What is Thyroid Gland
The thyroid gland, for which this classification system is used, is a vital endocrine gland located in the neck that produces hormones regulating metabolism, growth, and development. Its proper function is essential for maintaining overall health, influencing heart, muscle, and digestive function, brain development, and bone maintenance. The thyroid gland produces hormones, primarily thyroxine (T4) and triiodothyronine (T3), which control how quickly the body uses energy, makes proteins, and how sensitive it is to other hormones.
Normal thyroid tissue appears homogeneous and medium-to-high echogenicity. Abnormal findings like nodules, cysts, and other structural changes can be detected based on their appearance and characteristics on the ultrasound.
Appearance: Homogeneous (smooth, uniform), medium- to high-level echogenicity (brightness).
Size and Shape: Varies in the normal population, but generally, the mean length in adults is 40-60mm, and the mean thickness of the lateral lobes is 13-18mm.
Landmarks of Identifying Structures Surrounding the Thyroid Gland
The trachea, esophagus, blood vessels (carotid arteries and jugular vein), and surrounding muscle groups are key landmarks.
Abnormal Findings
Nodules:
Detection: Ultrasound can identify the presence, site, size, and number of nodules.
Characteristics: Nodules may be solid or contain fluid-filled areas. Some may appear hypoechoic (darker than normal thyroid tissue), while others may be more echo-dense.
SHAPE: May be ovoid or round, with smooth or ill-defined margins.
Vascularity
Intranodular vascularization (increased blood flow within the nodule) can be a sign of malignancy.
Calcifications
Presence of macro- or microcalcifications can also suggest malignancy.
Cysts
Smooth, globular areas without echoes, often representing epithelial-lined cysts.
Halo
A sonolucent rim (a clear area) around a nodule, potentially indicating a capsule, inflammation, or edema.
Enlargement
A thyroid gland may be considered enlarged if its thickness exceeds 20mm
Other Pathologies Associated With Thyroid Gland
Inflammation, fibrosis, and vascular regions can also manifest as nodule-like structures on ultrasound.
Ultrasonographic Characteristics of Thyroid Nodules
Ultrasound can detect the presence, site, size, and number of thyroid nodules
Goiter
A goiter (enlarged thyroid gland) typically appears as a well-defined, often heterogeneous, enlargement of the thyroid gland with multiple nodules. These nodules may contain cystic areas, calcifications, or fibrosis.
Details
Diffuse Enlargement: The thyroid gland lobes are larger than normal, exceeding the upper limits of normal volume (adult males: 12-18 mL, adult females: 10-15 mL). Micronodules (1-7mm).
Nodular Appearance: Multiple nodules of varying sizes are present, indicating a multinodular goiter.
Nodule Characteristics
Solid Nodules: Most nodules are predominantly solid with a smaller cystic component.
Cystic Nodules: Some nodules may have a larger cystic component, often due to colloid, degeneration, hemorrhage, or cystic change.
Halo: A sonolucent (hypoechoic) rim or halo may be seen around nodules, representing a capsule or interface between the nodule and surrounding tissue.
Calcifications: Calcifications are common in goiters and are often coarse and large.
Vascularity: Nodules may show peripheral vascularity on Doppler ultrasound, and hyperfunctioning nodules may have increased intranodular vascularity.
Heterogeneous Appearance: The goiter’s appearance on ultrasound is often heterogeneous due to the presence of different nodule types, calcifications, fibrosis, cystic changes, and hemorrhage.
How to Measure The Thyroid Lobes
Spongiform/Honeycomb Pattern
Some nodules may show a spongiform or honeycomb pattern, often associated with colloid.
Colloid
Colloid nodules may have tiny echogenic foci with comet-tail artifacts.
Clinical Significance
Diagnosis: Ultrasound is a valuable tool for diagnosing and characterizing goiter, including the presence and characteristics of nodules.
A risk assessment: Ultrasound helps assess the risk of malignancy in thyroid nodules, especially when combined with other clinical factors.
Guidance for Biopsy: Ultrasound can guide fine-needle aspiration (FNA) biopsies of thyroid nodules, which is essential for definitive diagnosis.
Monitoring: Ultrasound can be used to monitor goiter size and nodule characteristics over time.
Characterization of Goiter
Several ultrasound features are used in charactrizing, they include:
Echogenicity: Whether the nodule is hypoechoic (darker than surrounding tissue), isoechoic (similar to surrounding tissue), or hyperechoic (brighter).
Shape: Ovoid, round, or taller-than-wide shapes are considered.
Margins: Smooth, irregular, or spiculated margins can indicate malignancy.
Calcifications: Microcalcifications (small, bright spots), macrocalcifications, and rim calcifications are assessed.
Size: The size of the nodule is an important factor in determining the need for further investigation, such as biopsy.
Scoring is determined from five categories of ultrasound findings.the higher the cumulative score, the higher the tr (ti-rads) level and the likelihood of malignancy.
One score is assigned from each of the following categories:
Composition: (choose one)
- cystic or completely cystic *: 0 points
- spongiform *: 0 points
- mixed cystic and solid: 1 point
- solid or almost completely solid: 2 points
Echogenicity: (choose one)
- anechoic: 0 points
- hyper- or isoechoic: 1 point
- hypoechoic: 2 points
- very hypoechoic: 3 points
Shape: (choose one) (assessed on the transverse plane)
- wider than tall: 0 points
- taller than wide: 3 points
Margin: (choose one)
- smooth: 0 points
- ill-defined: 0 points
- lobulated/irregular: 2 points
- extra-thyroidal extension: 3 points
Any and all findings in the final category are also added to the other four scores.
Echogenic foci: (choose one or more)
- none: 0 points
- large comet-tail artifact: 0 points
- macrocalcifications: 1 point
- peripheral/rim calcifications: 2 points
- punctate echogenic foci: 3 points
List of Thyroid Pathologies
- 1. GOITER
- 2. GRAVES DISEASE
- 3. HASHIMOTO THYROIDITIS
- 4. BENIGN THYROID NODULES