MRI image plane nonuniformity in evaluation of ferrous sulphate dosimeter gel (FeGel) by means of T1-relaxation time |
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| Authors: | Magnusson P Bäck S A Olsson L E |
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| Institution: | 1. Cleveland Clinic, Cleveland OH;2. Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC;3. Duke Clinical Research Institute, Durham, NC;4. Saint Luke''s Mid America Heart Institute/University of Missouri- Kansas City, Kansas City, MO;5. Novartis Pharmaceuticals Corporation, East Hanover, NJ;6. Department of Medicine, University of Mississippi Medical Center, Jackson, MS;7. Mended Hearts, Huntsville, AL;8. Ronald Reagan UCLA Medical Center, Los Angeles, CA;1. School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 10083, China;2. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China;3. Department of Vascular Surgery, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100037, China;2. Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada;3. School of Life Sciences, Anhui University, Hefei, People''s Republic of China;1. School of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, China;2. Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China;3. Department of Systems and Computer Engineering, Carleton University, Ottawa, ON KIS 5B6, Canada |
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| Abstract: | MR image nonuniformity can vary significantly with the spin-echo pulse sequence repetition time. When MR images with different nonuniformity shapes are used in a T1-calculation the resulting T1-image becomes nonuniform. As shown in this work the uniformity TR-dependence of the spin-echo pulse sequence is a critical property for T1 measurements in general and for ferrous sulfate dosimeter gel (FeGel) applications in particular. The purpose was to study the characteristics of the MR image plane nonuniformity in FeGel evaluation. This included studies of the possibility of decreasing nonuniformities by selecting uniformity optimized repetition times, studies of the transmitted and received RF-fields and studies of the effectiveness of the correction methods background subtraction and quotient correction. A pronounced MR image nonuniformity variation with repetition and T1 relaxation time was observed, and was found to originate from nonuniform RF-transmission in combination with the inherent differences in T1 relaxation for different repetition times. The T1 calculation itself, the uniformity optimized repetition times, nor none of the correction methods studied could sufficiently correct the nonuniformities observed in the T1 images. The nonuniformities were found to vary considerably less with inversion time for the inversion-recovery pulse sequence, than with repetition time for the spin-echo pulse sequence, resulting in considerably lower T1 image nonuniformity levels. |
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