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Nuclear Medicine > Part IV > Flashcards

Part IV Flashcards

1
Q

generic term for device that transforms energy from one form to another

A

Transducer

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2
Q

2 classifications of radiation detector

A

non paralysable
paralysable

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3
Q

detector classification used for imaging PET or SPECT

A

non paralysable

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4
Q

detector classification that measures continuously, there is a need to reset device for it to detect other event

A

paralysable

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5
Q

properties of detectors

A

detector efficiency
energy resolution
temporal resolution
spatial resolution

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6
Q

ratio of gamma detector detected received over the no. of gamma rays emitted

A

detector efficiency

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7
Q

2 types of detector efficiency

A

geometric efficiency
intrinsic efficiency

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8
Q

configuration and the distance of the source

A

geometric efficiency

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9
Q

ability to absorb thickness and attenuation coefficient of the detecting material

A

intrinsic efficiency

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10
Q

energy resolution formula

A

100% x Full Wave at Half Maximum/ gamma energy

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11
Q

[..] keV good images detected by detector

A

50-300 keV

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12
Q

refers to the amount of blurring that is produced by an imaging system

A

spatial resolution

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13
Q

expresses how accurately a radiation detector system is able to determine the time of interaction

A

temporal resolution

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14
Q

the conversion of gamma ray energy into an electronic pulse and processing

A

dead time

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15
Q

two main types of detectors

A

scintillators
gas detectors

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16
Q

the basic of most diagnostic and imaging instruments
convert gamma in light -used in imaging

A

scintillators

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17
Q

typically used in non-imaging instrument,
use gases and once streak by gamma rays, there is ionization used

A

gas detectors

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18
Q

three main types of gas filled detectors

A

ionization chamber
proportional counters
geiger mueller counters

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19
Q

applied V for ionization chamber

A

100-400 V

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20
Q

[ionization chamber] used to assay activity levels in syringes. vials..etc.

A

dose calibrators

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21
Q

[ionization chamber] used for radiation protection purposes

A

survey meter

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22
Q

[ionization chamber] personnel monitoring

A

pocket dosimeters

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23
Q

T/F ionization chamber cannot detect a single radiation event

A

True

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24
Q

proportional counter gases

A

90% argon/xenon and 10% methane gas

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25
Q

applied voltage of proportional counters

A

400-800 V

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26
Q

adv. of proportional counters

A

greater electron amplification
pulse size is a factor 100-10000 times greater than ionization chamber
capable of detecting single radiation event

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27
Q

T/F Proportional Counters have little use in NM and is used mainly for measuring alpha and beta in research

A

T

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28
Q

applied V of geiger mueller counters

A

above 800 V

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29
Q

commonly used quenching gas in geiger mueller counters

A

heavy organic vapour (alcohol) and halogen gas (Cl)

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30
Q

T/F G-M counters is used in NM as survey meter to locate even a small amount of radioactivity

A

T

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31
Q

2 types of scintillation detectors

A

inorganic substances - solid
organic substances - liquid

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32
Q

Examples of inorganic substances

A

NaI (Tl), ZnS (Ag), CsI (Tl), CdS(Ag)

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33
Q

Example of organic substances

A

2,5 diphenyloxazole

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34
Q

basic components of scintillation counter

A
  1. Detector System -Scintillator and PMT
  2. Processing Unit - Gamma Spectrometer
  3. Display Unit
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35
Q

[detector system part] filter gamma, prevent misinterpretation, allows only parallel gamma rays to pass thru,
limits area of gamma camera

A

collimator

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36
Q

[detector system part] used to enhance and reshape photoactivity of the emitted light photons

A

pre-amplifier

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37
Q

[detector system part] refer to the dynodes of the PMT, amplify no. of electrons

A

amplifier

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38
Q

[processing unit part] to evaluate incoming electric signals coming from PMT
accept/reject signals not equivalent to predicted energy of radionuclide

A

PHA- Pulse Height Analyzer

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39
Q

counts on a scaler, needle deflection on a rate meter, a dot on a special type of paper, display data in monitor system

A

display unit

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40
Q

properties of ideal scintillator

A
  1. good absorber of incident photon
  2. conversion to light must be efficient and light intensity must be proportional to energy
  3. transparent to visible light
  4. wavelength of light emitted should correspond to PMT sensitivity
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41
Q

explain scintillation detectors

A

gamma is emitted → interacts with scintillator → ionization and excitation of other atoms (come back to ground state) → scintillator will emit light photons prop. to gamma photon → cause photocathode to emit electrons → dynodes attract incoming electrons (electron multiplier) emit secondary electrons → when electrons reach elec connectors potential pulse is generated (potential pulse generated identifies amount of energy coming from radiation → after measured/counted energy of radiation is converted to measurable V pulses

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42
Q

reasons to use NaI (Tl)

A
  1. relatively dense
  2. efficient
  3. transparent to its scintillation emission
  4. provide an output signal that is prop to amplitude to the the amt of energy absorbed in crystal
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43
Q

disadvantages of NaI (Tl)

A

fragile
hygroscopic - collects moisture
large crystal

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44
Q

Parts of PMT

A

crystal
reflector
Al or stainless steel jacket
transparent window
photocathode
focus grid
dynodes
MU metal (iron, nickel, copper, chromium)

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45
Q

[PMT part] reflect light emitted toward PMT

A

reflector

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46
Q

reflectors are made up of:

A

magnesium oxide
aluminum trioxide
titanium dioxide

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47
Q

[PMT part] protect the crystal

A

aluminum or stainless steel jacket

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48
Q

[PMT part] boundary between scintillator and PMT, permit exit of light from crystals t PMT

A

transparent window

49
Q

[PMT part] photoemissive material that affects electrons when strike by light photons

A

photocathode

50
Q

photocathode composition

A

cesium and antimony
sodium and potassium

51
Q

T/F at 7-10 light photons that is converted into 1 electron

A

T

52
Q

[PMT part] direct e- towards dynodes

A

focus grid

53
Q

[PMT part] amplify e-

A

dynodes

54
Q

[PMT part] collect all e- creating electrical signals

A

anode

55
Q

seals PMT

A

MU metal

56
Q

overall electron gain from dynode amplification

A

10^6

57
Q

applied V for liquid scintillators

A

below 40 keV

58
Q

[PET Scintillators] single crystals in early years of PET

A

NaI (Tl)

59
Q

[PET Scintillators] most detector designs convert to this material because of its greater efficiency to 5ll keV

A

Bismuth Germinate (BGO)

60
Q

[PET Scintillators] used widely in future gen PET scanners

A

Cesium doped Lutetium oxyorthosilicate LSO(Ce)

61
Q

[PET Scintillators] others

A

barium fluoride (BaF2)
Yttriumaluminate (YA103[Ce] or YAP)
Cesium doped - gadolinium oxyorthosilicate (GSO)

62
Q

4 components of LSC

A

organic solvent (cocktail)
primary solute (primary fluor)
secondary solute (wave shifter)
*additives

63
Q

[LS component] dissolves the scintillator and radioactive samples

A

organic solvent (cocktail)

64
Q

traditional and more environmentally harsh solvents

A

toluene, dioxane, xylene

65
Q

commonly used organic solvents

A

diisopropylnapthalene (DIN)
phenyl xylyl ethane (PXE)

66
Q

[LS component] absorbs the energy from the solvent and coverts light

A

primary solute (primary fluor)

67
Q

primary fluor composition

A

pterphenyl and 2,5 diphenyloxozole (PPO)/ bis-MSB [p-bis -(methylstyryl) benzene]

68
Q

[LS component] absorbs emissions of the primary solute and remit photons of longer wavelengths which are better matched to the PMT response

A

secondary solute (wave shifter)

69
Q

secondary solute (wave shifter) composition

A

1,4-di [2,5 phenyloxozole] benzene

70
Q

[LS component] improve some aspect of their performance (efficiency of energy transfer from the solvent to the primary solute)

A

additives

71
Q

sometimes added to improve the dissolution of added samples such as blood

A

solubilizers (hyamine or hydroxide)

72
Q

LS drawbacks

A
  1. insufficient
  2. low light output 1/3 of Na(Tl)
73
Q

undesirable reduction in light output from the scintillation cocktail

A

quenching

74
Q

caused by substances that compete with the primary fluor for absorption of energy from the solvent but not are not themselves scintillators

A

chemical quenching

75
Q

most troublesome chemical quenchers

A

dissolved oxygen

76
Q

caused by substances that absorb emissions of primary and secondary solute

A

color quenching

77
Q

examples of color quenching substances

A

blood and other colored materials
fogged and dirty containers

78
Q

occurs when a relatively large volume of sample is added to the scintillator solution, reducing concentration of solutes and output efficiency

A

dilute quenching

79
Q

** due to condensation presence of fingerprint or dirt on the vial

A

optical quenching

80
Q

semi conductor detectors composition

A

solid state gas analogs
- silicon or germanium coupled with lithium
-cadmium telluride (Cd Te)
-cadmium zinc telluride (CZT)

81
Q

disadvantages of SCD

A
  1. Si and Ge CONDUCT A SIGNIFICANT AMOUNT OF THERMALLY INDUCED CURRENT AT ROOM TEMP (NOISE CURRENT)
  2. presence of impurities in crystals (use HP Ge)
  3. time consuming and expensive prep
  4. small crystal size
82
Q

use of SCD in NM

A

in vitro applications
-tracer studies
-assay of radionuclidic purity of RPs
-handheld probes for lymphatic mapping
- compact gamma camera for scintimammography

83
Q

In vivo counting systems

A
  1. probe system
  2. whole body counters
84
Q

system designed to monitor radioactivity in localized parts of the body

A

probe system

85
Q

measure activity in specific organ aka thyroid
also known as Organ Uptake

A

single probe system

86
Q

used for renal function studies , lung clearance studies
also known as dynamic.perfusion counting

A

multi-probe systems

87
Q

system designed to measure the total amount of radioactivity distribution

A

whole body counters

88
Q

in vitro counting systems

A

well counters
dose calibrators

89
Q

constructed mainly for counting samples of urine, blood and feces
count samples in standard test tube

A

well counters

90
Q

major tool in “in vitro” assay

A

Na(Tl) well counters

91
Q

type of ionization chamber used for assaying relatively large quantities of gamma and x-ray
-used for measuring or verifying the activity eluates

A

dose calibrators

92
Q

difference b/w whole body counting and dose calibrators..

A

DC knows specific part of the body that receives the rad’n

93
Q

device used in NM to view and analyze images of the distribution injected, inhaled or ingested

A

gamma camera

94
Q

anger camera principles

A

gamma emmited by pt → collimator (allow only II gamma to pass thru) → scintillator material → convert rad’n to light photons → absorbed by PMT → electrical signals (1. x and y -plot location of radiation, used for spatial coordinate, z - analyzed by pulse height analyzer)

95
Q

types of gamma cameras

A
  1. stationary gc w/ scanning capabilities
  2. scanning systems (SPECT) based on single or multi-head gc
  3. mobile gc for irradiation scanning
  4. handheld gc
96
Q

stationary gc w/ scanning capabilities [purpose]

A

for determining distrib of administered RP in pt’s body
-gc produced planar images in cross sectional slices

97
Q

scanning systems (SPECT) based on single or multi-head gc [purpose]

A

used for cardiac, whole body imaging and brain perfusion
-some have multi camera heads
-tomo images

98
Q

mobile gc for irradiation scanning [purpose]

A

bedside assessment
only planar images
used for dx of cardiac pts
wheeled units - detector, stand, data processing console

99
Q

handheld gc [purpose]

A

portable for real-time visualization and localization of rad’n markers
used to locate sentinel lymph nodes
R.O.L.L (radioguided ocult lesion localization )
S.N.O.L (sentinel node and occult localization)

100
Q

image sensors used in handheld gc

A

cadmium zinc telluride

101
Q

[gc collimators] all holes II to each other

A

parallel hole collimators

102
Q

most common designs for parallel hole collimators

A

low-energy all-purpose (LEAP)
low-energy high-resolution (LEHR)
medium and high energy collimators

103
Q

holes with large diameter sensitivity is relatively high, resolution is moderate

A

LEAP collimators

104
Q

[gc collimators] oblique view for better visualization
adv. can be positioned close to body for max. gain resolution

A

slanthole collimators

105
Q

[gc collimators] create magnified images, for large POU

A

converging collimators

106
Q

[gc collimators] upside down converging, minified view

A

diverging collimators

107
Q

[gc collimators] applied for rectangular camera need to image small POI like brain, heart
1D parallel, other direction - converged

A

fanbeam collimators

108
Q

purpose of fanbeam collimators

A

arrangement allows data from the pt to use max. surface of the crystal

109
Q

fan beam when flipped over
used for whole body sweeps

A

single pass diverging collimator

110
Q

[gc collimators] cone shaped collimator have a single hole with interchangeable inserts that come w/ a 3,4,6mm aperture

A

pinhole colimators

111
Q

produce magnified images of small organ like the thyroid or a joint
designed for low energy isotopes

A

pinhole collimators

112
Q

distance from one septa to next

A

d- diameter

113
Q

dist. from source to collimator

A

D-distance of collimator

114
Q

thickness of colimator

A

L- length of colimator

115
Q

As d increases
As L increases
As D increases

A

Rg increases (res down)
Rg decreases (res up)
Rg increases (res down)

116
Q

efficiency of collimator
ratio of no of photons that paa thru the collimator to the n emitted

A

sensitivity

117
Q

sharpness or detail of NM image

A

Spatial resolution

118
Q

difference in density or intensity in parts of image corresponding to different concentration of activity in the pt

A

contrast

119
Q

factors that affect contrast

A

film contrast
presence background act
scattered rad’n

Nuclear Medicine (11 decks)

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