What does IR Exposure represent in digital imaging?
Exposure index
IR Exposure is one of the two photographic properties that comprise visibility of detail, the other being Contrast.
Define Milliamperage (mA).
Recording of the tube current
It represents the number of electrons moving from the cathode to the anode side of the tube per unit of time.
What is the relationship between exposure and milliamperage?
Direct relationship
An increase in milliamperage results in increased exposure.
What is Image Receptor Exposure?
Degree of overall exposure to the image receptor
It is one of the two photographic properties that comprise visibility of detail.
What happens to details on an underexposed image?
Details are not recorded
This occurs due to quantum mottle/noise.
What is the recommended approach when in doubt about exposure?
Choose to overexpose the image
This can help in capturing more details.
What are the factors affecting IR Exposure?
- Multiple variables
- Not an exact science
- Variables usually balance each other
The rules for changes in technical factors are guidelines that apply to a range of circumstances.
What is the major factor controlling IR exposure?
mAs
mAs gives the primary effect on the amount of IR Exposure.
As mAs increases, what happens to the quantity of radiation?
Increases
This leads to increased IR Exposure.
What is the Reciprocity Law in relation to IR exposure?
IR exposure stays the same if overall mAs stays the same
This applies regardless of the mA station or ms used.
What are the three types of noise in imaging?
- Quantum noise
- System noise
- Ambient noise
Quantum noise is the largest contributor and is best controlled with mAs.
What is quantum noise attributed to?
Random absorption of x-ray quanta
It causes ‘graininess’ on digital images that are underexposed.
What is the purpose of a control dosimeter?
Measure background radiation
It helps in calculating true occupational exposure.
When should you wear two dosimeters?
When you are pregnant
One is worn at the level of color and the other at the waistband for fetal dose monitoring.
What makes up sub details in an image?
- Photographic properties
- Geometric properties
These contribute to the overall detail visible in the image.
What is a data drop error?
So much radiation that you can’t see bone/anatomy
This can lead to significant loss of detail in imaging.
