Questions

Answers

1. What is the main difference between how the thyroid gland handles iodine and how it handles pertechnetate?

1. The thyroid gland organifies iodine but not technetium.

2. What are three disadvantages to using ¹³¹I for thyroid imaging?

2. ¹³¹I emits a beta (β) particle, has a high gamma (γ) energy, and has a long half-life; these factors combine to result in a high radiation dose to the thyroid.

3. What are the main contaminants of commercial ¹³¹I?

3. ¹²⁴I and ¹²⁵I (These contaminants increase the radiation dose.)

4. Name three advantages of ^99mTcpertechnetate over ¹²³I for thyroid imaging.

4. cost, convenience (one patient visit), availability

5. What percentage of a dose of radio-iodine is taken up by the thyroid of a euthyroid individual at 24 hours after dosing?

5. 10% to 30%

6. What percentage of a dose of radio-iodine is taken up by the thyroid of a euthyroid individual at four to six hours after dosing?

6. 4% to 15%

7. What percentage of a dose of ^99mTcpertechnetate is taken up by the thyroid of a euthyroid individual at 20 minutes after dosing?

7. 0.5% to 3.5%

8. True or false: The radioactive iodine uptake (RAIU) should always be interpreted in correlation with the thyroid function tests.

8. true

9. How long does nursing need to be stopped for diagnostic doses of ¹²³I for mothers?

9. two to three days

10. How long does nursing need to be stopped for diagnostic doses of ^99mTcpertechnetate for mothers?

10. 12 to 24 hours

11. For mothers, how long must nursing be stopped after uptake doses (less than 30 µCi or less than 1.11 MBq) of ¹³¹I?

11. weeks to months

12. True or false: For mothers, nursing should be stopped completely after ¹³¹I therapeutic doses.

12. true

13. When does the fetal thyroid gland begin to concentrate iodine?

13. at 12 weeks of gestation

14. How does exogenous iodine affect thyroid uptake of radioiodine?

14. Exogenous iodine suppresses thyroid uptake of radioiodine.

15. Which of the following factors are important when the uptake of radioactive iodine is considered?

A. food/intake history

B. drug/medication history

C. intravenous contrast administration

D. all of the above

E. none of the above

15. D, all of the above

16. What is the dose of ^99mTc-pertechne-tate for thyroid imaging?

16. 1 to 10 mCi (37 to 370 MBq)

17. What is the standard time procedure of delay between injection of ^99mTcpertechnetate and imaging?

17. 20 minutes

18. What type of collimator is usually used for ^99mTc-pertechnetate thyroid imaging?

18. a pinhole or high-resolution parallel

19. What views are typically obtained during ^99mTc-pertechnetate thyroid imaging?

19. anterior and 45 degrees left and right anterior obliques

20. How many counts are obtained during ^99mTc-pertechnetate thyroid imaging?

20. 200,000 to 250,000

21. What route is used to administer radioiodine?

21. oral

22. What is the dose of ¹²³I for thyroid imaging?

22. 100 to 400 µCi (3.7 to 14.8 MBq)

23. What is the usual time between administration of ¹³¹I and imaging?

23. 6 to 24 hours

24. What type of collimator is usually used for ¹²³I thyroid imaging?

24. a pinhole or high-resolution parallel

25. What views are typically obtained during ¹²³I thyroid imaging?

25. anterior and 45 degrees left and right anterior obliques

26. How many counts are obtained during ¹²³I thyroid imaging?

26. 200,000 to 250,000

27. What is the dose of ¹³¹I for thyroid whole body imaging for thyroid cancer?

27. 2 to 5 mCi (74 to 185 MBq)

28. What is the usual time between administration of ¹³¹I and the start of whole body imaging of thyroid cancer?

28. one to three days

29. What type of collimator is usually used for detection of thyroid cancer via ¹³¹I whole body imaging?

29. high-energy parallel

30. What views are typically obtained with ¹³¹I for thyroid whole body imaging cancer?

30. anterior and posterior chest, abdomen, and pelvis

31. How much time is used to obtain images with ¹³¹I for whole body imaging of thyroid cancer?

31. 10 to 20 minutes per image

32. How are markers used for thyroid imaging?

32. Markers are used to show the location of the sternal notch, chin, thyroid cartilage, and palpable nodules.

33. In an adult, how much does a normal thyroid gland weigh?

33. approximately 15 to 20 g

34. In an adult, what are the length and breadth of a normal thyroid gland?

34. 4 to 6 cm by 1.5 to 2 cm

35. What is meant by the term “pyramidal lobe”?

35. A pyramidal lobe is functioning thyroid tissue in the thyroglossal duct remnant that arises from the isthmus and extends superiorly just to the left or right of the midline.

36. How does one prove that activity on a thyroid scan is in the esophagus?

36. Have the patient drink water, and the activity will cease.

37. What is the normal pattern of up-take in the thyroid isthmus?

37. The isthmus may show uptake similar to a normal thyroid, or uptake may be absent.

38. What glands in the neck (other than the thyroid gland) can be visualized with thyroid imaging?

38. the salivary glands

39. What four features should be described on a thyroid scan?

39. thyroid size, homogeneity, and configuration; identification and description of hot and cold nodules; identification of extrathyroidal activity; correlation of abnormalities with palpation

40. Which of the following can cause thyrotoxicosis?

A. iodine induced (Jod-Basedow)

B. Amiodarone (type I and type II)

C. Struma ovarii/benign ovarian teratoma

D. all of the above

E. none of the above