Thyroid nodule echocardiography or ultrasound
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American Roentgen Ray Society Images of Thyroid nodule echocardiography or ultrasound |
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Risk calculators and risk factors for Thyroid nodule echocardiography or ultrasound |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Ultrasound
Thyroid nodule assessment
Thyroid gland ultrasound is one of the first steps of the thyroid nodule diagnostic evaluation. In the case of multiple nodules presentation, all the nodules should be assessed for suspicious ultrasound characteristics.The important points that can be characterized with ultrasound include:
- Confirmation of the diagnosis of a thyroid nodule
- Assess the size of the nodule
- Determining the location of the nodule
- Determination of the shape of the nodule
- Evaluation of the composition
- Evaluation of the echogenicity
- Evaluation of the margins
- Presence of calcification
- Evaluation of the vascularity of the nodules
- Evaluation of the adjacent structures in the neck including the lymph nodes
- FNA decision making
- Based on the size, vascularity, and shape
The following characteristics are associated with a higher likelihood of malignancy:
- Shape that is taller than wide measured in the transverse dimension
- Hypoechogenicity
- Irregular infiltrative margins
- Microcalcifications
- Absent halo
- Increased intranodular vascularity
The following characteristics are more likely to be a benign lesion:
- Purely cystic nodule (< 2 % risk of malignancy)
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Spongiform appearance (99.7 % specific for benign thyroid nodule)
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- the most common sonographic appearances of papillary and follicular thyroid cancer differ. A PTC is generally solid or predominantly solid and hypoechoic, often with infiltrative irregular margins and increased nodular vascularity. Microcalcifications, if present, are highly specific for PTC, but may be difficult to distinguish from colloid. Conversely, follicular cancer is more often iso- to hyperechoic and has a thick and irregular halo, but does not have microcalcifications (49). Follicular cancers that are <2 cm in diameter have not been shown to be associated with metastatic disease
- a benign nodule. A pure cystic nodule, although rare (<2% of all nodules), is highly unlikely to be malignant (47). In addition, a spongiform appearance, defined as an aggregation of multiple microcystic components in more than 50% of the nodule volume, is 99.7% specific for identification of a benign
- Elastography is an emerging and promising sonographic technique
- Shear wave elastography (SWE) provides a map of the elasticity in a region and allows stiffness quantification of lesions in kilopascals in order to reinforce the predictive value of malignancy. A tumour whose stiffness is greater than 65kPa or for which the stiffness ratio is greater than 3.7 compared to surrounding healthy tissue is highly suspicious. SWE may enable the detection of malignant follicular tumours that currently escape detection by the ultrasound-guided ultrasound/aspiration cytology couple. Lymph node metastasis of papillary thyroid cancer can also be detected by elastography due to its increased stiffness.
- a higher intensity pulse is transmitted to produce shear waves, which extend laterally from the insonated structure. The shear waves may then be tracked with low intensity pulses to find the shear velocity
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- Elastography is an emerging and promising sonographic technique
It is recommended that serial US be used in follow-up of thyroid nodules to detect clinically significant changes in size, Since the accuracy of physical examination for nodule size is likely inferior to that of US
Tan GH, Gharib H, Reading CC 1995 Solitary thyroid nodule. Arch Intern Med 155:2418–2423.
There is no consensus on the definition of nodule growth based on US, however, or the threshold that would require rebiopsy
A 50% cutoff for nodule volume reduction or growth, which is used in many studies, appears to appropriate and safe, since the false-negative rate for malignant thyroid nodules on repeat FNA is low
Brauer VF, Eder P, Miehle K, Wiesner TD, Hasenclever H, Paschke R 2005 Interobserver variation for ultrasound determination of thyroid nodule volumes. Thyroid 15:1169–1175
FNA criteria based on ultrasound
| Cystic nodule | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Solitary thyroid nodule | Spongiform nodule | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Solid nodule | Hyperechoic or isoechoic or partially cystic nodule with eccentric solid areas | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Hypoechoic solid nodule | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Cervical lymph node assessment
The most important nodules that should be evaluated in a patient with thyroid nodule include anterior, central and lateral compartment cervical nodules. During sevical lymph node assessment, the following characteristic should have FNA evaluation for cytology and washout Tg measurement:
- Microcalcification withing the lymph node
- Cystic lymph nodes
- Peripheral vascularity
- Hyperechogenicity of the lymph node
- Round shape lymph node