title: Quantitative Ultrashort Echo Time Magnetic Resonance Imaging Evaluation of Postoperative Menisci: a Pilot Study.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) visualization of meniscal signal is particularly challenging as the highly organized ultrastructure of meniscal fibrocartilage yields very short T2 values (∼6 ms) and a paucity of signal intensity during conventional image acquisition.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the feasibility of imaging postoperative menisci using an experimental, quantitative ultrashort echo time (UTE) MRI pulse sequence. This sequence acquires short echo images (echo time (TE) ∼0.3 ms) to produce multi-echo images for quantitative T2* calculations that provide an objective measure of collagen organization.
  
  
  METHODS
  MRI scans of the knee were acquired at 6- and 12-month intervals on a clinical 3.0 T scanner following meniscal surgery in eight patients (ages 13-41), four of whom underwent repair and the other four partial meniscectomy. Conventional MRI sequences were qualitatively evaluated for meniscal morphology and signal and correlated with quantitative UTE results.
  
  
  RESULTS
  A wide range of mean T2* values for both postsurgical groups was measured, and these values changed for each patient between the 6- and 12-month intervals. In many instances, the UTE sequence demonstrated quantitative differences between the two time intervals that were not detected with conventional sequences.
  
  
  CONCLUSIONS
  This pilot study presents preliminary, observational data to be used as a baseline for future studies. Although the T2* values did not reveal a trend in either group or correlate with expected signal changes on conventional MRI, we speculate that the UTE sequence may detect ultrastructural alterations in meniscal composition that are otherwise not perceived with routine fast spin echo (FSE) sequences.
authors.affiliation: Department of Radiology and Imaging, Hospital for Special Surgery, 535 East 70th Street, Basement-MRI, New York, NY 10021 USA.
authors.forename: Darryl B
authors.initials: DB
authors.lastname: Sneag
authors.affiliation: MRI Research Laboratory, Hospital for Special Surgery, New York, NY USA.
authors.forename: Parina
authors.initials: P
authors.lastname: Shah
authors.affiliation: MRI Research Laboratory, Hospital for Special Surgery, New York, NY USA.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Koff
authors.affiliation: MRI Research Laboratory, Hospital for Special Surgery, New York, NY USA.
authors.forename: Wei Y
authors.initials: WY
authors.lastname: Lim
authors.affiliation: Department of Sports Medicine, Hospital for Special Surgery, New York, NY USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rodeo
authors.affiliation: Department of Radiology and Imaging, Hospital for Special Surgery, 535 East 70th Street, Basement-MRI, New York, NY 10021 USA ; MRI Research Laboratory, Hospital for Special Surgery, New York, NY USA.
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
keywords: magnetic resonance imaging; meniscus; quantitative; ultrashort TE