SP14:Thyroid, Parathyroid, and Salivary Gland Scintigraphy Flashcards
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%
(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%.
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
(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.
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.
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
(d) Kelp tablets contain iodine and therefore may affect measured values of thyroid uptake.
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.
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).
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.
(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.
Most people have four parathyroid glands.
(a)True
(b)False
(a) Most people have four, but a small percentage of people may have more or less.
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.
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.
The collimator attached to a thyroid uptake probe is:
(a)Converging
(b) Diverging
(c) Pinhole
(d) Flat field
(e) Low energy all purpose
(d) The pinhole may be used for imaging, but the flat field is used for uptake.
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.
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%.
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.
What is the method of localization of 99mTc pertechnetate in the thyroid?
(a)Sequestration
(b) Active transport
(c) Receptor binding
(d) Diffusion
(e) Phagocytosis
(b) Pertechnetate localizes in the thyroid by active transport; it is trapped in the gland, but unlike iodine, not organified.
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.
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 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.
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.
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
(c) Pertechnetate is used for imaging the salivary glands, often to evaluate function or rule out masses.
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 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.
Which of the following are symptoms of hyperthyroidism?
(a)Exophthalmus
(b) Bradycardia
(c) Cold intolerance
(d) All of the above
(e) (b) and (c)
(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.