title: Comparison of lymph node metastases assessment with the use of USPIO-enhanced MR imaging at 1.5 T versus 3.0 T in a rabbit model.
abstract: OBJECTIVE
  To prospectively compare the diagnostic performances of 1.5 T and 3.0 T ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) for the detection of lymph node (LN) metastases in a rabbit model.
  
  
  METHODS
  Experiments were approved by the animal care committee. VX2 carcinomas were implanted into the thighs of 18 rabbits 3 or 4 weeks before MRI examinations. T2-weighted 1.5 T and 3.0 T MRI was performed 24 hours after USPIO (2.6 mg/kg iron) administration. Two radiologists calculated signal intensity (SI) ratios (ie, the ratios of postcontrast to precontrast signal intensity) of each LN and also evaluated for the presence of a metastasis in the iliac and retroperitoneal LNs at 1.5 T and 3.0 T MRI. Student's t-test, receiver operating characteristic (ROC) curve analysis, and a Z test were used for the statistical analysis.
  
  
  RESULTS
  Metastases were confirmed in 45 of 80 LNs by histopathology. For benign LNs the mean SI ratio at 1.5 T was higher (0.538) than at 3.0 T (0.463) (P = 0.004). In qualitative analysis, 1.5 T and 3.0 T USPIO-enhanced MRI showed similar Az values (0.951 vs. 0.939; P = 0.296). The specificity of 3.0 T USPIO-enhanced MRI was higher (91.4% [32 of 35]) than that of 1.5 T imaging (82.9% [29 of 35]) (P = 0.013); however, the sensitivities (88.9% [40 of 45]) were the same in the both modalities.
  
  
  CONCLUSIONS
  3.0 T USPIO-enhanced MRI shows a higher specificity as compared to 1.5 T imaging without a significant difference of sensitivity in a rabbit VX2 model.
authors.affiliation: Department of Radiology and Clinical Research Institute, Seoul National University Hospital, and Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seung Hong
authors.initials: SH
authors.lastname: Choi
authors.forename: Keon Ha
authors.initials: KH
authors.lastname: Kim
authors.forename: Woo Kyung
authors.initials: WK
authors.lastname: Moon
authors.forename: Hyo-Cheol
authors.initials: HC
authors.lastname: Kim
authors.forename: Joo Hee
authors.initials: JH
authors.lastname: Cha
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Paik
authors.forename: Kee-Hyun
authors.initials: KH
authors.lastname: Chang
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000175:diagnosis* / Q000556:secondary*; D045744:Cell Line, Tumor; D003287:Contrast Media; D003911:Dextrans; D004195:Disease Models, Animal; D052203:Ferrosoferric Oxide; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10; D052203:Ferrosoferric Oxide