Question | Answer |
Define "filtration" | The process of removing "undesirable" low energy xray photons via insertion of absorbing materials in the primary beam. |
What is another name for filtration? | Hardening |
What is the only purpose of filtration? | To lower the patient's radiation dose |
What are the 2 ways filtration is measured? | 1. Al/Eq (Aluminum Equivalent)
2. HVL (Half Value Layer) |
What is the HVL? | The amount of absorbing material that will reduce intensity by 1/2 |
____ mm Al/Eq is for equipment over 70 kVp | 2.5 |
____mm Al/Eq is for equipment between 50-70 kVp | 1.5 |
____mm Al/Eq is for equipment below 50 kVp | 0.5 |
HVL affects Quality or Quantity? | Quality |
What 2 areas of radiography use equipment below 50 kVp? | 1. Mammography
2. Dental radiography |
What are the 4 types of filtration? | 1. Inherent
2. Added
3. Total
4. Compensation |
What is inherent filtration | Filtration that is built into the x ray tube |
What 3 items are part of inherent filtration? | 1. Glass envelope
2. Di-electric oil
3. Glass window |
___mm Al/Eq makes up inherent filtration | 0.5-1.0 |
What material does mammography use for their tube window? As opposed to...?
Why? | Beryllium, instead of Pyrex.
So they don't filter out absorbing rays they need for extra detail. |
What is added filtration? | Any filtration outside of the tube & housing & before the IR |
___mm Al/Eq makes up the collimator | 1.0 |
What type of filtration is the mirror? | Added |
What is total filtration? | Inherent + Added |
What is a compensation filter? | A device providing a more uniform density |
What 4 substance can a compensation filter be made of? | 1. Aluminum
2. ClearPb(Lead)
3. Plastic
4. Saline bag |
What are 3 examples of when a compensation filter would be used? | 1. Foot x-ray
2. T-Spine x-ray
3. Chest x-ray |
What is a Wedge filter? | A wedge shaped device that gives a uniform density when the part is larger on one side than another |
When using a Wedge filter, the ___ end goes over the thinner area of the body part | Thicker |
When using a Wedge filter, the ___ end goes over the thicker area of the body part. | Thinner |
What is a Trough? | A device that gives a uniform density when the body part is thicker on the edges and thinner in the middle |
What is another name for a Trough? | Double Wedge |
What is an example of when a Trough would be used? | Chest x-ray |
What must happen to technique when adding a filter? | Technique must go up |
What happens to density when a filter is introduced?
Contrast? | Density decreases
Contrast decreases |