Assessing the Extent of Diffuse Liver Disease: Quality Assurance of Magnetic Resonance Elastography (MRE)

Sammanfattning: The mechanical properties of liver tissue such as stiffness are closely correlated with various diseases. Magnetic resonance elastography (MRE) aims at estimating these mechanical properties by imaging the waves induced by an external driver in the liver. Due to its promising ability to non-invasively diagnose and monitor the progression of disease, different methods to reduce technical limitations has been developed over the last years. This includes the use of newer MRE sequences, the capability of 3D MRE and different techniques of generating mechanical excitation in the liver tissue. Since there are different acquisition methods available it is of importance, from both a clinical as well as a research perspective, to have a reliable way of assuring the quality of the measurements. Therefore, this project investigates the image quality as well as the reproducibility of the mechanical properties for different systems and settings. This was done by analyzing 3D MRE measurements of 155 patients and 19 healthy volunteers from research studies at The University Hospital of Linköping. Additional data were collected to further evaluate reproducibility. These were taken on the same volunteer using different hardware, wave amplitudes and pulse sequences at 1.5 and 3 T. The different acquisition methods were shown to produce comparable measurements of the mechanical properties of the liver. However, further investigation would be of interest, namely due to a discrepancy between a clinical system with a 2D-GRE sequence and the corresponding research systems. It was also found that the values of the mechanical properties all increase with frequency with the exception for the attenuation of the waves. Furthermore, by using quality parameters in the software KIR, a method for determining when measurements using 3D MRE does not have sufficient image quality was implemented. This work paves the way for further development of methods to ensure the quality when assessing the extent of diffuse liver disease.