Systematized water content calculation in cartilage using T1-mapping MR estimations: design and validation of a mathematical model

Abstract

BackgroundUp to 80 % of cartilage is water; the rest is collagen fibers and proteoglycans. Magnetic resonance (MR) T1-weighted measurements can be employed to calculate the water content of a tissue using T1 mapping. In this study, a method that translates T1 values into water content data was tested statistically.Materials and methodsTo develop a predictive equation, T1 values were obtained for tissue-mimicking gelatin samples. 1.5 T MRI was performed using inverse angle phase and an inverse sequence at 37 (±0.5) °C. Regions of interest were manually delineated and the mean T1 value was estimated in arbitrary units. Data were collected and modeled using linear regression. To validate the method, articular cartilage from six healthy pigs was used. The experiment was conducted in accordance with the Danish Animal Experiment Committee. Double measurements were performed for each animal. Ex vivo, all water in the tissue was extracted by lyophilization, thus allowing the volume of water to be measured. This was then compared with the predicted water content via Lin’s concordance correlation coefficient at the 95 % confidence level.ResultsThe mathematical model was highly significant when compared to a null model (p < 0.0001). 97.3 % of the variation in water content can be explained by absolute T1 values. Percentage water content could be predicted as 0.476 + (T1 value) × 0.000193 × 100 %. We found that there was 98 % concordance between the actual and predicted water contents.ConclusionThe results of this study demonstrate that MR data can be used to predict percentage water contents of cartilage samples.Level of evidence3 (case-control study).

Autologous cartilage and fibrin sealant may be superior to conventional fat grafting in preventing physeal bone bridge formation – a pilot study in porcines

“…Less water in the gap indicates formation of bone or at least decreased cartilage and physeal health as cartilage is mainly composed of water. 11 The combined findings in the histological analysis and on MRI, including water content quantification, suggest that autologous cartilage chips in combination with Tisseel ® may be suitable in preventing bone bridges after physeal injuries in the distal femur.…”

“…T1 and T2-weighted 3D sequences were carried out in addition to T1-weighted quantitative water content sequences. 11 Presence and absence of a bone bridge was determined on MRI.…”

“…Water content was calculated using the software Siswin v.0.9. 11 A gap ratio (GR) was determined to assess the water content at the injury site in comparison to the totalphysis.…”

MR fingerprinting for rapid simultaneous T1, T2, and T1ρ relaxation mapping of the human articular cartilage at 3T

“…More specifically, early‐stage OA is associated with loss of proteoglycans, an increase in water content, and changes in the structure of collagen fibers 2 . Yao et al 8 showed the sensitivity of T 1 and T 2 relaxation to early‐stage OA, and it has been shown that T 1 mapping can be used to calculate the water content of the cartilage 9 . In addition to the longitudinal T 1 8 and transverse T 2 relaxation times, 8 the spin‐lattice relaxation in the rotating frame ( T 1 ρ ) can be used to quantify the biochemical changes in cartilage 2,7,10‐12 .…”

“…2 Yao et al 8 showed the sensitivity of T 1 and T 2 relaxation to early-stage OA, and it has been shown that T 1 mapping can be used to calculate the water content of the cartilage. 9 In addition to the longitudinal T 1 8 and transverse T 2 relaxation times, 8 the spin-lattice relaxation in the rotating frame (T 1ρ ) can be used to quantify the biochemical changes in cartilage. 2,7,[10][11][12] Both T 1ρ and T 2 have been consistently reported to be elevated with enzymatic cartilage degradation.…”