Comparison between RF spoiling schemes in the Actual Flip-angle Imaging (AFI) sequence for fast B1 mapping
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چکیده
Fig. 3. Simulated dependences of the measured flip angle on φ0 in the weak (a) and strong (b-d) spoiling regimes for n=5 (a,b: parameters from Fig. 2); n=4 (c: TR1/TR2=20/80 ms, AG1/AG2= 204/816 mT·ms/m); and n=3 (d: TR1/TR2=20/60 ms, AG1/AG2=255/765 mT·ms/m). Black and gray lines correspond to the standard (1,2) and modified (3) RF spoiling schemes. For plots (b-d), the constant spoiler area is maintained through the AFI repetition period, AG1+AG2=1020 mT·ms/m. Fig. 2. Simulated dependences of signals S1 (black) and S2 (gray) on the phase increment φ0 for the standard (1,2) (a,c) and modified (3) (b,d) RF phase incrementing schemes in the weak (a,b) and strong (c,d) spoiling regimes (AG1/AG2=17/85 and 170/850 mT·ms/m, respectively). Other simulation parameters were T1/T2=2000/2000 ms, D=2.2x10 mm/s, TR1/TR2=20/100 ms (n=5), and α=60°. Comparison between RF spoiling schemes in the Actual Flip-angle Imaging (AFI) sequence for fast B1 mapping
منابع مشابه
On the steady-state properties of actual flip angle imaging (AFI).
AFI (actual flip angle imaging) represents an interesting approach to map the B(1) transmit fields by measuring the spatial variations of the effective flip angle. However, the accuracy of the technique relies on the adequate spoiling of transverse magnetization. In the present work configuration theory was employed to develop a proper RF and gradient spoiling scheme for the AFI technique, maki...
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