SP14:Thyroid, Parathyroid, and Salivary Gland Scintigraphy Flashcards
An indication for a thyroid uptake is for use in calculation of the amount of radioiodine therapy for hyperthyroidism.
(a)True
(b)False
(a) The calculation of dose for radioiodine therapy takes the uptake into consideration.
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.
(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.
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.
(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.
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
(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.
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)
(e) Sometimes, one of these imaging agents is paired with pertechnetate imaging to create images that will allow subtraction of the thyroid.
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
(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.
Thyrotropin is also known as:
(a)TRH
(b) TSH
(c) T3
(d) T4
(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).
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.
(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.
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
(b) Imaging agents is paired with pertechnetate imaging to create images that will allow subtraction of the thyroid.
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
(d) All others are wrong.
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
(c) The therapeutic dose of radioiodine for thyroid cancer is 150-200 mCi and may be higher if distant metastases are being targeted.
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).
(d) Because of the proximity to the bladder, counts will be higher, and this will result in a falsely low uptake.
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)
(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%.
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
(d) The xiphoid process will not likely be in the FOV.
A patient with a 45% uptake of 123I sodium iodide at 24 h is:
(a)Euthyroid
(b) Hyperthyroid
(c) Hypothyroid
(d) Athyroid
(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.
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
(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.
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
(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.
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
(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.
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
(b) Lemon juice stimulates the salivary glands to secrete saliva and pertechnetate, with a resulting decrease in activity in the glands.
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.
(d) The finding are likely real. The technologist should consult a physician at this time.
Which of the following will not affect thyroid uptake?
(a)Iodinated contrast media
(b) Propylthiouracil
(c) Thyroid hormones
(d) Beta-blockers
(d) Choices (a), (b), and (c) may affect measured values of thyroid uptake, but beta-blockers should not.
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
(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.
A hot nodule on a thyroid image will most likely be benign.
(a)True
(b)False
(a) The majority of hot nodules seen on thyroid scans are benign.
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)
(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.
