Diagnostic ultrasound ( PDFDrive )

PART THREE: Small Parts, Carotid Artery, and
Peripheral Vessel Sonography
CHAPTER
19
The Thyroid Gland
Luigi Solbiati, J. William Charboneau, Vito Cantisani, Carl Reading, and Giovanni Mauri
SUMMARY OF KEY POINTS
• Ultrasound is the best imaging modality to study the
thyroid gland for both diffuse and nodular disease.
• The overwhelming majority of thyroid nodules are benign.
Thyroid cancer is rare and accounts for less than 1% of all
malignant neoplasms.
• Approximately 80% of nodular thyroid disease is caused
by hyperplasia. When hyperplasia leads to an overall
increase in size or volume of the gland, the term “goiter”
is used.
• Most hyperplastic or adenomatous nodules are isoechoic
compared with normal thyroid tissue, but may become
hyperechoic because of the numerous interfaces between
cells and colloid substance.
• Hyperfunctioning (autonomous) nodules often exhibit an
abundant perinodular and intranodular vascularity.
• Purely anechoic areas are caused by serous or colloid luid.
• Adenomas represent only 5% to 10% of all nodular
disease of the thyroid and are seven times more common
in women than men. In general, the cytologic features of
follicular adenomas are indistinguishable from those of
follicular carcinoma.
• Solid consistency, hypoechogenicity, microcalciications,
taller-than-wide appearance, hypervascularity, irregular
margins, invasion of adjacent structures, and presence of
cervical lymph node metastases are suspicious signs of
thyroid malignancy.
• Ultrasound-guided ine-needle aspiration is the most
effective method for diagnosing malignancy in a thyroid
nodule.
• After partial or near-total thyroidectomy for carcinoma,
sonography is the preferred method for follow-up, by
detecting residual, recurrent, or metastatic disease in the
neck.
• The Thyroid Imaging Reporting and Data System
(TIRADS) can be used to stratify the risk of malignancy of
a thyroid nodule according to its ultrasonographic
characteristics.
• Ultrasound-guided ablation with chemical agents (ethanol)
or thermal energy (radiofrequency and laser ablation) can
be used to treat thyroid adenoma, benign cold nodules,
and even nodal metastases of thyroid cancers.
CHAPTER OUTLINE
INSTRUMENTATION AND
TECHNIQUE
ANATOMY
CONGENITAL THYROID
ABNORMALITIES
NODULAR THYROID DISEASE
Pathologic Features and Sonographic
Correlates
Hyperplasia and Goiter
Adenoma
Carcinoma
Lymphoma
Thyroid Metastases
Fine-Needle Aspiration Biopsy
Sonographic Applications
Detection of Thyroid Masses
Differentiation of Benign and
Malignant Nodules
Thyroid Imaging Reporting and Data
System
Contrast-Enhanced Ultrasound and
Elastography
Guidance for Needle Biopsy
Guidance for Percutaneous
Treatment
The Incidentally Detected Nodule
DIFFUSE THYROID DISEASE
Acknowledgment
Because of the supericial location of the thyroid gland, highresolution
real-time gray-scale and color Doppler sonography
can demonstrate normal thyroid anatomy and pathologic conditions
with remarkable clarity. As a result, ultrasound plays an
increasingly important role in the diagnostic evaluation of thyroid
disease, although it is only one of several diagnostic methods
currently available. To use ultrasound efectively and economically,
it is important to understand its current capabilities and
limitations.
INSTRUMENTATION AND TECHNIQUE
High-frequency transducers (7.5-15.0 MHz) currently provide
both deep ultrasound penetration—up to 5 cm—and highdeinition
images, with a resolution of 0.5 to 1.0 mm. No other
clinically used imaging method can achieve this degree of spatial
resolution. Linear array transducers with either rectangular or
trapezoidal scan format are preferred to sector transducers because
of the wider near ield of view and the capability to combine
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