Nuclear Medicine Flashcards
(175 cards)
1
Q
The unit of radioactive decay is the Becquerel (Bq)
A
True
2
Q
Technetium-99m has a half-life of 6 hours
A
True
3
Q
The main radioisotope used in nuclear med is Technetium-99 (Tc99)
A
True
4
Q
The effective half-life of a radioisotope depends only on its physical half-life
A
False (The effective half-life of a radioisotope depends on both its physical half-life and it’s biological half-life)
5
Q
Radiation Protection in Nuclear Medicine applies what conditions?
A
Justification, Optimisation and DRLs
6
Q
What are some factors that need to be considered about Justification of NM scans?
A
- Is the test required?
- Are there alternative tests which can be performed? (using a lower dose or without using ionising radiation at all?)
- Does the benefit of the test outweigh the risks?
7
Q
What are some important factors regarding Optimisation of NM scans?
A
- ALARA principle
- patient age and body habitus should be taken into account
- for paediatrics, weight should be considered
- proper QA testing of all equipment (to ensure adequate function)
- adequate staff training
8
Q
The annual whole body dose limit for a member of the public is 1mSv
A
True
9
Q
The annual whole body dose limit for Category B workers (radiographers etc.) is 15 mSv
A
False (The whole body dose limit for category B workers is 6 mSv)
10
Q
NM procedures do not have dose limits for patients, instead DRLs are used.
A
True (produced by HIQA and used to guide recommended activity of the radioisotope to be administered to the average patient for a particular test)
11
Q
In NM, children are considered at lower risk from ionising radiation compared to adults
A
False (Children are at a higher risk, particularily for cancer induction)
12
Q
Fluid intake should be reduced following a NM scan
A
False (fluid intake and frequent bladder emptying should be encouraged to reduce patient dose through excretion)
13
Q
Distance and shielding are important safety measures for nuclear medicine staff
A
True
14
Q
Breastfeeding mothers are advised to avoid close contact with their babies for 48 hours after a NM injection
A
False (The recommendation is to avoid close contact for 24 hours. Breast milk can be aspirated in advance using a breast pump)
15
Q
Typical whole body dose for Tc-99 bone scan is ~5mSv
A
True
16
Q
The only method to measure detector uniformity in NM is using a Cobalt Flood Sheet.
A
False (Both a Cobalt Flood Sheet (expensive) and a Fillable Flood Source can be used)
17
Q
Technetium is readily-available in an NM department
A
True
18
Q
A fillable flood source phantom is a cheaper alternative to measure detector uniformity in NM than a Cobalt flood sheet.
A
True (As it uses Technetium + saline)
19
Q
The intrinsic resolution of a gamma camera refers to its spatial resolution WITHOUT a collimator
A
True
20
Q
The extrinsic resolution of a gamma camera is the spatial resolution of the system WITH a collimator
A
True
21
Q
Spatial resolution is often measured using a graph called a Modulation Transfer Function (MTF)
A
False (The graph is called a Line Spread Function)
22
Q
The broader the Line Spread Function graph is, the poorer the spatial resolution and vice versa (the narrower it is, the better the spatial resolution)
A
True
23
Q
The line spread function broadens with poorer spatial resolution
A
True
24
Q
The width of the Line Spread Function can be expressed as FWHM (full width at half maximum)
A
True
25
The main radionuclide used in NM is Iodine
False (The main radionuclide used is Technetium)
26
Technetium is produced from the decay of Molybdenum in a generator
True
27
The half-life of Technetium-99 is approx. 18 hours
False (The half-life of Tc99 is ~ 6 hours)
28
The 6 hour half-life of Tc99 makes it unusable in NM
False. (The 6 hour half-life of Tc99 is ideal for imaging)
29
The parent atom of Technetium is Gallium.
False. (The parent atom of Tc is Molybdenum)
30
The radioactive decay of 'parent' Molybdenum to Technetium-99m involves both beta-particle and gamma ray emission
True
31
Technetium-99m decays through gamma ray emission to a more stable form of Technetium
True (The more stable form of Tc has a half-life of ~2000 years)
32
As the parent atom (Mo) decays, the activity of the daughter radionuclide (Tc) increases
True
33
Sodium pertechnetate is the eluate from a Technetium generator
True
34
Molybdenum breakthrough in a Technetium generator should only be a trace amount
True
35
In NM, the gamma camera does not utilise a collimator
False (A collimator is used in the gamma camera system to improve image quality by blocking unwanted rays)
36
Thicker crystals in gamma cameras improve spatial resolution but decrease detection efficiency
False. (Thicker crystals improve detection efficiency but reduce spatial resolution due to the dispersion of light through the crystal)
37
The purpose of a collimator in a gamma camera is to reduce scatter from gamma rays
False. (The main purpose is to block rays not coming directly from the organ of interest)
38
The main role of the Pulse Height Analyser (PHA) is to exclude scatter
True. (It does so by ignoring pulses that do not meet the threshold)
39
Technetium-99m is a pure gamma emitter.
True. (Decay does not involve alpha or beta emission)
40
Tc-99m gamma ray has an energy of 640 keV, making it difficult to shield
False. (Tc-99m gamma ray has an energy of 140keV, making it relatively easy to shield).
41
Molybdenum breakthrough is entirely preventable
False
42
The gamma camera is the main imaging device used in NM
True
43
Name some important components of a gamma camera
- Collimator
- Crystal
- Light Guide
- PMT Array
44
Sensitivity of the gamma camera refers to the amount of gamma rays that reach the crystal
True
45
A very small % of gamma rays do not reach the crystal as they are either blocked by the collimator or scattered into space
False. (It is actually a large % of rays that are blocked or emitted into space)
46
Photomultiplier Tubes (PMTs) are arranged in a circular array
False. (PMTs are arranged usually in a hexagonal array)
47
The amplitude of signal detected by the PMTs is proportional to the amount of light emitted by the crystal, which is proportional to the energy of the gamma ray
True
48
The value of Z-signals are not related to the energy of the gamma rays
False. (The Z-signal is proportional to the energy of the gamma rays)
49
The position circuitry works out where the interaction took place by comparing outputs from individual PMTs
True
50
The PHA will ignore pulses that do not meet a specific threshold
True
51
The goal of nuclear medicine imaging is to provide clear anatomical detail
False. (The goal of NM imaging is to map the distribution of radiotracers. NM imaging is more functional than anatomical)
52
The photopeak in an energy spectrum represents the complete energy deposited by gamma rays in the detector
True
53
The Line Spread Function is used to measure spatial resolution in nuclear medicine imaging
True
54
Temporal resolution in NM depends largely on the decay time of the detector material
True
55
In NM imaging, increased dead time increases image quality
False. (Increased dead time degrades image quality)
56
Spatial resolution is affected heavily by the distance of the source from the collimator
True
57
The closer the patient is to the collimator, the worse the spatial resolution is
False. (The closer the patient is to the collimator, the better the spatial resolution)
58
Spatial resolution gets better when the patient is closer to the collimator
True. (Less spread = narrower resolution function)
59
Effective half life of a radionuclide is lower than physical half-life
True
60
Intrinsic spatial resolution measurements translate easily into a clinically useful value
False. (Extrinsic spatial resolution measures are made under more clinically realistic conditions)
61
The timing resolution of NM is limited by the decay time of the crystal
True
62
The decay time for semiconductor detectors is much smaller than scintillators
True
63
Spatial resolution depends on patient distance from the collimator
True
64
High-sensitivty collimators are optimal for procedures requiring very high spatial resolution
False. (High-sensitivty collimators sacrifice spatial resolution for improved detection efficiency)
65
Dual-headed gamma cameras are typically used in SPECT
True
66
Dual-headed gamma cameras with a 360 degree rotation are typically used for SPECT cardiac imaging
False. (360 degree rotation for general imaging and 180 degree rotation for cardiac imaging)
67
What does SPECT stand for?
Single Photon Emission Computed Tomography
68
SPECT is often described as Planar Nuclear Medicine Imaging
False. (Planar NM imaging obtains a 2-D image while SPECT can acquire projection data at multiple angles by rotating the gamma camera around the patient)
69
Parallel Hole Collimators are used for SPECT imaging
True
70
SPECT images often contain many artefacts
True
71
What are the most significant artefacts associated with SPECT imaging?
- Photon Attenuation (photons absorbed by other tissues eg. muscle, fat)
- Scatter
- Depth Dependent Collimator Response (closeness of collimator to patient will affect spatial resolution)
72
Image reconstruction techniques used in SPECT imaging are similar to that of CT
True. (Filtered Back Projection and Iterative Reconstruction)
73
In modern SPECT machines, Iterative Recontruction is preferred over Filtered Back Projection
True
74
Iterative Reconstruction is preferred over Filtered Back Projection in SPECT because it requires less computing power
False. (Although IR is prefered because it is more accurate, it requires more computing power than FBP)
75
Correction for photon attenuation in SPECT involves the use of Hybrid SPECT-CT systems
True. (SPECT systems are combined with a 16-slice CT scanner)
76
Attenuation correction in SPECT can be achieved by using transmission data from X-ray sources (CT data)
True. (Hybrid SPECT-CT systems uses CT data to correct attenuation).
77
SPECT-CT systems typically use a dual-headed gamma camera combined with a 4-16 slice CT scanner
True
78
In SPECT-CT imaging, the CT images are used to superimpose anatomical details on the functional SPECT images for better localisation
True
79
In SPECT imaging, a significant fraction of the detected photons are scattered in the body
True. (Resulting in loss of contrast - corrections need to be made to reduce scatter)
80
Quantum mottle is not an issue in SPECT imaging
False. (Quantum mottle is a major factor in SPECT due to the low number of photons used)
81
In SPECT imaging, each projection of the gamma camera takes about 2 seconds
False. (Each projection of the gamma camera takes about 20 seconds - full scan time will usually be about 20 mins)
82
SPECT produces an isotropic volume data set
True. (Images can be reconstructed in transverse, sagittal or coronal views)
83
SPECT imaging has better spatial resolution than planar gamma camera imaging
False. (SPECT has poorer spatial resolution but provides better contrast than planar gamma camera imaging)
84
Planar Gamma Camera imaging has better spatial resolution than SPECT
True
85
Spatial resolution in SPECT is poorer than Planar imaging
True
86
Misregistration artifacts can occur in SPECT-CT imaging if organs move between the SPECT and CT scans
True
87
In SPECT imaging, attenuation is significant as photons pass through varying tissue densities
True
88
Photon attenuation in the lungs is typically high
False. (Photon attenuation in the lungs is low due to air content).
89
The most common configurations for dual-headed gamma cameras in SPECT are 180 degrees for cardiac imaging and 90 degrees for general imaging
False. (180 is most common for cardiac imaging while 360 is typical for general imaging)
90
In SPECT-CT imaging, CT data is used for anatomical localisation only.
False. (CT data aids in both attenuation correction and anatomical localisation)
91
Spatial resolution in SPECT depends partly on the distance of the patient from the gamma camera's collimator
True
92
The contrast in SPECT images is generally better than planar imaging
True
93
The primary advantage of SPECT over planar imaging is improved spatial resolution
False. (The primary advantage is improved contrast and lesion detection by elimination overlapping structures)
94
What does PET stand for?
Positron Emission Tomography
95
PET is commonly used for oncology imaging
True
96
Radionuclides that decay via positron emission usually have a larger proportion of protons compared to neutrons
True
97
Positron emissions involves a proton decaying into a neutron + a positron
True
98
Positron emission involves a proton decaying into a neutron + an electron
False. (Positron emission involves a proton decaying into a neutron + a positron)
99
A positron is an antielectron
True
100
The distance the positron travels in tissue depends on the initial number of neutrons
False. (the distance the positron travels in tissue depends on its initial energy and the number of interactions with the atoms in the tissue)
101
In positron emission, the distance the positron travels in tissue depends on its initial energy and the number of interactions with the atoms in the tissue.
True
102
Positrons travels short distances in tissue
True
103
Positrons travel long distances in tissue
False. (Positrons travels short distances in tissue)
104
Positron emission is also known as Positive Beta Emission (or Positive Beta Decay)
True
105
When a positron meets an electron, an annihilation reaction occurs
True
106
When an annihilation reaction occurs between a positron and an electron, the two particles are converted into x-rays that travel in opposite directions
False. (The two particles are converted into two gamma rays that travel in opposite directions)
107
When an annihilation reaction occurs, the two particles are converted into two gamma rays that travel in the same direction
False. (The two particles are converted into two gamma rays that travel in opposite directions)
108
When an annihilation reaction occurs between a positron and an electron, the two particles are converted into two gamma rays that travel in opposite directions
True
109
The distance a positron will travel in tissue will depend on the type of radionuclide used
True.
110
The two gamma rays that are produced in an annihilation reaction will travel 90 degrees from each other
False. (The two gamma rays will travel 180 degrees from each other in opposite directions)
111
The two gamma rays produced in an annihilation reaction are of the same energy.
True. (511 keV)
112
The most commonly used radionuclide is Fluorine-18
True. (Combined with deoxyglucose as fluorodeoxyglucose (FDG).)
113
Fluorodeoxyglucose (FDG) is a tracer for potassium metabolism
False. (FDG is a tracer for glucose metabolism)
114
Fluorodeoxyglucose (FDG) is a tracer for glucose metabolism.
True. (It is distributed throughout the body but particularily taken up where there is increased glucose metabolism eg. tumours)
115
There is increased glucose metabolism in tumours.
True
116
There is increased glucose metabolism in tumours ONLY.
False. (There is also increased glucose metabolism where there is infection or inflammation)
117
Fluorine-18 has a half-life of 110 minutes.
True
118
The basis of PET imaging is positron emission and annihilation.
True
119
PET imaging requires the use of a collimator.
False. (PET does not require a collimator.)
120
The weakest link in the SPECT image formation process is the requirement for a collimator.
True
121
Coincidence detection is used to distinguish photons arising from positron annihilation
True
122
Coincidence detection is based on the energy of the gamma rays.
False. (It is based on temporal discrimination (timing).)
123
PET has better spatial resolution than SPECT
True
124
On a PET scanner, there is a single row of scintillation crystals (detectors).
False. (Blocks of scintillation crystals are arranged in a circle mounted on a gantry in multiple rings.)
125
In PET, two photomultiplier tubes are mounted on each detector block
False. (Four PMTs are mounted on each block)
126
Lutetium oxyorthosilicate (LSO) and Bismuth germanate (BGO) are used as scintillators in modern PET scanners
False. (BGO is not used anymore).
127
Lutetium oxyorthosilicate (LSO) and gadolinium orthosilicate (GSO) are used as scintillators in modern PET scanners
True
128
LSO has become the scintillator of choice in PET scanners because of its long decay time.
False. (It has become the scintillator of choice because of its short decay time - time to be ready for the detection of the next gamma ray.)
129
Photomultiplier tubes are the preferred photodetectors used in PET systems because of their good SNR
True
130
In PET imaging, multiple transverse slices can be simultaneously acquired because of the rings of detectors arranged around the patient.
True
131
In PET imaging, Digital Photon Counting (DPC-PET) is prefered over Photomulitplier Tube (PMT-PET).
False. (PMT-PET is preferred)
132
The main difference between PMT-PET and DPC-PET is how they detect and process the light photons generated by the scintillation crystals.
True
133
Digital Photon Counting (DPC) technology is based on semiconductor detectors over traditional PMTs
True
134
In PET-CT, a 64-slice scanner is usually used
True
135
In PET-CT, a 16-slice CT scanner is usually used.
False. (A 64-slice CT scanner)
136
Large FDG uptake in the brain is abnormal
False. (There is always massive FDG uptake in the brain as metabolism is entirely glucose based)
137
In coincidence counting, the line between the two detectors is called the Line of Response (LOR).
True
138
If two opposite detector elements detect a gamma ray photon simultaneously, it is considered a coincidence count
True
139
Gamma rays detected within seconds of each other are considered a coincidence
False. (Gamma rays detected simultaneously or within nanoseconds of each other are considered a coincidence count)
140
Coincidence detection involves the association of detection events at two opposite detectors, independent of arrival times
False. (Coincident detection is based upon the arrival times of the two photons)
141
The Line of Response (LOR) is assumed to intersect the unknown location of the annihilation event.
True. (ie. the annihilation event occurs somewhere along the LOR)
142
Photons are analysed in a Pulse Height Analyser (PHA) to determine whether it meets the energy acceptance criteria
True
143
The time interval determining when events are considered to be coincident is denoted 2τ
True
144
The time interval determining when events are considered to be coincident is denoted 4τ.
False. (2τ)
145
2-D acquisition of PET data is associated with a high rate of scattered coincidence events
False. (It is associated with a low rate of scattered coincidence events)
146
3-D acquisition of PET data is associated with high sensitivity but increased scatter
True
147
3-D acquisition of PET data is associated with less scatter than 2-D acquisition
False. (3D acquisition has more scatter than 2D)
148
In PET, the contribution of scatter will increase with increasing patient size
True
149
Data recorded during PET acquisition is transformed into a 2-D bell curve
False. (PET data is transformed into a 2D sinogram)
150
High-timing resolution is needed for Time of Flight (TOF) PET systems
True
151
The basis of TOF-PET imaging is that by knowing the time difference between the arrival of photons, you can accurately determine where the interaction took place
True
152
In conventional PET imaging, we can preciesly determine the location of the annihilation event
False. (No information is available about the location of the annihilation event in conventional PET imaging)
153
In Time of Flight-PET imaging, we can accurately estimate the position of the annihilation event along the LOR
True
154
TOF-PET imaging has improved spatial resolution over conventional-PET
True
155
TOF-PET has potential benefits for imaging paediatric patients
False. (It has potential benefits for imaging large patients where there is high amounts of attenuation and scatter)
156
Attenuation correction can be more easily corrected in SPECT over PET.
False. (It is easier to correct attenuation in PET over SPECT as it allows for patient thickness)
157
Attenuation can be corrected more easily in PET than SPECT
True. (This is because PET imaging allows for thickness of the patient)
158
Pulse Height Analysers (PHA) are used to help remove scatter from the image
True
159
Generally, scattered photons will have higher energy than the photons travelling directly to the detector
False. (Scattered photons will have lower energy)
160
Coincidence detection of two photons from separate annihilation events (random event) contributes to increased image contrast
False. (Random event detections do not contain any spatial information and lead to reduced image contrast and contribute to image artifacts.)
161
in PET imaging, random event detection must be corrected
True. (Although there are only approximate ways of correction)
162
Long dead times of detectors contributes to an effective loss of sensitivity due to photons getting lost
True
163
Dead time cannot be corrected
False. (Dead time corrections are based upon experimental measurements.)
164
Radioactivity decays as the scanner moves down the patient
True
165
PET is sensitive to patient motion as it experiences longer imaging times
True
166
Planar gamma cameras are more sensitive than PET scanners
False. (PET scanners are more sensitive due to higher counts and less mottle)
167
PET scanners suffer from less quantum mottle than planar gamma camera imaging
True
168
The spatial resolution of PET-CT is ~5mm
True. (This means if a nodule/lesion is less than 5mm, it is not likely to be picked up on a PET scan.)
169
Spatial resolution is better at the edge than the centre
False. (Spatial resolution is worse at the edge because some of the gamma photons may be detected by adjacent detectors)
170
Effective dose for a PET scan is about 8 mSv
True
171
Effective dose for a PET-CT using a low dose CT scan (for anatomical correlation and attenuation correction) is about 10 mSv
True. (8 mSv PET + 2 mSv low dose CT)
172
FDG is taken up by and accumulates in metabollically active cells
True
173
The most avid uptake of FDG occurs in bone cancers
False. (Head and neck cancers have the most avid uptake of FDG)
174
Gamma cameras are primarily used in SPECT imaging, not PET
True
175
