FERGUSON METHOD (PA / AP PROJECTION) | SCOLIOSIS SERIES

Friday, December 19, 2014

Pathology Demonstrated on Perguson Method

  • This method demonstrates different deforming primarily curve from compensatory curve.
  • Two images must be done in performing this method. The standard is in patient in erect AP or PA and the one is with foot or hip on the convex side of the elevated curve.

Technical Factors:

  • Cassette size 35 x 43cm or 14 x 17 inches, put in lengthwise,
  • 35 x 92 cm or 14 x 36 inches may also be used if available.
  • Moving or stationary grid
  • Erect marker
  • Compensating filters for uniformity of image and density along vertebral area.
  • SID 60 inches or 152 cm
  • kV 90
  • mAs 25
Perguson method
PA Projection without elevation

Use of Shielding:

  • Place lead shielding over gonads without obscuring the area being expose, breast shield for young female patients.


Patient Position:

  • Position patient, either seated or erect, and arms on side.
  • For 2nd image, put block under the patients foot or in hips if the patient is seated on the curve side so that the patient can barely maintain position without assistance.
  • If 3 to 4 inches block is available place it under the patients buttocks if patient is seated and under its foot if standing.

Part Position:

  • Mid-sagittal plane and cassette must be aligned with patient arms on side.
  • No rotation of torso or pelvis as possible.
  • A minimum of 1-2 inches of cassette below the iliac crest.

Central Ray:

  • Centeral ray is directed to and perpendicular to center of cassette.
  • SID is 40 to 60 inches, if IR is longer, longer SID is required to obtain adequate collimation if a 14 x 36 inches film is used.

Collimation:

  • Collimate on four sided area of interest.

Respiration:

  • Suspend respiration on expiration.

Note: compression band is not required on this method. For 2nd image, place block support under the patient foot on curve side unassisted.
PA projection should be done for radiographs, to reduce patient exposure to rediation sensitive area like thyroid and breast.

Radiographic Criteria | Ferguson Method


Structure Shown:

Ferguson method radiograph
PA projection WITH HIP ELEVATED
  • All thoracic and lumbar vertebrae should be demonstrated.
  • A minimum of 1 inch of iliac crest should be included on the image.

Proper Positioning:

  • Thoracic and lumbar vertebrae should be demonstrated in as true a AP or PA projection as possible.

Collimation and CR:

  • Vertebral column should be in the center of the image or in collimation field.

Exposure Criteria:

  • Optimal density and contrast will clearly demonstrate the lumbar and thoracic vertebrae.
  • A compensating filter may be useful for obtaining uniform density along the vertebral column.
  • Sharp bony margins indicate no motion.

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