Breast MRI is performed for pre-operative staging. A 1.5 cm lesion shows rapid initial enhancement (>100% signal increase in the first 2 minutes) followed by wash-out kinetics on the delayed phase. According to ACR BI-RADS MRI lexicon, this kinetic curve is classified as:
- A Type III (wash-out) — suspicious ✓
- B Type I (persistent) — benign
- C Type II (plateau) — intermediate
- D Type IV (rapid wash-in) — benign
Correct answer: A. Type III (wash-out) — suspicious
Explanation
The ACR BI-RADS MRI kinetic curve descriptors are Type I (persistent rise — most likely benign), Type II (plateau — indeterminate), and Type III (wash-out — most suspicious for malignancy). Rapid initial enhancement combined with wash-out on the delayed phase corresponds to Type III and is the kinetic pattern most predictive of malignancy. There is no 'Type IV' in the BI-RADS MRI lexicon.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.