title: T2 Relaxation Time Mapping of the Cartilage Cap of Osteochondromas.
abstract: OBJECTIVE
  Our aim was to evaluate the cartilage cap of osteochondromas using T2 maps and to compare these values to those of normal patellar cartilage, from age and gender matched controls.
  
  
  METHODS
  This study was approved by the Institutional Review Board and request for informed consent was waived. Eleven children (ages 5-17 years) with osteochondromas underwent MR imaging, which included T2-weighted fat suppressed and T2 relaxation time mapping (echo time = 9-99/repetition time = 1500 msec) sequences. Lesion origins were femur (n = 5), tibia (n = 3), fibula (n = 2), and scapula (n = 1). Signal intensity of the cartilage cap, thickness, mean T2 relaxation times, and T2 spatial variation (mean T2 relaxation times as a function of distance) were evaluated. Findings were compared to those of patellar cartilage from a group of age and gender matched subjects.
  
  
  RESULTS
  The cartilage caps showed a fluid-like high T2 signal, with mean thickness of 4.8 mm. The mean value of mean T2 relaxation times of the osteochondromas was 264.0 ± 80.4 msec (range, 151.0-366.0 msec). Mean T2 relaxation times were significantly longer than the values from patellar cartilage (39.0 msec) (p < 0.0001). These findings were observed with T2 spatial variation plots across the entire distance of the cartilage cap, with the most pronounced difference in the middle section of the cartilage.
  
  
  CONCLUSIONS
  Longer T2 relaxation times of the cartilage caps of osteochondromas should be considered as normal, and likely to reflect an increased water content, different microstructure and component.
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA.
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Kim
authors.affiliation: Department of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Horn
authors.affiliation: Department of Radiology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Dardzinski
authors.affiliation: Department of Pharmacology, Korea University College of Medicine, Seoul 02841, Korea.
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039, USA.
authors.forename: Tal
authors.initials: T
authors.lastname: Laor
mesh_terms: D000293:Adolescent; D001859:Bone Neoplasms / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005269:Femur; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015831:Osteochondroma / Q000473:pathology*; D010329:Patella / Q000473:pathology*; D012189:Retrospective Studies; D013977:Tibia
keywords: Cartilage cap; Osteochondroma; T2 relaxation time mapping