Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

IMAG 311- Med Img Fundmts & Physics > Interactions > Flashcards

Interactions Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Photoelectric (PE) Absorption

A

Incident photon energy is completely absorbed by an inner shell electron
-occurs when x-ray photon has just slightly more energy than the Eb (binding energy of the electron) of a k or l-shell electron

  • x-ray photon knocks the inner shell electron of an atom out of orbit causing the atom to ionize
  • *Patient tissues DO absorb radiation during this interaction**
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What type of electron goes along with PE absorption?

A

Photo electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How can the photoelectron energy be determined?

A

Ei = Eb + Eke

  • Ei: energy of incident photon
  • Eb: binding energy of the electron
  • Eke: Kinetic energy of the photoelectron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Characteristics of Photoelectron

A
  • Kinetic Energy
  • Mass
  • Reabsorbs quickly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Characteristic Cascade

A
  • Vacancy filled by an outer shell electron
  • electron undergoes change in energy level
  • emits characteristic photon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Secondary Radiation

A

-when a characteristic photon are emitted from atoms of the patient after PE absorption interaction has occurred
radiation that originates from irradiated material outside of xray tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q 
PE Absorption is most influenced by what?
A. Subject volume
B. Subject thickness
C. Subject mass density
D. Subject atomic #
A

D. Subject atomic #

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

As you increase kVp (increasing photon energy), what happens to the probability of absorption?

A

Decreases by 1/8 (inverse cubed relationship)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Low atomic number materials and soft tissue result in what?

A

-photoelectrons maintaining the majority of the incident photon’s energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What interactions are both energy and atomic number dependent?

A

Photoelectric Interactons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When kVp decreases the, what happens to the probability of interactions (PE and Compton)?

A

The probability of Interactions of PE or Compton decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Attenuation

A

The absorption or scatter of a beam as it travels through a target material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Coherent Scatter

A

Involves low energy photons (below 10 keV)
-Can also be called unodified scatter, classical scatter, thompson (single outer-shell e), or rayleigh (all electrons of the atom)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Transmission of an x-ray

A

When x-rays pass through a patient instead of being absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Compton Scatter

A 
Incident photon (Ei) interacts w. outer shell electron and knocks it out of orbit
-incoming xray does not lose all of its energy; it becomes a scattered xray photon and continues in a different direction with a lower amount of energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In what interaction is the energy of the incident photon shared between the scattered photon and the KE of the orbiting electron that was knocked out of its orbit?

A

Compton Scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

interactions that happen at low xray energies such as in mammography are called what?

A

Unmodified (coherent) scattering

-Instead of the atom losing an electron, the electron or atom vibrates and redirects incident photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which Interaction creates the vast majority of scatter in the range of xray energies used in diagnostic imaging?

A

Compton Scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What 3 variables affect the quality of an xray beam?

A

Part thickness, atomic number, and tissue density

20
Q

if a tissue made out of a substance with a very low atomic number and fewer inner shell electrons make up the tissue, then the chance of photoelectric absorption interactions increases or decreases?

A

Decreases

21
Q

Which atom would have an increased chance of photoelectric absorption occuring, calcium or oxygen and why?

A

Calcium, because it has a bigger atomic number, and there are more electrons orbiting around the nucleus for an incident photon to interact with than in an oxygen atom

22
Q

Tissue density affects how tightly bound atoms are in any given tissue.
True or False?

A

True

23
Q 
Which of the 4 major body tissues has the greatest effective atomic number
A. Bone
B. Muscle
C .Fat
D. Air
A

A. Bone

24
Q

What is the effective atomic number for Bone

A

14 (calcium)

25
Q

What is the predominant interaction taking place between bone and the x-ray beam?

A

Photoelectric Absorption

26
Q

Muscle is not the most difficult tissue for an x-ray beam to penetrate
True or False?

A

False…Muscle is the most difficult tissue for an x-ray beam to penetrate

27
Q

Less photoelectric absorption and more Compton scatter happens in what body tissue?

A

Muscle

28
Q

What two factors make fat easier for the x-ray beam to penetrate?

A

Both its atomic number and density being less than the other body tissues

29
Q

Why doesn’’t air attenuate more of the primary beam than muscle or fat?

A

Because air’s tissue density is much, much lower than muscle or fat.
-Therefore, air doesn’t absorb any of the x-ray beam at all.

30
Q

Thicker parts cause more beam scatter and greater secondary radiation.

True or False?

A

True

31
Q

increased kVp exposure produces more scatter and secondary photons in the patient that tend to travel in What direction?

A

a forward direction, toward the image receptor.

32
Q

The Compton interaction, which occurs between what three things?

A

The signal, x-ray beam, and the patients tissue

33
Q

Noise

A

The source of noise is anything that prevents information from reaching an image receptor.

34
Q

Sources of Noise?

A
  • Reduced signal strength from thicker parts
  • incorrect use of an anti-scatter grid and too few x-ray photons making it through the patient, table or grid
  • Scatter is also an example of noise
35
Q

Pair Production

A
  • When a super energetic photon enters an atom and interacts with the nucleus–nucleus can’t hold all of the energy, so it is given off as a negatron and positron
  • Nucleus becomes unstable - — Happens in therapy and PET scans
36
Q

Increasing kVp does what to the total attenuation?

A

Decreases total attenuation

37
Q

When kVp is increased extremely, what happens regarding PE Absorption and Compton Scatter?

A

PE Absorption decreases

Compton Scatter increases

38
Q

Photodisintegration

A

Happens with extremely high energy photon

  • Absorption of photon by nucleus
  • excited nucleus releases alpha particle
  • *Not significant in imaging
39
Q

As kVp increases,the # of photons transmitted without interactions increases or decreases?

A

Increases

40
Q

As kVp increases and the # of photons increases, what does this do to the PE and Compton interactions?

A

Decreases the probability of PE absorption and Compton interactions

41
Q

Within the attenuated beam… As kVp increases

A

PE absorption decreases
Compton increases

  • Increases percentage of scatter
  • Decreases percentage of absorption
42
Q

Differential Absorption

A

The difference in what is transmitted through different body parts
-result in image contrast

43
Q

Mass Density

A

Relates to how closely atoms are located within a material

44
Q

As Mass density increases, the space between atoms ___?

A

decreases

45
Q

X-ray transmission is reduced as what increases?

A

Mass Density

46
Q

Mass Density and X-ray attenuation coefficients are inversely proportional
True or False?

A

False, they are directly proportional–if you double the mass density, the the x-ray attenuation coefficients doubles

IMAG 311- Med Img Fundmts & Physics (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions