Compensating filters are shaped filters used to balance densities on an image when the part difference is large from one end to the other (i.e. foot).
What is an example of a compensating filter?
Fig. 2-3 Examples of compensating filters in use today. A, Supertech wedge, collimator-mounted Clear Pb filter used for AP projection of hips, knees, and ankles on long (51-inch) film. B, Trough, collimator-mounted aluminum filter with double wedge used for AP projections of thoracic spine.
How should the compensating filter be placed?
- a wedge-shaped filter affixed to the collimator of the x-ray tube.
- the thicker portion of the wedge is placed in the primary beam which passes through the less dense parts of the anatomy being imaged.
- common uses. horizontal beam hips, the thick portion of the wedge over the distal aspect of the femur.
