Parathyroid

Question 1

Most common cause Hyperparathyroidism?

Answer 1

Hyperfunctional adenoma (85%)

2nd MCC - Multiple gland hyperplasia (12%)
3rd MCC - Cancer (3%)

Question 2

What two parathyroid imaging techniques are there?

Answer 2

Dual phase and dual tracer

Question 3

What tracer is used for Dual phase? When is patient imaged?

Answer 3

Tc-99 Sestamibi. Imaged at 10 min and 3 hrs.

Question 4

What does sestamibi like? What does that mean for parathyroid imaging?

Answer 4

Blood flow and mitochondria (imaging depends on the blood flow and density of mitochondria), it will take up early in parathyroid pathology and stick around longer.

Question 5

Why image twice in dual phase images?

Answer 5

Uptake in thyroid and parathyroid on first phase, and will remain in abnormal parathyroid tissue on delayed phase.

Question 6

What can cause false positives in parathyroid pathology imaging?

Answer 6

Thyroid nodules, head/neck cancers, LAD

Question 7

What tracers are used in the dual tracer technique? Why are these chosen?

Answer 7

First chosen because it goes to both thyroid and parathyroid - can be sestamibi or 201-thallium chloride. Second is chosen because it only goes to thyroid - can be I-123 or pertechnetate.

Question 8

3 Problems with dual tracer technique?

Answer 8

1) More tracers - more problems with imaging
2) Motion - subtraction cant tolerate much motion
3) Recent procedures/injections can mess with tracers

Question 9

Should you be able to see lymph nodes on a MIBI scan?

Answer 9

No - think cancer, next step is US eval. Focal breast uptake makes you also think of cancer.