title: Multinuclear MR and multilevel data processing: an insight into morphologic assessment of in vivo knee articular cartilage.
abstract: OBJECTIVE
  Quantitative assessment of knee articular cartilage (AC) morphology using magnetic resonance (MR) imaging requires an accurate segmentation and 3D reconstruction. However, automatic AC segmentation and 3D reconstruction from hydrogen-based MR images alone is challenging because of inhomogeneous intensities, shape irregularity, and low contrast existing in the cartilage region. Thus, the objective of this research was to provide an insight into morphologic assessment of AC using multilevel data processing of multinuclear ((23)Na and (1)H) MR knee images.
  
  
  METHODS
  A dual-tuned ((23)Na and (1)H) radio-frequency coil with 1.5-T MR scanner is used to scan four human subjects using two separate MR pulse sequences for the respective sodium and proton imaging of the knee. Postprocessing is performed using customized routines written in MATLAB. MR data were fused to improve contrast of the cartilage region that is further used for automatic segmentation. Marching cubes algorithm is applied on the segmented AC slices for 3D volume rendering and volume is then calculated using the divergence theorem.
  
  
  RESULTS
  Fusion of multinuclear MR images results in an improved contrast (factor >3) in the cartilage region. Sensitivity (80.21%) and specificity (99.64%) analysis performed by comparing manually segmented AC shows a good performance of the automated AC segmentation. The average cartilage volume (23.19 ± 1.38 cm(3); coefficient of variation [COV] -0.059) measured from 3D AC models of four data sets shows a marked improvement over average cartilage volume (23.24 cm(3); COV -0.19) reported earlier.
  
  
  CONCLUSIONS
  This study confirms the use of multinuclear MR data for cartilage morphology (volume) assessment that can be used in clinical settings.
authors.affiliation: Centre for Intelligent Signal and Imaging Research, Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia.
authors.forename: Ahmad Fadzil Mohd
authors.initials: AF
authors.lastname: Hani
authors.affiliation: Centre for Intelligent Signal and Imaging Research, Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia. Electronic address: dileep.kumar@petronas.com.my.
authors.forename: Dileep
authors.initials: D
authors.lastname: Kumar
authors.affiliation: Centre for Intelligent Signal and Imaging Research, Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia.
authors.forename: Aamir Saeed
authors.initials: AS
authors.lastname: Malik
authors.affiliation: Centre for Intelligent Signal and Imaging Research, Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Walter
authors.affiliation: Department of Rheumatology, Pantai Hospital Ipoh, Ipoh, Perak, Malaysia.
authors.forename: Ruslan
authors.initials: R
authors.lastname: Razak
authors.affiliation: Imaging Department, Pantai Hospital Ipoh, Ipoh, Perak, Malaysia.
authors.forename: Azman
authors.initials: A
authors.lastname: Kiflie
mesh_terms: D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007719:Knee Joint / Q000033:anatomy & histology* / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium / Q000378:metabolism*; D012975:Sodium Isotopes / Q000493:pharmacokinetics
chemical_list: D019275:Radiopharmaceuticals; D012975:Sodium Isotopes; D012964:Sodium
keywords: 3D reconstruction; Multinuclear MRI; articular cartilage; morphology; segmentation