title: MRI of fat necrosis of the breast: the "black hole" sign at short tau inversion recovery.
abstract: OBJECTIVE
  To describe MRI features of fat necrosis of the breast.
  
  
  METHODS
  Twenty-five lesions in 16 patients were retrospectively analyzed. MRI was performed due to equivocal findings at conventional imaging after surgical treatment of cancer (n=14) or during anticoagulant therapy (n=1), after focal mastitis treated with ductal resection (n=1). In the 15 patients with previous surgery MRI was performed after a median interval of 24 months, using short tau inversion recovery (STIR) and contrast-enhanced dynamic T1-weighted sequences. Signal-to-noise ratio (SNR) inside the lesion and surrounding healthy fat was calculated on both STIR and unenhanced T1-weighted images. Maximal lesion diameter was measured on STIR images. All lesions had final clinical and imaging assessment in favor of fat necrosis and negative clinical and imaging follow-up (21-40 months; median 24 months).
  
  
  RESULTS
  At STIR sequence, fat necrosis appeared as a "black hole", being markedly hypointense (median SNR=29) compared with surrounding fat (median SNR=95) (P<0.001), while no significant difference was found at unenhanced T1-weighted sequence. No significant correlation with time from treatment was found. Of 25 lesions, 15 showed ring enhancement, with continuous increase (n=10), plateau (n=2), or wash-out curve (n=3). The 11 enhancing lesions in the 8 patients with previous radiation therapy showed an initial enhancement higher than that of the 4 enhancing lesions in the 2 patients who did not, although the difference was not significant (P=0.104).
  
  
  CONCLUSIONS
  Fat necrosis of the breast exhibits a "black hole" sign on STIR images, allowing for an easier diagnosis in clinical practice.
authors: Università degli Studi di Milano, Facoltà di Medicina e Chirurgia, Scuola di Specializzazione in Radiodiagnostica, Via Festa del Perdono 7, 20122 Milan, Italy.
authors: Rubina M
authors: RM
authors: Trimboli
authors: Luca A
authors: LA
authors: Carbonaro
authors: Francesco
authors: F
authors: Cartia
authors: Giovanni
authors: G
authors: Di Leo
authors: Francesco
authors: F
authors: Sardanelli
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001940:Breast / Q000473:pathology*; D001941:Breast Diseases / Q000473:pathology*; D005218:Fat Necrosis / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity