safety
what units are used to measure x-ray quantity?
1. roentgen (mR)
2. Air kerma (mGya)
what is half-value layer (HVL)?
the thickness of material needed to reduce the x-ray intensity by half
If we need to MAINTAIN our receptor exposure, we will used the _________?
the direct square law.
When is radiation considered Primary radiation?
X-ray beam prior to interaction with the patient.
What is another name for Remnant Radiation?
exit radiation.
what controls dose/rate/intensity of the exposure?
mAs.
What is the Inverse square law?
x-ray quantity (intensity) is inversely proportional to the square of the distance from the radiation source.
What is the formula for Direct square law?
mAs1/mAs2= (SID1)2/(SID2)2
X-ray photons in the primary beam are known as______?
Incident photons.
What is another name for the remnant x-ray beam?
the image-forming beam
what is the relationship between x-ray quantity and mAs?
directly proportional
What is the inverse square law used to calculate?
A change in beam, intensity, with changes in SID.
EXAMPLE QUESTION:
A satisfactory radiograph is produced using exposure factors of 75 kVp and 10 mAs at a distance of 40 inches. what new mAs would be required to produce a radiograph of similar density if the distance if increased to 80 inches?
1. 10 mAs/x= (40)2/ (80)2
2. 10/x= 1600/6400
3. 10/x= 1/4 (.25) NOW CROSS MULTIPLY
4. x=40 mAs
What is Secondary Radiation?
radiation that is emitted from atoms of matter after an x-ray photon from the primary beam interacts with matter.
What is Attenuation?
the progressive absorption of the x-ray beam as it passes through matter.
What formula shows the relationship between intensity and mAs?
I1/I2=mAs1/mAs2
EXAMPLE QUESTION:
an exposure taken at 40 inches (100 cm) yields and intensity of 200 mR c/kg. Assuming all other factors remain constant, what is the intensity if the distance is increased to 80 inches?
1. 200/x= (200)2/(100)2
2. 200/x= 40,000/ 10,000
3. 200/ x= 4/1
4. x= 200/4
5. x= 50 C/kg
what is another name for primary radiation?
Useful radiation.
What type of radiation is an example of secondary radiation?
characteristic radiation.
Attenuation is the sum of ______ and _______?
1. absorption
2. scatter
EXAMPLE QUESTION:
If exposure factors of 75 kVp and 20 mAs result in an x-ray intensity of 100 mR, c/kg or air kerma or mGya, what is the intensity if the exposure is made using factors of 75 kVp and 50 mAs?
1. 100/x=20/50
2. 20x=5000
3. x=5000/20
4. 250 mR (mGya)
What law will determine the change in mAs required if radiographic density is to remain constant and the SID is changed?
Direct square law.
What does Primary Radiation consist of?
x-ray photons directed through the x-ray tube's window port in a direction towards the patient.
What is Remnant Radiation?
the portion of the attenuated x-ray beam that emerges from the patient, and interacts with the IR.
How can attenuation be described in simpler terms?
the reduction of x-ray intensity as it passes through matter