MR Relaxometry of Indiana Limestone rock core

MR microscopy may provide essential information about the structure and dynamics of porous systems. One of the advantages compared to human or preclinical MR systems is that it may achieve higher resolutions, stronger gradient strengths and shorter echo times due to the smaller dimensions of hardware as well as the sample. 

In this work, a rock core sample of Indiana Limestone is embedded in H2O and imaged using an 400MHz Avance Neo Bruker system with a micro5 imaging probe. The sequence used for the results highlighted in Fig. 1 was a Multi Slice Multi Echo vtr (MSME) sequence, with a varying repetition time between TR = 200-7500 ms and a varying echo time between TE = 2.8-22.4 ms. Other experimental parameters include FOV = 6 x 6 mm2, resolution = 47 x 47 um2 (in-plane), a slice thickness of 500 μm and a total of four averages.

Figure 1 highlights the raw data acquired in this work with a variable TE on the x-axis and a variable TR on the y-axis. Figure 2 shows the signal intensity of H2O in the rock core with a fixed TE = 2.8 ms and a variable TR whereas Figure 3 shows the signal intensity of H2O in the rock core with a fixed TR = 7500 ms and a variable TE. A least squares fit procedure on the data shown in Figures 2-3 allows for the extraction of the signal intensity S0 and the longitudinal (T1) and transverse (T2) relaxation times. Figure 4 reveals the signal intensity S0 resulted from the variable TR data (left) and variable TE (right), and shows the internal structure of the rock core. Figure 5 shows the longitudinal (T1) and transverse (T2) relaxation times resulted from the fit.