Marcus Raudner^{1}, Markus Schreiner^{1,2}, Tom Hilbert^{3,4,5}, Tobias Kober^{3,4,5}, Vladimir Juras^{6}, Claudia Kronnerwetter^{6}, David Stelzeneder^{2}, and Siegfried Trattnig^{1}

Even though the measurement of T2 relaxation time is one of the most widespread available assets of quantitative MRI in clinical routine, it is left with untapped potential as the required scan time is too long. GRAPPATINI is a model-based iterative algorithm reconstructing T2 maps and T2-weighted images from highly-undersampled k-space data. The aim of this study was to compare the quantitative results of an established standard method with this novel technique in the intervertebral disc with the additional benefit of GRAPPATINI to simulate T2w contrasts at arbitrarily chosen echo times.

**Introduction**

**Methods**

**Results**

**Discussion**

This preliminary data from an ongoing study suggests that a quantitative disc assessment using GRAPPATINI is accurate, feasible and coherent when directly compared with established CPMG methods. GRAPPATINI enables T2 relaxation time measurement in less than a fifth of the scan time compared to a conventional CPMG sequence with twofold GRAPPA acceleration.

A direct comparison with the standard method showed good coherence as seen in Figure 5.

**Conclusion**

- Blumenkrantz, G. et al. In vivo 3.0-tesla magnetic resonance T1rho and T2 relaxation mapping in subjects with intervertebral disc degeneration and clinical symptoms. Magn Reson Med 63, 1193–1200 (2010).
- Marinelli, N. L., Haughton, V. M., Munoz, A. & Anderson, P. A. T2 relaxation times of intervertebral disc tissue correlated with water content and proteoglycan content. Spine (Phila Pa 1976) 34, 520–524 (2009).
- Sumpf, T. J., Uecker, M., Boretius, S. & Frahm, J. Model-based nonlinear inverse reconstruction for T2 mapping using highly undersampled spin-echo MRI. J. Magn. Reson. Imaging 34, 420–428 (2011).
- Galley, J., Maestretti, G., Koch, G. & Hoogewoud, H. M. Real T1 relaxation time measurement and diurnal variation analysis of intervertebral discs in a healthy population of 50 volunteers. Eur. J. Radiol. 87, 13–19 (2017).
- Marcus Raudner, Tom Hilbert, Tobias Kober, Vladimir Juras, Ewald Moser, Claudia Kronnerwetter, David Stelzeneder, S. T. GRAPPATINI put to use: How MSK applications benefit from highly undersampled T2 mapping and synthetic contrasts. Proc. Intl. Soc. Mag. Reson. Med. 25 25, 5090 (2017).

Figure 1 - Overview of mean nucleus pulposus T2 values in
sagittal and axial plane view with the three sampling and reconstruction
methods compared. Error bars are indicating the standard deviation of T2
values.

Figure 2 - Left: Sagittal T2w image with a TE of 109 ms
with color-coded T2 overlay from CPMG data.
Right: Synthetic sagittal T2w morphological contrast based on
GRAPPATINI-sampled model data rendered at TE = 109 ms with color-coded T2 overlay
from GRAPPATINI T2 map.

Figure 3 - Overview of mean nucleus pulposus T2 values in
sagittal and axial plane view with the three sampling and reconstruction
methods compared. Error bars are indicating the standard deviation of T2
values.

Figure 4 – Comparison of nucleus pulposus T2 values of
healthy and degenerated discs showing clear discriminability of healthy and impaired
tissue using T2 relaxation time measurement.

Figure 5 - Bland-Altmann plot comparing GRAPPATINI and
CPMG with only even echoes depicting a very homogeneous and statistically
insignifant deviation (p = .146)