Radiographic technique Charts Flashcards
As an RT we have a moral obligation to?
Provide the pt with quality radiographs with the least amount of exposure.
Technique charts are scientific aid to assist the RT in achieving this goal.
Prior to developing a technique chart, how can we standardize the equipment.
- Radiographic units should be calibrated for consistent output.
- Grids should be standardized (grid ratios)
- IR speed should be standardized and screens or imaging plates should be clean and undamaged
- Collimator light field/radiation field should be aligned
- When formulating the technique chart, use the same IR, grid and processor for each exposure.
Test exposures should be done
With phantoms and never on actual patients
Two types of technique charts
- Fixed or High kilovoltage technique charts
2. Variable kilovoltage technique chart
Fixes kilovoltage technique is aka
Optimal or high kVp
One a fixed technique chart, the kV selection is based on?
The penetrating quality of the beam for the average adult patient.
What is the variable when using a fixed kilovoltage technique chart?
mAs
Benefits of fixed kilovoltage technique
- Simple to use
- Greater technical accuracy
- Maintains a constant level of contrast.
- Achieve consistent quality; each radiographer should produce radiographs with similar quality.
When you vary your kV, you affect
Contrast Density Exposure latitude Quality of radiation Production of scatter radiation Production of secondary radiation
How does the decrease in quantity of radiation effect quality and wear on equipment
Increases quality and decreases wear in equipment.
Exposure to the pt is less with which kVp technique system? Why?
With variable kV systems since the kV used is higher
Using fixed kV system, and the optimal kV for part, what mAs adjustment occurs for small patients
1/2 “x” mAs
Using fixed kV system, and the optimal kV for part, what mAs adjustment occurs for average patient
“X” mAs
Using fixed kV system, and the optimal kV for part, what mAs adjustment occurs for large pt
2 “x” mAs
In a variable technique system, how are kVp mAs modified?
kVp is used to compensate for variations in the thickness of the part,
mAs is modified for tissue density if needed.
General rule for selecting technique;
Basic formula to determine appropriate kV
2 times centimeter thickness + 30 kV
When you use variable kV system, and use the basic formula, how is the contrast effected?
Gives more short scale contrast
For each centimeter increase in thickness, how do you adjust kV
Add 2 kV
Class A patients are
Emaciated
Easy to penetrate disease processes
Class B patients are
Normal patients
Class C patients are
Difficult to penetrate due to disease process or are muscular
Class A patients adjust mAs by
Decreasing mAs by 30%
Class C patients adjust mAs by
Increasing mAs by 30%
Parts in the recommended kVp range of 50-55
Wrist
Hand
Foot
Fingers
Parts in the recommended kVp range of 55-60
Ankle
Parts in the recommended kVp range of 60-70
Ribs
Knees
According to the ASRT the technique chart is called
Radiographic. Exposure Technique Guidelines
Radiographic. Exposure Technique Guidelines
All health care facilities develop, maintain, and make available optimal exposure technique guidelines for all Radiographic and fluoroscopic equipment.
Radiographic. Exposure Technique Guidelines 70-80 kVp
Skull
Spine
Abdomen
Radiographic. Exposure Technique Guidelines 65-80 kVp
Pelvis
Hip
Radiographic. Exposure Technique Guidelines 65-75kVp
Cervical spine
Femur
Increased attenuation conditions are aka
Additive
Increased attenuation conditions
