Radiopharmaceuticals and radiation safety Flashcards
(37 cards)
Rank the following radionuclides in order of their half lives from shortest to longest:
a. tech-99m, fluorine-18, cobalt-57, thallium-201
b. fluorine-18, tech-99m, thallium-201, cobalt 57
c. fluorine 18, cobalt-57, tech-99m, thall201
d. tech-99m, fluorine18, thallium-201, cobalt57
B. half-lives of fluorine tech thallium and cobalt are 110mins, 6 hrs, 3.04days, and 271.7 days
If a radiopharmaceutical labeled with tech-99m (1/2 life Tp=6hrs) has a biologic 1/2 life Tb of 3 hrs, then what is the effective 1/2 life?
a. 1 hr
b. 2 hrs.
3. 3 hrs
4. cannot determine from info given
B. 1/Te= 1/Tp + 1/Tb
Which of the following radionuclides is usefil for quality asurance and calibration of PET scanners?
a. germanium 68
b. tech-99m
c. cobalt-57
d. iodine-131
A. germanium-68 is long live 1/2life is 271 days and decays to the positron - emitting gallium -68 w/ 1/2 life of 68 mins, so a sealed germanium-68/galllium-68 source behaves in effect like a long-lived positron emitter. The other three choices emit single photons and are useless for PET scanners
For a same-day myocardial perfusion study using thall-201Cl and tech-99m sestamibi, which radiopharmaceutical should be scanned first and why ?
A. tech should be first because of its shorter half life
b. tech should be first, to maximize image counts
c. thall should be first to minimize contamination
d. thall should be first to minimize radiation dose to the patient
C. a main concern for image quality is that a large number of scattered tech-99 gamma rays are detected in the first 70 kev window of thallium-201 and thus thall should be imaged first. The tech half life is 6 hhrs so tech 99m persists for a same day study and produces sufficient counts. order of the studies doesn’t reduce radiation dose
Which PET radionuclide is produced from a generator?
a. carbon 11
b. nitrogen 13
c. fluorine 18
d. rubidium 82
D. Rubidium 82 is the daughter of strontium 82 1/2 life of 25 days and is eluted from a strontium82/rubidium82 generator. Other choices are produced in medical cyclotrons.
A 65 yo male presents with AF. He was started on heparin. A multigated acquisition (MUGA) scan was ordered to evaluate the LVEF; the most appropriate choice for labeling the rbc for thit pt would be:
a. Sn-pyrophate
b. ultratag
c. tech 99m tetrofosmin
d. tech 99 sestamibi
B. ultra tag is supplied commercially by mallinkrodt medical nad has stannous citrate along wiht acid citrate dextrose and sodium hypochlorite. This is done by invitro method. 1-3ml of heparinized blood is added to the vial containing stannous citrate and incubated at room temp for 5 mins. During incubation the stannous ion diffuses the RBC membrane and after the sodium hypochlorite and acid citrate dextrose are added to the rxn vial, followed by 30-40 millicuries of sodium pertechnetate tech-99m and incubates for 20mins. With the ICD the extracellular stannous ion is oxidized by the sodium hypochlorite, and the pertechnetate-tech-99m diffeses the rbc membrane and reduced intercellularly by the stannous ions. reduced pertechnetate tech-99m does not diffuse out of the rbs, and lableing is >97% effective.
Heparin inhibits the diffusion of stannous ion to the RBC with the use of Sn-pyrophosphate and the labeling is compromised in that some of tech-99m pertechnetate is reduced.
Tech-99m has a half-value layer of 0.33mm for lead. How many HVLs are needed to reduce the exposure from a 5-mR exposure to 0.7mR?
a. 2hvls
b. 3hvls
c. 1 hvls
d. 1.5 hvls
B the hvl is the amount of thickness of a material needed to reduce the exposure to half.
1 layer will reduce to 2.5mR
2 layers to 1.25
3 layers to 0.625
Use of inverse square law I1D2^2=I2D1^2 where I1 = initial radiation exposure rate at distance d1 from the source and i2 = radiation exposure rate at distance d2.
Which of the following is NOT required under the nuclear regulatory commission NRC, regulations for the possession of radioactive materials?
a. limits of radioactive material possessed at any given time
b. disposal of radioactive material
c. use of radioactive material
d. cost of the radioactive material
D. all possession, use, and disposal of radioactive material are controlled by the NRC.
In an unrestricted area of a nuclear imaging facility, which of the following signs is posted?
a. caution: radioactive material ahead
b. caution radioactive area
c. danger radiation area
d. none of the above no posting required
D areas not under the control of the licensee and areas where a person receives <2mrem per hr do not require posting
Caution: very high radiation area sign should be posted in an area where radiation exceeds:
a. 100 rads/hr
b. 200 rad/hr
c. 0.2mrem/hr
d. 500 rad/hr
D. NRC regulation states that when an individual could receive a dose >500rads/hr at 1 m from the source, the area should have CAUTION: High radiation area sign posted
Which of the following areas is considered a restricted area?
a. hallways
b. where radioactive material is stored and used (hot lab)
c. reading room
d. scanning room
b. radioactive signs are not required where radioactive materials are handled for <8hrs and are under constant observation, and in rooms where sealed sources are stored and the exposure doesn’t exceed 5mrem per hr at 1m. Restricted areas are those to which access is limited by the licensee for the purpose of protecting individuals against unnecessary risks from exposure to radiation adn radioactive materials. Usually hot labs, imaging rooms, and thyroid uptake room are considered restricted areas. Unrestricted areas are areas to which access is neither limited nor controlled by the licensee
Transportation index found on radioactive shipment packages is a measurement of
a. box type used
b. amount of radioactive material in the package
c. exposure measurement at 1 m from the surface of the package
d. exposure measurement at the surface of the package.
c. the transportation index of a package having radioactive materials is to be measured at a distance of 1 m from the surface.
Which of these instruments is used to measure removable contamination on a radioactive package?
a. dose calibrator
b. ioniztion chamber
c. well counter
d. geiger counter
All of these can be used to measure radiation, but the well counter is hte most sensitive and practical for measuring the swipes that re used to test packages delivered to a nuclear laboratory. It is a solid scintillation counter and is very sensitive to low levels of radioactivity.
A patient who is breast-feeding, is scheduled for an exercise stress thallium-201 study. What instruction is critical to be given to the patient before the test is performed?
a. abstain from caffeine for 24 hrs
b. discontinue all antianginal medications for 24 hrs
c. discontinue breast-feeding for 2 weeks after the test
d. no instructions needed
C.
Since the patient is undergoing exercise stress, caffeine abstention is not required. Caffeine abstention is required for 12-24hrs when patients are scheduled to undergo dipyridamole, adenosine, or regadenoson pharm stress. Caffeine may interfere iwht the vasodilatory effects of these drugs and lower overlal accuracy by decreasing sensitivity. Beta-blockers and nitrates taken porior to exercise stress will decrease the detection of ischemia. They should be held 12-24hrs prior. Thallium-201 will contaminate breast mild, and due to the 72hr half life, will expose the infant to unnecessary radiation. Radionuclide stress testing in such patients should be delayed if possible until the patient stops breast feeding or alternative methods of testing are considered.
Dose calibrator is used for what?
measures radiotracer doses prior to being injected into the patient
What is an ionization chamber
gas-filled enclosure between to conducting electrodes that can be used to measure gases, liquids, or solids.
What are geiger counters used for
Used to detect ionizing radiation (usually beta particles and gamma rays, but certain models can detect alpha particles). It is an inert gas filled tube usually helium neon or argon with halogens added, when it briefly conducts electricity when a particle or photon of radiation makes the gas conductive. The tube amplifies this conduction by a cascade effect and outputs a current pulse, which is then displayed by a needle or lamp
Which of the following monitoring devices is most appropriate for the measurement of occupational dose for a radiation worker?
a. photographic film badges
b. thermoluminescent ring badge
c. survery meter
d. geiger counter
A. photographic film badges consist of a holder and a radiation sensitive film. they are used for monitoring cumulativ whole body exposure to ionizing radiation. they record both high and low radiation levels are generally worn on the torso outside of clothing. Thermoluminescent material may in some cases be used in place of photographic films ot measure whole-body exposure.
thermmoluminescent ring badges are used to measure the amount of exposure received by the hands, consists of an inorganic crystal held in a hand ring device.
Survey meter and geiger counters are hand held devices used to measure contamination.
The NRC annual body radiation exposure limit for a radiation is?
a. 1.25rem/quarter year
b. 50 rem/quarter year
c. 15rem/quarter year
d. 50 rem/year
A. The NRC limits radiation to occuptional workers to receive a total whole-body dose to 5rem/year. It is measured in quareterly intervals so that individuals getting high rates can be identified and corrective actions taken to limit further exposure in order to avoid exceeding the yearly total.
Which of the following radioactive materials can be released into the sewer system?
a. unused radioactive patient doses
b. sealed radioactive sources
c. pt urine or feces
d. contaminated paper towel used to clean a spill
C.
some radioactive material may be eliminated through the urine or feces but usually in small quantities. When released into sewage, they are diluted and do not pose a risk to patients or the public. Radionuclides in nuclear cardiology there is minimla excretion. All other options should be allowed to decay for 10 1/2 lives and then disposed in the same manner used for nonradioactive materials.
Sealed radioactive sources usually have very long 1/2 lives adn special precautions must be taken.
How much total radiation can the eyes and extremities take?
eyes 15rems and extremities 50rems
What survey frequency is mandated by the NRC for radioactive materials areas?
a. daily
b. weekly
c. monthly
d. yearly
C. In accordance with the ALARA principles, the NRC requires that daily surveys be performed with a survey instrument at the end of each day. Less frequent surveys would fail to detect unsafe radiation use practices that may result in unnecessary radiation exposure to patients, staff, or the public. Documentation is necessary.
Radioactive contamination on the skin is best removed by:
a. cleaning with paper towels.
b. cleaning with stiff brush
c. cleaning with hot water and soap
d. cleaning with lukewarm water and soap
D.
Dry paper towels or a stuff brush are best used as the initial step in decontamination of solid radioactive materials. Hot water opens pores and allows more radioactivity to be absorbed into the dermal layers. Lukewarm water with soap is best for removal of contamination.
The maximum exposure amount allowed by the NRC to a fetus of a pregnant occupational worker is:
a. 500mrem/month of pregnancy
b. 500mrem/quarter of pregnancy
c. 500mrem for entire pregnancy
d. 50mrem for entire pregnancy
C.
the dose to the embryo/fetus shall not exceed more than 500mrem from occupational exposure for a declared pregnant worker. To monitor a separate radiation film badge is used and worn over fetal area. Pregnant employees need to be counseled on appropriate radiation safety measures and duties without radiation exposure considered. Risks to fetus are highest during 1st trimester.
