Nuclear Medicine Flashcards
The unit of radioactive decay is the Becquerel (Bq)
True
Technetium-99m has a half-life of 6 hours
True
The main radioisotope used in nuclear med is Technetium-99 (Tc99)
True
The effective half-life of a radioisotope depends only on its physical half-life
False (The effective half-life of a radioisotope depends on both its physical half-life and it’s biological half-life)
Radiation Protection in Nuclear Medicine applies what conditions?
Justification, Optimisation and DRLs
What are some factors that need to be considered about Justification of NM scans?
- 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?
What are some important factors regarding Optimisation of NM scans?
- 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
The annual whole body dose limit for a member of the public is 1mSv
True
The annual whole body dose limit for Category B workers (radiographers etc.) is 15 mSv
False (The whole body dose limit for category B workers is 6 mSv)
NM procedures do not have dose limits for patients, instead DRLs are used.
True (produced by HIQA and used to guide recommended activity of the radioisotope to be administered to the average patient for a particular test)
In NM, children are considered at lower risk from ionising radiation compared to adults
False (Children are at a higher risk, particularily for cancer induction)
Fluid intake should be reduced following a NM scan
False (fluid intake and frequent bladder emptying should be encouraged to reduce patient dose through excretion)
Distance and shielding are important safety measures for nuclear medicine staff
True
Breastfeeding mothers are advised to avoid close contact with their babies for 48 hours after a NM injection
False (The recommendation is to avoid close contact for 24 hours. Breast milk can be aspirated in advance using a breast pump)
Typical whole body dose for Tc-99 bone scan is ~5mSv
True
The only method to measure detector uniformity in NM is using a Cobalt Flood Sheet.
False (Both a Cobalt Flood Sheet (expensive) and a Fillable Flood Source can be used)
Technetium is readily-available in an NM department
True
A fillable flood source phantom is a cheaper alternative to measure detector uniformity in NM than a Cobalt flood sheet.
True (As it uses Technetium + saline)
The intrinsic resolution of a gamma camera refers to its spatial resolution WITHOUT a collimator
True
The extrinsic resolution of a gamma camera is the spatial resolution of the system WITH a collimator
True
Spatial resolution is often measured using a graph called a Modulation Transfer Function (MTF)
False (The graph is called a Line Spread Function)
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)
True
The line spread function broadens with poorer spatial resolution
True
The width of the Line Spread Function can be expressed as FWHM (full width at half maximum)
True
The main radionuclide used in NM is Iodine
False (The main radionuclide used is Technetium)
Technetium is produced from the decay of Molybdenum in a generator
True
The half-life of Technetium-99 is approx. 18 hours
False (The half-life of Tc99 is ~ 6 hours)
The 6 hour half-life of Tc99 makes it unusable in NM
False. (The 6 hour half-life of Tc99 is ideal for imaging)
The parent atom of Technetium is Gallium.
False. (The parent atom of Tc is Molybdenum)
The radioactive decay of ‘parent’ Molybdenum to Technetium-99m involves both beta-particle and gamma ray emission
True
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)
As the parent atom (Mo) decays, the activity of the daughter radionuclide (Tc) increases
True
Sodium pertechnetate is the eluate from a Technetium generator
True
Molybdenum breakthrough in a Technetium generator should only be a trace amount
True
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)
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)
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)
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)
Technetium-99m is a pure gamma emitter.
True. (Decay does not involve alpha or beta emission)
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).
Molybdenum breakthrough is entirely preventable
False
The gamma camera is the main imaging device used in NM
True
Name some important components of a gamma camera
- Collimator
- Crystal
- Light Guide
- PMT Array
Sensitivity of the gamma camera refers to the amount of gamma rays that reach the crystal
True
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)
Photomultiplier Tubes (PMTs) are arranged in a circular array
False. (PMTs are arranged usually in a hexagonal array)
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
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)
The position circuitry works out where the interaction took place by comparing outputs from individual PMTs
True
The PHA will ignore pulses that do not meet a specific threshold
True
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)
The photopeak in an energy spectrum represents the complete energy deposited by gamma rays in the detector
True
The Line Spread Function is used to measure spatial resolution in nuclear medicine imaging
True
Temporal resolution in NM depends largely on the decay time of the detector material
True
In NM imaging, increased dead time increases image quality
False. (Increased dead time degrades image quality)
Spatial resolution is affected heavily by the distance of the source from the collimator
True
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)
Spatial resolution gets better when the patient is closer to the collimator
True. (Less spread = narrower resolution function)
Effective half life of a radionuclide is lower than physical half-life
True
Intrinsic spatial resolution measurements translate easily into a clinically useful value
False. (Extrinsic spatial resolution measures are made under more clinically realistic conditions)
The timing resolution of NM is limited by the decay time of the crystal
True
The decay time for semiconductor detectors is much smaller than scintillators
True
Spatial resolution depends on patient distance from the collimator
True
High-sensitivty collimators are optimal for procedures requiring very high spatial resolution
False. (High-sensitivty collimators sacrifice spatial resolution for improved detection efficiency)
Dual-headed gamma cameras are typically used in SPECT
True
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)
What does SPECT stand for?
Single Photon Emission Computed Tomography
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)
Parallel Hole Collimators are used for SPECT imaging
True
SPECT images often contain many artefacts
True