Xiaoke Wang1,2, Diego Hernando1,3, Scott B Reeder1,2,3,4,5. 1. Department of Radiology, University of Wisconsin, Madison, Wisconsin. 2. Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin. 3. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin. 4. Department of Medicine, University of Wisconsin, Madison, Wisconsin. 5. Department of Emergency Medicine, University of Wisconsin, Madison, Wisconsin.
Abstract
PURPOSE: Transverse relaxation time (T2 ) mapping with MRI has a plethora of clinical and research applications. Current T2 mapping techniques are based primarily on spin-echo (SE) relaxometry strategies that rely on the signal magnitude, and often suffer from lengthy acquisition times. In this work, we propose a phase-based T2 mapping technique where T2 information is encoded into the signal phase of rapid gradient echo (GRE) acquisitions. THEORY: Bloch equation simulations demonstrate that the phase of GRE acquisitions obtained with a very small inter-repetition RF phase increment has a strong monotonic dependence on T2 , resulting from coherent transverse magnetization. This T2 -dependent phase behavior forms the basis of the proposed T2 mapping technique. To isolate T2 -dependent phase from background phase, at least 2 data sets with different RF phase increments are acquired. The proposed method can also be combined with chemical shift encoded MRI to separate water and fat signals. METHODS: The feasibility of the proposed technique was validated in a phantom experiment. In vivo feasibility was demonstrated in the brain, knee, abdomen, and pelvis. Comparisons were made with SE-based T2 mapping, spectroscopy, and T2 values from the literature. RESULTS: The proposed method produced accurate T2 maps compared with SE-based T2 mapping in the phantom. Good qualitative agreement was observed in vivo between the proposed method and the reference. T2 measured in various anatomies agreed well with values reported in the literature. CONCLUSION: A phase-based T2 mapping technique was developed and its feasibility demonstrated in phantoms and in vivo.
PURPOSE: Transverse relaxation time (T2 ) mapping with MRI has a plethora of clinical and research applications. Current T2 mapping techniques are based primarily on spin-echo (SE) relaxometry strategies that rely on the signal magnitude, and often suffer from lengthy acquisition times. In this work, we propose a phase-based T2 mapping technique where T2 information is encoded into the signal phase of rapid gradient echo (GRE) acquisitions. THEORY: Bloch equation simulations demonstrate that the phase of GRE acquisitions obtained with a very small inter-repetition RF phase increment has a strong monotonic dependence on T2 , resulting from coherent transverse magnetization. This T2 -dependent phase behavior forms the basis of the proposed T2 mapping technique. To isolate T2 -dependent phase from background phase, at least 2 data sets with different RF phase increments are acquired. The proposed method can also be combined with chemical shift encoded MRI to separate water and fat signals. METHODS: The feasibility of the proposed technique was validated in a phantom experiment. In vivo feasibility was demonstrated in the brain, knee, abdomen, and pelvis. Comparisons were made with SE-based T2 mapping, spectroscopy, and T2 values from the literature. RESULTS: The proposed method produced accurate T2 maps compared with SE-based T2 mapping in the phantom. Good qualitative agreement was observed in vivo between the proposed method and the reference. T2 measured in various anatomies agreed well with values reported in the literature. CONCLUSION: A phase-based T2 mapping technique was developed and its feasibility demonstrated in phantoms and in vivo.
Authors: Ryan S Dolan; Amir A Rahsepar; Julie Blaisdell; Kenichiro Suwa; Kambiz Ghafourian; Jane E Wilcox; Sadiya S Khan; Esther E Vorovich; Jonathan D Rich; Allen S Anderson; Clyde W Yancy; Jeremy D Collins; James C Carr; Michael Markl Journal: JACC Cardiovasc Imaging Date: 2019-03-13
Authors: Houchun Harry Hu; Peter Börnert; Diego Hernando; Peter Kellman; Jingfei Ma; Scott Reeder; Claude Sirlin Journal: Magn Reson Med Date: 2012-06-12 Impact factor: 4.668
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