Clinical high-resolution mapping of the proteoglycan-bound water fraction in articular cartilage of the human knee joint

Abstract

Purpose we applied a recently introduced method to achieve clinically-feasible in-vivo mapping of the proteoglycan water fraction (PgWF) of human knee cartilage with improved spatial resolution and stability as compared to existing methods. Material and Methods Multicomponent driven equilibrium single-pulse observation of T1 and T2 (mcDESPOT) datasets were acquired from the knees of two healthy young subjects and one older subject with previous knee injury. Each dataset was processed using Bayesian Monte Carlo (BMC) analysis incorporating a two-component tissue model. We assessed the performance and reproducibility of BMC and of the conventional analysis of stochastic region contraction (SRC) in the estimation of PgWF. Stability of the BMC analysis of PgWF was tested in two independent high-resolution (HR) datasets from each of the two young subjects. Results Unlike SRC, the BMC-derived maps from the two HR datasets were essentially identical. Furthermore, SRC maps showed substantial random variation in estimated PgWF, and mean values that differed from those obtained using BMC. In addition, PgWF maps derived from conventional low-resolution (LR) datasets exhibited partial volume and magnetic susceptibility effects. These artifacts were absent in HR PgWF images. Finally, our analysis showed regional variation in PgWF estimates, and substantially higher values in the younger subjects as compared to the older subject. Conclusions BMC-mcDESPOT permits HR in-vivo mapping of PgWF in human knee cartilage in a clinically-feasible acquisition time. HR mapping reduces the impact of partial volume and magnetic susceptibility artifacts compared to LR mapping. Finally, BMC-mcDESPOT demonstrated excellent reproducibility in the determination of PgWF.

T1ρ mapping of articular cartilage grafts after autologous osteochondral transplantation for osteochondral lesions of the talus: A longitudinal evaluation

“…Although there is an established association between T1ρ values and histologic features of cartilage, T1ρ is not specific to in vivo changes in proteoglycan content in humans, and changes in T1ρ can be due to various factors. Multi‐component analysis (MCA) has been shown to provide a sensitive and specific marker of change in the proteoglycan content of articular cartilage . The main advantage of using T1ρ instead of MCA to investigate restoration of the proteoglycan content after AOT was that extensive data from T1ρ MRI of both healthy knee cartilage and osteoarthritic cartilage are available.…”

Cartilage biomechanics: From the basic facts to the challenges of tissue engineering

“…Aggrecan is directly linked to hyaluronic acid (HA) or via the link protein and fills the space between collagen fibrils. The carboxyl and sulfate groups of carbohydrate chains bind cations and about 30% of the water in AC 31,32 . Biglycan, decorin and fibromodulin are small PGs present in the ECM that play a role in fibrillogenesis by interacting with COL II fibers 33–35 .…”

“…The carboxyl and sulfate groups of carbohydrate chains bind cations and about 30% of the water in AC. 31,32 Biglycan, decorin and fibromodulin are small PGs present in the ECM that play a role in fibrillogenesis by interacting with COL II fibers. [33][34][35] Biglycan and decorin, which are also found close to chondrocytes, participate in their anchoring in ECM by interacting directly with COL VI, and COL II fibers via matrilines 1 and 3.…”

Steady‐state double‐angle method for rapid B1 mapping

“…Quantitative determination of MR parameters is affected by inaccuracies in the RF flip angle (FA) such that accurate parameter estimation requires calibration of the RF transmit field, B 1 . This has become particularly problematic with the growing use of high‐field MRI systems because at high field the spatial inhomogeneity of B 1 is increased due to the smaller RF wavelength compared to sample size .…”