Lecture 7

Question 1

What is scattered radiation?

Answer 1

Scattered radiation are low energy x-rays that deflect in several directions and interact with an object.

Question 2

What is coherent scatter?

Answer 2

When the x-ray photon interacts with the atom, it has a binding energy below that of the electron and thus is unable to liberate the electron. As a result, the photon has a change in direction.

Question 3

What is compton scatter?

Answer 3

A high energy x-ray photon interacts with with a loosely bounded electron, ejecting it and the photon continues in a different direction.

Question 4

What is photoelectric effect?

Answer 4

With photoelectric effect, the incident photon interacts with an inner orbital electron & liberating it. An outer shell electrons moves to fill the space of ejected electron. The difference in binding energy between the shells is emitted in the form of characteristic radiation.

Question 5

1. Scatter radiation during an exposure results in ____ on the radiograph.
2. What does kilovoltage affect?
3. Higher kVp results in more or less scatter radiation?

Answer 5

1. fog
2. Kilovoltage affects the quantity of scatter radiation that reaches the IR.
3. More

Question 6

What are other factors that affect scatter?

Answer 6

Volume of tissue, density of matter & field size

Question 7

1. What is the relationship between volume of tissue and scatter produced?
2. How can reducing scatter be achieved?

Answer 7

1. Proportional. The less volume of tissue exposed, the less scatter will be produced.
2. Using beam-restricting devices

Question 8

Who or what is the major source of scattered radiation?

Answer 8

The patient.

Question 9

1. What are grids?
2. What do grids consist of?
3. What are the two categories of grids?

Answer 9

1. Grids are used to absorb scatter radiation exiting the patient
2. Grids consist of lead & sandwiching radiolucent material (fiber, plastic & aluminum).
3. Parallel & Focused

Question 10

Focused Grids are ______ dependent. What does that mean?

Answer 10

focused

This means they have to be used with the correct focal distance from the x-ray tube.

Question 11

Parallel Grid may be used at ____ or ____ FFD

Answer 11

short or long

Question 12

1. What is the grid ratio?
2. Higher grid ratios require _____ radiation exposure.

Answer 12

1. The ratio of the height of the lead strips to the distance between them.
2. higher

Question 13

Incorrect use of grids can cause?

Answer 13

Grid cut off