Radiopharmaceuticals and radiation safety

Question 1

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

Answer 1

B. half-lives of fluorine tech thallium and cobalt are 110mins, 6 hrs, 3.04days, and 271.7 days

Question 2

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

Answer 2

B. 1/Te= 1/Tp + 1/Tb

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

Question 5

Which PET radionuclide is produced from a generator?
a. carbon 11
b. nitrogen 13
c. fluorine 18
d. rubidium 82

Answer 5

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.

Question 6

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

Answer 6

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.

Question 7

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

Answer 7

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.

Question 8

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

Answer 8

D. all possession, use, and disposal of radioactive material are controlled by the NRC.

Question 9

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

Answer 9

D areas not under the control of the licensee and areas where a person receives <2mrem per hr do not require posting

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 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 package.

Answer 12

c. the transportation index of a package having radioactive materials is to be measured at a distance of 1 m from the surface.

Question 13

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

Answer 13

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.

Question 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 hrs
b. discontinue all antianginal medications for 24 hrs
c. discontinue breast-feeding for 2 weeks after the test
d. no instructions needed

Answer 14

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.

Question 15

Dose calibrator is used for what?

Answer 15

measures radiotracer doses prior to being injected into the patient

Question 16

What is an ionization chamber

Answer 16

gas-filled enclosure between to conducting electrodes that can be used to measure gases, liquids, or solids.

Question 17

What are geiger counters used for

Answer 17

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

Question 18

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

Answer 18

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.

Question 19

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

Answer 19

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.

Question 20

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

Answer 20

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.

Question 21

How much total radiation can the eyes and extremities take?

Answer 21

eyes 15rems and extremities 50rems

Question 22

What survey frequency is mandated by the NRC for radioactive materials areas?
a. daily
b. weekly
c. monthly
d. yearly

Answer 22

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.

Question 23

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

Answer 23

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.

Question 24

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

Answer 24

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.

Question 25

The amount of radiation exposure can be reduced by:
a. time
b. distance
c. shielding
d. all of choices

Answer 25

D. total exposure is directly proportional to the time of exposure, shielding with the highest possible density material reduces radiation exposure by attenuation; for gamma radiation, higher atomic number materials should be used. distance alone reduces exposure and varies inversely as teh square of the distance from the source to exposure ie >distance = less exposure

Question 26

A pt undergoing a cardiac stress test is adminsistered tech-99m-sestamibi. Effective 1/2 life for the heart is 3 hrs. What is the biologic 1/2 life.

Answer 26

B.
1/Te= 1/Tb + 1/Tp
1/3=1/Tb + 1/6
Tb = 6 hrs

Question 27

A package containing radioactive material is received in the hot lab and found to have a radiation exposure of 5Mr/h at the surface and 0.2mR/h at 1 m from the surface. Under which of the following Department of Transportation (DOT) labeling categories was the package shipped?
A. white I
b. Yellow II
c. Yellow III
d. Limited quantity shipment

Answer 27

B.
DOT and NRC have set limits on the amount of radiation that can be detected at the surface and at 1 m from a package containing radioactivity.
White I: Surface (mR/h) <0.5 and at 1m <1.0
Yellow I: Surface >0.5 , <50 and at 1 m >1 <10
Yellow II: Surface >50, <200

Question 28

For laboratory efficiency and patient convenience, most tech-99m protocols are performed in 1 day using a rest/stress sequence. How long after the resting injection should the acquisition be performed?
a. immediately
b. 15mins
c. 30mins
d. 2 hrs

Answer 28

C.
Time delay after injection of a tech-99m perfusion agent is to allow clearance from the liver and maximize the myocardial uptake. Immediately and 15mins after a resting or pharmacologic stress injection, there is too much liver activity present to see inferior wall of the heart. At 30-60 mins, tehre is adequate liver clearance to visualize the inferior wall. By 2 hrs the liver will hav cleared, but there is a greater probablity of having loops of bowel adjacent to the heart and there is greater decay of the radioactivity in the heart.

Question 29

A pt undergoes a 1 day rest/stress tech-99m single photon emeission computed tomography (SPECT) myocardial perfusion study. What is the dose range for the resting study ?
a. 8-12mCi
b. 15-20 mCi
c. 24-36 mCi
d. 45 mCi

Answer 29

A.
rest dose should be approx 1/3 the stress dose, with some variation introduced by the length of time between the two studies. If interval between studies is short, stress requires a higher dose, and if it is long, the full 3x greater dose may not be needed dude to decay of the resting injections. With 1:3 dosing, the higher stress dose overcomes the smaller rest dose so that the stress images have less residual activity from the rest study. If rest dose is high, stress dose will need to be 3x higher, and this will give the patient an unacceptably high level of radiation. If lower dose is used for stress without enoguh time between injections there iwll be residual activity from rest study that can underestimate amoutn of ischemia present. Rest imaging can be started 30-60 mins post injection, and stress started 10-20 mins after exercise stress and 30-60 after pharmacologic.

Question 30

Tech - 99m labeled perfusion tracers have improved SPECT perfusion imaging relative to thall-201 due to which characteristic?
a. longer 1/2 life allowing administration of a higher dose
b. higher photon energy resulting in less tissue attenuation
c. higher liver and GI uptake
d. higher extraction fraction across the coronary bed

Answer 30

B. Tech-99m labeled agents have improved spect imaging characteristics compared to thallium due to higher photon energy 140kev vs 60-80kev, which has less total attenuation and shorter 1/2 life 6hrs vs 72hr allowing administration of a much higher dose but less total body radiation.
Liver and GI activity assoc wiht the tech-99m tracers have proven to be a major problem due to scatter, scaling or normalization problems, and ramp filter artifacts assoc w/ filtered back projection during reconstruction.
Extraction fraction across the coronary bed is lower for both tech-99m agents in comparison to thall-201, and this raises theoretical concerns regarding lower sensitivity for tech-99m during high coronary flow rates with vasodilatory pharm stress.

Question 31

Attenuation correction techniques have which of the following in common?
a. a patient specific attenuation map is created
b. all techniques are generated by an cray of the pateitn
c. a standard method of attenuation correction has been applied industry wide.
d. attenuation correction increases the percent of studies that are read as abnormal.

Answer 31

A.
Various methods have been utilizzed for attenuation correction including a radioactive line source gadolinium and xray based techniques ie CT. Both methods create a patient specific tissue attenuation map that is used to correct for the loss of counts due to differences in the amount and type of tissue between the heart and the detector. Attenuation correction remains a vendor-specific tool with no uniform stnadards established by industry or professional societies. When applied correctly, attenuation correction reduces soft-tissue related defects and specificity increases, so fewer studies are read as abnormal due to attenuation that may frequently be misinterpreted as a prior infarction.

Question 32

Quantitative analysis and attenuation correction have both been used to improve the diagnostic accuracy of SPECT myocardial perfusion imaging. The interaction between these two methods is best described in which statement?
a. In contrast to uncorrected spect studies, there is no difference in perfusion distributions between normal men and women with attenuation corrected studies.
b. more sutides are interpreted as normal with quantittive analysis than with attenuation correction.
c. the specificity of attenuation corrected images is lower than the images interpreted with quantitative analysis
d. both of these methods lead to a lower sensitivity to detect coronary artery disease

Answer 32

A.
Attenuation corrected gender maps are not different between males and females. Attenuation correction improves the normalcy rate to a larger extent than does quantitative analysis alone. Therefore, the specifity of a positive finding is higher in images interpreted in the setting of attenuation corrected.

Question 33

The max perimissible activity concentration of molybedenumm-99 to tech-99m as stipulated by NRC is:
a. 0.15microCi/mCi at time of elution of tech-99m from the generator
b. 0.15micro/Ci/mCi at expiration time of tech-99m
c. 0.15microCi/mCi at the time of administration to the patient
d. 0.15microCi/mCi at time of compounding with radiopharmaceuticals

Answer 33

C.
Title 10 of the Code of Federal Regulations, part 35, Section 35.204

Question 34

Aluminum ion concentration in tech-99 is regulated by NRC, true or false.

Answer 34

False
NRC regulates the safe use and handling of all radioactive materials. Al ions limits are recommended by US Pharmacopeia - limits are 10microg/ml of eluate

Question 35

When a radioactivity ackage is delivered to the hot lab of a nuclear med department, when must the package be monitored for radioactive contamination?
a. w/in 3 hrs after receiving in the hot lab
b. w/in 3 hrs after receiving in the hot lab or within 3 hrs from the beginning of the next working day if received after hrs
c. w/in 1 hr after receiving in hot lab
d. radioactive packages must be monitored immediately after receipt

Answer 35

B.

Question 36

Member of the public in the US are subject to ionization radiation exposure from natural and man-made rad sources. On avg, they receive approximately half ffrom natural occurring and the other 1/2 from man-made, predominately medical sources. How much is received annually from all sources?
a. 620millirem (6.2mSv)/year
b. 310 millirem (3.1mSv)/year
c. 620 millirem or 6.2 mSv per adult
d. 310 millirem 3.1msv per adult

Answer 36

A.
NCRP decided that the average exposure to the public in the US has increased from 360mrem in 1980s to 620mrems in 2006. This increase is from medical uses of radiation from nuc med and xr, predominately diagnostic CT.

Question 37

How should tech-99m radioactive waste generated in a nuclear med department be disposed?
a. store in lead box indefinitely
b. dispose to landfill
c. store in house for decay to background radiation level before disposal
d. sent to approved nrc site

Answer 37

C.