Triangulation

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Triangulation is a technique for localizing lesions seen on at least two views on 2D mammography.

Technique

  • hang the CC, MLO, and 90° lateral films (in that order) on the view box
  • the nipple on each film must be at the same level
  • use a ruler and place one end over the lesion on the 90° lateral view 
  • place the ruler through the lesion on the MLO view
  • on the CC, the lesion will be found somewhere along the ruler

Interpretation

Relative to its distance from the nipple, if the lesion moves down on the lateral film or is located lower than it was on the mediolateral oblique film, the lesion is in the lateral aspect of the breast. However, if the lesion moves up relative to the nipple or is located higher than it was on the Mediolateral Oblique film, the lesion is in the medial aspect of the breast. If no significant change in the location is noted, then the lesion must be located in the central aspect of the breast.

  • a medial lesion will move up on the 90° lateral (remember: muffins rise) 
  • a lateral lesion will move down on the 90° lateral (remember: lead falls) 
  • a central lesion will not move up or down

Clinical application

This technique is extremely helpful when trying to image a lesion that is not seen on all views, asymmetric, non-palpable density or when dealing with a breast that has multiple masses. It can even be an asset when dealing with large breasts.

See also