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Radiographic Positioning


Adult
Other related pages of interest

Name of projection Thoracic Spine - AP
Area Covered C7 to L1
Pathology shown Fractures, scoliosis/kyphosis, tumour, infection, congenital abnormality
Radiographic Anatomy Thoracic Spine Radiographic Anatomy
IR Size & Orientation 35 x 43 cm Portrait
Film / Screen Combination Regular
(CR and DR as recommended by manufacturer)
Bucky / Grid Moving or Stationary Grid
Filter Decubitus filter over the superior thoracic spine when using film, not required with DR CR
Exposure 66 kVp 20 mAs or 66 kVp 20mA 1sec for breathing technique
FFD / SID 100 cm
Central Ray Directed to T7 (to the midsaggital plane, midway between the jugular notch and the xiphoid process)
Perpendicular to the IR
Collimation Centre: To the midsaggital plane, midway between the jugular notch and the xiphoid process
Shutter A: Open to include the hyoid bone
Shutter B: Open approximately 10 - 12 cm (5 - 6 inches) to include the paraspinal soft tisues (this may need to be open wider in the case of scoliosis)
Markers Superior and LateralMarker orientation AP
Shielding Gonadal (check your department's policy guidelines)
Respiration On suspended deep inspiration or gentle breathing for breathing technique
Positioning
  • The patient is supine on the table bucky, arms at their sides
  • Align the midsaggital plane so it is in line with the midline of the IR
  • Ensure there is no patient rotation
  • Flexing the patient's knees up, with the soles of their feet flat on the table helps to reduce the curve of the lower back and is often more comfortable for the patient
  • Position so that the top of the IR is approximately 5 cm (2 inches) above the shoulders
Critique

Positioning
  • No rotation is evidenced by
    • The spinous processes are seen in the midline of the vertebral bodies (see notes below)
    • The pedicles are equidistant from the vertebral body edges (see notes below)
  • Correct central ray angulation is evidenced by
    • The intervertebral disc spaces are seen open (see notes below)
  • The midsagittal plane is centred to the long axis of the film
Area Covered
  • C7 through to L1
Collimation
  • Centre: To T7
  • Shutter A: Open to include C7 through to L1
  • Shutter B: Open to include the entire thoracic spine, including the soft tissue of the neck
Exposure
  • Bony trabecular patterns and cortical outlines are sharply defined
  • The vertebral bodies, spinous and transverse processes and pedicles are distinguishable
  • Soft tissues such as an air filled trachea are visualised
Special Notes Determining the direction of rotation
Using spinous process alignment:
When the spinous processes are not seen in the midline of the vertebral bodies this usually indicates rotation of that part of the cervical spine. As the head is rotated in a particular direction, the spinous process tip will move in the opposite direction. For example, if the spinous process tip is closer to the left vertebral body edge, then the patient's neck is rotated so they are looking towards the right side.

Using pedicle alignment:
In an AP view the pedicles are seen laterally in the area between the transverse process and the vertebral body. With correct positioning the pedicles should be equidistant from the vertebral body edges. Example: If the right pedicle is more towards the midline of the vertebral body (it is rolled under/behind the vertebral body), indicating the patient is rotated so they are looking towards the right side.

Demonstrating intervertebral disc spaces
Successful demonstration of the intervertebral disc spaces is largely dependent on correct central ray angulation.
Generally, the central ray is perpendicular to the film.