title: Delayed Gadolinium-Enhanced MR Imaging of Cartilage (dGEMRIC) following ACL injury.
abstract: OBJECTIVE
  Early detection of glycosaminoglycan (GAG) loss may provide insight into mechanisms of cartilage damage in the anterior cruciate ligament (ACL)-injured patient. We hypothesized that tibial and femoral Delayed Gadolinium-Enhanced MR Imaging of Cartilage (dGEMRIC) indices would be lower in the medial compartment of the ACL-injured knee than in the contralateral, uninjured knee, and that scan order (i.e., whether the injured or the uninjured knee was imaged first) would not affect the indices.
  
  
  METHODS
  15 subjects with unilateral ACL injuries received a double dose of gadolinium [Gd(DTPA)(2-)] intravenously. After 90 min, both knees were sequentially imaged. The injured knee was scanned first in the odd-numbered subjects and second in the even-numbered subjects. The dGEMRIC indices of the median slice of the medial compartment were determined using the MRIMapper software. Index comparisons were made between knee status (ACL-injured vs uninjured), scan order (ACL-injured first vs uninjured first), and cartilage location (tibia vs femur) using a mixed model.
  
  
  RESULTS
  There was a significant difference in the mean dGEMRIC indices of the medial compartment between injured and uninjured knees (P<0.007). On average, there was a 13% decrease in the dGEMRIC index of the injured knee compared to the uninjured knee. There were no significant effects due to test order (P=0.800) or cartilage location (P=0.439).
  
  
  CONCLUSIONS
  The results demonstrate lower GAG concentrations in the medial compartment of the femoral and tibial articular cartilage of the ACL-injured knee when compared to the contralateral uninjured knee. The dGEMRIC indices were not sensitive to scan order; thus, sequential imaging of both knees is possible in this patient population.
authors.affiliation: Bioengineering Laboratory, Department of Orthopaedics, Warren Alpert Medical School of Brown University/Rhode Island Hospital, Providence, RI 02903, United States. braden_fleming@brown.edu
authors.forename: B C
authors.initials: BC
authors.lastname: Fleming
authors.forename: H L
authors.initials: HL
authors.lastname: Oksendahl
authors.forename: W A
authors.initials: WA
authors.lastname: Mehan
authors.forename: R
authors.initials: R
authors.lastname: Portnoy
authors.forename: P D
authors.initials: PD
authors.lastname: Fadale
authors.forename: M J
authors.initials: MJ
authors.lastname: Hulstyn
authors.forename: M E
authors.initials: ME
authors.lastname: Bowers
authors.forename: J T
authors.initials: JT
authors.lastname: Machan
authors.forename: G A
authors.initials: GA
authors.lastname: Tung
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D002358:Cartilage, Articular / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA