Low-field one-dimensional and direction-dependent relaxation imaging of bovine articular cartilage

Feasibility of high-resolution one-dimensional relaxation imaging at low magnetic field using a single-sided NMR scanner applied to articular cartilage

“…As has been discussed in [23] the longitudinal relaxation time T 1 shows a significant variation across the cartilage tissue when measured at low magnetic field strengths, i.e. well below 1 T.…”

“…The number of echoes was chosen to obtain a sufficient averaging and to ignore contributions from times when the signal has decayed significantly. When curved samples with a depth-dependent relaxation time profile, such as the cartilage cores used in [23], are measured using a single-sided NMR profiler, averaging processes necessarily occur. This happens due to the horizontally aligned finite sensitive volume, which is moved through the sample and therefore collects signals from different spatial positions inside the volume.…”

“…In the same way as described above, averaging calculations were carried out on T 1 relaxation profiles as they typically occur in cartilage profiling experiments at the corresponding field strength, see Fig. 7a: an initial increase of T 1 is followed by a gradual decrease towards the cartilage/bone interface (see [23] for comparison). The percentage deviation plot in Fig.…”

“…Different aspects of low-field and high-field cartilage imaging are reviewed in [21,22]. Based on these findings, it could be shown in [23] that advantage can be taken of the increased contrast of the longitudinal relaxation rate towards lower Larmor frequencies in bovine articular cartilage. In particular the values of T 2 and T 1 at 0.27 T across the tissues were shown to vary by up to 250 % and 400 %, respectively.…”

NMR dispersion investigations of enzymatically degraded bovine articular cartilage

“…Nevertheless, it has been shown to be the most promising parameter for assessing tissue properties . In a previous work, it was demonstrated that the contrast of T 1 becomes much more pronounced when the experiments are carried out at field strengths well below 1T ; in that work, spatially resolved data at 0.27 Tesla (T) and averaged relaxation times down to 0.2 mT were shown. The variation induced by addition of the standard contrast agent Gd(DTPA) 2− , however, becomes less pronounced toward very low fields; a similar observation was made for frequency‐dependent T 1ρ .…”