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Radiation biology > chapter 3 EXAM 2 > Flashcards

chapter 3 EXAM 2 Flashcards

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1
Q

milliampere seconds mAs

A

quantity
product of exposure time and tube current
a measure of the total number of electrons that travel from the cathode to the anode

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2
Q

peak kilovoltage kVp

A

quality

controls the quality or penetrating power of the photons in xray beam

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3
Q

when radiation interacts with matter (the body) some photons are….

A

some photons are absorbed

some are scattered and some pass through without interacting at all

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4
Q

absorption

A

transference of electromagnetic energy from an xray beam to the atoms or molecules of the matter through which it passes

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5
Q

scatter

A

a change in direction of travel of an xray photon that may also involve a potential loss of radiation energy

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6
Q

absorption + scatter =

A

attenuation

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7
Q

direct transmission

A

when photons pass through the patient without interacting and reach the IR

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8
Q

primary radiation

A

emerging xray photon beam

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9
Q

indirect transmission

A

primary photons that undergo compton and or coherent interactions and are scattered or deflected after they go through an object

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10
Q

an optimal xray image is formed only when

A

direct transmission xrays reach the IR

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11
Q

a radiographic image is formed from

A

directly transmitted photons and indirectly transmitted (scattered) photons

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12
Q

attenuation

A

refers to any process decreasing the intensity of the primary photon beam

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13
Q

radiographic fog

A

undesirable additional density on a radiographic image caused by scatter reaching the IR

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14
Q

true or false

photon interaction is random

A

true

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15
Q

an xray image results from the difference between

A

the xrays absorbed photoelectrically by the patient and those transmitted to the IR

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16
Q

differential absorption

A

different degrees of absorption in different tissues that result in image contrast and formation of the image

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17
Q

what are the 4 factors that influence probability of interactions of photons

A
  1. photon energy
  2. atomic number
  3. mass density
  4. tissue thickness
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18
Q

as photon energy increases,

A

kvp increases and absorption is reduced

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19
Q

as atomic number increases,

A

it increases the chances that the xray photon will be absorbed to the 3rd power

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20
Q

as xray energy increases

A

fewer compton interactions
fewer photoelectric interactions
more passing through without interacting

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21
Q

as tissue atomic number increases

A

no change in compton interactions
more photoelectric interactions
less passing through without interacting

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22
Q

as tissue mass density increases

A

proportional increasie in compton interactions
proportional increase in photoelectric interactions
proportional reduction in passing through without interacting

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23
Q

5 types of interaction between x radiation and matter

A
  1. coherent scattering
  2. compton scattering
  3. photoelectric absorption
  4. pair production
  5. photodisintegration
24
Q

coherent scattering is also called

A

classic, elastic or unmodified scattering

25
Q

coherent scattering

A

involves low energy photons below 10 KeV
when the low energy photon interacts with tissue, it does not loose energy. It just changes direction and becomes excited.
no ionization occurs here.

26
Q

photoelectric absorption is the most important

A

mode of interaction between xray photons and the atoms of the pts. body for producing useful images

27
Q

photoelectric absorption

A

interaction between the dray photon and an inner shell electron (k shell)

28
Q

to dislodge an inner shell electron from its orbit, the xray photon must

A

be able to transfer a quantity of energy equal to or greater than the electron binding energy

29
Q

on interacting with the inner shell electron, the xray photon surrenders

A

all of its energy to the orbital electron and ceases to exist
it gets absorbed

30
Q

the ejected electron is called a

A

photoelectron

31
Q

auger effect

A

process that can occur as a result of photoelectric interactions
occurs when an inner shell electron is removed from an atom causing an inner shell vacancy

32
Q

what are the byproducts of photoelectric absorption

A

photoelectrons

characteristic xray photons

33
Q

probability of occurrence of photoelectric absorption depends on

A

the energy of the xray photons and the atominc number of the atoms it interacts with

34
Q

photoelectric absorption increases to the 3rd power dramatically as the

A

energy of the incident photon decreases.

35
Q

the probability of photoelectric absorption increases dramatically when

A

the atomic number of the atoms increases

36
Q

when mass density is doubled, the chance for xray interaction is doubled because

A

twice as many electrons are available for interaction

37
Q

the interaction of xrays with tissues is proportional to the

A

mass density of the tissue

38
Q

T or F
if 2 structures have the same mass density and atomic number, but one is twice as thick, the thicker structure will absorb twice as many photons

A

True

39
Q

T or F

the less a given structure attenuates xrays, the darker its radiographic appearance

A

true

40
Q

the greater the difference in the amount of photoelectric absorption, the greater the

A

contrast will be between adjacent structures of differing atomic numbers.

41
Q

as absorption increases, so does

A

the patient dose :(

42
Q

compton scattering is also called

A

incoherent scattering
inelastic scattering
modified scattering

43
Q

what is compton scattering

A

the interaction of xrays with matter that is responsible for most of the scattered radiation produced during radiologic procedures

44
Q

process of compton scattering

A

incoming photon interacts with loosely bound outer shell electron. it surrenders part of its energy to dislodge the electron ionizing the atom

45
Q

the ejected electron in compton scattering is called

A

compton scattered electron
secondary electron
recoil electron

46
Q

what can happen to the compton scattered photon

A

it can interact with other atoms
it may emerge from the pt. and reach the IR causing fog
it could emerge from the pt. and expose personnel

47
Q

compton scattering is the source of

A

most of the occupational radiation exposure that radiographers receive

48
Q

the probability of the compton scattering effect does not depend on

A

the atomic number of the atom

doesn’t matter what it hits. it will effect an atom of soft tissue the same way as an atom of bone

49
Q

compton scattering provides no useful info on the radiograph. it results in

A

reduced image contrast

50
Q

Pair production does not occur unless

A

energy of the incoming xray photon is at least 1.022 mega electron volts
this is far above the energy used in diagnostic radiology

51
Q

pair production process

A

incoming photon interacts with the nucleus of an atom of biologic tissue and disappears
in the process energy of the photon is transformed into 2 new particles

52
Q

what are the 2 new particles the photon is transformed into in pair production

A

negatron (ordinary electron)

positron (positively charged electron)

53
Q

annihilation event

A

the positron and the electron it interacted with are destroyed and their energy is converted into 2 xray photons that radiate out of the atom

54
Q

photodisintegration

A

energy above 10 Megaelectron volts

energy too high for diagnostic radiation

55
Q

process of photodisintegration

A

high energy photon collides with the nucleus of an atom and the nucleus emits a neutron
this makes the nucleus radioactive

Radiation biology (19 decks)

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