Imaging of the Endocrine System

Question 1

Are the superior or inferior parathyroid glands more consistent in location?

Answer 1

Superior

Question 2

Structural imaging is used to look at… (4)

Answer 2

Location
Morphology
Density
Relation to adjacent structures

Question 3

4 examples of structural imaging

Answer 3

Radiograpthy
Ultrasound
CT
MRI

Question 4

4 examples of functional imaging

Answer 4

Radionuclide imaging (nuclear medicine)
PET
Bone densitometry (DEXA)
Functional MRI

Question 5

3 structural and 2 functional ways to image the thyroid

Answer 5

S: radiography, x-ray, CT/MRI
F: nuclear medicine, PET

Question 6

4 things that an enlarged neck/mass might be on x-ray

Answer 6

Lymphoma, thymoma, teratoma, goiter

Question 7

Thyroid ultrasound

Answer 7

Widely available
Cost effective
No ionizing radiation
Excellent resolution
Not specific

Question 8

CT thyroid scan

Answer 8

Good resolution
Reasonably available
Good visualization of extrathyroidal tissues
Ionizing radiation
IV contrast blocks iodine uptake for 4-8 weeks (so problems for radioiodine therapy or staging)

Question 9

Thyroid MRI

Answer 9

No radiation
Good soft tissue definition
Less available
Expensive
Lower resolution

Question 10

Thyroid Uptake and Scan

Answer 10

Uses radioactive isotopes of iodine or iodine analogs
Provides a measurement of thyroid function (uptake) or a map of function (scan)
Dependent of iodine transport and organification (normally controlled by TSH)

Question 11

2 forms of iodine used

Answer 11

I-123 (scan)

I-131 (treat)

Question 12

Is there a role of nuclear medicine in the evaluation of nodules in a euthyroid patient?

Answer 12

No!

Both benign and malignant nodules can be hypofunctioning

Question 13

What will uptake be line in

1. Subacute thyroiditis
2. Grave’s disease
3. Toxic multinodular goiter

Answer 13

1. Low iodine uptake
2. Increased diffuse iodine uptake
3. Increased heterogenous iodine uptake

Question 14

Nuclear medicine for thyroid carcinoma

Answer 14

I-123 and I-131 imaging used to search for metastasis (staging)
I-131 used in high doses for therapy

Question 15

Radiation precautions

Answer 15

Mandatory isolation at home or in hospital
4 meters apart from everyone for 3-5 days
Push fluids
Sit to urinate, flush 2-3 times after urination
Sleep in separate beds for 7-10 days
No sex or kissing for 7 days
Avoid pregnant women and children for 7 days
Can trigger gamma ray detectors for up to 95 days

Question 16

Benefits of I-131 therapy

Answer 16

Effective (90% of people only need 1 dose)
Increases disease free survival
Ease of administration
Generally well tolerated

Question 17

Limitations/risks of I-131 therapy

Answer 17

Thyroid storm from tissue damage
Requires some degree of prep and isolation
Family must be aware of precautions
Pregnancy and breastfeeding are absolute contraindications
Higher doses can result in mild acute radiation effects
Low risk of cancer induction

Question 18

18F-FDG PET Scans

Answer 18

Fluoro Deoxyglucose
Glucose analog that is trapped in cells
Effectively a marker of glucose metabolism
Sensitive but not specific (malignant and benign lesions demonstrate activity)
Limited spatial resolution

Question 19

What is the role of FDG PET scanning in thyroid carcinoma?

Answer 19

Definite role in evaluating thyroid cancer patients with elevated thyroglobulin but negative radioiodine scan
Possible role in selected patients for primary evaluation and follow up
No role in routine follow up

Question 20

3 things to look at on ultrasound for a thyroid nodule

Answer 20

Size (diameter and orientation)
Margins (round, how well defined, capsule)
Internal structure (cyst, solid, echoic, calcifications)

Question 21

Are malignant lesions more likely hyper, iso, or hypoechoic?

Answer 21

Hypo

Question 22

TI-RADS

Answer 22

Thyroid Imaging Reporting and Data System
Reporting system for thyroid nodules based on ultrasound
Standardized scoring system for reports with recommendations for follow-up and/or biopsy

Question 23

3 structure and 3 function ways to image the parathyroid

Answer 23

Structure: Ultrasound, CT, MRI
Function: Nuclear medicine, PET-FDG, DEXA