Radiopharmaceuticals and Radiation Safety
Frank P. DiFilippo
Wael A. Jaber
Premium Wordpress Themes by UFO Themes
1. Rank the following radionuclides in order of their half-lives (from shortest to longest):
A. Technetium-99m, fluorine-18, cobalt-57, thallium-201
B. Fluorine-18, technetium-99m, thallium-201, cobalt-57
C. Fluorine-18, cobalt-57, technetium-99m, thallium-201
D. Technetium-99m, fluorine-18, thallium-201, cobalt-57
1. ANSWER: B. The half-lives of fluorine-18, technetium-99m, thallium-201, and cobalt-57 are 110 minutes, 6.0 hours, 3.04 days, and 271.7 days, respectively.
2. If a radiopharmaceutical labeled with technetium-99m (physical half-life Tp = 6 hours) has a biologic half-life (Tb) of 3 hours, then what is the effective half-life (Te)?
A. 1 hour
B. 2 hours
C. 3 hours
D. Cannot be determined from the given information
2. ANSWER: B. The relationship is given by (1/Te) = (1/Tp) + (1/Tb).
3. Which of the following radionuclides is useful for quality assurance and calibration of positron emission tomography (PET) scanners?
3. ANSWER: A. Germanium-68 is long-lived (half-life = 271 days) and decays to the positron-emitting gallium-68 (half-life = 68 minutes), so a sealed ger-manium-68/gallium-68 source behaves in effect like a long-lived positron emitter. The other three choices emit single photons and are useless for PET scanners.
4. For a same-day myocardial perfusion study using thallium-201-chloride and technetium-99m-sestamibi, which radiopharmaceutical should be scanned first and why?
A. Technetium-99m-sestamibi should be first, because of its shorter half-life.
B. Technetium-99m-sestamibi should be first, to maximize image counts.
C. Thallium-201-chloride should be first, to minimize scatter contamination.
D. Thallium-201-chloride should be first, to minimize radiation dose to the patient.
4. ANSWER: C. A main concern for image quality is that a large number of scattered technetium-99m gamma rays are detected in the 70-keV window of thallium-201, and thus, thallium-201 should be imaged first. The technetium-99m half-life is 6 hours, so technetium-99m persists for a same-day study and produces sufficient counts. The order of the studies does not reduce radiation dose.
5. Which PET radionuclide is produced from a generator?
5. ANSWER: D. Rubidium-82 is the daughter of strontium-82 (half-life = 25 days) and is eluted from a strontium-82/rubidium-82 generator. The other three choices are produced in medical cyclotrons.
6. ANSWER: B. Ultratag is supplied commercially by Mallinckrodt Medical and has stannous citrate along with acid citrate dextrose and sodium hypochlorite. Labeling RBCs using this pharmaceutical is by in vitro method. One to three milliliters of heparinized blood is added to the vial containing stannous citrate and incubated at room temperature for 5 minutes. During the incubation period, the stannous ion diffuses the RBC membrane after which sodium hypochlorite along with acid citrate dextrose is added to the reaction vial, followed by the addition of 30 to 40 millicuries of sodium pertechnetate-technetium-99m and incubation for another 20 minutes. With the addition of implantable cardioverter defibrillator (ICD), the extracellular stannous ion is oxidized by the sodium hypochlorite. The pertechnetate-technetium-99m diffuses the RBC membrane and is reduced intercellularly by the stannous ions. Reduced pertechnetate-technetium-99m does not diffuse out of the RBC. Typical labeling efficiency is >97%.
Heparin is one of the drugs that inhibit the diffusion of stannous ion to the RBC with the use of Sn-Pyrophate, and the labeling is compromised in that some of technetium-99m-pertechnetate is reduced.
Package Insert. Ultratag RBC kit for the preparation of Technetium-Tc99m labeled Red Blood Cell. Mallinckrodt Medical. April 2005.
Saha GB. Fundamentals of Nuclear Pharmacy. 3rd ed. New York, NY: Springer-Verlag; 1992.
7. Technetium-99m has a half-value layer (HVL) of 0.3 mm for lead. How many HVLs are needed to reduce the exposure from a 5-mR exposure to 0.7 mR?
A. 2 HVLs
B. 3 HVLs
C. 1 HVLs
D. 1.5 HVLs
7. ANSWER: B. The HVL is the amount of thickness of a material needed to reduce the exposure to half.
One layer will reduce to 2.5 mR.
Two layers will reduce to 1.25 mR.
Three layers will reduce to 0.625 mR.
The use of inverse square law I1 (d2)2 = I2 (d1)2, where I1 = initial radiation exposure rate at distance d1 from the source and I2 = radiation exposure rate at distance d2.
Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine. St. Louis, MO: Mosby; 1985.
8. Which of the following is not required under the Nuclear Regulatory Commission (NRC) regulations for the possession of radioactive material?
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
9. In an unrestricted area of a nuclear imaging facility, which of the following signs is posted?
A. Caution: Radioactive Material
B. Caution: Radioactive Area
C. Danger: Radiation Area
D. None of the above (no posting required)
10. Caution: Very High Radiation Area sign should be posted in an area where radiation exceeds:
A. 100 rads per hour.
B. 200 rads per hour.
C. 0.2 mrem per hour.
D. 500 rads per hour.
10. ANSWER: D. NRC regulation states that when an individual could receive a dose > 500 rads per hour at 1 m from the source, the area should have the Caution: High Radiation Area sign posted.
Nuclear Regulatory Commission (NRC), Code of Federal Regulation, Title 10, Part 20.1003 and 20.1902.
11. Which of the following areas is considered a restricted area?
B. Where radioactive material is stored and used (hot lab)
C. Reading room
D. Scanning room
11. ANSWER: B. Radioactive signs are not required where radioactive materials are handled for <8 hours and are under constant observation, and in rooms where sealed sources are stored and the exposure doesn’t exceed 5 mrem per hour at 1 m. 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 and radioactive materials. Usually, the hot lab, imaging room(s), and thyroid uptake room are considered restricted areas. Unrestricted areas are those areas to which access is neither limited nor controlled by the licensee.
NRC Regulation 10 Code of Federal Regulation, Title 10, Part 20.1003.
12. 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 packages.
12. ANSWER: C. The transportation index of a package having radioactive materials is to be measured at a distance of 1 m from the surface.
Transportation regulation Code of Federal Regulations, Title 49, Part 172.403 and 172.436-440.
13. Which of the following instruments is used to measure removable contamination on a radioactive package?
A. Dose calibrator
B. Ionization chamber
C. Well counter
D. Geiger counter
13. ANSWER: C. All of these instruments can be used to measure radiation, but the well counter is the most sensitive and practical for measuring the swipes that are used to test packages delivered to a nuclear laboratory. It is a solid scintillation counter and is very sensitive to low levels of radioactivity.
The dose calibrator is used routinely to measure radiotracer doses prior to being injected into the patient. An ionization chamber is a gas-filled enclosure between two conducting electrodes that can be used to measure gases, liquids, or solids. Geiger counters are used to detect ionizing radiation (usually beta particles and gamma rays, but certain models can detect alpha particles). An inert gas-filled tube (usually helium, neon, or argon with halogens added) 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 often displayed by a needle or lamp and/or audible.
Saha GB. Physics and Radiobiology of Nuclear Medicine. 3rd ed. New York, NY: Springer-Verlag; 1993.
14. 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 hours.
B. Discontinue all antianginal medications for 24 hours.
C. Discontinue breast-feeding for 2 weeks after the test.
D. No instructions needed.
14. ANSWER: C. Since the patient is undergoing exercise stress, caffeine abstention is not required. Caffeine abstention is required for 12 to 24 hours when patients are scheduled to undergo dipyridamole, adenosine, or regadenoson pharmacologic stress. Caffeine may interfere with the vasodilatory effects of these drugs and lower overall accuracy by decreasing sensitivity. Beta-blockers and nitrates taken prior to stress will decrease the detection of ischemia. They should be held 12 to 24 hours prior to testing. Thallium-201 will contaminate breast milk and, due to the 72-hour 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.
Nuclear regulatory commission, Consolidated Guidance About Materials Licenses (NUREG-1556), Volume 9, Appendix U.
15. 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. Survey meter
D. Geiger counter
15. ANSWER: A. Photographic film badges consist of a holder and a radiation-sensitive film. They are used for monitoring cumulative whole-body exposure to ionizing radiation. They record both high and low radiation levels and are generally worn on the torso outside of clothing. In some circumstances, they may be worn underneath a protective lead shield to record the actual exposure to critical organs. Thermoluminescent material may in some cases be used in place of photographic films to measure whole-body exposure.
Thermoluminescent ring badges are used to measure the amount of exposure received by the hands and consist of an inorganic crystal held in a hand ring device.
A survey meter and Geiger counter are handheld devices used to measure contamination.
Nuclear Regulatory commission (NRC), Code of Federal Regulation, Title 10, Part 20.1502.
Saha GB. Fundamentals of Nuclear Pharmacy. 3rd ed. New York, NY: Springer-Verlag; 1992.
16. The NRC annual body radiation exposure limit for a radiation is:
A. 1.25 rem per quarter year.
B. 50 rem per quarter year.
C. 15 rem per quarter year.
D. 50 rem per year.
16. ANSWER: A. The NRC limits a radiation occupational worker to receive a total whole-body dose of 5 rem per year. It is measured in quarterly 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. Specific organ limits include 15 rems to the eyes and 50 rems to the extremities.
Nuclear Regulatory Commission (NRC), Code of Federal Regulation, Title 10, Part 20.1201.
17. Which of the following radioactive materials can be released into the sewer system?
A. Unused radioactive patient doses
B. Sealed radioactive sources
C. Patient urine or feces
D. Contaminated paper towel used to clean spill
17. ANSWER: C. Some radioactive materials 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. For radionuclides used in nuclear cardiology procedures, there is minimal excretion. All of the other forms of radioactivity listed, unused patient doses and contaminated materials, should not be released directly into the sewage system. They should be allowed to decay for 10 half-lives and then disposed in the same manner used for nonradioactive materials.
Sealed radioactive sources usually have very long half-lives, and special precautions must be taken for disposal.
Nuclear Regulatory commission (NRC), Code of Federal Regulation Title 10, Art 20, Subpart K—Waste Disposal (20.2001).
18. What survey frequency is mandated by the NRC for radioactive materials areas?
18. ANSWER: A. In accordance with the ALARA (as low as reasonable achievable) 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 that such surveys were performed is necessary.
Nuclear Regulatory Commission (NRC), Code of Federal Regulation Title 10, Part 20 and Part 35.70.
19. 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.
19. ANSWER: D. Dry paper towels or a stiff brush are best used as the initial step in decontamination of solid radioactive materials. Using hot water opens the skin pores and allows more radioactivity to be absorbed into the dermal layers. Lukewarm water with soap is best for removal of contamination.
Christian PE, Waterstram-Rich K. Nuclear Medicine and PET/CT: Technology and Techniques. 6th ed. St. Louis, MO: Mosby/Elsevier; 2007.
WordPress theme by UFO themes