Ch. 2 Compensating Filters Flashcards
Compensating filters
Specially designed attenuating devices for the purpose of producing images w. even density on anatomic structures that vary greatly in tissue thickness
What do certain filters do to skin entrance exposure?
Certain filters decrease skin entrance exposure, by absorption of low-
energy photons
What is the wedge filter used for?
Wedge filter are used for areas of the body where tissue density varies gradually from one end to the other along the long axis.
What filter is used to improve image quality of AP projections of the thoracic spine?
Wedge Filter
What is the trough filter?
Double-wedge is best used for areas of the body where density in the center is greater than the edges
What is the Boomerang Filter?
Contact filter, designed to conform to the shape of the shoulder
- placed between anatomy and IR
What is the Ferlic Filter?
Collimator-mounted filter used for AP and PA oblique (scapular Y) projections of the shoulder
What is the Ferlic Filter used for?
-Lateral projections of cervicothoracic region (swimmer’s technique) and axiolateral projections (Danelius-Miller method) of the hip
What is the swimmer’s technique for Ferlic collimator-mounted filters?
-Lateral projection of cervicothoracic region
What is the Danelius-Miller Method technique for Ferlic collimator-mounted filters?
-Axiolateral projections of the hip
What are some basic Physical Principles regarding Filters?
- Shape
- Composition
- Placement
What is the most common filter?
Wedge
-Used on body parts that vary in thickness along the long axis
Which Filters have been specially designed for technically challenging exams?
Trough, Ferlic, and Boomerang
What are the most common filter materials?
Aluminum, and high-density plastics
What are the properties of Aluminum regarding filters?
- Aluminum blocks the field light when placed between tube and patient
- makes positioning more challenging
- Must complete positioning before mounting filter to collimator
What is a Boomerang filter made out of?
Silicone Rubber
What are the two categories of Filter placement?
Collimator-mounted and
Contact
-Filters can be placed on patient or between patient and IR
What body parts vary in thickness along the long axis, and what filter is used for them?
- T-spine
- Foot
- Upright AP abdomen
-Wedge Filter is used
What type of filter is used for PA/AP chest projections?
Trough filter - used on parts that are thick on the edges and thinner in the center
What does Ferlic Swimmer’s filter improves quality of what radiographic projection?
Lateral projection of cervicothoracic spine
What two filters can be used for the Shoulder?
Ferlic and Boomerang filter
What involves using a Scoliosis filter for AP and Lateral projections?
- For AP projection, the wedge filter is used over cervical and thoracic regions
- Lateral requires two double-wedge filters
What are special filter applications of digital fluoroscopy?
-Use of convex and concave cone-shaped filters compensate for round image intensifier
What are special filter applications for CT?
-“Bow-tie” shaped filters compensate for rounded shape of head
How is exposure reduced by using compensating filters?
- Eliminates need for two separate images
- Many absorb low-energy radiation
What is the disadvantage of clear plastic leaded filter?
They are heavy
Which of the following radiographic projections would benefit from the use of compensating filters?
- AP projections of thoracic spine
- AP projections of foot
- Lateral projections of chest
a. 1 and 2 only
b. 1 and 3 only
c. 2 and 3 only
d. 1,2, and 3
A. 1 and 2 only
- AP projections of thoracic spine and foot
What is the disadvantage of an aluminum filter?
Blocks the collimator (field) light
