SP2:Radioactivity, Radiopharmacy, and Quality Assurance

Question 1

How does 201Tl decay?
(a)By positron emission

(b) By electron capture
(c) By beta emission

Answer 1

(b) 201Tl decays by electron capture with gamma emissions of 0.135 MeV and 0.167 MeV.

Question 2

What is the role of the stannous ion in the preparation of pharmaceuticals labeled with 99mTc?
(a)To increase the valence state from +4 to +7

(b) To reduce the amount of Al3+ present
(c) To reduce the valence state of 99mTc
(d) To reduce the radiation dose

Answer 2

(c) Stannous chloride is a reducing agent which changes the valence state of Tc in pertechnetate. It has no effect on either the amount of Al3+ or the radiation dose.

Question 3

If an assay of a vial containing 131I shows 50 mCi present on May 2, approximately what will the assay show on May 18?
(a)25 mCi

(b) 12.5 mCi
(c) 40 mCi
(d) 6 mCi

Answer 3

(b) The half-life of 131I is 8.06 days. Since the time elapsed is about two half-lives, the original activity would be halved twice (50 mCi/2 = 25 mCi, 25 mCi/2 = 12.5 mCi).

Question 4

If a bone scan has been ordered on a 5-year-old girl and the physician prescribes 62% of the adult dose to be given, how many mCi should be administered?
(a)5 mCi

(b) 12.4 mCi
(c) 7.4 mCi
(d) 3.1 mCi

Answer 4

(b) 20 mCi × 0.62 = 12.4 mCi

Question 5

If the biological half-life of an isotope is 6 h and the physical half-life is 12 h, what is the effective half-life?
(a)6 h

(b) 12 h
(c) 2 h
(d) 4 h

Answer 5

(d) To find the effective half-life, we use the formula
Te=(Tp x Tb) / (Tp + Tb)
Te=(12x6) / (12+6) = 72/18 = 4h

Question 6

Which of the following is used to abbreviate physical half-life?
(a)Tp

(b) T/2
(c) T2
(d) P1/2

Answer 6

(a) Tp is used to abbreviate physical half-life as in the formula in the answer to Chap. 2 (“Radioactivity, Radiopharmacy, and Quality Assurance”), question 5.

Question 7

The physical half-life of a radionuclide is the time it takes
(a)For half of the substance to leave the body

(b) For the nuclide to decay to one-half of the original activity
(c) For the kit to become half expired
(d) For half of the substance to be metabolized

Answer 7

(b) The physical half-life is fixed for any radionuclide and is the time necessary for the activity to be reduced to half its current activity. The biologic half-life is the time it takes for the body to eliminate half of the compound administered.

Question 8

If a kit has 310 mCi of activity present at 8:00a.m., what will the vial assay show in 4 h and 10 min if the decay factor is 0.618?
(a)175mCi

(b) 192mCi
(c) 501mCi
(d) 155mCi

Answer 8

(b) Activity at time t = original activity x decay factor.

At = Ao x DF (310 mCi) x (0.618) = 191.58

Question 9

A vial containing 99mTc is assayed at 9:00 a.m. and contains 255 mCi. Calculate the remaining activity at 3:00 p.m?
(a)721

(b) 595
(c) 127.5
(d) 600

Answer 9

(c) The physical half-life for 99mTc is 6 h . Since one half-life has elapsed, the original activity must be multiplied by 0.5.

Question 10

A vial of technetium eluate contains 50mCi/ml. If 4 ml is withdrawn and added to a diphosphonate kit containing 16 ml of solution, what volume would then need to be withdrawn to prepare a 20 mCi dose at that moment?
(a)1.0

(b) 1.5
(c) 2.0
(d) 2.5

Answer 10

(c) First it is necessary to multiply 4 ml by 50 mCi/ml to arrive at the total activity in the diphosphonate kit. Then the total volume can be calculated (16 ml solution +4 ml 99mTc = 20 ml). The specific concentration of the kit is activity/volume or 10 mCi/ml (200 mCi/20 ml). Then one uses the formula below:

Required volume = activity desire/specific concentration

20 mCi / 10 mCi/ml = 2 ml

Question 11

If a preparation of 99mTc mertiatide has 60 mCi of activity present at 8:30 a.m., how many mCi will be present at 9:00 a.m. (DF = 0.944)?
(a)63.6

(b) 56.6
(c) 59.6
(d) 53.6

Answer 11

(b) Activity at time t = original activity x decay factor.

At = Ao x DF (60 mCi x 0.944 = 56.6)

Question 12

Which of the following is boiled during preparation?
(a)MAA

(b) Sulfur colloid
(c) Albumin colloid
(d) Diphosphonates

Answer 12

(b) Following the addition of pertechnetate, sulfur colloid is heated in a shielded, boiling water bath. During this time, the 99mTc is rapidly incorporated into the sulfur colloid particles. Albumin colloid, disphosphonate kits, and MAA do not need to be heated during preparation.

Question 13

The presence of 12 ug Al+3 in 1 ml of 99mTc eluate is:
(a)An example of radionuclidic impurity

(b) An example of chemical impurity
(c) An example of radiochemical impurity
(d) Acceptable since it is less tahn 15 ug/ml

Answer 13

(b) Al3+ in 99mTc eluate is an example of chemical impurity. Al3+ ions from the alumina column of the molybdenum generator must be less than 10 ug Al+/ml of eluate, the limit set by the US Pharmacopeia. This chemical impurity may result in reduced image quality due to poor labeling.

Question 14

Which body decides on the acceptable levels of radionuclidic impurity?
(a)DEP

(b) NRC
(c) FDA

Answer 14

(b)The Nuclear Regulatory Commission has set a limit of 99Mo in 99mTc eluate at 0.15 uCi/mCi of 99mTc at the time the dose is administered. The US Pharmacopeia regulates this radionuclidic impurity as well.

Question 15

Which of the following is an example of radionuclidic impurity?
(a)Presence of free 99mTc in a preparation of 99mTc sulfur colloid

(b) Presence of 99Mo in 99mTc eluate
(c) Presence of aluminum ions in 99mTc eluate
(d) Presence of pyrogens in eluate

Answer 15

(b) Radionuclidic impurity is the activity present in the form of an unwanted radionuclide. In the case of 99Mo in 99mTc eluate, this results in increased radiation dose and reduced image quality. Radiochemical impurity is the presence of the radionuclide in chemical forms other than that desire, for instance, the presence of free pertechnetate in a prepared kit of 99mTc sulfur colloid. Chemical impurity refers to the presence of other, nonradioactive chemicals in teh sample, i.e., Al3+ in 99mTc eluate.

Question 16

16. What is the maximum amount of aluminum ions (Al+3) allowed in 1ml of 99mTc eluate according to the USP?
    (a) None is allowed

(b) 5ug
(c) 10ug
(d) 15ug

Answer 16

(c) 10 ug Al3+/ml of eluate is the limit set by the US Pharmacopeia.

Question 17

17. What is indicated by the front of an instant thin layer chromatography (ITLC) strip?
    (a) Radionuclidic impurity

(b) Particles of incorrect size
(c) Pyrogens
(d) This depends on the solvent and strip used

Answer 17

(d) The upper portion of the strip is the solvent front, and the lower portion is the origin (where the radiopharmaceutical being tested is introduced), but without further information about the chromatography kit, one cannot say what they specifically indicate.

Question 18

18. If a kit contains 140 mCi of 99mTc in 23 ml, how much volume must be withdrawn to obtain a dose of 5 mCi?
    (a) 0.8 ml

(b) 30 ml
(c) 1.2 ml
(d) 0.6 ml

Answer 18

(a) Specific concentration is 140 mCi/23 ml or 6.1 mCi/ml. Required volume is equal to the activity desired divided by the specific concentration (5 mCi/6.1 mCi/ml = 0.8 ml).

Question 19

19. If a kit contains 140 mCi of 99mTc in 23 ml at 9:00 a.m., how much volume must be withdrawn to obtain a dose of 5 mCi at 3:00 p.m.?
    (a) 0.8 ml

(b) 1.6 ml
(c) 2.4 ml
(d) 0.6 ml

Answer 19

(b) Specific concentration is activity/volume or 6.1 mCi/ml. Since one half-life has elapsed, the specific concentration in the vial is 3.05 mCi/ml assuming nothing has been withdrawn from the vial in the meantime. Required volume is activity desired divided by specific concentration (5 mCi/3.01 mCi/ml = 1.6 ml).

Question 20

20. An MAA kit contains 40 mCi of 99mTc in 5 ml at 8:00 a.m. What would be the best volume to be withdrawn for a 4 mCi dose at 10:00 a.m. if a perfusion lung scan is planned (DF=0.794)?
    (a) 0.63 ml

(b) 1.54 ml
(c) 2.2 ml
(d) 0.25 ml

Answer 20

(a) Original activity is multiplied by the decay factor to give the activity at 10:00 a.m. (40 mCi x 0.794 = 31.76 mCi). Activity divided by the volume gives teh specific concentration (31.76 mCi/5 ml = 6.35 mCi/ml). If we assume a 4-mCi dose is desired, we must divide the activity desired by the specific concentration to obtain the volume needed (40 mCi/6.35 mCi/ml = 0.63 ml).

Question 21

What is the most likely size of an MAA particle if correctly prepared?
(a)0–100 mm

(b) 10–30 μm
(c) 10–30 mm
(d) 0–250 μm

Answer 21

(b) Particles 10 um or larger will be trapped by the capillaries in the lung, which measure 7-10 um. Particles are formed which measure 5-100 um, bust most are in the range of 10-30 um. An adult should receive 100,000-500,000 particles which will occlude less than 1 in 1000 of the capillaries, in general

Question 22

99mTc MAA has a biologic half-life of 2–4 h; what will the effective half-life be?
(a)1.5–3.0 h

(b) 2.0–4.0 h
(c) 0.5–1.0 h
(d) 1.5–2.4 h

Answer 22

(d) To find the effective half-life, we use the formula

Te = (Tp x Tb) / (Tp + Tb)

Since the biologic half-life is in the range of 2-4 h, the equation is solved twice, first using two and then four to obtain the effective half-life of 1.5-2.4 h.

Question 23

Which radiopharmaceutical is made with 99mTc without a reducing agent?
(a)MAG3

(b) MAA
(c) Sulfur colloid
(d) Sestamibi

Answer 23

(c) 99mTc sulfur colloid is formed when elemental sulfur condenses in a heated solution forming colloid particles that incorporate 99mTc in the +7 valence state.

Question 24

Which of the following is an example of radiochemical impurity?
(a)Presence of free 99mTc in a preparation of 99mTc sulfur colloid

(b) Presence of 99Mo in 99mTc eluate
(c) Presence of aluminum ions in 99mTc eluate
(d) Presence of pyrogens in eluate

Answer 24

(a) Radionuclidic impurity is the activity present in the form of an unwanted radionuclide. In the case of 99Mo in 99mTc eluate, this results in increased radiation dose and reduced image quality. Radiochemical impurity is the presence of the radionuclide in chemical forms other than that desire, for instance, the presence of free pertechnetate in a prepared kit of 99mTc sulfur colloid. Chemical impurity refers to the presence of other, nonradioactive chemicals in teh sample, i.e., Al3+ in 99mTc eluate.

Question 25

Which of the following can be said regarding effective half-life?
(a)It is always longer than the physical half-life.

(b) It is always shorter than both the physical and the biologic half-life.
(c) It is always shorter than physical half-life but longer than the biologic half-life.
(d) It is always longer than the biologic half-life but shorter than the physical half-life.

Answer 25

(b) Effective half-life must be shorter than either physical half-life or biologic half-life

Te = (Tp x Tb) / (Tp + Tb)

Question 26

The purpose of adding EDTA to sulfur colloid when labeling with 99mTc is:
(a)To prevent aggregation of sulfur colloid

(b) To bind excess Al3+
(c) To prevent loss of the radiolabel
(d) (a) and (b) only
(e) (b) and (c) only

Answer 26

(d) EDTA is a chelating agent that will sequester the Al3+ ion, thereby helping to prevent aggregates from forming.

Question 27

A diphosphonate kit should generally be used within how many hours after preparation?
(a)2 h

(b) 12 h
(c) 4–6 h
(d) 24 h

Answer 27

(c) Although package inserts state that doses should not be used after 6-8 h following kit preparation (depending on the particular kit used), most imaging departments prefer to use them within 4 h to obtain the best image quality.

Question 28

What is the usual particle size of sulfur colloid?
(a)0.3–1.0 μm

(b) 0.03–0.1 μm
(c) 2.0–10 μm
(d) 4.0–15 μm

Answer 28

(a) The appropriate particle size of sulfur colloid is 0.3 - 1.0 um, which allows them to be phagocytized by the Kupffer cells of the liver.

Question 29

Which radiopharmaceutical, when correctly prepared, will have the smallest particle size?
(a)99mTc sulfur colloid

(b) 99mTc albumin colloid
(c) 99mTc human serum albumin
(d) 99mTc macroaggregated albumin

Answer 29

(c) 99mTc human serum albumin has the smallest particle of the compounds listed, making it useful for applications like lymphoscintigraphy.

Question 30

The advantages of albumin colloid over sulfur colloid include:
(a)Does not require heating

(b) Less expensive
(c) Smaller dose can be administered

Answer 30

(a) It is not necessary to heat 99mTc albumin colloid during preparation, it is more expensive, and the recommended dose is comparable for both radiopharmaceuticals.

Question 31

Following injection of 99mTc MAA for a perfusion lung scan, activity is seen in the kidneys and brain. This is indicative of:
(a)Right to left cardiac shunt

(b) Renal failure
(c) Congestive heart failure
(d) Incorrect particle size

Answer 31

(a) In the absence of a shunt, 95% of 99mTc MAA particles injected will be trapped in the lung capillaries. In the event of a shunt, however, particles enter the left ventricle and the arterial blood. This results in the activity from the 99mTc MAA in the brain and lungs.

Question 32

At 7:00 a.m., a technologist prepares a dose of 99mTc MDP for injection at 10:00 a.m. that day. The desired dose is 22 mCi and no precalibration factors are available. The 3-h decay factor for the isotope is 0.707. What amount of activity should the technologist draw up into the syringe at 7:00 a.m.?
(a)15.6 mCi

(b) 27.07 mCi
(c) 29.5 mCi
(d) 31.1 mCi

Answer 32

(d) Since there is no precalibration factor available, we can use the decay factor and rearrange the formula At = Ao x DF to read Ao = At / DF and solve for the original activity
(22 mCi/0.707 = 31.1 mCi).

Question 33

What can be said regarding precalibration factors?
(a)It is not necessary for problem solving if the decay factor is available.

(b) It is always <1.0.
(c) It is always >1.0.
(d) Both (a) and (c).

Answer 33

(d) Precalibration factors will always be greater than 1.0 since the activity precalibrated will be greater than the activity at the time of radiopharmaceutical administration. Similarly, decay factors will always be less than 1.0, since the activity is decreasing. We can use decay factors to solve precalibration problems. (rearrange the formula At = Ao x DF to read Ao = At / DF)

Question 34

What method is used to calculate pediatric dose?
(a)According to weight

(b) Clark’s formula
(c) According to body surface area
(d) Using Talbot’s nomogram
(e) All of the above

Answer 34

(e) Some radiopharmaceutical doses are calculated according to weight. Clark’s formula allows for the calculation of a pediatric dose by comparing the weight of a pediatric patient to an average adult weight (pediatric dose = (patient’s weight in lb x adult dose)/150 lb). A patient’s body surface area can be calculated, and the appropriate fraction of the adult dose can either be calculated or found on a body surface area table. Talbot’s nomogram is a calculated table relating body weight to surface area and the appropriate percentage of the adult dose. If the child’s weight is known, the percentage can be found on the table and the dose calculated.

Question 35

If the recommended volume for a MAG3 kit ranges from 4 to 10 ml, and the 99mTc eluate that will be used contains 820 mCi in 10 ml, and 41 mCi will be used, what is the minimum amount of diluent that should be added?
(a)0.5 ml

(b) 1 ml
(c) 3.5 ml
(d) 9.5 ml

Answer 35

(c) First, specific concentration is calculated (820 mCi/ 10 ml = 82 mCi/ml). Since 41 mCi will be added, 41 mCi is divided by 82 mCi/ml (volume required = desired activity/specific concentration) to find a volume of 0.5 ml. Since 4-10 ml is the recommended total volume, at least 3.5 ml of diluent must be added.

Question 36

If a 20 mCi dose of 99mTc HDP is needed at 9:00 a.m., how much activity should the syringe contain if the technologist prepares it at 7:00 a.m.? You may use the table of precalibration factors (Table 1) to determine the answer. (2 hr = 1.259)
(a)15.9 mCi

(b) 21.259 mCi
(c) 25.18 mCi
(d) 26.7 mCi

Answer 36

(c) It is necessary to multiply 20 mCi by 1.259 to obtain the answer 25.18 mCi

Question 37

Using Table 2, determine the decay factor for 99mTc at 7 h. (3 hr = 0.707)(4 hr = 0.630)
(a)1.337

(b) 0.445
(c) 0.432
(d) 0.551

Answer 37

(b) If the decay factor needed is not available, it can be calculated by multiplying the decay factors for times that add together to make the elapsed time. In this case, the decay factor for 7 h is not available, so the decay factors for 3 and 4 h are multiplied to find the decay factor (0.707 x 0.630 = 0.445).

Question 38

On a Monday morning at 6:00 a.m., a technologist is preparing a 99mTc ECD kit that is to be used for SPECT brain scan injections at 8:00 a.m., 9:00 a.m., and 10:00 a.m. Each patient should receive 10 mCi. What is the minimum activity that should be added to the kit during preparation? Use Table 1 if necessary. (2 hr = 1.259)(3 hr = 1.414)(4 hr = 1.587)
(a)42. 6 mCi

(b) 30.0 mCi
(c) 44.5 mCi
(d) 52.0 mCi

Answer 38

(a) Precalibration factors for each of the doses must be used. At 6:00 a.m., the dose of 10 mCi for 8:00 a.m. requires 12.59 mCi (10 mCi x 2 h. decay factor of 1.259 = 12.59), the dose for 9:00 a.m. requires 14.14 (using decay factor 1.414), and the dose for 10:00 a.m. requires 15.87 (decay factor 1.587). The three precalibrated doses are added together to obtain a total of 42.6 mCi as the minimum activity to be added to the kit.

Question 39

A chromatography strip is used to test a kit for radiochemical impurity and is counted in a well counter. Part A contains 99mTc pertechnetate, and Part B contains bound 99mTc in the desired form. If the results show 258,000 cpm in Part B and 55,000 cpm in Part A, can this kit be used for injection into patients?
(a)Yes

(b)No

Answer 39

(b) The counts for technetium in the desired form are expressed as a percentage of the total counts (258,000/313,000 X 100), and the result is 82%. The lower limits of radiochemical purity differ according to radiopharmaceutical but typically are 90% and above, so this cannot be used.

Question 40

What is the approximate radiochemical purity for the kit described? Part A contains 99mTc pertechnetate, and Part B contains bound 99mTc in the desired form. If the results show 258,000 cpm in Part B and 55,000 cpm in Part A.
(a)21%

(b) 79%
(c) 18%
(d) 82%

Answer 40

(d) The counts for technetium in the desired form are expressed as a percentage of the total counts (258,000/313,000 X 100), and the result is 82%. The lower limits of radiochemical purity differ according to radiopharmaceutical but typically are 90% and above, so this cannot be used.

Question 41

What is the approximate radiochemical impurity of the kit described? Part A contains 99mTc pertechnetate, and Part B contains bound 99mTc in the desired form. If the results show 258,000 cpm in Part B and 55,000 cpm in Part A.
(a)21%

(b) 79%
(c) 18%
(d) 82%

Answer 41

(c) The counts in the undesired form are expressed as a percentage of total counts to find radiochemical impurity (55,000/313,000 x 100 = 17.6%).

Question 42

A vial of 99mTc eluate is tested for 99Mo breakthrough, and the amount of breakthrough is 25 uCi in 775 mCi at 6:00 a.m. Following the preparation of all kits to be used that day, 450 mCi of 99mTc is left. That night, a technologist is asked to perform a scrotal scan at 11:00 p.m. Must the generator be eluted again?
(a)Yes, because the amount of eluate will have decayed to below the amount needed for a patient dose.

(b) Yes, because the molybdenum breakthrough will now exceed the limit allowed by the NRC.
(c) No.

Answer 42

(b) Because of a shorter half-life (6.01 h vs. 66.7 h), the technetium has decayed to a greater extent than has the molybdenum, and the breakthrough now exceeds of that allowed by the NRC.

Question 43

A 99mTc MDP bone scan dose was prepared at 7:00 a.m. and contained 32 mCi/2 ml. At 9:00 a.m., when the patient arrives, the technologist realizes that the patient’s age was overlooked (13 years). The technologist would now like to adjust the dose to 11 mCi. Given a 2-h decay factor of 0.794, what volume should be discarded so that the correct dose remains in the syringe?
(a)0.65 ml

(b) 0.87 ml
(c) 1.13 ml
(d) 1.5 ml

Answer 43

(c) First, the activity at 9:00 a.m. has to be determined by measuring the 2-h decay factor by the original activity (32 mCi x 0.794 = 25.4). The specific concentration is 12.7 mCi/ml (25.4 mCi/2 ml = 12.7), and the desired dose must be divided by the specific concentration to find the volume to be retained in the syringe (11 mCi/(12 mCi/ml) = 0.87 ml to be retained.) Therefore 1.13 ml must be discarded.

Question 44

A dose of 99mTc DMSA is prepared and calibrated to contain 5.0 mCi at 8:00 a.m. The patient arrived late at 10:00 a.m. Without using any tables of decay factors, determine what activity will remain in the dose at that time.
(a)3.40 mCi

(b) 3.54 mCi
(c) 3.62 mCi
(d) 3.97 mCi

Answer 44

(d) The formula for decay calculation using half-life can be used:
At=Aoe ^(-0.693t/half life)
where At is the activity at time t, Ao is the original activity, and t is the elapsed time:
At = 5 mCi x e^(-0.693x0.3328)
At = 5 mCi x e^(-0.2306)
At = 5 mCi x 0.794

Question 45

An MAA kit contains 950,000 particles per ml. The activity in the kit is 50 mCi of 99mTc in 5 ml. If a 4 mCi dose is drawn up, how many particles will be in the dose?
(a)76,000

(b) 380,000
(c) 410,000
(d) 450,000

Answer 45

(b) In order to find the number of particles, first it is necessary to know the volume of the 4-mCi dose. If the specific concentration is 10 mCi/ml (50 mCi/ml divided by 5 ml), the required volume is 0.4 ml (required volume is equal to the activity desired divided by the specific concentration). If there are 950,000 particles in 1 ml, there are 380,000 in the dose (particle concentration x volume of dose = particles in dose). Since most patients should receive 100,000-600,000 particles, this amount is acceptable.

Question 46

What will happen to the dose if it sits for 1 h? An MAA kit contains 950,000 particles per ml. The activity in the kit is 50 mCi of 99mTc in 5 ml. If a 4 mCi dose is drawn up
(a)The number of particles per mCi will increase.

(b) The number of particles per mCi will decrease.
(c) The number of particles per mCi will remain unchanged.

Answer 46

(a) After 1 h, the number of particles will remain unchanged, but the activity will decrease, so the number of particles per ml will increase.

Question 47

A volume of 5 ml containing 40 mCi of 99mTc is added to an MAA kit with an average of 3,000,000 particles. What volume of the reconstituted kit should be withdrawn to prepare a dose for a patient with severe pulmonary hypertension?
(a)0.25 ml

(b) 0.40 ml
(c) 0.45 ml
(d) 0.50 ml

Answer 47

(a) Various sources state different particle numbers for patients with pulmonary hypertension, ranging from 60,000 to 200,000. The Society of Nuclear Medicine Procedure Guidelines recommend 100,000-200,000 particles. It is optimal to give the minimum number of particles, so the best choice from the answers given is 0.25 ml, which will give contained particles of 150,000 (600,000 particles per ml x 0.25 ml = 150,000 particles).

Question 48

To reduce the possibility of pyrogenic reactions, all kits should be prepared using saline that contains bacteriostatic preservatives.
(a)True

(b)False

Answer 48

(b) Bacteriostatic sodium chloride will increase the oxidation products and can affect the radiochemical purity and distribution of the tracer.

Question 49

While performing a GI bleeding study with labeled red blood cell, a technologist notices gastric activity that he suspects is the result of free pertechnetate. What could be done to support this suspicion?
(a)Reimage the patient in the erect position.

(b) Narrow the window around the photopeak.
(c) Image the thyroid.
(d) Have the patient drink two glasses of water and empty his or her bladder.

Answer 49

(c) If there is also activity in the thyroid, the suspicion that the gastric activity is the result of free pertechnetate is supported. Providing the radiologist with a thyroid image will thus aid the interpretation of the scan.

Question 50

Convert 23 mCi to SI units.
(a)from 850 to 851 MBq

(b) 850 kBq
(c) 850 GBq
(d) None of the above

Answer 50

(a) 1 mCi is equal to 37 MBq, so to convert mCi to MBq, one must multiply it by 37. To convert curies to SI (international System of Units), one must again multiply by 37; 1 Ci is equal to 37 GBq and 1 uCi is equal to 37 kBq

Question 51

If excessive aluminum is present in 99mTc eluate, which of the following would be expected on a bone scan?
(a)Lung uptake

(b) Liver uptake
(c) Thyroid uptake
(d) Gastric uptake

Answer 51

(b) Liver uptake on a bone scan can be the result of suboptimal pharmaceutical preparation from excessive aluminum ions in the eluate as well as excessive stannous ions which may form tagged tin colloids that will be sequestered in the liver. It may also be the result of hydrolyzed, reduced 99mTc in the prepared kit. Additionally, various liver neoplasms also take up 99mTc-labeled phosphates, or the patient may have had a recent liver spleen scan. Lung uptake, if diffused, could be due to metastatic pleural effusion. Thyroid and gastric activities are usually the result of free pertechnetate.

Question 52

Radiochemical impurities often result from:
(a)Introduction of water into the kit

(b) Introduction of oxygen into the kit
(c) Introduction of nitrogen into the kit
(d) (a) and (b) only

Answer 52

(d) Radiochemical impurity is the activity that is present in forms other than the desired form and will affect the biodistribution of the radiopharmaceutical. Introduction of air or water into the preparation vial can result in radiochemical impurity. During kit preparation, following addition of the isotope, an equivalent amount of gas may be withdrawn into the syringe to normalize the pressure in the vial.

Question 53

It is proper technique to clean the septum of a kit reaction vial and inject an amount of air equal to the volume being withdrawn when preparing a unit dose.
(a)True

(b)False

Answer 53

(b) The process of injecting air into the reaction may result in spillage and contamination of work areas and doing so will reduce the stability of the prepared radiopharmaceutical. Swabbing the vial spetum maintains sterility.

Question 54

15 rem is equal to:
(a)150 mSv

(b) 15 grays
(c) 15 Sv
(d) 150 MBq

Answer 54

(a) The sievert is an SI (international System of Units) unit for dose equivalent. Since 1 rem is equal to 0.01 Sv, or 10 mSv, one multiples 15 rem by 10 mSv to find 150 mSv.

Question 55

What is the purpose of adding hetastarch to a blood sample drawn for the purpose of leukocyte labeling?
(a)To act as an anticoagulant

(b) To hasten the settling of erythrocytes
(c) To separate platelets from leukocytes
(d) To improve labeling efficiency

Answer 55

(b) The addition of hetastarch facilitates leukocyte labeling by assisting the settling of erythrocytes.

Question 56

Following reconstitution of a kit with 99mTc pertechnetate, a technologist should ensure that all of the following are present on the vial except:
(a)Date and time of preparation

(b) Lot number
(c) Concentration and volume
(d) Patient name or identification number

Answer 56

(d) Since kits are usually prepared to contain multiple patient doses, the patient name or ID number is not noted on the vial. Date, time, lot number, concentration, and volume should be noted on the vial. NRC licensees must maintain records regarding the dispensation of the vial contents, and this is where patient name and ID, administering technologist, isotope and radiopharmaceutical, activity of both prescribed and prepared dosages, and date and time of administration are listed.

Question 57

If proper centrifuge speed is not used during separation of cell types for leukocyte labeling with 111In oxine, what may happen?
(a)Platelets may be inadvertently labeled.

(b) 111In oxine will not tag WBCs.
(c) Red blood cells may become damaged.
(d) White blood cells may become damaged.

Answer 57

(a) Labeled platelets may localize in thrombosis and cause a false-positive interpretation. If leukocytes are damaged during labeling, their normal function may be disrupted resulting in a false-negative interpretation. All cell types will be labeled, so leukocytes must be labeled with care.

Question 58

In most reconstituted radiopharmaceutical kits, in what form is 99mTc present?
(a)Free pertechnetate

(b) Bound technetium
(c) Reduced, hydrolyzed technetium
(d) All of the above

Answer 58

(d) This is true for most radiopharmaceuticals labeled with 99mTc; one exception is sulfur colloid which uses unreduced 99mTc. In the other 99mTc radiopharmaceuticals, most of the 99mTc should be bound. The other forms are radiochemical impurity.

Question 59

For determination of plasma volume, 10 uCi of human serum albumin in 2.5 ml is added to 500 ml of water. What is the concentration of the resulting solution?
(a)0.019 uCi/ml

(b) 0.020 uCi/ml
(c) 50.00 uCi/ml
(d) 50.20 uCi/ml

Answer 59

(a) The total volume is 502.5 ml, and 10 uCi is divided by the volume to find the concentration of 0.019 uCi/ml

Question 60

A 99Mo/99mTc generator exists in _____ equilibrium and the parent isotope has a _____ physical half-life than the daughter isotope.
(a)Transient, longer

(b) Transient, shorter
(c) Static, longer
(d) Static, shorter

Answer 60

(a) In transient equilibrium, the parent isotope has a somewhat longer half-life than the daughter isotope. The combined activity rises initially, then transient equilibrium is reached, and there is slightly more activity present in the daughter. If the parent has a much longer half-life, the daughter isotope activity increases until it begins to decay at the same rate as it is produced. This is called secular equilibrium. If the daughter isotope has a longer half-life, no equilibrium is reached. Static equilibrium means that an object is at rest.

Question 61

If 630 mCi of 99mTc is eluted from a 99Mo/99mTc generator, what is the NRC limit of total 99Mo activity that may be present?
(a)0.15 uCi

(b) 94.5 uCi
(c) 42 mCi
(d) 94.5 uCi/ml
(e) 42 uCi

Answer 61

(b) Since a radiopharmaceutical may not contain more than 0.15 uCi of 99Mo per ml of 99mTc, 630 must be multiplied by 0.15.