Nuclear: Parathyroid

Question 1

Common causes of hyperparathyroidism

Answer 1

• Hyperfunctional parathyroid adenoma (85%)
• Multigland parathyroid hyperplasia (12%)
• Parathyroid cancer (3%)

Question 2

What are the two main parathyroid nuclear imaging studies?

Answer 2

• Dual phase (Tc-99m sestamibi)
• Dual tracer (one that does to thyroid and parathyroid and another that goes only to thyroid)

Question 3

Dual phase parathyroid study

Answer 3

Tc-99m sestamibi is administered and both early (10 min) and delayed (3 hours) imaging is performed

Question 4

What does Tc-99m sestamibi localize to?

Answer 4

Cells with lots of mitochondria and lots of blood flow

Note: Parathyroid pathology tends to have both of these.

Question 5

What are common causes of false positives on dual phase Tc-99m sestamibi studies?

Answer 5

• Thyroid nodules
• Head and neck cancers
• Lymphadenopathy

Question 6

Hyperparathyroidism

Answer 6

Parathyroid adenoma

Question 7

Dual phase Tc-99m sestamibi scan in a pt with hyperparathyroidism

Answer 7

Parathyroid hyperplasia

Question 8

What radio tracers are used in a dual tracer parathyroid scan?

Answer 8

• Radiotracer with thyroid and parathyroid uptake (Tc-99m sestamibi or 201-thallium chloride)
• Radiotracer with only thyroid uptake (I-123 or pertechnetate)

Note: Subtraction images are then used to show parathyroid tissue.

Question 9

What are the common problems encountered during a dual tracer parathyroid study?

Answer 9

• Motion artifact on subtraction imaging
• Stuff messing with the thyroid tracers (e.g. recent iodinated contrast)

Question 10

Answer 10

Parathyroid adenoma

Question 11

Parathyroid hyperplasia surgery usually involves removing all 4 parathyroid glands and then surgically reimplanting 1/2 of one of the glands into the…

Answer 11

Forearm

Question 12

Common causes of false positive for parathyroid adenoma on a dual tracer parathyroid study

Answer 12

• Thyroid adenoma (most common)
• Thyroid cancer
• Parathyroid cancer

Question 13

Common causes of false negative of a dual tracer parathyroid study

Answer 13

• Adenoma is too small (most common)
• 4 gland hyperplasia

Question 14

Is sestamibi uptake in the lymph nodes normal?

Answer 14

No, any lymph node uptake of sestamibi is cancer until proven otherwise

Note: Recommend ultrasound for further evaluation.

Question 15

Tc-99m sestamibi

Answer 15

Breast cancer

Note: You should not see breast uptake when using sestamibi.