0.5T Benchtop Magnet: Development of a MR Elastography Setup and Tissue Samples Characterization
thesisposted on 27.11.2018, 00:00 by Marco Andrea Zampini
Magnetic Resonance at low-intensity eld has been employed mainly for NMR spectroscopy even though low-intensity eld MRI scanners can be of small size and their use would allow lower artifacts impact, lower price and operational costs as well as lower SAR within very sensible samples. The present dissertation reports an analysis of both animal tissues samples and water-based solution carried out with a benchtop 0.5 T scanner. Relaxometry parameters were computed for liver and muscle samples and were found to be consistent with literature values and in agreement with an exponential model. Relaxation rates of liver (muscle) for T1 and T2 were 219+-3 ms (610+-8 ms) and 41+-1 ms (51+-1 ms), respectively. A custom-made di ffusion sequence was developed and measurements of ADC were carried out, and results suggest that a 20% gelatine could be useful as a liver and muscle phantom. Nevertheless, the sequence needs to be further improved in order to compensate for possible artifacts contributions. Muscle Mean Di ffusivity values along the three orthogonal directions respected the known anisotropic water motion behavior. Along with an MRI approach, a physical support for the piezoelectric actuator and an algorithm for the computation of the complex displacement maps from the MRE signal were created. The complex modulus for gelatine, liver and muscle samples was assessed: gelatine samples showed an increase of the average storage shear modulus with both frequency and also with higher concentration. Liver storage modulus ranged from 6.49+-1.53 to 19.67+-3.56 kPa in MEG frequency range between 500 and 2000 Hz, while muscle storage modulus was one order of magnitude higher with respect to both liver and gelatine samples.