27 February 2009 Improved T1 mapping by motion correction and template based B1 correction in 3T MRI brain studies
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Accurate estimation of relaxation time T1 from MRI images is increasingly important for some clinical applications. Low noise, high resolution, fast and accurate T1 maps from MRI images of the brain can be performed using a dual flip angle method. However, accuracy is limited by the scanners ability to deliver the prescribed flip angle due to the B1 inhomogeneity, particularly at high field strengths (e.g. 3T). One of the most accurate methods to correct that inhomogeneity is to acquire a subject-specific B1 map. However, since B1 map acquisition takes up precious scanning time and most retrospective studies do not have B1 map, it would be desirable to perform that correction from a template. For this work a dual repetition time method was used for B1 map acquisition in five normal subjects. Inaccuracies due to misregistration of acquired T1-weighted images were corrected by rigid registration, and the effects of misalignment were compared to those of B1 inhomogeneity. T1-intensity histograms were produced and three-Gaussian curves were fitted for every fully-, partially- and non-corrected histogram in order to estimate and compare the white and gray matter peaks. In addition, in order to reduce the scanning time we designed a template based correction strategy. Images from different subjects were aligned using a twelve-parameter affine registration, and B1 maps were aligned according to that transformation. Recomputed T1 maps showed a significant improvement with respect to non-corrected ones. These results are very promising and have the potential for clinical application.
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Marcelo A. Castro, Marcelo A. Castro, Jianhua Yao, Jianhua Yao, Christabel Lee, Christabel Lee, Yuxi Pang, Yuxi Pang, Eva Baker, Eva Baker, John Butman, John Butman, David Thomasson, David Thomasson, } "Improved T1 mapping by motion correction and template based B1 correction in 3T MRI brain studies", Proc. SPIE 7262, Medical Imaging 2009: Biomedical Applications in Molecular, Structural, and Functional Imaging, 726202 (27 February 2009); doi: 10.1117/12.811180; https://doi.org/10.1117/12.811180

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