Thyroid radiology

Question 1

PET/CT scan-

Answer 1

Useful to define extension to lymph nodes and distant metastasis.

Good anatomic evaluation of the thyroid bed

Staging and restaging of differentiated thyroid cancer.

Question 2

Functional Imaging- Iodine ( I123 or I131) scan.

Answer 2

To evaluate for function of the thyroid gland or nodule in patient with abnormal thyroid function. Evaluate for distant metastatic disease.

Thyroid imaging with radioiodine demonstrates the distribution of functioning thyroid tissue, including ectopic tissue, since thyroid tissue is the only tissue that concentrates large amounts of iodine.
Must discontinue iodine containing preparation and medications that could potentially affect the ability of thyroid tissue to accumulate iodide.

I 123 scan- To evaluate function of the thyroid gland and thyroid nodule in patient with abnormal thyroid function.
Half life of I-123 is 13 hrs.

I131 scan- Diagnostic and therapeutic role.
Half life of I-131 is 8 days.

Detect local and distant thyroid cancer metastasis.
Treatment of hyperthyroidism as well as for well differentiated thyroid cancer.

Question 3

Anatomic imaging-

Answer 3

Ultrasound, CT and MRI.

Indicated to detect or characterize palpable or incidentally found thyroid nodule on other modalities.

• US is the best modality.

Question 4

Radiograph

Answer 4

Not useful to detect thyroid disease
May incidentally suggest a thyroid lesion by noting mass effect on the soft tissues (often more obvious clinically) or on tracheal air column

Question 5

Ultrasound –

Answer 5

• No radiation, real time, doppler capability
  
  • The best modality to detect and characterize thyroid nodule.
  • Best modality to detect lymph node metastasis in post-op patient of thyroid cancer.

-Real-time guidance for FNA (tissue diagnosis)

Question 6

thyroid nodule

Answer 6

A thyroid nodule on Ultrasound is a discrete lesion within the thyroid gland that is radiologically distinct from the surrounding thyroid parenchyma.

Nonpalpable nodules detected on US or other anatomic imaging studies are termed incidentally discovered nodules or “incidentalomas.”
Nonpalpable nodules have the same risk of malignancy as palpable nodules with the same size.

Generally, only nodules >1 cm should be evaluated, since they have a greater potential to be clinically significant cancers.

Occasionally, there may be nodules

Question 7

The imaging test of choice to evaluate a thyroid lesion size, location, and simple cyst vs not simple cyst is:

a. A lateral skull X-ray
b. A CT (computed tomography) scan without contrast
c. An MRI (magnetic resonance imaging) with contrast
d. A PET (Positron emission tomography) scan
e. Ultrasound

Answer 7

e. Ultrasound

Question 8

What is the imaging testof choice to evaluate a patient with hyperthyroidism?

a. Radioactive iodine scan
b. Ultrasound
c. CT (computed tomography) scan
d. MRI (magnetic resonance imaging)

Answer 8

a. Radioactive iodine scan