X-Ray Interaction with Matter Ch 9

Question 1

How many types of interactions are there with matter?

Answer 1

1. Compton
2. Photoelectric effect
3. Coherent
4. Pair Production
5. Photodisintegration

Question 2

What happens to the x-ray beam as it passes through matter?

Answer 2

1. Penetration

2. Attenuation

Question 3

What is penetration?

Answer 3

Photon passes through unchanged to produce a black area on the image receptor

Question 4

What are the two factors that allow penetration?

Answer 4

1. x-rays are electrically neutral

2. Atoms consist mainly of empty space

Question 5

The probability of penetration increases with

Answer 5

1. Higher quantity of short wavelength radiation
2. Less tissue thickness
3. Lower tissue density (z)

Question 6

High frequency is ____ wavelength.

Answer 6

Short

Question 7

How do you get a higher quantity of short wavelength radiation?

Answer 7

• Increase kVp
• Increase Filtration
• Increase atomic number (z) of the target

Question 8

What is attenuation?

Answer 8

• Exposure rate is decreased

- X-ray beam can be absorbed or scattered

Question 9

In attenuation (absorption), the exposure rate is decreased due to what (3) factors?

Answer 9

1. Photon is absorbed in the body producing secondary radiation (characteristic)
2. Part of the body undergoes a change in direction resulting in scatter radiation (Compton or Coherent)
3. Inverse Square Law

Question 10

The probability of attenuation increases with…

Answer 10

• Higher quantity of long wavelength radiation
• Increased tissue thickness
• Higher tissue density

Question 11

The ______ the wavelength the greater the probability of photons interacting with one of the electrons in the shells surrounding the nucleus of an atom in the body.

Answer 11

Higher

Question 12

What is the photoelectric effect?

Answer 12

• The photon entering the body being completely absorbed

- True absorption

Question 13

What are the results of the photoelectric effect?

Answer 13

• Characteristic radiation (true secondary radiation)
• Photoelectron (Neg ion)
  
  • K shell electron that was kicked out
• Positive Ion
  
  • Atom that was left behind

Question 14

If you do not have photoelectric effect, you do not have an…

Answer 14

Image

Question 15

What two things together make up an ion pair?

Answer 15

Photoelectron (Neg ion)

Positive Ion

Question 16

The probability of the photoelectric effect increase with what?

Answer 16

• Atoms with a high atomic number
• Incident photon having keV = or higher than the binding energy of the inner shell electron
• Lower energy x-ray photons

Question 17

What is Compton Interaction?

Answer 17

?

Question 18

What is another word for Compton Interaction?

Answer 18

Modified Scatter

Question 19

What are the results of Compton Interactions?

Answer 19

Scattered Photon
Ion Pair
*Recoil Electron- Neg ion
*Positive Ion-

Question 20

The energy of the scattered photon will be dependent on what?

Answer 20

It’s angle of deflection

Question 21

If a photon just glances off the e- and is scattered by a small angle, it will retain a ____ _____ of it’s original angle.

Answer 21

Large amount

Question 22

The larger the angle, the ____ energy it will retain and the ____ energy is transmitted to the recoil e-.

Answer 22

Less/ More

Question 23

The scattered photon will retain up to ____ of it’s original energy.

Answer 23

2/3

Question 24

What happens to a scattered photon (produced in the body?)

Answer 24

• It can be transmitted through matter
• It can be absorbed in a photoelectric interaction with another atom
• It may result in further Compton interactions

Question 25

Where is a scattered photon produced?

Answer 25

In the body

Question 26

The ______ of Compton scatter is a complex function of the energy of the incident x-ray.

Answer 26

Probability

Question 27

In general, the probability of the Compton Effect _____ as x-ray energy increases.

Answer 27

Decreases

Question 28

As kVp is increased the probability of Compton Interaction...

Answer 28

Decreases

Question 29

The probability of Compton scattering does not depend on the ___ ____ of the atom.

Answer 29

Atomic number

Question 30

With higher kVp, the Compton photons that do occur have ____ energy.

Answer 30

Higher

Question 31

With higher kVp, the Compton photons that do occur have more energy and move in a _____ direction.

Answer 31

Forward (toward the IR) | Angle of deflection is small

Question 32

The photons that increase the likelihood of their passing through the body and reaching the image receptor constitutes the scatter radiation, which in radiography impairs the image _______ by an overall fogging effect.

Answer 32

Contrast

Question 33

What is the fogging effect?

Answer 33

A form of noise that degrades recorded detail

Question 34

Even though fog is on the image, do you still have the detail of the image?

Answer 34

Yes, you just can't see it very well.

Question 35

Compton scattering ______ image contrast.

Answer 35

Reduces

Question 36

The photoelectric effect is _____ x-ray absorption.

Answer 36

Total

Question 37

What two interactions with matter are important in making an x-ray image?

Answer 37

Compton scattering and Photoelectric effect

Question 38

Do x-rays have short or long wavelengths?

Answer 38

Very short

Question 39

In Compton scattering, the incident x-ray interacts with an outer shell electron and ____ it from the atom.

Answer 39

Ejects

Question 40

What is the ejected electron in Compton scattering called?

Answer 40

Compton electron

Question 41

Scattered x-rays provide ___ useful information on the radiograph.

Answer 41

No

Question 42

A _____ amount of radiation can be scattered from the patient during fluoroscopy.

Answer 42

Large

Question 43

________ radiation during fluoroscopy is the source of most of the occupational radiation exposure that radiographers receive.

Answer 43

Scatter

Question 44

What earned Albert Einstein the nobel peace prize in 1921?

Answer 44

The discovery of the photoelectric effect

Question 45

The photoelectric effect occurs when an incident x-ray is ______ absorbed during the ionization of an inner shell electron.

Answer 45

Totally