ULTRASOUND - THYROID

Alternative Names:  thyroid ultrasound, thyroid sonography, ultrasound of the thyroid

ROLE OF ULTRASOUND

Ultrasound is a valuable diagnostic tool in assessing the following indications;

• Classification of a palpated lump. eg solid, cystic, mixed

• Evaluate adjacent structures

• Determining the location of a palpable lump (within or outside of the thyroid)

• Identifying a cause for Hyperthyroidism

• Identifying a cause for Hypothyroidism

• Post surgical complications eg abscess, oedema

• Multi Nodular Goiter (MNG): Follow up nodules

• Guidance of injection, aspiration or biopsy

• Relationship of normal anatomy and pathology to each other

DIFFERENTIAL DIAGNOSES

If the patient presents with a neck lump/swelling for investigation, common possible diagnoses other than the thyroid are:

• Fat roll at the base of the neck

• Lymphadenopathy

• Branchial cleft cyst (supero-lateral to the thyroid. May be transient)

• Thyroglossal duct cyst (midline superior to the thyroid)

• Parathyroid gland mass (Usually small and inferior on the throid)

LIMITATIONS

The inferior most aspect of an enlarged thyroid with marked retrosternal extension will not always be visible on ultrasound.

PREPARATION

• Low collared shirt

• Remove jewellery around the neck

• Towel across the shoulders/chest

• Lie the patient so their head is at the top of pillow and tipped right back.

• A pillow or towel can be placed under the shoulders

EQUIPMENT SELECTION AND TECHNIQUE

•  A 7-14mHz linear transducer

• Deep seated tumours, retrosternal thyroids or large patients may require a curvi-linear array transducer of 3.5MHz

• Good colour / power / Doppler capabilities when assessing vessels or vascularity of a structure.

SCANNING TECHNIQUE

• Begin with a survey scan in transverse down the midline to assess for tracheal deviation and obvious pathology.

• Tilt the patients head slightly to the contralateral side and scan down in transverse.

• Rotate into longitudinal and scan from medial to lateral.

• Repeat this for the other side with the head tilted the other way.

• With the patients head/neck straight, scan the isthmus in longitudinal and transverse.

• Scan down each side of the neck in transverse for alternative pathology.

PATHOLOGY

Thyroid Nodules

Usually is a MULTINODULAR GOITRE (MNG) but....

Malignant V's Benign

Click here to read a great article on differentiating benign versus malignant thyroid nodules. There is no single ultrasonographic feature to distinguish between the two. Features to assist in differentiating include:

Cystic v's solid

• Rare to have just a pure epithelial cyst

• Nodules which contain a cystic component nearly always have a solid component.

• They are benign lesions which have undergone cystic degeneration or haemorrhage.

• However, Papillary carcinoma can also have a cystic component.

Single v's multinodularity

• Multinodularity does NOT indicate all are benign.

• Comet Tail Sign usually signifies a thyroid colloid nodule.

Hypoechoic v's hyperechoic

• Generally hyperechoic are benign ,usually malignant tumours are hypoechoic or isoechoic.

• Halo

• The margin of a nodule with a halo effect is usually benign however this has also been described in some malignant lesions

• So this is not a reliable indicator

Macro v's microcalcification

• Can be a good indicator of benign nodules if macro-calcification

• Microcalcification is described in many malignancies

• Vascularity

• Not a good indicator.

THYROID MALIGNANCIES

• Malignancy occurs in approximately 1% of thyroid nodules.

• Papillary and/or mixed papillary/follicular carcinomas are by far the most common malignancy.

• The incidence is dramatically increased in post head/neck radiotherapy patients.

  • Papillary Carcinoma 78%

  • Follicular Lesion Carcinoma 17%

  • Medullary Carcinoma 4%

  • Anaplastic Carcinoma 1%/li>

  • Thyroid lymphoma - rare

  • Thyroid metastases - rare

A 'cold nodule' on nuclear medicine increases the suspicion of malignancy however the liklihood is still low.

Sonographic signs increasing the suspicion of malignancy:

• Solitary nodule

• Punctate calcification (rather than large or peripheral calcifications)

• Irregular surrounding halo

• Solid

Importantly, a diagnosis of malignancy cannot be made without biopsy.

Again, keep in mind that the vast majority of thyroid nodules are benign.

THYROIDITIS

• Hashimoto's Thyroiditis

• Graves disease

• De Quervain's subacute thyroiditis

• Acute suppurative thyroiditis

THYROID ULTRASOUND SAMPLE PROTOCOL TYPICALLY)

This sample protocol is meant for educational purposes and the exact technique will depend on the patient's clinical indication for the examination and the radiologist's guidance.

A thyroid series should include the following minimum images:

It is a superficial gland which should be homogeneous in it's echotexture. There are 2 sides of the gland with an isthmus joining the left and right sides.

1. Transverse isthmus long axis

2. Transverse isthmus w/measurement

3. Transverse right lobe midline

4. Transverse right lobe w/color

5. Transverse right lobe w/measurement

6. Transverse right lobe superior pole

7. Transverse right lobe inferior pole

8. Sagittal right lobe midline

9. Sagittal right lobe w/measurement

10. Sagittal right lobe w/color flow

11. Sagittal right lobe medial

12. Sagittal right lobe lateral

• Do the same protocol for LEFT LOBE

Document the normal anatomy. Any pathology found in 2 planes, including measurements and any vascularity

Useful Links:

Head and Neck Cancer - www.RadiologyInfo.org/en/info.cfm?PG=hdneck

Radiation Therapy for Head and Neck Cancer - www.rtanswers.org/treatmentinformation/cancertypes/headneck/index.aspx

Schedule Your Thyroid Ultrasound Today!

• If you are looking for professional radiology services at your imaging site/center, call us at 1-800-626-8315 or contact us for a consultation. 

• If you live in Los Angeles, Century City, Glendale, Mid-Wilshire and need to schedule a radiology examination such as a MRI, CT Scan, Ultrasound, X ray, or PET scan, contact us to schedule an appointment. 

• If you are in search of other things, we're surprisingly resourceful!  Call us 1-800-626-8315 or contact us via our contact form.

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• Thyroid Ultrasound, Thyroid sonography, Ultrasound of the Thyroid
• Thyroid ultrasound informational page including role of ultrasound, differential diagnoses, limitations, preparation, equipment selection and technique, scanning technique, pathology, and basic hard copy imaging.
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