Part IV Flashcards
(119 cards)
1
Q
generic term for device that transforms energy from one form to another
A
Transducer
2
Q
2 classifications of radiation detector
A
non paralysable
paralysable
3
Q
detector classification used for imaging PET or SPECT
A
non paralysable
4
Q
detector classification that measures continuously, there is a need to reset device for it to detect other event
A
paralysable
5
Q
properties of detectors
A
detector efficiency
energy resolution
temporal resolution
spatial resolution
6
Q
ratio of gamma detector detected received over the no. of gamma rays emitted
A
detector efficiency
7
Q
2 types of detector efficiency
A
geometric efficiency
intrinsic efficiency
8
Q
configuration and the distance of the source
A
geometric efficiency
9
Q
ability to absorb thickness and attenuation coefficient of the detecting material
A
intrinsic efficiency
10
Q
energy resolution formula
A
100% x Full Wave at Half Maximum/ gamma energy
11
Q
[..] keV good images detected by detector
A
50-300 keV
12
Q
refers to the amount of blurring that is produced by an imaging system
A
spatial resolution
13
Q
expresses how accurately a radiation detector system is able to determine the time of interaction
A
temporal resolution
14
Q
the conversion of gamma ray energy into an electronic pulse and processing
A
dead time
15
Q
two main types of detectors
A
scintillators
gas detectors
16
Q
the basic of most diagnostic and imaging instruments
convert gamma in light -used in imaging
A
scintillators
17
Q
typically used in non-imaging instrument,
use gases and once streak by gamma rays, there is ionization used
A
gas detectors
18
Q
three main types of gas filled detectors
A
ionization chamber
proportional counters
geiger mueller counters
19
Q
applied V for ionization chamber
A
100-400 V
20
Q
[ionization chamber] used to assay activity levels in syringes. vials..etc.
A
dose calibrators
21
Q
[ionization chamber] used for radiation protection purposes
A
survey meter
22
Q
[ionization chamber] personnel monitoring
A
pocket dosimeters
23
Q
T/F ionization chamber cannot detect a single radiation event
A
True
24
Q
proportional counter gases
A
90% argon/xenon and 10% methane gas
25
applied voltage of proportional counters
400-800 V
26
adv. of proportional counters
greater electron amplification
pulse size is a factor 100-10000 times greater than ionization chamber
capable of detecting single radiation event
27
T/F Proportional Counters have little use in NM and is used mainly for measuring alpha and beta in research
T
28
applied V of geiger mueller counters
above 800 V
29
commonly used quenching gas in geiger mueller counters
heavy organic vapour (alcohol) and halogen gas (Cl)
30
T/F G-M counters is used in NM as survey meter to locate even a small amount of radioactivity
T
31
2 types of scintillation detectors
inorganic substances - solid
organic substances - liquid
32
Examples of inorganic substances
NaI (Tl), ZnS (Ag), CsI (Tl), CdS(Ag)
33
Example of organic substances
2,5 diphenyloxazole
34
basic components of scintillation counter
1. Detector System -Scintillator and PMT
2. Processing Unit - Gamma Spectrometer
3. Display Unit
35
[detector system part] filter gamma, prevent misinterpretation, allows only parallel gamma rays to pass thru,
limits area of gamma camera
collimator
36
[detector system part] used to enhance and reshape photoactivity of the emitted light photons
pre-amplifier
37
[detector system part] refer to the dynodes of the PMT, amplify no. of electrons
amplifier
38
[processing unit part] to evaluate incoming electric signals coming from PMT
accept/reject signals not equivalent to predicted energy of radionuclide
PHA- Pulse Height Analyzer
39
counts on a scaler, needle deflection on a rate meter, a dot on a special type of paper, display data in monitor system
display unit
40
properties of ideal scintillator
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
41
explain scintillation detectors
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
42
reasons to use NaI (Tl)
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
43
disadvantages of NaI (Tl)
fragile
hygroscopic - collects moisture
large crystal
44
Parts of PMT
crystal
reflector
Al or stainless steel jacket
transparent window
photocathode
focus grid
dynodes
MU metal (iron, nickel, copper, chromium)
45
[PMT part] reflect light emitted toward PMT
reflector
46
reflectors are made up of:
magnesium oxide
aluminum trioxide
titanium dioxide
47
[PMT part] protect the crystal
aluminum or stainless steel jacket
48
[PMT part] boundary between scintillator and PMT, permit exit of light from crystals t PMT
transparent window
49
[PMT part] photoemissive material that affects electrons when strike by light photons
photocathode
50
photocathode composition
cesium and antimony
sodium and potassium
51
T/F at 7-10 light photons that is converted into 1 electron
T
52
[PMT part] direct e- towards dynodes
focus grid
53
[PMT part] amplify e-
dynodes
54
[PMT part] collect all e- creating electrical signals
anode
55
seals PMT
MU metal
56
overall electron gain from dynode amplification
10^6
57
applied V for liquid scintillators
below 40 keV
58
[PET Scintillators] single crystals in early years of PET
NaI (Tl)
59
[PET Scintillators] most detector designs convert to this material because of its greater efficiency to 5ll keV
Bismuth Germinate (BGO)
60
[PET Scintillators] used widely in future gen PET scanners
Cesium doped Lutetium oxyorthosilicate LSO(Ce)
61
[PET Scintillators] others
barium fluoride (BaF2)
Yttriumaluminate (YA103[Ce] or YAP)
Cesium doped - gadolinium oxyorthosilicate (GSO)
62
4 components of LSC
organic solvent (cocktail)
primary solute (primary fluor)
secondary solute (wave shifter)
*additives
63
[LS component] dissolves the scintillator and radioactive samples
organic solvent (cocktail)
64
traditional and more environmentally harsh solvents
toluene, dioxane, xylene
65
commonly used organic solvents
diisopropylnapthalene (DIN)
phenyl xylyl ethane (PXE)
66
[LS component] absorbs the energy from the solvent and coverts light
primary solute (primary fluor)
67
primary fluor composition
pterphenyl and 2,5 diphenyloxozole (PPO)/ bis-MSB [p-bis -(methylstyryl) benzene]
68
[LS component] absorbs emissions of the primary solute and remit photons of longer wavelengths which are better matched to the PMT response
secondary solute (wave shifter)
69
secondary solute (wave shifter) composition
1,4-di [2,5 phenyloxozole] benzene
70
[LS component] improve some aspect of their performance (efficiency of energy transfer from the solvent to the primary solute)
additives
71
sometimes added to improve the dissolution of added samples such as blood
solubilizers (hyamine or hydroxide)
72
LS drawbacks
1. insufficient
2. low light output 1/3 of Na(Tl)
73
undesirable reduction in light output from the scintillation cocktail
quenching
74
caused by substances that compete with the primary fluor for absorption of energy from the solvent but not are not themselves scintillators
chemical quenching
75
most troublesome chemical quenchers
dissolved oxygen
76
caused by substances that absorb emissions of primary and secondary solute
color quenching
77
examples of color quenching substances
blood and other colored materials
fogged and dirty containers
78
occurs when a relatively large volume of sample is added to the scintillator solution, reducing concentration of solutes and output efficiency
dilute quenching
79
** due to condensation presence of fingerprint or dirt on the vial
optical quenching
80
semi conductor detectors composition
solid state gas analogs
- silicon or germanium coupled with lithium
-cadmium telluride (Cd Te)
-cadmium zinc telluride (CZT)
81
disadvantages of SCD
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
use of SCD in NM
in vitro applications
-tracer studies
-assay of radionuclidic purity of RPs
-handheld probes for lymphatic mapping
- compact gamma camera for scintimammography
83
In vivo counting systems
1. probe system
2. whole body counters
84
system designed to monitor radioactivity in localized parts of the body
probe system
85
measure activity in specific organ aka thyroid
also known as Organ Uptake
single probe system
86
used for renal function studies , lung clearance studies
also known as dynamic.perfusion counting
multi-probe systems
87
system designed to measure the total amount of radioactivity distribution
whole body counters
88
in vitro counting systems
well counters
dose calibrators
89
constructed mainly for counting samples of urine, blood and feces
count samples in standard test tube
well counters
90
major tool in "in vitro" assay
Na(Tl) well counters
91
type of ionization chamber used for assaying relatively large quantities of gamma and x-ray
-used for measuring or verifying the activity eluates
dose calibrators
92
difference b/w whole body counting and dose calibrators..
DC knows specific part of the body that receives the rad'n
93
device used in NM to view and analyze images of the distribution injected, inhaled or ingested
gamma camera
94
anger camera principles
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
types of gamma cameras
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
stationary gc w/ scanning capabilities [purpose]
for determining distrib of administered RP in pt's body
-gc produced planar images in cross sectional slices
97
scanning systems (SPECT) based on single or multi-head gc [purpose]
used for cardiac, whole body imaging and brain perfusion
-some have multi camera heads
-tomo images
98
mobile gc for irradiation scanning [purpose]
bedside assessment
only planar images
used for dx of cardiac pts
wheeled units - detector, stand, data processing console
99
handheld gc [purpose]
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
image sensors used in handheld gc
cadmium zinc telluride
101
[gc collimators] all holes II to each other
parallel hole collimators
102
most common designs for parallel hole collimators
low-energy all-purpose (LEAP)
low-energy high-resolution (LEHR)
medium and high energy collimators
103
holes with large diameter sensitivity is relatively high, resolution is moderate
LEAP collimators
104
[gc collimators] oblique view for better visualization
adv. can be positioned close to body for max. gain resolution
slanthole collimators
105
[gc collimators] create magnified images, for large POU
converging collimators
106
[gc collimators] upside down converging, minified view
diverging collimators
107
[gc collimators] applied for rectangular camera need to image small POI like brain, heart
1D parallel, other direction - converged
fanbeam collimators
108
purpose of fanbeam collimators
arrangement allows data from the pt to use max. surface of the crystal
109
fan beam when flipped over
used for whole body sweeps
single pass diverging collimator
110
[gc collimators] cone shaped collimator have a single hole with interchangeable inserts that come w/ a 3,4,6mm aperture
pinhole colimators
111
produce magnified images of small organ like the thyroid or a joint
designed for low energy isotopes
pinhole collimators
112
distance from one septa to next
d- diameter
113
dist. from source to collimator
D-distance of collimator
114
thickness of colimator
L- length of colimator
115
As d increases
As L increases
As D increases
Rg increases (res down)
Rg decreases (res up)
Rg increases (res down)
116
efficiency of collimator
ratio of no of photons that paa thru the collimator to the n emitted
sensitivity
117
sharpness or detail of NM image
Spatial resolution
118
difference in density or intensity in parts of image corresponding to different concentration of activity in the pt
contrast
119
factors that affect contrast
film contrast
presence background act
scattered rad'n
