On- and off-resonance spin-lock MR imaging of normal human brain at 0.1 T: possibilities to modify image contrast |
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Authors: | Usama Abo Ramadan,Antti T Markkola,Juha Halavaara,Jukka Tanttu,Anna-Maija Hä kkinen,Hannu J Aronen |
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Affiliation: | *Department of Radiology, Helsinki University Central Hospital, Helsinki, Finland †Department of Physics, University of Helsinki, Helsinki, Finland ‡Picker Nordstar, Inc., Finland §Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland ¶Department of Clinical Radiology, Kuopio University Hospital, Finland |
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Abstract: | The aim of the present investigation was to determine spin lock (SL) relaxation parameters for the normal brain tissues and thus, to provide basis for optimizing the imaging contrast at 0.1 T. 68 healthy volunteers were included. On-resonance spin lock relaxation time (T1ρ) and off-resonance spin lock relaxation parameters (T1ρoff, Me/Mo), MT parameters (T1sat, Ms/Mo), and T1, T2 were determined for the cortical gray matter, and for the frontal and parietal white matters. The T1ρ for the frontal and parietal white matters ranged from 110 to 133 ms and from 122 to 155 ms with locking field strengths from 50 μT to 250 μT, respectively. Accordingly, the values for the gray matter ranged from 127 to 155 ms. With a locking field strength of 50 μT, T1ρoff for the frontal and parietal white matters were from 114 to 217 ms and from 126 to 219 ms, and for the gray matter from 136 to 267 ms with the angle between the effective magnetic field (Beff) and the z-axis (θ) ranging from 60° to 15°, respectively. The T1ρ of the white and gray matters increased significantly with increasing locking field amplitude (p < 0.001). The T1ρoff decreased significantly with increasing θ (p < 0.001). T1ρ and T1ρoff with θ ≥ 30° were statistically significantly shorter in the frontal than in the parietal white matters (p < 0.05). The duration, amplitude and θ of the locking pulse provide additional parameters to optimize contrast in brain SL imaging. |
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Keywords: | On-resonance spin lock Off-resonance spin lock MT Brain |
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