title: Ultrasonic reflection coefficient and surface roughness index of OA articular cartilage: relation to pathological assessment.
abstract: BACKGROUND
  Early diagnosis of osteoarthritis (OA) is essential for preventing further cartilage destruction and decreasing severe complications. The aims of this study are to explore the relationship between OA pathological grades and quantitative acoustic parameters and to provide more objective criteria for ultrasonic microscopic evaluation of the OA cartilage.
  
  
  METHODS
  Articular cartilage samples were prepared from rabbit knees and scanned using ultrasound biomicroscopy (UBM). Three quantitative parameters, including the roughness index of the cartilage surface (URI), the reflection coefficients from the cartilage surface (R) and from the cartilage-bone interface (Rbone) were extracted. The osteoarthritis grades of these cartilage samples were qualitatively assessed by histology according to the grading standards of International Osteoarthritis Institute (OARSI). The relationship between these quantitative parameters and the osteoarthritis grades was explored.
  
  
  RESULTS
  The results showed that URI increased with the OA grade. URI of the normal cartilage samples was significantly lower than the one of the OA cartilage samples. There was no significant difference in URI between the grade 1 cartilage samples and the grade 2 cartilage samples. The reflection coefficient of the cartilage surface reduced significantly with the development of OA (p < 0.05), while the reflection coefficient of the cartilage-bone interface increased with the increase of grade.
  
  
  CONCLUSIONS
  High frequency ultrasound measurements can reflect the changes in the surface roughness index and the ultrasound reflection coefficients of the cartilage samples with different OA grades. This study may provide useful information for the quantitative ultrasonic diagnosis of early OA.
authors.affiliation: Key Laboratory of the Ministry of Education for Biomechanics and Mechanobiology, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China. hjniu@buaa.edu.cn
authors.forename: Hai-jun
authors.initials: HJ
authors.lastname: Niu
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.forename: Yue-xiang
authors.initials: YX
authors.lastname: Wang
authors.forename: De-yu
authors.initials: DY
authors.lastname: Li
authors.forename: Yu-bo
authors.initials: YB
authors.lastname: Fan
authors.forename: Wu-fan
authors.initials: WF
authors.lastname: Chen
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology; D004195:Disease Models, Animal; D042241:Early Diagnosis; D005260:Female; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D033401:Microscopy, Acoustic; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000473:pathology; D011237:Predictive Value of Tests; D011817:Rabbits; D012720:Severity of Illness Index; D013499:Surface Properties