Small Parts and Superficial Structures
Small Parts and Superficial Structures tests high-frequency imaging of the thyroid, breast, scrotum and superficial neck, where risk stratification systems and probe technique determine whether a biopsy is warranted.
Core rules
- ACR TI-RADS scores five features: composition (cystic 0, spongiform 0, mixed 1, solid 2); echogenicity (anechoic 0, hyper/isoechoic 1, hypoechoic 2, very hypoechoic 3); shape (wider-than-tall 0, taller-than-wide 3); margin (smooth 0, ill-defined 1, lobulated 2, extrathyroidal extension 3); echogenic foci (none 0, macrocalcification 1, peripheral 2, punctate 3).
- Categories: TR1 = 0, TR2 = 2, TR3 = 3, TR4 = 4–6, TR5 ≥7. FNA thresholds: TR3 ≥2.5 cm, TR4 ≥1.5 cm, TR5 ≥1.0 cm.
- Testicular torsion shows an enlarged, heterogeneous testis with absent or reduced flow; epididymitis shows increased flow with epididymal enlargement.
- Breast lesions are categorized by BI-RADS, with suspicious features including irregular shape, non-circumscribed margins and shadowing.
Worked example
A 1.8 cm thyroid nodule is solid (2 points), hypoechoic (2), wider-than-tall (0), smooth margins (0) with no echogenic foci (0). Total 4 = TR4. Because TR4 nodules are biopsied at ≥1.5 cm and this one is 1.8 cm, FNA is indicated. If the same nodule were 1.2 cm, it would be followed rather than sampled.
Traps that cost marks
Scoring hypoechoic and very hypoechoic identically; assessing taller-than-wide on a longitudinal rather than transverse image; calling a simple cyst complex because of posterior enhancement; and excluding torsion on the basis of preserved flow.