SP15:Non-imaging Procedures and Radionuclide Therapy

Question 1

Radioiodine therapy is given for:
(a)Hyperthyroidism

(b) Thyroid cancer
(c) Grave’s disease
(d) All of the above
(e) (a) and (b) only

Answer 1

(d) 131I is used to treat thyroid cancer and hyperthyroidism by ablation. Grave’s disease is the most common cause of hyperthyroidism.

Question 2

During a Schilling test, a flushing dose of B 12 is given:
(a)Intramuscularly

(b) Intravenously
(c) Subcutaneously
(d) Orally

Answer 2

(a) The intramuscular injection of nonradioactive B12 is given to preload the liver and to saturate receptor sites in plasma so that the portion of radioactive B12 absorbed will be passed through the urine.

Question 3

32P chromic phosphate is a:
(a)Clear solution

(b) Bluish-green colloid
(c) Beta emitter
(d) (b) and (c)
(e) (a) and (c)

Answer 3

(d) 32P chromic phosphate is a bluish green colloid and is used for intracavitary therapy. 32P sodium phosphate is a clear solution that is used to treat polycythemia vera and bone pain from metastasis and is administered intravenously. 32P is a beta emitter.

Question 4

Before administration, 89Sr chloride must be assayed in a dose calibrator.
(a)True

(b)False

Answer 4

(b) As with all radioactive materials, 89Sr should be assayed prior to administration. However, the NRC allows administration of 89Sr unit doses without assay because not all dose calibrators assay them accurately.

Question 5

32P sodium phosphate is for:
(a)Intracavitary use

(b) Intravenous injection
(c) Intrathecal injection
(d) Inhalation

Answer 5

(b) 32P sodium phosphate is a clear solution that is used to treat polycythemia vera and bone pain from metastasis and is administered intravenously. 32P is a beta emitter.

Question 6

89Sr chloride is used to treat:
(a)Malignant ascites

(b) Polycythemia vera
(c) Bone pain caused by metastases
(d) Grave’s disease
(e) (a) and (c)

Answer 6

(c) 32P chromic phosphate is useful in treating malignant ascites. 32P sodium phosphate is used to treat polycythemia vera. 89Sr (as well as 32P sodium phosphate and 153Sm-EDTMP) is used to treat malignant bone pain by localizing where there is bone mineral turnover. 131I may be used to treat Grave’s disease.

Question 7

89Sr chloride should be administered:
(a)Via intracavitary injection

(b) Via direct venous injection
(c) Through a patent intravenous line
(d) Orally

Answer 7

(c) 89Sr chloride can be administered by direct venous access, but as it is a beta emitter, it is a better option to access the vein with an intravenous line and check the patency of the system before injection. If the dose is infiltrated into the tissue surrounding the vein, the tissue will be unnecessarily irradiated.

Question 8

89Sr and 32P are effectively shielded by:
(a)Lead pings

(b) Plastic syringes
(c) Paper
(d) None of the above

Answer 8

(b) 89Sr and 32P are beta emitters and will be effectively shielded with the plastic syringe. Using a lead syringe shield will cause bremsstrahlung.

Question 9

32P chromic phosphate is used to treat:
(a)Polycythemia vera

(b) Malignant ascites
(c) Bone pain caused by metastases
(d) Grave’s disease
(e) (a) and (c)

Answer 9

(b) 32P chromic phosphate is useful in treating malignant ascites. 32P sodium phosphate is used to treat polycythemia vera. 89Sr (as well as 32P sodium phosphate and 153Sm-EDTMP) is used to treat malignant bone pain by localizing where there is bone mineral turnover. 131I may be used to treat Grave’s disease.

Question 10

Absorption of vitamin B12 in the small bowel requires:
(a)A flushing dose of B12

(b) Intrinsic factor
(c) 0.5 mg of 57Co orally
(d) 24 h urine collection

Answer 10

(b) Intrinsic factor is a glycoprotein. It is secreted by the gastric mucosa, and without it vitamin B12 cannot be absorbed. If a Schilling test shows a B12 deficiency, the test can be repeated with the intrinsic factor to determine if the lack of it is the cause of malabsorption.

Question 11

What will be the effect on the results of a Schilling test if the patient urinates once and forgets to collect it?
(a)The percent excretion may be falsely high.

(b) The percent excretion may be falsely low.
(c) There will be no effect.

Answer 11

(b) The radioactivity in the urine represents the amount of vitamin B12 absorbed. The labeled B12 is excreted through the urine, so if any urine is not collected, the percent excretion will be falsely low.

Question 12

A patient has a 24-h dose excretion of 4% on a stage I Schilling test. A stage II test is performed and the patient now has a 24 h excretion of 12%. What is the most likely diagnosis?
(a)Malabsorption caused by drug therapy

(b) Parasitic competition
(c) Pernicious anemia
(d) None of the above

Answer 12

(c) The results from the first 24-h sample collected during Stage I are abnormal (normal is >8–10%), and the result from Stage II is 12%, which is normal. This indicates that the addition of intrinsic factor has corrected the malabsorption, meaning the patient has pernicious anemia, which is a vitamin B12 deficiency resulting from lack of intrinsic factor. There are other causes of B12 which include low intake, pancreatic insufficiency, and various medications.

Question 13

Calculate the percent excretion from a Schilling test given the following values: 55 cpm background, 13,500 cpm in the 1% standard, and 850 cpm in the 5 ml urine sample. The total volume of urine collected was 1100 ml.
(a)13.9%

(b) 12.9%
(c) 1.3%
(d) 13.0%

Answer 13

(d) To calculate the percent excreted, one uses the following formula:

%=(net cpm of urine sample)(total urine vol / urine sample) x100% / (net cpm of standard)(standard diluation factor)

= (850 cpm - 55 cpm)(1,100 ml / 5 ml)x100% / (13,500 cpm - 55 cpm)(100)

=174,900x100%/1,344,500 = 13%

The standard dilution factor is a fraction of the patient’s dose. If the standard is 5%, the dilution factor is found by dividing 100 by the percentage of standard. In this example, the standard was 1; we divide 100 by 1 to find a dilution factor of 1. In most cases, the standards are 1, 2, or 5%.

Question 14

Patient instructions for a Schilling test should include all of the following except:
(a)Careful collection of all urine for 48 h in a single container

(b) NPO from midnight before the examination begins
(c) No vitamin B12 for at least 3 days before the study
(d) No enemas or laxatives during the study

Answer 14

(a) Patients should collect their urine in two separate containers for each 24 h period because although the first collection may be abnormal in some disease states, the total excretion may be normal. The second collection may also suggest that the first collection may have been faulty.

Question 15

Simultaneous performance of stage I and stage II Schilling test uses:
(a)IV injection of 57Co-labeled B12 bound to intrinsic factor and oral 58Co-labeled B12

(b) Oral 57Co-labeled B12 bound to intrinsic factor and oral 58Co-labeled B12
(c) IV injection of 57Co-labeled B12 bound to intrinsic factor and oral 60Co-labeled B12
(d) Oral 57Co-labeled B12 bound to intrinsic factor and oral 60Co-labeled B12

Answer 15

(b) Various methods have been used; the most common is 57Co and 58Co, both given orally, with one of the isotope bound to intrinsic factor.

Question 16

Why must the cpm measured in the standard during a Schilling test be multiplied by a standard dilution factor?
(a)To account for the standard containing only a portion of the radioactive dose administered to the patient

(b) Because an undiluted standard would contain too much activity to be efficiently counted in a well counter
(c) To account for fecal excretion
(d) None of the above
(e) Both (a) and (b)

Answer 16

(e) The standard is prepared using a percentage of the patient dose; therefore a dilution factor must be used. The same dose as given to the patient is not used because the standard is counted in a well counter so a lower count rate is necessary.

Question 17

Beta emitters are effective for therapy because:
(a)They have a short range in soft tissue.

(b) They do not harm healthy tissue.
(c) They can be used for imaging as well as for therapy.
(d) They have short half-lives.

Answer 17

(a) A beta particle with energy of 2 MeV has a range of about 1 cm in soft tissue. That means it will expand its energy locally, regardless of tissue type. Some beta emitters are not useful for imaging because of their short range, although higher energy beta emitters may be imaged, for example, 131I. Half-life varies according to the isotope; 32P has a half-life of 14.3 days, but 60Co has a half-life of 5.26 years.

Question 18

What is the meaning of polycythemia?
(a)An excess of white blood cells

(b) An excess of platelets
(c) An excess of red blood cells
(d) An excess of plasma

Answer 18

(c) Polycythemia means too many red blood cells. Polycythemia vera is a disease of the bone marrow which may be treated using 32P sodium phosphate.

Question 19

Which of the following measure the amount of red cells in circulating blood?
(a)Red cell volume

(b) Hemoglobin
(c) Hematocrit
(d) (a) and (c)
(e) All of the above

Answer 19

(d) Red cell volume and hematocrit are measures of red blood cells in whole blood. Hemoglobin is a specific iron-rich protein that carries oxygen, so it does not directly measure the number of red blood cells. Hemoglobin may be decreased with or without a decrease in the number of red blood cells.

Question 20

The normal life span of a red blood cell is _____ days, following which it is removed from circulation by the _____.
(a)120, spleen

(b) 60, spleen
(c) 120, bone marrow
(d) 60, bone marrow

Answer 20

(a) Red blood cells, or erythrocytes, are produced in bone marrow, live for about 120 days, and are then phagocytized, mainly by the spleen. This is why damaged red blood cells may be used to image the spleen.

Question 21

Red blood cells are also known as:
(a)Leukocytes

(b) Erythrocytes
(c) Granulocytes
(d) Platelets
(e) (a) and (d)

Answer 21

(b) Blood contains red blood cells, white blood cells, and platelets (thrombocytes). Red blood cells are erythrocytes, leukocytes are white blood cells, and granulocytes are a kind of white blood cells.

Question 22

An empty syringe is used to draw 5 ml of blood. After several minutes the blood appears separated into a liquid and a solid portion. The liquid portion is called:
(a)Serum

(b) Plasma
(c) Anticoagulant
(d) None of the above

Answer 22

(a) In the absence of an anticoagulant, the blood will separate into serum and a clot containing cells and coagulation proteins.

Question 23

The functions of white blood cells include:
(a)Ingestion of bacteria by phagocytosis

(b) Antibody production
(c) Producing cellular immunity
(d) All of the above
(e) (b) and (c) only

Answer 23

(d) B cells initiate the production of antibodies, T helper cells mediate cellular immunity, and macrophages (a kind of white blood cell) phagocytize pathogens.

Question 24

A patient should be supine for at least 15 min before the start of a plasma volume determination because the plasma volume _____ when a patient is standing.
(a)Increase

(b)Decreases

Answer 24

(b) Plasma contains mostly water, with dissolved salts and proteins. In many patients, water will move from the bloodstream into the extravascular space in the legs as a result of standing, thus changing the plasma volume.

Question 25

If the dose rate measured at the bedside of a radioiodine therapy patient is 10 mrem/h, how long may a visitor (who is seated at bedside) stay?
(a)8 min

(b) 12 min
(c) 20 min
(d) 33 min

Answer 25

(b) Since the limit for exposure to nonoccupational individuals is 2 mrem/h, we can use the formula below:
Total dose = dose rate x time
Rearrange to: Dose rate x time = Total dose
10mrem/h x time = 2mrem
Time=2mrem / (10 mrem/h)
0.2 h

Question 26

A patient receives 45 mCi of 131I to treat thyroid cancer. A survey taken at 3 m immediately after administration of the dose reveals 60 mrem/h. If a survey taken 12 h later shows a dose rate of 30 mrem/h, how many mCi are left in the patient?
(a)15.5 mCi

(b) 22.5 mCi
(c) 35 mCi
(d) 40 mCi

Answer 26

(b) The formula below can be used:

Initial dose rate/ initial mCi = new dose rate / mCi remaining
(60mrem/h)/45 mCi = (30mrem/h)/mCi remaining
remaining = ((30mrem/h)x45mCi)/60mrem/h
mCi remaining = 22.5 mCi

Of course, these numbers are meant as an exercise and do not reflect actual practice since the half-life of 131I is 8.06 days.

Question 27

A patient advocate decides to question a patient undergoing radioiodine therapy regarding his or her opinion of the care provided. The dose at 1.5 m from the patient is 5 mrem/h, and it will take at least 30 min for her to interview the patient. What should be done?
(a)Have her sit 3 m from the patient

(b) Have her sit at 1.5 m from the patient, and let a colleague take over questioning after 20 min
(c) Have her interview the patient the following day
(d) Any of the above

Answer 27

(d) The exposure limit for nonoccupational individuals is 2 mrem/h. The dose rate is the question 5 mrem/h, so if she stays for one-half hour, she receives a dose of 2.5 mrem. If she doubles her distance from the patient, she will decrease her dose by one-fourth of the original so she would receive 1.25. If she stays only 20 min, she receives a dose of 1.7 mrem ((5 mrem/ 1 h) x 0.3 h = 1.5), and if she returns the next day, she will receive much less because of the physical half-life. Therefore, any of these options are effective for reducing the dose to meet NRC requirements. However, principles of ALARA state that the dose should be as low as is reasonably achievable. So she should not interview the patient at all or wait as long as possible before performing the interview.

Question 28

According to the Code of Federal Regulations, at what point may a patient who has undergone radioiodine therapy leave the hospital?
(a)When another person is unlikely to receive a total effective dose of 0.5 rem or 5 mSv from exposure to the patient

(b) If the remaining dose in the thyroid is less than 33 mCi
(c) If the remaining dose in the thyroid is less than 35 mCi
(d) If the time spent in the hospital is greater than four times the physical half-life of the isotope
(e) (a) and (b)

Answer 28

(e) 10 CFR 35.75 states that a patient can be released if the total effective dose equivalent to any other individual from exposure to the released individual is not likely to exceed 5 mSv (0.5 rem). Patients who have received (or determined to have retained) <33 mCi of 131I may be released.

Question 29

Which of the following objects in a patient’s room have the potential to become contaminated from a patient who has received radioiodine?
(a)Television

(b) Mattress
(c) Bathroom fixtures
(d) All of the above
(e) (b) and (c) only

Answer 29

(d) Although bathroom surfaces are most likely to be contaminated, anything the treated patient comes in contact with has the potential to become contaminated.

Question 30

Preparations for radioiodine therapy include:
(a)NPO from midnight

(b) Screening for pregnancy or breast-feeding
(c) Discontinuance of antithyroid drugs for 5-7 days prior to treatment
(d) All of the above

Answer 30

(d) All patients who are scheduled for nuclear medicine examinations or therapy should be screened for pregnancy and breast-feeding. Radioiodine will be better absorbed if the patient has been fasting. Patients should avoid iodine-containing substances (including contrast agents and food), thyroid hormones, and medications that would interfere with iodine uptake into the thyroid. The necessary delay before imaging after stopping various medications varies, and the SNM Guidelines provide detailed information about this.

Question 31

Which of the following are used to calculate the dose of 131I needed for administration in a patient with hyperthyroidism?
(a)Weight of the gland

(b) Percent uptake
(c) Presence or absence of nodules
(d) All of the above

Answer 31

(d) The dose necessary for 131I therapy for hyperthyroidism takes into consideration the weight of the gland (normally 15-20 g, but this is estimated by palpation and imaging) and the uptake. In general, 80-200 uCi of 131I per gram of thyroid tissue is desirable. One formula used to calculate dosage is thyroid weight/ 24 h uptake x 10 = dose of 131I in mCi. Other methods consider nodularity as well.

Question 32

A patient has a 6-h thyroid uptake of 25% and receives a 20 uCi dose of 131I for a thyroid uptake prior to radioiodine therapy. What will the concentration of activity in the patient’s thyroid gland be at 6 h if his thyroid weighs 45 g?
(a)11 mCi/g

(b) 11 uCi/g
(c) 0.11 uCi/g
(d) 1.1 uCi/g

Answer 32

(c) The uptake is multiplied by the dose administered to find the amount of activity in the gland; this is then divided by the weight of the gland to find the activity/gram.

20uCi x 0.25 = 5 uCi
5uCi / 45 g = 0.1 uCi/g

Question 33

Which of the following make 131I suitable for therapy?
(a)Uptake in thyroid tissue regardless of function

(b) Alpha emissions
(c) Short half-life
(d) Beta emissions

Answer 33

(d) 131I is a pure beta emitter; the beta emission is responsible for the local effect of treatment. Radioiodine therapy depends on functioning thyroid tissue, so choice a. is incorrect. The half-life of 131I is 8.06 days which is desirable; a beta emitter with a very short half-life would not have the same treatment benefit.

Question 34

Alternatives to radioiodine therapy for patients with hyperthyroidism are:
(a)Surgery

(b) Antithyroid drugs
(c) Thyroid storm
(d) All of the above
(e) (a) and (b) only

Answer 34

(e) Hyperthyroidism may be treated with surgery, radioiodine, or drugs to disrupt the production of thyroid hormones. Thyroid storm is potentially a life-threatening condition requiring emergency treatment caused by excessive thyroid hormone; symptoms include high fever, increased heart rate, and sweating.

Question 35

The wash method of labeling red blood cells for the determination of red cell volume involves repeated centrifugation of the collected sample. The advantage of this technique is that:
(a)Anticoagulants are unnecessary.

(b) Free chromate ion is removed.
(c) The use of expensive ascorbic acid is avoided.
(d) Less 51Cr can be used.

Answer 35

(b) During the wash method of red cell labeling, the free chromate ion is removed and so is the possibility that they will label circulating red blood cells after reinjection of the labeled preparation. This is a major advantage to the method. Anticoagulant is still used in the initial blood draw, and the same amount of radioactive chromium is used as in the ascorbic acid method. It also negates the need for adding ascorbic acid to reduce the free chromate ion.

Question 36

If a technologist mistakenly administered 32P chromic phosphate intravenously, what is likely to be the result?
(a)The urine will be bluish green for about a week.

(b) Severe radiation damage to the liver.
(c) Hypothyroidism will occur within 1 year.
(d) None of the above.

Answer 36

(b) 32P chromic phosphate is a colloid and therefore will be phagocytized by the Kupffer cells of the liver if injected intravenously. Because it is a pure beta emitter, it will cause local radiation damage.

Question 37

Discharge instructions for a patient who underwent therapy with 131I may include all of the following except:
(a)Patient is encouraged to increase fluids and void frequently.

(b) Patient should avoid close contract with others.
(c) Patient should collect excreta and store for ten half-lives.
(d) Patient should flush toilet at least twice after use.

Answer 37

(c) Patients need to continue efforts to decrease radiation exposure to others and themselves, including limiting contact with others, frequent voiding, and flushing multiple times after using the toilet. Patients do not need to collect and store excreta.

Question 38

A survey taken at 1 m from a patient who receive 35 mCi of 131I revealed a dose rate of 9 mrem/h. If the survey made 24 h later shows 6.9 mrem/h, what is the remaining dose in the patient, and can he or she be discharged?
(a)27 mCi, yes

(b) 27 mCi, no
(c) 4.3 mCi, yes
(d) 4.3 mCi, no
(e) Cannot be determined from the information given

Answer 38

(a) The formula (Initial dose rate/ initial mCi = new dose rate / mCi remaining) is applied to find 27 mCi remaining, so the patient can be released. 10 CFR 35.75 states that a patient can be released if the total effective dose equivalent to any other individual from exposure to the released individual is not likely to exceed 5 mSv (0.5 rem). Patients who have received (or determined to have retained) <33 mCi of 131I may be released.

Question 39

The NRC requires 131I therapy patients to have private rooms, although they may share with another 131I therapy patient.
(a)True

(b)False

Answer 39

(b) The patient must have a private room with a private bathroom or may share a room and a bathroom with another patient who also cannot be released under 10 CFR 37.75 (see also 10 CFR 35.315)

Question 40

According to the NRC, records of dose rate measurements taken immediately after administration of radioiodine to therapy patients must be kept for:
(a)6 months

(b) 1 year
(c) 3 years
(d) 5 years

Answer 40

(c) The NRC requires that these records be kept for 3 years.

Question 41

After injection of 125I human serum albumin for determination of plasma volume, it is important to withdraw a small amount of blood into the syringe and reinject it, to ensure that the entire radioactive dose is administered.
(a)True

(b)False

Answer 41

(b) Because the injected dose volume must be determined by weighting the syringe before and after injection, one should perform the injection without rinsing the syringe with blood.

Question 42

A patient who receives 89Sr chloride for palliation of pain from bone metastases does not have to be admitted to the hospital.
(a)True

(b)False

Answer 42

(a) Because the patient dose is 40-60 uCi/kg, the dose is usually not high enough to require hospitalization.

Question 43

Which of the following is used in the treatment of non-Hodgkin’s lymphoma?
(a)82Rb

(b) 32P chromic phosphate
(c) 90Y ibritumomab tiuxetan
(d) 153 Sm microspheres

Answer 43

(c) 90Y ibritumomab tiuxetan is a monoclonal antibody used in the treatment of non-Hodgkin’s lymphoma. 82Rb decays by positron emission and also electron capture and is used in PET imaging. 32P chromic phosphate is a beta emitter used for intracavitary therapy. 153Sm microspheres are being developed for radiosynovectomy but are not FDA approved at the time of writing.

Question 44

Patients who have previously demonstrated allergic reactions to mouse proteins have an increased risk of allergic response to:
(a)131I tositumomab

(b) 90Y ibtritumomab tiuxetan
(c) 153Sm lexidronam
(d) (a) and (b) only
(e) (b) and (c) only

Answer 44

(d) 90Y ibritumomab tiuxetan and 131I tositumomab are labeled monoclonal antibodies produced using mouse cells and will likely cause an allergic response in those patients who have previously demonstrated allergy to mouse proteins.

Question 45

To perform a thyroid scintigraphy, which of the following is correct?
(a)99mTc pertechnetate has the advantage of no special patient preparation.

(b) 99mTc pertechnetate has the advantage of high dose and high count.
(c) 99mTc pertechnetate has the advantage of lower radiation exposure
(d) All of the above

Answer 45

(d) When 99mTc pertechnetate is used for thyroid scintigraphy, the dose is higher and the radiation exposure is lower, the imaging is obtained 10 min after injection, and no special patient preparation is needed. However, no thyroid uptake ratio can be calculated.

Question 46

To perform a thyroid scintigraphy, which of the following is correct?
(a)If 99mTc pertechnetate is used, imaging can be obtained at 24 h after tracer injection.

(b) If 99mTc pertechnetate is used, imaging can be obtained after 2 h but before 24 h after tracer injection.
(c) If 99mTc pertechnetate is used, thyroid uptake can be obtained either 2 or 24 h after tracer injection.
(d) If 99mTc pertechnetate is used, imaging can be obtained 10 min after tracer injection.

Answer 46

(d) When 99mTc pertechnetate is used for thyroid scintigraphy, the dose is higher and the radiation exposure is lower, the imaging is obtained 10 min after injection, and no special patient preparation is needed. However, no thyroid uptake ratio can be calculated.

Question 47

To perform a whole body radioiodine scintigraphy for thyroid cancer, which of the following is not correct?
(a)Patient should be on low iodine food for 5-7 days.

(b) Patient should discontinue thyroid hormone replacement or have received Thyrogen injection before the study.
(c) Pregnancy is an absolute contraindication if 131I is used.
(d) Breast-feeding should be stopped and cannot be resumed for either 123I or 131I test.

Answer 47

(d) Breast-feeding should be stopped and cannot be resumed if 131I is used. If 123I is used, breast-feeding can be resumed 1 week later.

Question 48

What is the half-life of radium-225 dichloride?
(a)11.4 days

(b) 6 h
(c) 78 h
(d) 110 min

Answer 48

(a) Half-life is 11.4 days

Question 49

Radium-225 dichloride is currently FDA approved for patients with what disease process?
(a)Metastatic lung cancer

(b) Metastatic thyroid cancer
(c) Metastatic prostate cancer

Answer 49

(c) Metastatic prostate cancer

Question 50

How is radium-225 dichloride administered?
(a)Intravenous injection

(b) Intrathecal injection
(c) Orally
(d) Inhalation

Answer 50

(a) Intravenous injection