Exposure factors in practice (primary factors )

Question 1

what are the primary factors that effect exposure

Answer 1

kvp and mas

Question 2

why is photon energy increasewd when the kvp is increased

Answer 2

because when the kvp is increased, the potential difference across the xray tube is increased meaning that the electrons will strike the anode at higher speeds as they have more kinetic energy meaning that there will be a production of higher energy xray photons

the increase in kvp also increased bremsstralung radiation production as it is more efficient than characteristic radiation

Question 3

is intensity proportional to kvp squared

Answer 3

yes

Question 4

how does increasing kvp increase scatter

Answer 4

because increasing the kvp will change the inner body interactions from photoelectric to compton scatter interactions

Question 5

what is the 15% rule

Answer 5

increasing the kvp by 15% is the same as doubling the mAs
decreasing the kvp by 15% is the same as decreasing the mAs by half

Question 6

what happens when mAs is increased

Answer 6

when mAs is increased, the amount of electrons travelling accross the tube will increase meaning that the amount of xray photons produced will also increase

Question 7

how would you use the 15% rule to reduce patient dose

Answer 7

if you half the mAs you will have to increase the kvp by 15%

Question 8

how does a low and high mAs affect image density

Answer 8

an mAs which is too low will produce quantum noise which produces a grainy image which lack density

using an mAs settimng that is too high will resault in an image with poor definition and the ir will be ogver saturated and this also means that the patient does will be too high