SP14:Thyroid, Parathyroid, and Salivary Gland Scintigraphy

Question 1

A technologist is performing a thyroid uptake with 123I sodium iodide. The capsule is counted before being administered to the patient, and 850,192 cpm is obtained. Six hours after swallowing the capsule, the counts from the patient’s neck are 116, 239 and from the thigh, 34,982. Background for the uptake probe is 239 cpm, and the 6-h decay factor for 123I is 0.730. What is the 6-h uptake?
(a)7.0%

(b) 9.5%
(c) 13.1%
(d) 18.7%

Answer 1

(c) The percent uptake is calculated by the following formula:

thyroid counts-thigh counts/(capsule counts-background) (decay factor) × 100%. Because a standard is not being used, the capsule has been counted before administration, background is subtracted, and the activity is multiplied by the decay factor. If a standard was used, the formula would be

thyroid counts-thigh counts/counts in standard × 100%.

Question 2

Is the uptake value determined in (123I sodium iodide. The capsule is counted before being administered to the patient, and 850,192 cpm is obtained. Six hours after swallowing the capsule, the counts from the patient’s neck are 116, 239 and from the thigh, 34,982. Background for the uptake probe is 239 cpm, and the 6-h decay factor for 123I is 0.730) a normal value?
(a)Yes

(b)No

Answer 2

(a) The normal range for 6 h uptake is about 6–18%; for 24 h, it is 20–30%, although these numbers vary according to the laboratory.

Question 3

What will the effect be if a technologist places the uptake probe over the proximal thigh when counting background in the patient?
(a)The background will be falsely elevated.

(b) The background will be falsely decreased.
(c) The calculated uptake will decrease.
(d) (a) and (c).
(e) (b) and (c).

Answer 3

(d) Because of the proximity to the bladder, counts will be higher, and this will result in a falsely low uptake.

Question 4

Which of the following dietary supplements will affect thyroid uptake?
(a)Vitamin A

(b) Vitamin B
(c) St. John’s wort
(d) Kelp tablets
(e) Lactobacillus

Answer 4

(d) Kelp tablets contain iodine and therefore may affect measured values of thyroid uptake.

Question 5

Which of the following will not affect thyroid uptake?
(a)Iodinated contrast media

(b) Propylthiouracil
(c) Thyroid hormones
(d) Beta-blockers

Answer 5

(d) Choices (a), (b), and (c) may affect measured values of thyroid uptake, but beta-blockers should not.

Question 6

Thyrotropin is also known as:
(a)TRH

(b) TSH
(c) T3
(d) T4

Answer 6

(b) Thyrotropin is also known as TSH (thyroid-stimulating hormone). It is secreted by the anterior pituitary and causes the thyroid to release thyroxine (T4).

Question 7

Which of the following statements is not true?
(a)TRH stimulates the release of TSH by the anterior pituitary.

(b) Release of T3 is inhibited by elevation of T4
(c) T3 and T4 are both hormones which are manufactured and released by the thyroid.
(d) TRH is synthesized in the hypothalamus.

Answer 7

(b) TRH is thyrotropin-releasing hormone which is secreted by the hypothalamus and stimulates the secretion of TSH by the anterior pituitary. The thyroid releases the hormones T3 (triiodothyronine) and T4.

Question 8

Most people have four parathyroid glands.
(a)True

(b)False

Answer 8

(a) Most people have four, but a small percentage of people may have more or less.

Question 9

The salivary glands include:
(a)The parotid glands

(b) Sublingual salivary glands
(c) Submaxillary salivary glands
(d) All of the above
(e) (b) and (c) only

Answer 9

(d) The major salivary glands include the parotid, the sublingual, and submaxillary glands. There are also minor glands in the cheeks, lips, mouth, and throat.

Question 10

Which of the following are used to image the parathyroid?
(a)99mTc pertechnetate

(b) 99mTc sestamibi
(c) 201Tl chloride
(d) (a) and (b)
(e) (b) and (c)

Answer 10

(e) Sometimes, one of these imaging agents is paired with pertechnetate imaging to create images that will allow subtraction of the thyroid.

Question 11

The collimator attached to a thyroid uptake probe is:
(a)Converging

(b) Diverging
(c) Pinhole
(d) Flat field
(e) Low energy all purpose

Answer 11

(d) The pinhole may be used for imaging, but the flat field is used for uptake.

Question 12

Which of the following is part of the preparation for a thyroid uptake?
(a)NPO from midnight

(b) Administer Lugol’s solution
(c) Have the patient void before administration of radiopharmaceutical.
(d) Withhold caffeine-containing beverages for 24 h prior to examination.
(e) None of the above.

Answer 12

(a) Lugol’s solution is iodine and should not be administered. Voiding is not necessary before administration of the radiopharmaceutical, nor is withholding caffeine. Most laboratories have a policy of fasting before and for a few hours following the dosing, the enhance digestion of the dose.

Question 13

When performing a thyroid uptake, the technologist neglects to count the capsule before it is administered to the patient. What are the implications?
(a)It will not be possible to calculate uptake values.

(b) An identical capsule must be counted in a neck phantom in order to obtain uptake values.
(c) No decay factor will be used in the calculation of uptake values.
(d) None of the above.
(e) (b) and (c)

Answer 13

(e) The percent uptake is calculated by the following formula:

thyroid counts-thigh counts/(capsule counts-background) (decay factor) × 100%. Because a standard is not being used, the capsule has been counted before administration, background is subtracted, and the activity is multiplied by the decay factor. If a standard was used, the formula would be

thyroid counts-thigh counts/counts in standard × 100%.

Question 14

While taking information from a patient who is scheduled for a thyroid uptake and scan with 123I sodium iodide, a technologist learns that he has been taking Cytomel that week. What does this mean?
(a)Nothing: thyroid uptake will not be affected by Cytomel.

(b) Imaging may still be obtained using 201Tl chloride.
(c) Both the uptake and scan can be performed using 131I.
(d) Study should be performed as ordered, but the uptake will be inaccurate.
(e) None of the above.

Answer 14

(b) Cytomel is a synthetic form of T3 and will affect iodine uptake, so if images are needed, they can be obtained using thallium. Any uptake values obtained would be falsely low; this medication should be stopped at least 2 weeks before uptake and scanning using radioiodine.

Question 15

What is the method of localization of 99mTc pertechnetate in the thyroid?
(a)Sequestration

(b) Active transport
(c) Receptor binding
(d) Diffusion
(e) Phagocytosis

Answer 15

(b) Pertechnetate localizes in the thyroid by active transport; it is trapped in the gland, but unlike iodine, not organified.

Question 16

Imaging of the thyroid takes place:
(a)Approximately 20 min after injection of 99mTc pertechnetate

(b) 6 h after administration of an 123I sodium iodide capsule
(c) 24 h after administration of an 123I sodium iodide capsule
(d) All of the above

Answer 16

(d) Imaging may be performed in all cases, but images taken at 6 h after radioiodine ingestion will have a higher body background relative to 24 h images. Those obtained at 24 h will have a lower count rate, but images may be superior due to the decreased body background.

Question 17

Which of the following will not optimize images of the thyroid?
(a)Use of a pinhole collimator

(b) Having the patient avoid swallowing during images acquisition
(c) Hyperextending the neck
(d) Placing a radioactive marker on the xiphoid process

Answer 17

(d) The xiphoid process will not likely be in the FOV.

Question 18

A linear area of activity in the esophagus is seen on a thyroid image taken using 99mTc pertechnetate. What does it represent?
(a)Sublingual thyroid

(b) Parathyroid
(c) Pertechnetate that was secreted by the salivary glands and swallowed
(d) Parotid gland

Answer 18

(c) Activity that localizes in the salivary glands and is secreted may be swallowed resulting in esophageal activity. If this is seen on a pertechnetate scan, the artifact can be distinguished from the pyramidal lobe by having the patient drink.

Question 19

The use of 131I for thyroid imaging:
(a)Is common if an uptake is also planned

(b) Is typically only used when scanning the whole body for metastatic thyroid disease after thyroidectomy
(c) Delivers a lower radiation dose to the thyroid than does 99mTc pertechnetate, since only uCi amounts are administered
(d) All of the above

Answer 19

(b) Whole body scanning with 131I to rule out metastatic disease is often performed after thyroidectomy. The dose used is 3-5 mCi. Thyroid uptake and scanning is typically performed using 123I.

Question 20

A patient receives both 3 mCi of 201Tl chloride and 5 mCi of 99mTc pertechnetate, and pinhole images of the neck are taken after each administration. If the pertechnetate image is subtracted from the 201Tl image, the activity that remains represents:
(a)Thyroid

(b) Parathyroid
(c) Salivary glands
(d) Hypothalamus
(e) Nonfunctioning thyroid tissue

Answer 20

(b) Imaging agents is paired with pertechnetate imaging to create images that will allow subtraction of the thyroid.

Question 21

The salivary glands may be imaged using:
(a)3 mCi of 201Tl

(b) 5 mCi of 99mTc sestamibi
(c) 5 mCi of 99mTc pertechnetate
(d) 200 uCi of 123I sodium iodide

Answer 21

(c) Pertechnetate is used for imaging the salivary glands, often to evaluate function or rule out masses.

Question 22

Which of the following describes delayed images at 2-3 h after injection of 99mTc sestamibi?
(a)Persistent activity in the normal thyroid with complete washout of activity in the parathyroid

(b) Persistent activity in parathyroid adenomas and decreased activity in the thyroid relative to early images
(c) Persistent activity in hyperfunctioning thyroid tissue and no activity in the parathyroid or salivary glands
(d) Activity in the salivary glands and normal parathyroid tissue

Answer 22

(b) 99mTc sestamibi washes out of the thyroid over time, and parathyroid adenomas, which may appear more intense than the thyroid on early images, often retain activity on delayed images.

Question 23

A hot nodule on a thyroid image will most likely be benign.
(a)True

(b)False

Answer 23

(a) The majority of hot nodules seen on thyroid scans are benign.

Question 24

Which of the following are symptoms of hyperthyroidism?
(a)Exophthalmus

(b) Bradycardia
(c) Cold intolerance
(d) All of the above
(e) (b) and (c)

Answer 24

(a) Bradycardia means a slowing of the heart rate; rapid heart rate may be a symptom of hyperthyroidism. Cold intolerance is one of the symptoms of hypothyroidism. Exopthalmus, or protrusion of the eyeballs, may be seen in hyper thyroid patients.

Question 25

The highest doses of therapeutic 131I are given to patients with:
(a)Grave’s disease

(b) Toxic multinodular goiter
(c) Thyroid cancer
(d) Chronic thyroiditis

Answer 25

(c) The therapeutic dose of radioiodine for thyroid cancer is 150-200 mCi and may be higher if distant metastases are being targeted.

Question 26

A patient with a 45% uptake of 123I sodium iodide at 24 h is:
(a)Euthyroid

(b) Hyperthyroid
(c) Hypothyroid
(d) Athyroid

Answer 26

(b) The normal range for 6 h uptake is about 6–18%; for 24 h, it is 20–30%, although these numbers vary according to the laboratory.

Question 27

The part of the thyroid that lies anterior to the trachea and is often not seen on thyroid imaging is the:
(a)Right lobe

(b) Left lobe
(c) Isthmus
(d) Parathyroid
(e) Superior thyroid notch

Answer 27

(c) The thyroid appears as a butterfly shape on imaging, with the isthmus often not visualized, or displaying decreased activity relative to the right and left lobes

Question 28

On anterior-view thyroid images taken using 123I sodium iodide, the right lobe appears to be larger than the left. The explanation for this is:
(a)A right hemigoiter.

(b) A hypofunctioning left lobe.
(c) A normal finding.
(d) The patient’s head was turned slightly to the left.
(e) The patient’s head was turned slightly to the right.

Answer 28

(c) The thyroid appears as a butterfly shape on imaging, with the isthmus often not visualized, or displaying decreased activity relative to the right and left lobes. A slightly larger right lobe is commonly seen and is usually a normal finding.

Question 29

Iodine is needed for the thyroid gland to synthesize T3 and T4.
(a)True

(b)False

Answer 29

(a) Ingested iodine is absorbed in the small intestine and transported to the thyroid where it is needed for the synthesis of T3 and T4.

Question 30

About 90% of the thyroid hormone secreted into the blood is in the form of:
(a)Thyroxine

(b) Triiodothyronine
(c) Thyroglobulin
(d) Thyrotropin
(e) Iodotyrosine

Answer 30

(a) The thyroid secretes much more thyroxin (T4) than triiodothyronine (T3). Both are secreted by the follicular cells of the gland. If too little T4 is secreted, myxedema will result.

Question 31

A patient with hyperparathyroidism will have:
(a)Myxedema

(b) Exophthalmus
(c) Cold nodules in the thyroid
(d) Increased fracture risk
(e) More than four parathyroid glands

Answer 31

(d) Hyperparathyroidism may be caused by hyperplasia of the glands or by a tumor and will result in increased PTH secretion. This causes an increased risk of bone fractures because PTH, when elevated, will foster the removal of calcium from bone. The high PTH can also affect the nervous system.

Question 32

Why is a 6-h thyroid uptake obtained?
(a)In case the patient does not show up the following day for the 24 uptake

(b) To detect hyperthyroidism when the turnover is so rapid that the 24-h uptake may be normal
(c) In case an error is made in the calculation of the 24-h uptake
(d) So that the patient can resume eating

Answer 32

(b) In cases of extremely rapid iodine turnover, only the 6 h uptake may be abnormal, for example, in Grave’s disease.

Question 33

Which patient will have the longest wait before an accurate thyroid uptake with 123I can be obtained?
(a)A patient who had a myelogram

(b) A patient who took Synthroid
(c) A patient who had an IVP
(d) A patient who was given Lugol’s solution
(e) A patient who took kelp tablets

Answer 33

(a) The SNM recommends that patients wait 2-4 weeks after examinations using iodinated contrast agents before having a thyroid uptake measurement, but many departments recommend up to 6 weeks. If the myelogram was performed using Pantopaque, 2 years’ delay may be needed, but this is not often used because of the possible association with arachnoiditis.

Question 34

To stimulate secretion during salivary gland scintigraphy, which of the following is often used?
(a)99mTc sestamibi

(b) Lemon juice
(c) Lugol’s solution
(d) Captopril
(e) Furosemide

Answer 34

(b) Lemon juice stimulates the salivary glands to secrete saliva and pertechnetate, with a resulting decrease in activity in the glands.

Question 35

Ectopic thyroid tissue may occur:
(a)In the pelvis

(b) In the neck
(c) In the mediastinum
(d) At the base of the tongue
(e) All of the above

Answer 35

(e) Ectopic thyroid tissue may be present in many places; in this case, 131I imaging may be helpful. It is not taken up by the salivary glands, the long half-life allows imaging after the target to background ratio has become higher, and there has been urinary excretion of much of the dose.

Question 36

If the salivary glands are not seen on a thyroid scan obtained with the use of 99mTc pertechnetate, it may mean:
(a)That the thyroid is hyperfunctioning and trapped the majority of the tracer

(b) That the salivary gland function is compromised
(c) That the salivary glands lie inferior to the thyroid and cannot be seen on anterior images
(d) (a) and (b)
(e) (b) and (c)

Answer 36

(d) It is typical to see salivary glands superior to the thyroid on images obtained using pertechnetate. If they are not seen, it may be because the patient has Grave’s disease or because salivary gland function is compromised.

Question 37

When would a low-energy all-purpose collimator be used for thyroid examinations?
(a)During uptake counting

(b) When searching for ectopic thyroid with 131I sodium iodide
(c) When performing whole body with 131I sodium iodide scanning after thyroidectomy
(d) When obtaining a blood pool image of the thyroid with 99mTc pertechnetate to differentiate cystic and solid masses
(e) All except a

Answer 37

(d) The LEAP collimator is ideal for imaging with technetium if magnification of the gland is not needed. Images obtained with the pinhole collimator may follow. Uptake counting requires a flat-field collimator, and medium or high energy may be used for 131I.

Question 38

Radioactive iodine and 99mTc pertechnetate cross the placenta.
(a)True

(b)False

Answer 38

(a) Both radioiodine and pertechnetate will cross the placenta.

Question 39

A technologist performs a thyroid uptake using an identical capsule to the one administered to the patient as a standard. Given the following data obtained 6 h after the capsule was swallowed, what is the uptake?
Neck - 55,213 cpm
Thigh - 2085 cpm
Standard - 345,987 cpm
Background - 48 cpm
(a)1.5%

(b) 15.4%
(c) 16.6%
(d) 30.7%

Answer 39

(b) The percent uptake is calculated by the following formula:

thyroid counts-thigh counts/(capsule counts-background) (decay factor) × 100%. Because a standard is not being used, the capsule has been counted before administration, background is subtracted, and the activity is multiplied by the decay factor. If a standard was used, the formula would be

thyroid counts-thigh counts/counts in standard × 100%.

Question 40

An indication for a thyroid uptake is for use in calculation of the amount of radioiodine therapy for hyperthyroidism.
(a)True

(b)False

Answer 40

(a) The calculation of dose for radioiodine therapy takes the uptake into consideration.

Question 41

When performing a thyroid scintigraphy, tc-99 m pertechnetate is preferred when:
(a)Patient is not able to swallow radioiodine pill.

(b) Patient had CT scan last week with IV contrast.
(c) Patient is taking amiodarone.
(d) All of the above.

Answer 41

(d) Amiodarone is an antiarrhythmic drug and contains high level of iodine.

Question 42

When performing a radioiodine thyroid scintigraphy for a patient with suspected hyperthyroidism, a technologist found that the thyroid radioiodine uptake is close to zero, and there is only background activity on the images. Which of the following is correct:
(a)The imaging time should be extended until good image of the thyroid gland is seen.

(b) There is likely a technical problem with the gamma camera.
(c) Patient should be re-dosed as the findings are not consistent with provided history of hyperthyroidism.
(d) Talk to your nuclear medicine physician.

Answer 42

(d) The finding are likely real. The technologist should consult a physician at this time.

Question 43

When performing a radioiodine thyroid scintigraphy, the major advantage of using 131-I is:
(a)Lower dose

(b) Less radiation exposure
(c) Better imaging quality
(d) Higher sensitivity for detecting occult lesions

Answer 43

(d) All others are wrong.