3. Prime Factors

Question 1

What factors are directly proportional to mAs, s, and mA?

Answer 1

The intensity
Radiation reaching the IR
Patient dose

Question 2

What is mAs?

Answer 2

The total amount of current across the tube during the exposure

Question 3

What are the 3 units that intensity is measured in?

Answer 3

○ Roentgens (R)
○ milliRoentgens (mR)
○ Coulombs/kg (C/kg)

Question 4

In which way is intensity measured?

Answer 4

With a dosimeter

Question 5

What is a focus cup?

Answer 5

Keeps electrons in a stream so that they hit the target

Question 6

Define EI value:

Answer 6

Measure of how much radiation the IR saw

Question 7

What is the mass and charge of a photon?

Answer 7

No charge or mass

Question 8

What are the 3 advantages of reciprocity?

Answer 8

1. Control motion
2. Control of focal Spot Size
3. Control of breathing techniques

Question 9

What are two ways that you control motion for a patient that can’t hold still?

Answer 9

1. Immobilization device (pigg o stat for infants)
2. Shorten exposure time

Question 10

What is the focal spot limited by?

Answer 10

The mA

Question 11

With a further SID, what happens to intensity?

Answer 11

Decreases due to beam geometry

Question 12

To have the same intensity with a further SID, what do you have to increase?

Answer 12

mAs

Question 13

For the same body part, which distance will require a higher technique to get the same amount of radiation to the IR, 100cm or 180cm?

Answer 13

180 cm