The comparison of the performance of 3 T and 7 T T mapping for untreated low-grade cartilage lesions.

Objective: To investigate T mapping as a possible marker for low-grade human articular cartilage lesions during a one-year follow-up, possible changes during the follow-up and compare the reliability and sensitivity of these measurements on high-field (3 T) and ultra-high-field (7 T) MRI scanners.

Design: Twenty-one patients with femoral, tibial and patellar cartilage defect in the knee joint participated in the study. The MRI protocol consisted of morphological, as well as three-dimensional triple-echo steady-state (3D-TESS) T mapping sequences with similar parameters at 3T and 7T. Patients were scanned at five time-points up to 12 months. T values were evaluated in the lesion and healthy-appearing regions for superficial and deep cartilage zone. The repeated ANOVA was used to determine differences in T values at various time points.

Results: A significant decrease in T values was observed between baseline and six months in the superficial layer of the lesion in patients at 3 T (decrease from 41.89 ± 9.3 ms to 31.21 ± 7.2 ms, which is a difference of -5.67 ± 2.2 ms (p = 0.031)), and at 12 months in the superficial layer of the lesion in patients at 3 T (decrease from 41.89 ± 9.3 ms to 35.28 ± 4.9 ms, which is a difference of -6.60 ± 4.4 ms (p = 0.044). No significant differences were recorded at 7 T.

Conclusion: The change in T values acquired with 3 T 3D-TESS appears to be reflecting subtle changes of cartilage composition in the course of low-grade lesion development. 7 T T mapping does not reflect these changes probably due to completely decayed short T component.