title: MR T(1)ρ quantification of cartilage focal lesions in acutely injured knees: correlation with arthroscopic evaluation.
abstract: OBJECTIVE
  Quantitative T1ρ MRI has been suggested as a promising tool to detect changes in cartilage composition that are characteristic of cartilage damage and degeneration. The objective of this study was to evaluate the capability of MR T1ρ to detect cartilage lesions as evaluated by arthroscopy in acutely ACL-injured knees and to compare with the Whole-Organ Magnetic Resonance Imaging Score (WORMS) using clinical standard MRI.
  
  
  METHODS
  Ten healthy controls (mean age 35) with no ACL injury or history of osteoarthritis (OA) and 10 patients with acute ACL injuries (mean age 39) were scanned at 3 Tesla (3T). ACL patients underwent ACL reconstruction, where focal lesions were graded according to an Outerbridge grading system during arthroscopic evaluation. Normalized MR T1ρ values (T1ρ z-scores normalized to control values in matched regions) in full thickness, and superficial and deep layers of cartilage were compared between defined sub-compartments with and without focal lesions. Intraclass (ICC) correlation and the root mean square coefficient of variation (RMS-CV) were performed to evaluate the inter-observer reproducibility of T1ρ quantification. Sub-compartments of cartilage were also evaluated using WORMS scoring and compared to their Outerbridge score respectively.
  
  
  RESULTS
  The inter-observer ICC and the RMS-CV of the sub-compartment T1ρ quantification were 0.961 and 3.9%, respectively. The average T1ρ z-scores were significantly increased in sub-compartments with focal lesions compared to those without focal lesions and to the control cohort (p<0.05).
  
  
  CONCLUSIONS
  Our results indicate that T1ρ provided a better diagnostic capability than clinical standard MRI grading in detecting focal cartilage abnormalities after acute injuries. Quantitative MRI may have great potential in detecting cartilage abnormalities and degeneration non-invasively, which are occult with standard morphological MRI.
authors.affiliation: Musculo-skeletal and Quantitative Imaging Research (MQIR), Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA; Department of Bioengineering, University of California, Berkeley, Berkeley, CA, USA. Electronic address: ritigupta11@gmail.com.
authors.forename: Riti
authors.initials: R
authors.lastname: Gupta
authors.affiliation: Musculo-skeletal and Quantitative Imaging Research (MQIR), Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA. Electronic address: kaooat7@hotmail.com.
authors.forename: Warapat
authors.initials: W
authors.lastname: Virayavanich
authors.affiliation: Musculo-skeletal and Quantitative Imaging Research (MQIR), Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA. Electronic address: dankuo@gmail.com.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kuo
authors.affiliation: Musculo-skeletal and Quantitative Imaging Research (MQIR), Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA. Electronic address: faviansu@gmail.com.
authors.forename: Favian
authors.initials: F
authors.lastname: Su
authors.affiliation: Musculo-skeletal and Quantitative Imaging Research (MQIR), Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA. Electronic address: thomas.link@ucsf.edu.
authors.forename: Thomas
authors.initials: T
authors.lastname: Link
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, USA. Electronic address: maben@orthosurg.ucsf.edu.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ma
authors.affiliation: Musculo-skeletal and Quantitative Imaging Research (MQIR), Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA. Electronic address: Xiaojuan.li@ucsf.edu.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Li
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D001182:Arthroscopy; D015992:Body Mass Index; D002358:Cartilage, Articular / Q000473:pathology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results
keywords: ACL injuries; Arthroscopy; Cartilage degeneration; Magnetic resonance imaging; Outerbridge; T(1)ρ quantification
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