Diagnosis of articular cartilage abnormalities of the knee: Prospective clinical evaluation of a 3D water-excitation true FISP sequence

Purpose: To prospectively evaluate the accuracy of three-dimensional ( 3D) water-excitation true fast imaging with steadystate precession ( FISP) in the assessment of cartilage abnormalities of the knee, by using surgery as the reference standard. Materials and Methods: The study was approved by the hospital institutional review board. Written informed consent was obtained from all patients. Twenty-nine patients ( 30 knees) with a mean age of 56 years ( range, 18-86 years) were prospectively evaluated with a sagittal 3D true FISP magnetic resonance ( MR) sequence. The mean interval between MR imaging and surgery was 1 day ( range, 0-9 days). During surgery, the articular surfaces of the knee were evaluated by using a modified Noyes score. The MR images were evaluated by two blinded readers on two separate occasions. Diagnostic performance was evaluated by setting the cutoff for abnormality between grade 1 ( intact cartilage surface) and grade 2 ( cartilage defects). Statistical methods used included calculation of sensitivity, specificity, and accuracy, with 95% confidence intervals ( Wilson score method) and calculation of kappa values with standard errors. Results: Overall sensitivity, specificity, and accuracy for the two readers and the two evaluations ranged from 56% to 66%, 78% to 93%, and 71% to 75%, respectively. Interobserver agreement was substantial for both the first ( kappa = 0.73) and the second ( kappa = 0.65) evaluation. Intraobserver agreement was almost perfect ( kappa = 0.84) for reader 1 and moderate (kappa = 0.60) for reader 2. Conclusion: The 3D water-excitation true FISP MR sequence allows assessment of the articular cartilage of the knee with moderateto- high specificity and low-to-moderate sensitivity. (c) RSNA, 2007.