title: Does decreased T1 signal intensity in the retrodiscal tissue of the temporomandibular joint reflect increased density of collagen fibres?
abstract: OBJECTIVE
  To evaluate whether decreased signal intensity on T(1) weighted MR images of the retrodiscal tissue of the temporomandibular joint (TMJ) reflects increased density of collagen fibres.
  
  
  METHODS
  Corrected sagittal T(1) weighted MR images of six TMJs from six fresh cadavers (three males and three females; age range 76-87 years, mean 80.8 years) were obtained. Following MRI, slices of tissue samples were taken from the cadavers that exactly matched the planes of the MR image. These samples were fixed, decalcified and stained (haematoxylin-eosin stain, Elastica van Gieson's stain) for light microscopy. The samples were evaluated for density of collagen fibres according to Hall et al (1984) and for vascularity, arterial wall thickness, fat content and elastin. In these sagittal samples, the retrodiscal tissue was divided anteroposteriorly and vertically into six areas and each area was classified by histological parameters. The MR images were similarly divided into six areas. Areas with reduced signal intensity were classified as the low signal group and those with no reduced signals were classified as the control group.
  
  
  RESULTS
  Collagen density assessed histologically differed between the low signal intensity group and the control group, and loose collage density on the histological samples was observed significantly more often in the low signal group (Fisher's exact test, P=0.03). There were no statistically significant differences in the other categories between the two groups.
  
  
  CONCLUSIONS
  The results suggest that reduced T1 signals of retrodiscal tissue do not necessarily reflect a dense distribution of collagen fibres.
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001158:Arteries / Q000473:pathology; D002102:Cadaver; D003094:Collagen; D004396:Coloring Agents; D004549:Elastin / Q000032:analysis; D005260:Female; D024022:Fibrillar Collagens; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008055:Lipids / Q000032:analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D013704:Temporomandibular Joint / Q000033:anatomy & histology*; D019224:Temporomandibular Joint Disc / Q000033:anatomy & histology* / Q000098:blood supply
chemical_list: D004396:Coloring Agents; D024022:Fibrillar Collagens; D008055:Lipids; D003094:Collagen; D004549:Elastin