title: Age and sex dependency of cartilage T2 relaxation time mapping in MRI of children and adolescents.
abstract: OBJECTIVE
  T2 relaxation times on MRI are sensitive to the configuration of cartilage collagen and continually increase during aging in adults. In children, T2 relaxation times increase as a result of cartilage microstructure changes in early inflammatory arthritis. The purpose of this study was to determine age- and sex-related differences in T2 mapping of the patellar cartilage in children and adolescents during normal skeletal maturation.
  
  
  METHODS
  Ninety-seven subjects (age range, 5-22 years; 51 females and 46 males; mean age, 14.3 and 13.7 years, respectively) without patellofemoral instability or inflammatory arthritis were included. All subjects underwent 1.5-T knee MRI with T2 mapping. The mean T2 relaxation time and thickness of the patellar cartilage were documented for each MRI examination. Skeletal maturation was determined by physeal patency (open; or closed or closing) on MRI. The associations between T2 relaxation times, cartilage thickness, sex, age, and physeal patency were assessed using Wilcoxon rank sum test and least-squares means regression models.
  
  
  RESULTS
  T2 relaxation times and thickness of the patellar cartilage significantly decreased (p<0.0001) with increasing chronologic age. T2 relaxation times and cartilage thickness in the open physis group were found to be greater than in the closed or closing physis group (p<0.0001). T2 relaxation times and cartilage thickness were greater in males than in females (p<0.05).
  
  
  CONCLUSIONS
  In contrast to senescent changes in adults, skeletal maturation in children results in a sequential decrease in T2 relaxation times that are age- and sex-dependent. Similar to cartilage in adults, cartilage in children gets progressively thinner during skeletal maturation.
authors.affiliation: 1 Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229-3039.
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Kim
authors.forename: Sahar
authors.initials: S
authors.lastname: Shiraj
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Anton
authors.forename: Paul S
authors.initials: PS
authors.lastname: Horn
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Dardzinski
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D000375:Aging / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data*; D008297:Male; D009820:Ohio / Q000453:epidemiology; D010329:Patella / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D012737:Sex Factors; D055815:Young Adult