title: Bias of cartilage T2 values related to method of calculation.
abstract: OBJECTIVE
  To determine how different methods for calculating T2 affect the resulting T2 values of patellar cartilage.
  
  
  METHODS
  T2-weighted images of patellar cartilage for 10 subjects were acquired using two MRI scanners. T2 values of patellar cartilage were calculated using linear, weighted and nonlinear fitting algorithms for a monoexponential decay equation. T2 values were also calculated for the superficial, middle and deep zones of the cartilage.
  
  
  RESULTS
  All three methods of calculation resulted in significantly different T2 values (P<.0001). The weighted calculation produced the highest T2 values, and the nonlinear calculation produced the lowest T2 values. The average difference of T2 value between the methods was under 5 ms. Similar results were found in a zonal analysis of the tissue. The nonlinear calculation of T2 consistently had the best fit to the acquired data.
  
  
  CONCLUSIONS
  The T2 value of patellar cartilage depends on the method of calculation. It is unclear if larger T2 value differences would be seen in subjects diagnosed with osteoarthritis. This study highlights the potential difficulty of comparing different studies with one another based on the method of T2 calculation.
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55901, USA.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Koff
authors.forename: Kimberly K
authors.initials: KK
authors.lastname: Amrami
authors.forename: Joel P
authors.initials: JP
authors.lastname: Felmlee
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Kaufman
mesh_terms: D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016018:Least-Squares Analysis; D008297:Male; D010329:Patella / Q000033:anatomy & histology*; D012984:Software