Quantitative T2 mapping during follow‐up after matrix‐associated autologous chondrocyte transplantation (MACT): Full‐thickness and zonal evaluation to visualize the maturation of cartilage repair tissue

Abstract

The purpose of this article was to evaluate the potential of in vivo zonal T2-mapping as a noninvasive tool in the longitudinal visualization of cartilage repair tissue maturation after matrix-associated autologous chondrocyte transplantation (MACT). Fifteen patients were treated with MACT and evaluated cross-sectionally, with a baseline MRI at a follow-up of 19.7 AE 12.1 months after cartilage transplantation surgery of the knee. In the same 15 patients, 12 months later (31.7 AE 12.0 months after surgery), a longitudinal 1-year followup MRI was obtained. MRI was performed on a 3 Tesla MR scanner; morphological evaluation was performed using a double-echo steadystate sequence; T2 maps were calculated from a multiecho, spin-echo sequence. Quantitative mean (full-thickness) and zonal (deep and superficial) T2 values were calculated in the cartilage repair area and in control cartilage sites. A statistical analysis of variance was performed. Full-tickness T2 values showed no significant difference between sites of healthy cartilage and cartilage repair tissue (p < 0.05). Using zonal T2 evaluation, healthy cartilage showed a significant increase from the deep to superficial cartilage layers (p < 0.05). Cartilage repair tissue after MACT showed no significant zonal increase from deep to superficial cartilage areas during baseline MRI (p > 0.05); however, during the 1-year follow-up, a significant zonal stratification could be observed (p < 0.05). Morphological evaluation showed no significant difference between the baseline and the 1-year follow-up MRI. T2 mapping seems to be more sensitive in revealing changes in the repair tissue compared to morphological MRI. In vivo zonal T2 assessment may be sensitive enough to characterize the maturation of cartilage repair tissue. ß

Biochemical (T2, T2* and magnetisation transfer ratio) MRI of knee cartilage: feasibility at ultra-high field (7T) compared with high field (3T) strength

“…The basis of the stratification of T2 values becomes obvious when considering in vitro studies on articular cartilage, suggesting that the appearance of T2 relaxation times is strongly influenced by the anisotropic arrangement of the collagen fibres and by their orientation to the main magnetic field [13][14][15]. The importance of considering the stratification of T2 values from the subchondral border to the cartilage surface has already been noted by many in vivo studies [16][17][18][19]. Smith and coworkers [17] reported a zonal stratification in the patella, with a maximum of 33% at 3 Tesla, which falls between our findings at 3T and 7T.…”

Longitudinal analysis of MRI T2 knee cartilage laminar organization in a subset of patients from the osteoarthritis initiative

“…In recent studies of knee cartilage repair tissue by Welsch et al (13,18), the authors reported a gradual recovery of cartilage T 2 zonal variation after surgery. Furthermore, the authors reported that differences between healthy cartilage and cartilage repair tissue were most obvious within the deep cartilage layer for both the PAT and the MFC (18).…”

Image interpolation improves the zonal analysis of cartilage T2 relaxation in MRI

“…With the improvement of clinical MRI technology, resolving cartilage thickness in 2-4 or more pixels becomes possible for quantitative human MRI (39). Consequently, these pixels of equal size could be used to represent different depths of cartilage (40,41). This type of depth-dependent regional analysis is superior to the bulk analysis, since a regional analysis separates the different characteristics between surface and deep cartilage.…”