title: Manganese-enhanced MRI of minimally gadolinium-enhancing breast tumors.
abstract: OBJECTIVE
  To investigate the potential of manganese (Mn)-enhanced MRI for sensitive detection and delineation of tumors that demonstrate little enhancement on Gd-DTPA.
  
  
  METHODS
  Eighteen nude rats bearing 1 to 2 cm in diameter orthotopic breast tumors (ZR75 and LM2) were imaged on a 3 Tesla (T) clinical scanner. Gd-DTPA was administered intravenously and MnCl2 subcutaneously, both at 0.05 mmol/kg. T1 -weighted imaging and T1 measurements were performed precontrast, 10 min post-Gd-DTPA, and 24 h post-MnCl2 . Tumors were excised and histologically assessed using H&E (composition and necrosis) and CD34 (vascularity).
  
  
  RESULTS
  Most tumors (78%) demonstrated little enhancement (< 20% change in R1 ) on Gd-DTPA. MnCl2 administration achieved greater and more uniform enhancement throughout the tumor mass (i.e., not restricted to the tumor periphery), with R1 changing over 20% in 72% of tumors. MnCl2 -induced R1 changes compared with Gd-induced changes were significantly greater in both ZR75 (P < 0.01) and LM2 tumors (P < 0.05). Histology confirmed very low vascularity in both tumor models, and necrotic areas were well delineated only on Mn-enhanced MRI.
  
  
  CONCLUSIONS
  Mn-enhanced MRI is a promising approach for detection of low-Gd-enhancing tumors.
authors.affiliation: The Research Institute (Physiology & Experimental Medicine) and Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada; Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada.
authors.forename: Tameshwar
authors.initials: T
authors.lastname: Ganesh
authors.forename: Reza Bayat
authors.initials: RB
authors.lastname: Mokhtari
authors.forename: Mosa
authors.initials: M
authors.lastname: Alhamami
authors.forename: Herman
authors.initials: H
authors.lastname: Yeger
authors.forename: Hai-Ling Margaret
authors.initials: HL
authors.lastname: Cheng
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001943:Breast Neoplasms / Q000175:diagnosis*; D003287:Contrast Media; D004195:Disease Models, Animal; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008345:Manganese; D051381:Rats; D011923:Rats, Nude
chemical_list: D003287:Contrast Media; D008345:Manganese; D019786:Gadolinium DTPA
keywords: contrast-enhanced imaging; gadolinium chelate; low vascularity cancer; manganese chloride; nonenhancing; rat breast tumor model