Nuclear - Radiation Safety, Radiopharmaceuticals Flashcards
What is the uniformity standard performance parameter for detectors in SPECT?
Describe the findings
Uniformity test
Describe the findings
Cracked crystal
Describe how to measure change in sensitivity?
record the time taken to acquire a preset number of counts using a set dose
What is the cause of “ring artifact” on SPECT imaing?
non-uniformity on SPECT
How frequently should these QC measures be performed:
- COR
- Plexiglas phantom
- Uniformity correction
- COR –> weekly or monthly
- Plexiglas phantom –> quarterly or annually
- Uniformity correction –> manufacturer recommendation
What are examples of COR artifacts?
- Doughnut artifact (360 degrees)
- Tuning fork artifact (180 degrees)
What is a survery meter (Geiger counter, Geiger-Mueller counter, GM counter)?
used daily to detect radioactive contamination in labs
What are QC checks that should be done on survey counters daily?
- Battery check
- Source check
- ensure meter responds to radiation
How often should survey counter calibration be performed?
annually
What are the standard testing done on dose calibrators?
- Background
- Voltage
- Accuracy
- Constancy
- Linearity
- Geometry
What are common isotopes used for annual dose calibrator accuracy testing?
- Co-57
- Cs-137
*** Results must be within 5%
****sources must be traceable to the National Institute of Standards and Technology (NIST)
What does a geometry test measure?
ability of the dose calibrator to measure accurately with consistent activity at different volumes
- performed at installation, recalibration, “plug-in”
What is a constancy test?
- designed to show that a long half-life source yields reproducible readings
- within 5% of decay corrected accuracy readings
- check each setting (isotope) button
What is a linearity test?
assesses ability to read both high and low activity (range)
- performed quarterly
What is a Rad?
- radiation absorbed dose
- energy absorbed in material
What is a Gray?
100 Rad = 1 Gray
SI unit for Radiation Absorbed Dose
Define Relative Biological Effectivenss (RBE)
- ratio of biological effectiveness of one type of ionizing radiation relative to another, given the same amount of absorbed energy
- different types of radiation have diffierent biologic burdens
How can you calculate a Roentgen Equivalent Man (Rem)?
Rem = Rad x QF
- 1 Rad gamma rays = 1 Rem
- 1 Rad alpha particles = 20 Rem
What is the international unit for Rem
Sievert (Sv)
- 100 Rem = 1 Sv
Describe the radiological units summary
- Roentgen (R)
- Rad
- Rem
- SI units
- Gray (Gy)
- Sievert (Sv)
What are the Quality Factors (QF):
- XR, Gamma rays
- Beta particles
- Neutrons and Protons
- Alpha particles
- XR, Gamma rays –> 1.0
- Beta particles –> 1.0
- Neutrons and Protons –> 10
- Alpha particles –> 20
What is the international unit to express dose equivalent?
Sievert (Sv)
What are the assumptions and limitations of the Medical Internal Radiation Dose (MIRD) method?
- radioactivity is uniformly distributed in the organ
- organ size assumed for the standard person
- cellular level micro-dosimetry is not modeled
What is the effective radiation dose per examination:
- Tc99m Sestamibi
- Tl201
- Cardiac cath
- CT angio
- CXR
What is the dose limit:
- non-occupational dose limits from occupational sources (shielding of rooms, breastfeeding)
1 mSv (100 mRem)
What is the dose limit:
- infrequent exposure from other’s medical procedures (family member, release to public)
5 mSv (500 mRem)
What is the dose limit:
- occupational dose limits
- models determining the equivalent chance of developing major cancer = as that of a major work related event
What are the Quarterly ALARA Investigational Levels?
What steps should be taken if you reach a Quarterly ALARA investigational level?
- Level I –> Notify and action taken at RSO discretion
- Level II –> Investigate and take action
What is the natural background received by a person living the US each year?
300 mRem/year
What is the annual whole-body dose limit for an occupational worker?
5 Rem or 0.05 Sv
What is the dose limit:
- Pregnant workers
500 mRem (5 mSv) over gestation period
- < 50 mRem / month
- fetus is a non-occupational worker
What are the regulations for breastfeeding?
reduce the dose to a newborn infant to < 1 mSv (actual regulation is < 5 mSv)
What is the unit equivalent:
- 1 Rem –> mSv
1 Rem –> 10 mSv
What are the requirements for personnel monitoring?
- any occupational woker likely to exceed 500 mRem/year
and/or
- those who handle millicurie amounts of radioactive material (license requirement)
What are the main types of devices used for personnel monitoring?
- Film badges
- Thermo Luminscent Devices (TLD)
- Optically Stimulated Luminescence (OSL)
- Pocket Ion Chamber
What is ALARA?
As Low as Reasonably Achievable
- 10% of occupational dose limits
- 10% of limit (5 Rem/yr) = 500 mRem/year
What are the components of ALARA?
- Time
- Distance
- Shielding
Define Inverse Square Law
maintain a distance from a known radiation source
- Intensity = 1 / d2
- increase distance –> reduce by a squared factor
What is the unit equivalent:
- 1 mRem –> μSv
1 mRem –> 10 μSv
What is the unit equivalent:
- 100 Rem –> Sv
100 Rem –> 1 Sv
What are the principles of shielding:
- Alpha particles
- Beta particles
- Gamma rays
Define Half-Value Layer
amount of material needed to reduce the intensity by half
- synonymous with half-life
What are the HVL’s (in Pb):
- Tc99m
- F18
- Cs137
Describe deterministic effects
- Threshold dose below which no effect is observed
- Severity increases with dose (commonly from cell death)
- Examples: skin erythema, dermatitis, cataracts, sterility, hematopoietic syndrome
Describe Stochastic Effects
- Incidence (probability) increases with dose - not severity
- No dose threshold
- Basis for ALARA principle of radiation protection
- Example: Late induced malignant neoplasm
- “Linear No-threshold” theory
What are the ways to handle waste management?
- Decay in storage
- Transfer to authorized recipient
- Sewage
- Atmosphere
What are the rules for Decay In Storage?
- Waste with half-life of < 120 days
- Store in shielded container
- Label with date and longest lived isotope
- Survey to ensure indistinguishable from background
- Remove all radioactive labels prior to final disposal
- Maintain record of disposal for a minimum of 3 years
What are the rules for receiving radioactive material?
- Package must be monitored within 3 hours (start of buisness, if before hours)
- Wear gloves
- Visually inspect for problems
- Measure 1 meter exposure (report if problem; > 10 mR/hr report to DOH)
- Wipe test if contamination is suspected
Describe the meaning of the package:
Type III - Yellow
- Surface exposure < 200 mRem/hr
- 1 meter exposure < 10 mRem/hr
- Surface wipe test < 6600 dpm/300 cm2
Describe the meaning of the package:
- Surface exposure < 50 mRem/hr
- 1 meter exposure < 1 mRem/hr
- Surface wipe test < 6600 dpm / 300 cm2
Describe the meaning of the package:
- Surface exposure < 0.5 mRem/hr
- 1 meter exposure - not detectable
- Surface wipe test < 6600 dpm / 300 cm2
What is the package label required for limited quantities of radioactive material?
Excepted Package, Limited Quantity
What are the Excepted Package, Limited Quantities of the following:
- Tc99m
- Co57
- Tl201
- F18
- Tc99m –> 11 mCi
- Co57 –> 27 mCi
- Tl201 –> 11 mCi
- F18 –> 1.6 mCi
What if a package has more than one isotope, how is the amount quantified?
max quantity defaults to the lower limit
When are medical misadministrations reportable to NRC?
- > 5 Rem (0.05 Sv) to the whole body
- > 50 Rem (0.5 Sv) to any individual organ
Describe the meaning of the sign
Radioactive material
- areas where material are used / stored
Describe the meaning of the sign
Radiation area
- Individuals could exceed a dose of > 5 mRem in an hour
- 30 cm from a source or any surface where radiation penetrates
Describe the meaning of the sign
High Radiation Area
- Individuals could exceed a dose of > 100 mRem in an hour
- 30 cm from a source or any surface where radiation penetrates
What are the half-lives of the following radionuclides?
- F18
- Tc99m
- Tl201
- Co57
- F18 –> 110 minutes
- Tc99m –> 6 hours
- Tl201 –> 73 hours / 3 days
- Co57 –> 271.7 days
Describe the relationship between:
- physical half-life
- biologic half-life
(1/Te) = (1/Tp) + (1/Tb)
- Tp = physical half life
- Tb = biologic half life
- Te = effective half-life
What is an example of a radionuclide useful for quality assurance and calibration of PET scanners?
Germanium-68
What are required regulations under the Nuclear Regulatory Commission (NRC) for the possession of radiaoctive material?
- Limits of radioactive material possessed at any given time
- Disposal of radioactive material
- Use of radioactive material
*** Cost of radioactive material not required
What is the radiation cut-off that does not require posting of a sign?
areas where a person receives < 2 mrem / hr
Caution: Very High Radiation Area sign should be posted in an area where radiation exceeds this amount?
500 rads / hr at 1m from the source
What does the transportation index found on a radioactive shipment package measure?
Exposure measurement at 1m from the surface of the package
What instrument is used to measure removable contamination on a radioactive package?
well counter
- most sensitive and practical for measuring the swipes that are used to test packages delivered to a nuclear laboratory
A 65 year old male presents with A-fib. He was started on a Heparin drip. A multigated (MUGA) acquisition scan was ordered to evaluate the LVEF.
What is the most appropriate choice for labeling the RBC for this patient?
Ultratag
- composed of stannous citrate along with acid citrate dextrose and sodium hypochlorite
- labeling RBCs by this pharmaceutical is by in “in vitro” method
- labeling efficiency > 97%
What RBC labeling agent is contraindicated with Heparin use?
Sn-Pyrophate
- heparin is one of the drugs that inhibit the diffusion of stannous ion to the RBC with the use of Sn-Pyrophate
- labeling is compromised –> some of Tc99m-pertechnetate is reduced
Why should BB and nitrates be held prior to stress testing?
How long should they be held prior to testing?
- they may decrease the detection of ischemia
- should be held 12-24 hours prior to testing
What is the most appropriate monitoring device for measurement of occupational dose for a radiation worker?
Photographic film badge
How long should one abstain from breastfeeding following a stress Tl201 study?
at least 2 weeks following the study
- T 1/2 = 73 hours
What is the NRC annual body radiation exposure limit for radiation?
- 1.25 Rem/quarter year
- 5 Rem / year
What survey frequency is mandated by the NRC for radioactive materials areas?
Daily
- in accordance with ALARA principles, the NRC requires that daily surveys be performed with a survey instrument at the end of each day
What is the appropriate DOT label for package shipping:
- Surface radiation exposure - 5 mR/h
- 1 m from surface - 0.2 mR/h
Yellow II
For a Tc99m, 1 day, rest/stress sequence, How long after the resting injection should the acquisition be performed?
30 minutes (ideally 30-60 minutes)
- time delay after injection is to allow clearance from the liver and maximize the myocardial uptake
- at 15 minutes –> too much liver activity –> contaminates inferior wall
- > 2 hours –> liver clearance but increased probability of bowel loop uptake
What is the optimum “rest” dose range for a 1-day rest/stress Tc99m SPECT MPI study?
8-12 mCi
- rest dose should be approximately 1/3 of the stress dose
- with some variation introduced by the length of time between the 2 studies
Describe 1-day rest/stress Tc99m SPECT MPI study rest/stress doses
- Why?
- What are the effect on intervals?
- 1:3 ratio (rest/stress)
- stress dose overcomes the smaller rest dose so that the stress images have less residual activity form the rest study
- Interval between studies
- Short –> higher stress dose
- Longer –> lower stress dose (1:3 may not be needed)
1-day rest/stress Tc99m SPECT MPI study
- What is the effect if a lower stress dose is used without enough time between injections?
- there will be residual activity from the rest study
- this can underestimate the amount of ischemia present
When can rest/stress imaging be started in a 1-day rest/stress Tc99m SPECT MPI study:
- Rest images
- Stress images
- Rest images –> 30-60 minutes post-injection
- Stress images –>
- 10-20 minutes after exercise
- 30-60 minutes after pharmacologic
Tc99m labeled perfusion tracers have improved SPECT perfusion imaging relative to Tl201 due to this characteristic?
Higher photon energy resulting in less tissue attenuation
- also has shorter half-life allowing administration of a much higher dose but less total body radiation
Describe the interaction between Quantitative analysis and AC in SPECT imaging?
- gender differences
- normalcy
- specificity
- AC gender maps are not different between males and females
- AC improves normalcy > Quantitative analysis
- Specificity of a positive finding is higher in images interprested with AC
What is the maximum permissible activity concentration of molybdenum-99 to Tc99m as stipulated by NRC?
0.15 μCi / mCi at the time of administration to the patient
What are regulations related to Aluminum ion concentrations?
Who regulates these concentrations?
- Limts are 10 μg/mL of eluate
- US Pharmacopeia (USP-XXIII)
What is the average ionizing radiation received annually?
620 mRem (6.2 mSv) per year
How should Tc99m radioactive waste generated in a nuclear medicine department be disposed?
Store in-house for decay to background radiation level before disposal
