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COLLEGE(2) FINALS > RADPRO MODUE 7 and 8 > Flashcards

RADPRO MODUE 7 and 8 Flashcards

1
Q

The x-ray beam is characterized by

A

quantity and quality

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2
Q

The intensity of the x-ray beam of an x-ray imaging system is measured in

A

milligray in air/mGya
miliroentgen
qunaitiy

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3
Q

Another term for x-ray intensity

A

radiation exposure

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4
Q

is a measure of the number of ion pairs produced in air by a quantity of x-rays.

A

mGya (mR)

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5
Q

Ionization of __ increases as the number of x-rays in the beam increases.

A

air

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6
Q

Most general-purpose radiographic tubes, when operated at approximately ___-

A

70 kvp

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7
Q

effect of mas in quantity

A

increased

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8
Q

effect of kvp to qunatitiy

A

The change in x-ray quantity is proportional to the square of the ratio of the kVp;

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9
Q

note

A

that by increasing kVp and reducing mAs so that image receptor exposure remains constant, the patient dose is reduced significantly.

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10
Q

note

A

There is no change in contrast when using digital image receptors.

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11
Q

relationship between quantity and distance

A

X-ray intensity varies inversely with the square of the distance from the x-ray tube target. This relationship is known as the inverse square law.

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12
Q

note

A

When SID is increased, mAs must be increased by SID² to maintain constant exposure to the image receptor.

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13
Q

The purpose of these is to reduce the number of low-energy x-rays.

A

filtration

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14
Q

Disadvantage of x-ray beam filtration:

A

Reduced image contrast when using screen film caused by x-ray beam hardening. X-ray beam hardening increases the number of high energy x-rays in the beam by removing the lower-energy non-penetrating x-rays.

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15
Q

As the energy of an x-ray beam is increased, the penetrability is

A

increased

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16
Q

one description of the ability of an x-ray beam to pass through tissue.

A

Penetrability

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17
Q

___ and ___do not affect radiation quality; they do affect radiation quantity.

A

mas and distance

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18
Q

note

A

Factors that affect x-ray beam quality also influence radiographic contrast when screen film is the image receptor.

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19
Q

Whereas 100-keV x-rays are attenuated at the rate of approximately

A

3%/cm of soft tissue

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20
Q

10-keV x-rays are attenuated at approximately

A

15%/cm of soft tissue

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21
Q

In radiography, the quality of x-rays is measured by

A

HVL

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22
Q

In radiography, the quality of x-rays is measured by

A

3 to 5 mm Al or 3 to 6 cm of soft tissue.

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23
Q

NOTE

A

To improve image contrast, it is also desirable to remove x-rays with energies above a certain level. Unfortunately, such removal of regions of an x-ray beam is not normally possible.

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24
Q

NOTE

A

As filtration is increased, so is beam quality, but quantity is decreased

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25
Q

the glass or metal enclosure of an x-ray tube filters the emitted x-ray beam

A

INHERETN FILTER

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26
Q

The inherent filtration of a general purpose x-ray tube is approximately

A

0.5 mm Al equivalent.

27
Q

thin sheet of Al positioned between the protective x-ray tube housing and the x-ray beam collimator is the usual form of added filtration.

A

ADDED FILTRATION

28
Q

2 Sources of Added Filtration:

A

1.1-mm or more sheets of Al
Collimator contributes an additional 1 mm Al

29
Q

compensates for differences in subject radiopacity.

A

compensating filters

30
Q

X-ray interact with matter in the following five ways

A

coherent scattering, (2) Compton scattering, (3) photoelectric effect, (4) pair production, and (5) photodisintegration.

31
Q

on __ and __ are important in making an x-ray image.

A

compton and pohotelectric

32
Q

low-energy x-rays tend to interact with whole atoms, which have diameters of approximately

A

10−9 to 10−10 m

33
Q

moderate energy x-rays generally interact

A

electron

34
Q

high-energy x-rays generally interact with

A

nuclei

35
Q

low-energy x-rays tend to interact with

A

whole atoms

36
Q

X-rays with energies below approximately __keV interact with matter by coherent scattering,

A

10

37
Q

the incident x-ray interacts with a target atom, causing it to become excited

A

Coherent Scattering

38
Q

measurement of wavelength in coherent scattering

A

equal to that of the incident x-ray (λ = λ′) and therefore of equal energy

39
Q

Note

A

in cohenrent direction of the scattered x-ray is different from that of the incident x-ray.

40
Q

There is no energy transfer and therefore no ionization.

A

Coherent Scattering

41
Q

Most coherently scattered x-rays are scattered in the

A

forward direction

42
Q

X-rays throughout the diagnostic range can undergo an interaction with outer-shell electrons

A

Compton Scattering

43
Q

the ejected electron in compton scattering is called

A

compton electron

44
Q

what happen to the x-ray ejected in compton

A

The x-ray continues in a different direction with less energy

45
Q

X-rays in the diagnostic range also undergo ionizing interactions with inner-shell electrons.

A

Photoelectric Effect

46
Q

The x-ray is not scattered, but it is totally absorbed

A

Photoelectric Effect

47
Q

photoelectric effect and earned Albert Einstein the __ Nobel Prize in physics in

A

1921

48
Q

kinetic energy equal to the difference between the energy of the incident x-ray and the binding energy of the electron.

A

Photoelectric Effect

49
Q

NOTE

A

For higher atomic number target atoms, electron binding energies are higher (37 keV for barium K-shell electrons). Therefore, the kinetic energy of the photoelectron from barium is proportionately lower.

50
Q

NOTE

A

For low atomic number atoms, such as those found in soft tissue, the binding energy of even K-shell electrons is low (e.g., 0.3 keV for carbon). Therefore, the photoelectron is released with kinetic energy nearly equal to the energy of the incident x-ray.

51
Q

RELATIONSUIP OF PHOTOEELCTRIC EFFECT TO ENERGY

A

The probability of the photoelectric effect is inversely proportional to the third power of the x-ray energy (1/E)³

52
Q

The interaction between the x-ray and the nuclear field causes the x-ray to disappear, and in its place, two electrons appear, one positively charged (positron) and one negatively charged.

A

Pair Production

53
Q

The positron unites with a free electron, and the mass of both particles is converted to energy in a process called

A

annihilation radiation.

54
Q

pair production involves only x-rays with energies greater than

A

1.02 MEV

55
Q

X-rays with energy above approximately ___ can escape interaction with electrons and the nuclear field and be absorbed directly by the nucleus.

A

10 MeV

56
Q

the nucleus is raised to an excited state and instantly emits a nucleon or other nuclear fragment.

A

photodisintegration

57
Q

contributes no useful information

A

Compton-scattered x-rays

58
Q

provide diagnostic information. (radiopaque)

A

Photoelectric x-rays

59
Q

produce dark areas in the radiograph. (radiolucent)

A

Transmitted x-rays

60
Q

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

A

attenuation.

61
Q

the product of absorption and scattering.

A

attenuation.

62
Q

an all-or none condition for x-ray interaction.

A

Absorption

63
Q

An interaction such as the photoelectric effect is called an

A

Absorption process

COLLEGE(2) FINALS (6 decks)

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