Three-Dimensional T1rho Using Spiral Fast Spin Echo

Liver fibrosis is the main feature in early chronic liver diseases. If identified early, liver fibrosis is reversible. The current gold standard for diagnosing liver fibrosis is invasive liver biopsy. Existing non-invasive methods still have significant limitations. T1rho imaging is a promising non-invasive technology evaluating liver fibrosis. It does not require exogenous contrast agent or extra hardware. However, it remains challenging to perform T1rho measurements of the liver. The rich blood signal in the liver introduces quantification errors of liver parenchyma. The existing black blood MRI technologies are based on Cartesian FSE acquisitions, which are not optimal for liver imaging. The residual blood signal is often observed which confounds the measurement. Current T1rho measurement of the liver is mostly performed in two-dimension. 3D coverage of liver is desirable. However, 3D T1rho imaging of liver suffers from long scan time due to increased spatial coverage, reduced scan time efficiency from motion compensation, and high specific absorption rate (SAR). The investigators aim to overcome these challenges by developing 3D T1rho imaging technologies based on magnetization prepared spiral FSE acquisition. Compared to Cartesian FSE, Spiral FSE traverses k-space more efficiently per unit of time, and has reduced SAR due to significantly decreased number of radiofrequency pulses in the echo trains. Spiral acquisition has zero gradient moment at the kspace center, which substantially reduces its sensitivity to respiratory motion. The residual motion manifests as benign incoherent artifacts in the image domain rather than detrimental structured artifacts. Differently to Cartesian FSE, Spiral FSE provides flexibility to design and optimize flow-sensitizing gradients throughout the echo trains to achieve superior suppression of blood signal. The investigators will evaluate the proposed pulse sequences in both healthy controls and patients with liver fibrosis. This project will provide new black blood imaging technologies and a 3D diagnostic tool for early detection of liver fibrosis. This will improve clinical outcomes for patients with chronic liver disease, and provide a springboard for further development of MRI technology for other purposes.