T1ρ is superior to T2 mapping for the evaluation of articular cartilage denaturalization with osteoarthritis: radiological-pathological correlation after total knee arthroplasty

Purpose: We compared the diagnostic performance of T1ρ and T2 mappings in the evaluation of denatured articular cartilage with osteoarthritis of the knee.

Materials and methods: 2D-Sagittal T1ρ and T2 mappings of the knee were obtained from 16 patients before total knee arthroplasty. After surgery, specimens of the femur and tibia were regionally segmented according to a 5-point scale of the severity of denaturalization. The T1ρ and T2 values in the full thickness of the articular cartilage in each region were measured by two observers. The two mappings were compared for their ability to differentiate between normal and denatured articular cartilage and also for their usefulness in grading the severity of the denaturalization using the area under receiver operating characteristic curves (Az). A p<0.05 was considered significant for each analysis.

Results: The T1ρ mapping showed a significantly higher Az value than the T2 mapping for the differentiation between normal and denatured articular cartilage (p<0.05). Regarding the assessment of the severity of denaturalization, T1ρ mapping could differentiate between normal and mild denaturalization (p<0.05), but T2 mapping could not. However, there were no significant differences between the two mappings in the discrimination of mild versus moderate denaturalization or of moderate versus severe denaturalization. The two observers showed good agreement in the results (intraclass correlation coefficient=0.81 for T1ρ and 0.92 for T2).

Conclusion: T1ρ mapping is superior to T2 mapping for the evaluation of denatured articular cartilage with osteoarthritis of the knee.