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Dx Imaging Physics > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

What are the 5 basic interactions with matter?

A 
Coherent scattering
Photoelectric interaction*
Compton interaction*
Pair production 
Photodisintrigration
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2
Q

Which 2 of the 5 basic interactions with matter pertain to diagnostic x-ray?

A

Photoelectric interaction

Compton interaction

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3
Q

Photons of electromagnetic radiation interact with structures of similar ___ and ___ of the radiation

A

Size and wavelength

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4
Q

Low energy x-rays tend to interact with what?

A

Whole atoms

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5
Q

Moderate energy x-rays tend to interact with what?

A

Electrons

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6
Q

High energy x-rays tend to interact with what?

A

Nuclei

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7
Q

What are the two other names for coherent scattering?

A

Classical scattering

Thompson scattering

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8
Q

Term for an interaction between low-energy x-rays and atoms. The xray loses no energy but changes direction slightly. The wavelength of the scattered x-ray is equal to the wavelength of the incident x-ray

A

Coherent scattering

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9
Q

The result of coherent scattering is a change in _____ of the xray without a change in its ____.

A

Direction

Energy

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10
Q

The general graying of an image that reduces image contrast

A

Image noise

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11
Q

Term for when the incident x-ray interacts with an outer-shell electron not only scattering the x-ray but reducing its energy and ejecting it from the atom thereby ionizing the atom.

A

Compton scattering

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12
Q

X-rays scattered back in the direction of the incident x-ray beam.

A

Backscatter radiation

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13
Q

The probability of Compton scattering ____ as x-ray energy increases.

A

Decreases

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14
Q

What does Compton scattering do to image contrast?

A

Reduces

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15
Q

Radiation which is the source of most of the occupational radiation exposure that radiographers receive

A

Compton Scattering

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16
Q

Term for x-rays in the diagnostic range undergoing ionizing interactions with inner shell electrons in which the x-ray is not scattered but is totally absorbed.

A

Photoelectric effect

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17
Q

Term for the electron removed from the atom during a photoelectric effect that escapes with kinetic energy equal to the differecne between the energy of th incident x-ray and the binding energy of the electron

A

Photoelectron

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18
Q

The photoelectric effect is…

A

Total x-ray absorption

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19
Q

The k shell electron binding energy (keV) ____ as atomic number ____

A

Increases

Increases

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20
Q

A photoelectric interaction cannot occur unless the incident x-ray has what?

A

Energy equal to or grater than the electron binding energy

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21
Q

The probability of the photoelectric effect is directly proportional to what?

A

The third power of the atomic number of the absorbing material

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22
Q

K shell electron binding energy

A

keV

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23
Q

Atomic number affects the probability of ______ interaction but not _____ interaction

A

Photoelectric

Compton

24
Q

Pair production does not occur during what?

A

X-ray imaging

25
Q

Positively charged electron

A

Positron

26
Q

Interaction of a high energy photon and the electromagnetic field of the nucleus (nuclear field) in which the photon disappears and 2 electrons appear; one positively charged (positron) and one negatively charged.

A

Pair production

27
Q

An electron with less that 1.02 MeV cannot undergo what?

A

Pair production

28
Q

Pair production is not an important factor in x-ray imaging but IS important in what diagnostic imaging?

A

PET scans (Positron emission tomography)

29
Q

When x-rays with energy above approximately 10 MeV escape interaction with electrons and the nuclear field and are absorbed directly by the nucleus and is raised to an excited state and instantly emits a nucleion or other nuclear fragment.

A

Photodisintegration

30
Q

Photodisintegration does not occur in what?

A

Diagnostic imaging

31
Q

Differential absorption occurs because of what?

A

Compton scattering, photoelectric effect and x-rays transmitted through the patient.

32
Q

What three types of x-rays are important to the making of a radiograph?

A

Those scattered by Compton interaction

Those absorbed photoelectrically

Those transmitted through the patient without interaction

33
Q

The difference in x-ray interaction between those x-rays absorbed photoelectrically in the patient and those transmitted by the image receptor

A

Differential absorption

34
Q

Differential absorption increases as what is reduced?

A

kVp

35
Q

Reducing the kVp to increase differential absorption and therefor image contrast results in what?

A

Increased radiation doseage to the patient

36
Q

With higher x-ray energy, _____ interactions occur, so ____ x-rays are transmitted without interaction

A

Fewer, more

37
Q

Compton scattering is ____ of the atomic number of tissue. (Dependent or independent)

A

Independent

38
Q

At low energies, most x-ray interaction with tissue are _____. At high energies most x-ray interaction with tissue is ______

A

Photoelectric, Compton

39
Q

To image small difference in soft tissue, one must use ____ kVp to get maximum differential absorption

A

Low

40
Q

___ kVp = high contrast

A

Low

41
Q

____ kVp technique is used for examination of barium studies and chest radiography in which the intrinsic subject contrast is ___, resulting in much lower patient radiation dose

A

High, high

42
Q

A beam containing x-rays that all have the same energy

A

Monoenergetic

43
Q

Clinical xrays are ___ meaning they are emitted over an entire spectrum of energies

A

Polyenergetic

44
Q

Quantity of matter per unit volume (specified in kilograms per cubic meter) aka number of atoms present per unit volume of material; basically tells how tightly the atoms of a substance are packed

A

Mass density

45
Q

The total reduction in the number of x-rays remaining in an x-ray beam after penetration through a given thickness of tissue

A

Attenuation

46
Q

An interaction such as the photoelectric effect is called _____ because the x-ray disappears

A

Absorption

47
Q

Absorption + scattering =

A

Attenuation

48
Q

A change in the direction of an incident x-ray without a loss of energy

A

Coherent scattering

49
Q

This type of scattering occurs when incident x-rays ionize atoms and the x-ray then changes direction with a loss of energy

A

Compton scattering

50
Q

This occurs when the incident x-ray is absorbed into one of the inner electron shells and emits a photoelectron

A

Photoelectric effect

51
Q

This occurs when the incident x-ray interacts with the electric field of the nucleus. The x-ray disappears, and two electrons appear - one positively charged (positron) and one negatively charged (electron)

A

Pair production

52
Q

This occurs when the incident x-ray is directly absorbed by the nucleus. The x-ray disappears and the nuclear fragments are released

A

Photodisintegration

53
Q

What controls the contrast of the x-rays image?

A

Differential absorption

54
Q

Differential absorption and attenuation of the x-ray beam depend on what 3 factors?

A

The atomic number of atoms in tissue
The mass density of tissue
The x-ray energy

55
Q

What constrast agent is used in vascular, renal, and biliary imaging and why?

A

Iodine has a greater atomic number and mass density greater than that of soft tissue

56
Q

What radiologic contrast agent is used for gastrointestial imaging and why?

A

Barium; it has a greater atomic number and mass density greater than that of soft tissue

Dx Imaging Physics (8 decks)

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