Nuclear Medicine Flashcards

1
Q

The unit of radioactive decay is the Becquerel (Bq)

A

True

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2
Q

Technetium-99m has a half-life of 6 hours

A

True

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3
Q

The main radioisotope used in nuclear med is Technetium-99 (Tc99)

A

True

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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)

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5
Q

Radiation Protection in Nuclear Medicine applies what conditions?

A

Justification, Optimisation and DRLs

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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?
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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
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8
Q

The annual whole body dose limit for a member of the public is 1mSv

A

True

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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)

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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)

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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)

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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)

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13
Q

Distance and shielding are important safety measures for nuclear medicine staff

A

True

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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)

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15
Q

Typical whole body dose for Tc-99 bone scan is ~5mSv

A

True

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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)

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17
Q

Technetium is readily-available in an NM department

A

True

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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)

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19
Q

The intrinsic resolution of a gamma camera refers to its spatial resolution WITHOUT a collimator

A

True

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20
Q

The extrinsic resolution of a gamma camera is the spatial resolution of the system WITH a collimator

A

True

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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)

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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

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23
Q

The line spread function broadens with poorer spatial resolution

A

True

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24
Q

The width of the Line Spread Function can be expressed as FWHM (full width at half maximum)

A

True

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25
Q

The main radionuclide used in NM is Iodine

A

False (The main radionuclide used is Technetium)

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26
Q

Technetium is produced from the decay of Molybdenum in a generator

A

True

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27
Q

The half-life of Technetium-99 is approx. 18 hours

A

False (The half-life of Tc99 is ~ 6 hours)

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28
Q

The 6 hour half-life of Tc99 makes it unusable in NM

A

False. (The 6 hour half-life of Tc99 is ideal for imaging)

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29
Q

The parent atom of Technetium is Gallium.

A

False. (The parent atom of Tc is Molybdenum)

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30
Q

The radioactive decay of ‘parent’ Molybdenum to Technetium-99m involves both beta-particle and gamma ray emission

A

True

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31
Q

Technetium-99m decays through gamma ray emission to a more stable form of Technetium

A

True (The more stable form of Tc has a half-life of ~2000 years)

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32
Q

As the parent atom (Mo) decays, the activity of the daughter radionuclide (Tc) increases

A

True

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33
Q

Sodium pertechnetate is the eluate from a Technetium generator

A

True

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34
Q

Molybdenum breakthrough in a Technetium generator should only be a trace amount

A

True

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35
Q

In NM, the gamma camera does not utilise a collimator

A

False (A collimator is used in the gamma camera system to improve image quality by blocking unwanted rays)

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36
Q

Thicker crystals in gamma cameras improve spatial resolution but decrease detection efficiency

A

False. (Thicker crystals improve detection efficiency but reduce spatial resolution due to the dispersion of light through the crystal)

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37
Q

The purpose of a collimator in a gamma camera is to reduce scatter from gamma rays

A

False. (The main purpose is to block rays not coming directly from the organ of interest)

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38
Q

The main role of the Pulse Height Analyser (PHA) is to exclude scatter

A

True. (It does so by ignoring pulses that do not meet the threshold)

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39
Q

Technetium-99m is a pure gamma emitter.

A

True. (Decay does not involve alpha or beta emission)

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40
Q

Tc-99m gamma ray has an energy of 640 keV, making it difficult to shield

A

False. (Tc-99m gamma ray has an energy of 140keV, making it relatively easy to shield).

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41
Q

Molybdenum breakthrough is entirely preventable

A

False

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42
Q

The gamma camera is the main imaging device used in NM

A

True

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43
Q

Name some important components of a gamma camera

A
  • Collimator
  • Crystal
  • Light Guide
  • PMT Array
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44
Q

Sensitivity of the gamma camera refers to the amount of gamma rays that reach the crystal

A

True

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45
Q

A very small % of gamma rays do not reach the crystal as they are either blocked by the collimator or scattered into space

A

False. (It is actually a large % of rays that are blocked or emitted into space)

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46
Q

Photomultiplier Tubes (PMTs) are arranged in a circular array

A

False. (PMTs are arranged usually in a hexagonal array)

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47
Q

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

A

True

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48
Q

The value of Z-signals are not related to the energy of the gamma rays

A

False. (The Z-signal is proportional to the energy of the gamma rays)

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49
Q

The position circuitry works out where the interaction took place by comparing outputs from individual PMTs

A

True

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50
Q

The PHA will ignore pulses that do not meet a specific threshold

A

True

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51
Q

The goal of nuclear medicine imaging is to provide clear anatomical detail

A

False. (The goal of NM imaging is to map the distribution of radiotracers. NM imaging is more functional than anatomical)

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52
Q

The photopeak in an energy spectrum represents the complete energy deposited by gamma rays in the detector

A

True

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53
Q

The Line Spread Function is used to measure spatial resolution in nuclear medicine imaging

A

True

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54
Q

Temporal resolution in NM depends largely on the decay time of the detector material

A

True

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55
Q

In NM imaging, increased dead time increases image quality

A

False. (Increased dead time degrades image quality)

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56
Q

Spatial resolution is affected heavily by the distance of the source from the collimator

A

True

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57
Q

The closer the patient is to the collimator, the worse the spatial resolution is

A

False. (The closer the patient is to the collimator, the better the spatial resolution)

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58
Q

Spatial resolution gets better when the patient is closer to the collimator

A

True. (Less spread = narrower resolution function)

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59
Q

Effective half life of a radionuclide is lower than physical half-life

A

True

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60
Q

Intrinsic spatial resolution measurements translate easily into a clinically useful value

A

False. (Extrinsic spatial resolution measures are made under more clinically realistic conditions)

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61
Q

The timing resolution of NM is limited by the decay time of the crystal

A

True

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62
Q

The decay time for semiconductor detectors is much smaller than scintillators

A

True

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63
Q

Spatial resolution depends on patient distance from the collimator

A

True

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64
Q

High-sensitivty collimators are optimal for procedures requiring very high spatial resolution

A

False. (High-sensitivty collimators sacrifice spatial resolution for improved detection efficiency)

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65
Q

Dual-headed gamma cameras are typically used in SPECT

A

True

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66
Q

Dual-headed gamma cameras with a 360 degree rotation are typically used for SPECT cardiac imaging

A

False. (360 degree rotation for general imaging and 180 degree rotation for cardiac imaging)

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67
Q

What does SPECT stand for?

A

Single Photon Emission Computed Tomography

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68
Q

SPECT is often described as Planar Nuclear Medicine Imaging

A

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)

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69
Q

Parallel Hole Collimators are used for SPECT imaging

A

True

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70
Q

SPECT images often contain many artefacts

A

True

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71
Q

What are the most significant artefacts associated with SPECT imaging?

A
  • 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
Q

Image reconstruction techniques used in SPECT imaging are similar to that of CT

A

True. (Filtered Back Projection and Iterative Reconstruction)

73
Q

In modern SPECT machines, Iterative Recontruction is preferred over Filtered Back Projection

A

True

74
Q

Iterative Reconstruction is preferred over Filtered Back Projection in SPECT because it requires less computing power

A

False. (Although IR is prefered because it is more accurate, it requires more computing power than FBP)

75
Q

Correction for photon attenuation in SPECT involves the use of Hybrid SPECT-CT systems

A

True. (SPECT systems are combined with a 16-slice CT scanner)

76
Q

Attenuation correction in SPECT can be achieved by using transmission data from X-ray sources (CT data)

A

True. (Hybrid SPECT-CT systems uses CT data to correct attenuation).

77
Q

SPECT-CT systems typically use a dual-headed gamma camera combined with a 4-16 slice CT scanner

A

True

78
Q

In SPECT-CT imaging, the CT images are used to superimpose anatomical details on the functional SPECT images for better localisation

A

True

79
Q

In SPECT imaging, a significant fraction of the detected photons are scattered in the body

A

True. (Resulting in loss of contrast - corrections need to be made to reduce scatter)

80
Q

Quantum mottle is not an issue in SPECT imaging

A

False. (Quantum mottle is a major factor in SPECT due to the low number of photons used)

81
Q

In SPECT imaging, each projection of the gamma camera takes about 2 seconds

A

False. (Each projection of the gamma camera takes about 20 seconds - full scan time will usually be about 20 mins)

82
Q

SPECT produces an isotropic volume data set

A

True. (Images can be reconstructed in transverse, sagittal or coronal views)

83
Q

SPECT imaging has better spatial resolution than planar gamma camera imaging

A

False. (SPECT has poorer spatial resolution but provides better contrast than planar gamma camera imaging)

84
Q

Planar Gamma Camera imaging has better spatial resolution than SPECT

A

True

85
Q

Spatial resolution in SPECT is poorer than Planar imaging

A

True

86
Q

Misregistration artifacts can occur in SPECT-CT imaging if organs move between the SPECT and CT scans

A

True

87
Q

In SPECT imaging, attenuation is significant as photons pass through varying tissue densities

A

True

88
Q

Photon attenuation in the lungs is typically high

A

False. (Photon attenuation in the lungs is low due to air content).

89
Q

The most common configurations for dual-headed gamma cameras in SPECT are 180 degrees for cardiac imaging and 90 degrees for general imaging

A

False. (180 is most common for cardiac imaging while 360 is typical for general imaging)

90
Q

In SPECT-CT imaging, CT data is used for anatomical localisation only.

A

False. (CT data aids in both attenuation correction and anatomical localisation)

91
Q

Spatial resolution in SPECT depends partly on the distance of the patient from the gamma camera’s collimator

A

True

92
Q

The contrast in SPECT images is generally better than planar imaging

A

True

93
Q

The primary advantage of SPECT over planar imaging is improved spatial resolution

A

False. (The primary advantage is improved contrast and lesion detection by elimination overlapping structures)

94
Q

What does PET stand for?

A

Positron Emission Tomography

95
Q

PET is commonly used for oncology imaging

A

True

96
Q

Radionuclides that decay via positron emission usually have a larger proportion of protons compared to neutrons

A

True

97
Q

Positron emissions involves a proton decaying into a neutron + a positron

A

True

98
Q

Positron emission involves a proton decaying into a neutron + an electron

A

False. (Positron emission involves a proton decaying into a neutron + a positron)

99
Q

A positron is an antielectron

A

True

100
Q

The distance the positron travels in tissue depends on the initial number of neutrons

A

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
Q

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.

A

True

102
Q

Positrons travels short distances in tissue

A

True

103
Q

Positrons travel long distances in tissue

A

False. (Positrons travels short distances in tissue)

104
Q

Positron emission is also known as Positive Beta Emission (or Positive Beta Decay)

A

True

105
Q

When a positron meets an electron, an annihilation reaction occurs

A

True

106
Q

When an annihilation reaction occurs between a positron and an electron, the two particles are converted into x-rays that travel in opposite directions

A

False. (The two particles are converted into two gamma rays that travel in opposite directions)

107
Q

When an annihilation reaction occurs, the two particles are converted into two gamma rays that travel in the same direction

A

False. (The two particles are converted into two gamma rays that travel in opposite directions)

108
Q

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

A

True

109
Q

The distance a positron will travel in tissue will depend on the type of radionuclide used

A

True.

110
Q

The two gamma rays that are produced in an annihilation reaction will travel 90 degrees from each other

A

False. (The two gamma rays will travel 180 degrees from each other in opposite directions)

111
Q

The two gamma rays produced in an annihilation reaction are of the same energy.

A

True. (511 keV)

112
Q

The most commonly used radionuclide is Fluorine-18

A

True. (Combined with deoxyglucose as fluorodeoxyglucose (FDG).)

113
Q

Fluorodeoxyglucose (FDG) is a tracer for potassium metabolism

A

False. (FDG is a tracer for glucose metabolism)

114
Q

Fluorodeoxyglucose (FDG) is a tracer for glucose metabolism.

A

True. (It is distributed throughout the body but particularily taken up where there is increased glucose metabolism eg. tumours)

115
Q

There is increased glucose metabolism in tumours.

A

True

116
Q

There is increased glucose metabolism in tumours ONLY.

A

False. (There is also increased glucose metabolism where there is infection or inflammation)

117
Q

Fluorine-18 has a half-life of 110 minutes.

A

True

118
Q

The basis of PET imaging is positron emission and annihilation.

A

True

119
Q

PET imaging requires the use of a collimator.

A

False. (PET does not require a collimator.)

120
Q

The weakest link in the SPECT image formation process is the requirement for a collimator.

A

True

121
Q

Coincidence detection is used to distinguish photons arising from positron annihilation

A

True

122
Q

Coincidence detection is based on the energy of the gamma rays.

A

False. (It is based on temporal discrimination (timing).)

123
Q

PET has better spatial resolution than SPECT

A

True

124
Q

On a PET scanner, there is a single row of scintillation crystals (detectors).

A

False. (Blocks of scintillation crystals are arranged in a circle mounted on a gantry in multiple rings.)

125
Q

In PET, two photomultiplier tubes are mounted on each detector block

A

False. (Four PMTs are mounted on each block)

126
Q

Lutetium oxyorthosilicate (LSO) and Bismuth germanate (BGO) are used as scintillators in modern PET scanners

A

False. (BGO is not used anymore).

127
Q

Lutetium oxyorthosilicate (LSO) and gadolinium orthosilicate (GSO) are used as scintillators in modern PET scanners

A

True

128
Q

LSO has become the scintillator of choice in PET scanners because of its long decay time.

A

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
Q

Photomultiplier tubes are the preferred photodetectors used in PET systems because of their good SNR

A

True

130
Q

In PET imaging, multiple transverse slices can be simultaneously acquired because of the rings of detectors arranged around the patient.

A

True

131
Q

In PET imaging, Digital Photon Counting (DPC-PET) is prefered over Photomulitplier Tube (PMT-PET).

A

False. (PMT-PET is preferred)

132
Q

The main difference between PMT-PET and DPC-PET is how they detect and process the light photons generated by the scintillation crystals.

A

True

133
Q

Digital Photon Counting (DPC) technology is based on semiconductor detectors over traditional PMTs

A

True

134
Q

In PET-CT, a 64-slice scanner is usually used

A

True

135
Q

In PET-CT, a 16-slice CT scanner is usually used.

A

False. (A 64-slice CT scanner)

136
Q

Large FDG uptake in the brain is abnormal

A

False. (There is always massive FDG uptake in the brain as metabolism is entirely glucose based)

137
Q

In coincidence counting, the line between the two detectors is called the Line of Response (LOR).

A

True

138
Q

If two opposite detector elements detect a gamma ray photon simultaneously, it is considered a coincidence count

A

True

139
Q

Gamma rays detected within seconds of each other are considered a coincidence

A

False. (Gamma rays detected simultaneously or within nanoseconds of each other are considered a coincidence count)

140
Q

Coincidence detection involves the association of detection events at two opposite detectors, independent of arrival times

A

False. (Coincident detection is based upon the arrival times of the two photons)

141
Q

The Line of Response (LOR) is assumed to intersect the unknown location of the annihilation event.

A

True. (ie. the annihilation event occurs somewhere along the LOR)

142
Q

Photons are analysed in a Pulse Height Analyser (PHA) to determine whether it meets the energy acceptance criteria

A

True

143
Q

The time interval determining when events are considered to be coincident is denoted 2τ

A

True

144
Q

The time interval determining when events are considered to be coincident is denoted 4τ.

A

False. (2τ)

145
Q

2-D acquisition of PET data is associated with a high rate of scattered coincidence events

A

False. (It is associated with a low rate of scattered coincidence events)

146
Q

3-D acquisition of PET data is associated with high sensitivity but increased scatter

A

True

147
Q

3-D acquisition of PET data is associated with less scatter than 2-D acquisition

A

False. (3D acquisition has more scatter than 2D)

148
Q

In PET, the contribution of scatter will increase with increasing patient size

A

True

149
Q

Data recorded during PET acquisition is transformed into a 2-D bell curve

A

False. (PET data is transformed into a 2D sinogram)

150
Q

High-timing resolution is needed for Time of Flight (TOF) PET systems

A

True

151
Q

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

A

True

152
Q

In conventional PET imaging, we can preciesly determine the location of the annihilation event

A

False. (No information is available about the location of the annihilation event in conventional PET imaging)

153
Q

In Time of Flight-PET imaging, we can accurately estimate the position of the annihilation event along the LOR

A

True

154
Q

TOF-PET imaging has improved spatial resolution over conventional-PET

A

True

155
Q

TOF-PET has potential benefits for imaging paediatric patients

A

False. (It has potential benefits for imaging large patients where there is high amounts of attenuation and scatter)

156
Q

Attenuation correction can be more easily corrected in SPECT over PET.

A

False. (It is easier to correct attenuation in PET over SPECT as it allows for patient thickness)

157
Q

Attenuation can be corrected more easily in PET than SPECT

A

True. (This is because PET imaging allows for thickness of the patient)

158
Q

Pulse Height Analysers (PHA) are used to help remove scatter from the image

A

True

159
Q

Generally, scattered photons will have higher energy than the photons travelling directly to the detector

A

False. (Scattered photons will have lower energy)

160
Q

Coincidence detection of two photons from separate annihilation events (random event) contributes to increased image contrast

A

False. (Random event detections do not contain any spatial information and lead to reduced image contrast and contribute to image artifacts.)

161
Q

in PET imaging, random event detection must be corrected

A

True. (Although there are only approximate ways of correction)

162
Q

Long dead times of detectors contributes to an effective loss of sensitivity due to photons getting lost

A

True

163
Q

Dead time cannot be corrected

A

False. (Dead time corrections are based upon experimental measurements.)

164
Q

Radioactivity decays as the scanner moves down the patient

A

True

165
Q

PET is sensitive to patient motion as it experiences longer imaging times

A

True

166
Q

Planar gamma cameras are more sensitive than PET scanners

A

False. (PET scanners are more sensitive due to higher counts and less mottle)

167
Q

PET scanners suffer from less quantum mottle than planar gamma camera imaging

A

True

168
Q

The spatial resolution of PET-CT is ~5mm

A

True. (This means if a nodule/lesion is less than 5mm, it is not likely to be picked up on a PET scan.)

169
Q

Spatial resolution is better at the edge than the centre

A

False. (Spatial resolution is worse at the edge because some of the gamma photons may be detected by adjacent detectors)

170
Q

Effective dose for a PET scan is about 8 mSv

A

True

171
Q

Effective dose for a PET-CT using a low dose CT scan (for anatomical correlation and attenuation correction) is about 10 mSv

A

True. (8 mSv PET + 2 mSv low dose CT)

172
Q

FDG is taken up by and accumulates in metabollically active cells

A

True

173
Q

The most avid uptake of FDG occurs in bone cancers

A

False. (Head and neck cancers have the most avid uptake of FDG)

174
Q

Gamma cameras are primarily used in SPECT imaging, not PET

A

True

175
Q
A