology provides a clear and consistent approach to describing the location of anatomical structures and is used by a range of healthcare professionals. The use of this shared language enables clinicians and radiographers to communicate effectively in order to obtain the necessary diagnostic images.

The basic terminology descriptions refer to the standard reference position/orientation of the human body. This is known as the anatomical position.

FIGURE 1.1 The anatomical position.

Using the anatomical position as the standard reference, the patient aspect can be described in the following terms.

• Anterior aspect: this is seen when viewing the patient from the front.
• Posterior aspect: this is seen when viewing the patient from the back.
• Lateral aspect: this refers to any view of the patient (or any anatomical part) from the side e.g. the outer side of a limb.
• Medial aspect: this refers to any view of the patient (or any anatomical part) which is closest to the midline, e.g. the inner side of a limb.

FIGURE 1.2 Anterior aspect.

FIGURE 1.3 Posterior aspect.

FIGURE 1.4 Lateral aspect.

Positioning Terminology

Planes of the Body

There are three planes of the body which are regularly used to describe the position of a patient in both projection and cross‐sectional imaging.

• Median sagittal plane: divides the body into equal left and right parts. Any plane parallel to this which divides the body into unequal right and left parts is known as a sagittal plane.
• Coronal plane: divides the body into anterior and posterior parts.
• Transverse/axial plane: divides the body into superior and inferior parts.

FIGURE 1.5 Anatomical body planes.

Skull Positioning Lines and Planes

Skull, facial bone and dental radiography is undertaken with reference to recognised imaginary lines and planes of the skull. These assist radiographers (and others) when describing an area of interest or in positioning.

Lines of the Skull

• Interpupillary (interorbital) line: this is an imaginary line which joins the centre of the two pupils when the eyes are looking straight ahead.
• Radiographic baseline (also known as the orbitomeatal line): this extends from the outer canthus of the eye on a slight diagonal line to the centre of the external auditory meatus (EAM).
• Infraorbital line: joins the two infraorbital points.
• Anthropological baseline (also known as the Frankfurt line): passes from the infraorbital point to the upper border of the EAM.

FIGURE 1.6 Anatomical positioning lines of the skull and face.

Planes of the Skull

• Median sagittal plane: divides the skull into equal left and right parts. Any plane parallel to this which divides the body into unequal right and left parts is known as a sagittal plane.
• Coronal planes: these run at right angles to the median sagittal plane and divide the head into anterior and posterior parts.
• Transverse/axial plane: divides the head into superior and inferior parts.
• Auricular plane: is perpendicular to the transverse/axial plane. It passes through the centre of the external auditory meatuses.

FIGURE 1.7 Planes of the skull.

Patient Positioning Terminology

The following terms are used to describe how the patient is positioned for a range of radiographic examinations/projections.

• Erect: the projection is taken with the patient either standing or sitting upright.
• Decubitus: the projection is taken with the patient lying down in any of the following positions.
  1. – Supine: the patient is lying on their back, face up.
  2. – Prone: the patient is lying on their front, and is face down.
  3. – Lateral decubitus: the patient is lying on their side. A right lateral decubitus is when the patient is lying on the right side; if the patient is facing the opposite side, this would be a left lateral decubitus.
  4. – Semi‐recumbent: the patient is reclining, lying halfway between supine and sitting erect.

FIGURE 1.8 Supine.

FIGURE 1.9 Prone.

FIGURE 1.10 Lateral decubitus (left).

All these positions can be described more precisely by using a reference to the body planes, which ensures that the patient is accurately positioned, e.g. the patient is lying supine on the bed with the median sagittal plane at 90° to the image receptor (IR).

There are also some terms which are used to describe the anatomical position of the limbs which are explained in the Glossary of Terms at the end of this chapter.

Projection Terminology

A radiographic projection is described by the direction of the central ray in relation to the anatomical position and planes of the body.

• Antero‐posterior (AP): the central ray enters the anterior aspect of the body, passes through the body parallel to the median sagittal plane and exits from the posterior aspect.
• Postero‐anterior (PA): the central ray enters the posterior aspect of the body, passes through the body parallel to the median sagittal plane and exits from the anterior aspect.
• Lateral (Lat): the central ray passes from one side of the body to the other, parallel to the coronal and axial planes. A right lateral is when the central ray enters the left aspect of the body and exits from the right side and vice versa for a left lateral.

FIGURE 1.11 AP projection of the left knee.

FIGURE 1.12 PA projection of the chest.

FIGURE 1.13 Lateral projection of the foot (right).

Additional projection terminology, e.g. oblique, can be found in the Glossary of Terms.

To accurately describe a radiographic projection, the following should always be included.

• The position of the patient or area of interest in relation to the IR.
• The movements and degree of movement of the relevant joints, if appropriate.
• The direction and centring of the X‐ray beam, e.g. a vertical central ray is centred to the lateral epicondyle
• The X‐ray beam angulation relative to a starting point of vertical or horizontal.

In all the chapters, you will find that each radiographic projection has been described using this systematic approach.

Glossary of Terms

Abduct

to move a limb away from the middle of the body.

Adduct

to bring a limb toward the middle of the body.

Align

to place/arrange something in a straight line.

Anatomical position

a common visual reference point, with the person standing erect with feet together and eyes forward, palms face anteriorly with the thumbs pointed away from the body.

Anterior

towards or at the front.

Antero‐posterior (AP)

term used to describe a radiographic projection in which the X‐ray beam enters the anterior and then exits the posterior aspect of the body.

Artefact

something that appears on the resultant radiographic image that should not be there and detracts from the quality of the image. This could be caused by extraneous material on the patient or positioning aids or result from errors in the image processing.

Axial plane

an anatomical plane that divides the body into superior and inferior sections. Also known as the transverse plane.

Caudal

away from the head.

Contralateral

on the opposite side.

Coronal plane

a vertical plane running from side to side; divides the body or any of its parts into anterior and posterior portions.

Cranial

towards the head.

Decubitus

lying down.

Deep...