title: Synthetic-echo time postprocessing technique for generating images with variable T2-weighted contrast: diagnosis of meniscal and cartilage abnormalities of the knee.
abstract: OBJECTIVE
  To assess the feasibility and accuracy of a synthetic-echo time (TE) magnetic resonance (MR) postprocessing technique for the diagnostic evaluation of abnormalities of menisci and articular cartilage in the knee.
  
  
  METHODS
  This study was approved by the institutional review board. Twenty-four patients (three women, 21 men; mean age, 44.8 years) gave informed written consent to prospectively undergo evaluation of their knees (10 left and 14 right knees) with standard sagittal intermediate-weighted (repetition time msec/TE msec, 2200/17) and fat-saturated T2-weighted (3600/88) fast spin-echo sequences. In addition, sagittal multiecho fast gradient-echo sequences were performed for the generation of synthetic-TE images with variable T2- or T2(*)-weighted contrast by using a newly developed synthetic-TE analysis tool that was incorporated directly into the picture archiving and communication system. Sensitivity, specificity, and accuracy values for detection of lesions in menisci and articular cartilage were calculated by using findings at surgery as reference standard.
  
  
  RESULTS
  The standard intermediate-weighted and fat-suppressed T2-weighted MR sequences had overall sensitivity, specificity, and accuracy values of 100% and 100%, 88% and 93%, and 95% and 95% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 82%, 97%, and 95%, respectively, for articular cartilage defects. Corresponding sensitivity, specificity, and accuracy values for multiecho MR imaging with synthetic-TE MR image generation were 92% and 100%, 88% and 87%, and 90% and 90% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 70%, 99%, and 95%, respectively, for articular cartilage defects.
  
  
  CONCLUSIONS
  For the evaluation of menisci and articular cartilage, images generated with the synthetic-TE technique are a potentially viable alternative to standard T2-weighted images obtained at different TEs. Furthermore, the synthetic-TE approach allowed assessment of abnormalities of menisci and articular cartilage with high sensitivity and specificity.
authors.affiliation: Department of Medical Imaging, Mount Sinai Hospital and the University Health Network, University of Toronto, 600 University Ave, Toronto, ON, Canada.
authors.forename: Gustav
authors.initials: G
authors.lastname: Andreisek
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: White
authors.forename: John S
authors.initials: JS
authors.lastname: Theodoropoulos
authors.forename: Ali
authors.initials: A
authors.lastname: Naraghi
authors.forename: Norman
authors.initials: N
authors.lastname: Young
authors.forename: Claire Y
authors.initials: CY
authors.lastname: Zhao
authors.forename: Tallal C
authors.initials: TC
authors.lastname: Mamisch
authors.forename: Marshall S
authors.initials: MS
authors.lastname: Sussman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002358:Cartilage, Articular / Q000473:pathology*; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007718:Knee Injuries / Q000175:diagnosis*; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012984:Software