title: Optimal TE for SPIO-enhanced gradient-recalled echo MRI for the detection of focal hepatic lesions.
abstract: OBJECTIVE
  The objective of our study was to determine the optimal TE for superparamagnetic iron oxide (SPIO)-enhanced gradient-recalled echo (GRE) MRI for the detection of focal hepatic lesions.
  
  
  METHODS
  Ferucarbotran-enhanced GRE sequences, performed on a 1.5-T MR system, were used to evaluate 131 lesions (38 hepatocellular carcinomas, 37 metastases, 21 hemangiomas, 7 cholangiocarcinomas, 15 cysts, and 13 miscellaneous lesions) at four different TEs: 9, 13.5, 18, and 22.5 milliseconds. The lesion-to-liver signal difference-to-noise ratio (SDNR) was compared among the four GRE sequences by paired Student's t tests and among lesion types by an independent samples Student's t test. The McNemar test was used to compare the sensitivity for the detection of focal hepatic lesions. Wilcoxon's signed rank test was used to compare the subjective lesion conspicuity.
  
  
  RESULTS
  The SDNRs of lesions on GRE images obtained at a TE of 13.5 milliseconds (mean +/- SD, 60 +/- 24) were significantly (p < 0.001) higher than those at TEs of 9 (55 +/- 23), 18 (55 +/- 22), and 22.5 milliseconds (47 +/- 19). The SDNR was highest at a TE of 13.5 milliseconds for SPIO-uptake lesions and was comparable on images obtained with TEs of 18 and 13.5 milliseconds for non-SPIO-uptake lesions. The non-SPIO-uptake lesions showed a significantly higher SDNR than the SPIO-uptake lesions at a TE of 22.5 milliseconds (p = 0.007). The overall sensitivity for lesion detection was not significantly different among the four GRE sequences, and the subjective ratings of lesion conspicuity were comparable for images obtained using TEs of 8, 13.5, and 18 milliseconds, but the ratings of lesion conspicuity were significantly lower for images obtained using a TE of 22.5 milliseconds (p < 0.001).
  
  
  CONCLUSIONS
  For ferucarbotran-enhanced MRI, lesion SDNR was highest on images obtained using a TE of 13.5 milliseconds, but the sensitivity and lesion conspicuity were comparable at TEs of 9 and 18 milliseconds. The SDNR of liver lesions varied according to the lesion's potential capability of taking up SPIO agents.
authors.affiliation: Department of Diagnostic Radiology, Yonsei University College of Medicine, Seodaemun-ku Shinchon-dong 134, Seoul 120-752, Republic of Korea. kimnex@yumc.yonsei.ac.kr
authors.forename: Myeong-Jin
authors.initials: MJ
authors.lastname: Kim
authors.forename: Joo Hee
authors.initials: JH
authors.lastname: Kim
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Choi
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Jae-Joon
authors.initials: JJ
authors.lastname: Chung
authors.forename: Ki Whang
authors.initials: KW
authors.lastname: Kim
authors.forename: Donald G
authors.initials: DG
authors.lastname: Mitchell
mesh_terms: D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis*; D003287:Contrast Media / Q000008:administration & dosage; D003560:Cysts / Q000175:diagnosis*; D005260:Female; D005290:Ferric Compounds / Q000008:administration & dosage; D006391:Hemangioma / Q000175:diagnosis*; D006801:Humans; D008107:Liver Diseases / Q000175:diagnosis*; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000556:secondary; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide