Positioning Terminology
Planes of the body
of positioning both in plain-film imaging and in cross-sectional
imaging techniques. The planes described are mutually at rightangles to each other:
• Median sagittal plane: divides the body into right and left halves. Any plane that is parallel to this but divides the body into unequal right and left portions is known simply as as sagittal plane or parasagittal plane.
• Coronal plane: divides the body into an anterior part and a posterior part.
• Transverse or axial plane: divides the body into a superior part and an inferior part.
This section describes how the patient is positioned for the various radiographic projections described in this text:
Erect: the projection is taken with the patient sitting or standing. In the erect position, the patient may be standing or sitting:
• with the posterior aspect against the cassette; or
• with the anterior aspect against the cassette; or
• with the right or left side against the cassette.
Decubitus: the patient is lying down. In the decubitus position, the patient may be lying in any of the following positions:
• Supine (dorsal decubitus): lying on the back.
• Prone (ventral decubitus): lying face-down.
• Lateral decubitus: lying on the side. Right lateral decubitus –lying on the right side.
Left lateral decubitus – lying on the
left side.
• Semi-recumbent: reclining, part way between supine and sitting erect, with the posterior aspect of the trunk against the cassette.
All the positions may be described more precisely by reference to the planes of the body. For example, ‘the patient is supine with the median sagittal plane at right-angles to the tabletop’ or ‘the patient is erect with the left side in contact with the cassette and the coronal plane perpendicular to the cassette’.
When describing positioning for upper-limb projections, the patient will often be ‘seated by the table’. The photograph below shows the correct position to be used for upper-limb radiography, with the coronal plane approximately perpendicular to the short axis of the tabletop. The patient’s legs will not be under the
table, therefore avoiding exposure of the gonads to any primary radiation not attenuated by the cassette or the table.
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Terminology used to describe the limb position
Positioning for limb radiography may include:
• a description of the aspect of the limb in contact with the cassette;
• the direction of rotation of the limb in relation to the anatomical position, e.g. medial (internal) rotation towards the midline, or lateral (external) rotation away from the midline;
• the final angle to the cassette of a line joining two imaginary landmarks;
• the movements, and degree of movement, of the various joints concerned.
• Extension: when the angle of the joint increases.
• Flexion: when the angle of the joint decreases.
• Abduction: refers to a movement away from the midline.
• Adduction: refers to a movement towards the midline.
• Rotation: movement of the body part around its own axis,
e.g. medial (internal) rotation towards the midline, or lateral (external) rotation away from the midline.
• Pronation: movement of the hand and forearm in which the palm is moved from facing anteriorly (as per anatomical position) to posteriorly. Supination is the reverse of this.
Other movement terms applied to specific body parts are described
in the diagrams.