title: Usefulness of using laser-induced photoacoustic measurement and 3.0 Tesla MRI to assess knee cartilage damage: a comparison study.
abstract: BACKGROUND
  T2 mapping is an MRI method particularly reflective of the collagen arrangement in the cartilage, and diffusion tensor (DT) imaging captures the diffusion of water molecules. Laser-induced photoacoustic measurement (LIPA) makes it possible to assess not only the thickness of the cartilage layer but also its viscoelastic properties. By assessing cartilage damage assessment using LIPA and 3.0 Tesla MRI (T2 mapping and DT imaging), this study investigates the usefulness of the various methods.
  
  
  METHODS
  The International Cartilage Repair Society (ICRS) classification was used to classify 29 bone cartilage pieces excised during surgical procedures. At the same time, LIPA was performed at sites matching the area of cartilage damage. MRI was performed preoperatively to measure the T2 and the apparent diffusion coefficient. In addition, tissue sections for histological assessment using the Mankin score were prepared for each ICRS grade, and the results with the various methods were compared.
  
  
  RESULTS
  With DT imaging, significant differences were observed in all grades (P < 0.01). With T2 mapping, significant differences were observed in all grades except for grade 1 versus grade 2 (P < 0.01). With LIPA, significant differences were observed in ICRS grade 1 versus grade 3 (P < 0.05), grade 1 versus grade 4 (P < 0.01), grade 2 versus grade 4 (P < 0.01), and grade 3 versus grade 4 (P < 0.05). With the Mankin score, significant differences were observed in ICRS grade 1 versus grade 3 (P < 0.01), grade 1 versus grade 4 (P < 0.01), grade 2 versus grade 4 (P < 0.01), and grade 3 versus grade 4 (P < 0.01). Correlations were observed in all combinations of ICRS grade with DT imaging, T2 mapping, LIPA, and Mankin score. Correlations were observed between the degree of histological degeneration and DT imaging, T2 mapping, and ICRS grade, but LIPA had a weaker correlation than MRI.
  
  
  CONCLUSIONS
  In the assessment of knee osteoarthritis, there are instances where it is difficult to assess the damaged cartilage site with MRI alone, and we believe that it is desirable to use a combination of LIPA and MRI.
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. taku115@is.icc.u-tokai.ac.jp.
authors.forename: Taku
authors.initials: T
authors.lastname: Ukai
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. sato-m@is.icc.u-tokai.ac.jp.
authors.forename: Masato
authors.initials: M
authors.lastname: Sato
authors.affiliation: Department of Medical Engineering, National Defence Medical Collage, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan. kobako@ndmc.ac.jp.
authors.forename: Miya
authors.initials: M
authors.lastname: Ishihara
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. munetaka198297@yahoo.co.jp.
authors.forename: Munetaka
authors.initials: M
authors.lastname: Yokoyama
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. t-tom8@pc4.so-net.ne.jp.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Takagaki
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. genya@syd.odn.ne.jp.
authors.forename: Genya
authors.initials: G
authors.lastname: Mitani
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. seagulls11@tokai-u.jp.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Tani
authors.affiliation: Department of Radiology, Specialized Clinical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. tomyam999@gmail.com.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamashita
authors.affiliation: Department of Radiology, Specialized Clinical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. imaiy@is.icc.u-tokai.ac.jp.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Imai
authors.affiliation: Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa, 259-1193, Japan. jomo@is.icc.u-tokai.ac.jp.
authors.forename: Joji
authors.initials: J
authors.lastname: Mochida
mesh_terms: D000368:Aged; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000473:pathology; D007834:Lasers; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D020370:Osteoarthritis, Knee / Q000473:pathology*; D061088:Photoacoustic Techniques / Q000379:methods*