Interactions of x-ray with matter

Question 1

Describe DC rectification

Answer 1

reduces exposure time but same amount of x-ray (homogenous energy)

Question 2

coherent scatter

Answer 2

photon path is deviated

Question 3

photoelectric absorption

Answer 3

gets blocked by patient and gives us the image

Question 4

Compton scatter

Answer 4

photon gets deviated

Question 5

What is coherent scatter’s effect on patient’s tissue?

Answer 5

no effect

Question 6

What % is coherent scatter?

Answer 6

very small

Question 7

What happens during photoelectric absorption?

Answer 7

incoming photons collides and loses all its energy to inner shell e-

Question 8

Which interaction causes ionization of the biological atom?

Answer 8

photoelectric absorption and Compton scatter

Question 9

What is photoelectric absorption directly proportional to?

Answer 9

atomic # (Z^3)

Question 10

What is photoelectric absorption inversely proportional to?

Answer 10

photon energy (E^3)

Question 11

A material with a higher atomic # – more photons

Answer 11

blocks

Question 12

Probability of photoelectric absorption of a material with more photon energy

Answer 12

lower

Question 13

Compton scatter: photon takes out and transfer SOME energy to –

Answer 13

outer shell e-

Question 14

What is Compton scatter bad?

Answer 14

the incoming photon retains some energy and can go in any direction (eg inside patient) and degrades image

Question 15

Where should you stand in relation to the x-ray beam?

Answer 15

behind a barrier
90-135 degrees from radiation source
6 feet away

Question 16

How can you reduce scatter?

Answer 16

collimation

Question 17

What happens when more x-rays hit the receptor?

Answer 17

darker image

Question 18

How does collimation work?

Answer 18

reduce x-ray beam size (blocks off unimportant tissue)