High fidelity magnetic resonance imaging by frequency sweep encoding and Fourier decoding.
Using a RF pulse with linear frequency sweep and a simultaneous encoding gradient, magnetization is sequentially excited accompanied by a quadratic phase profile. This quadratic dependence of magnetization phase on position dephases magnetization away from its vertices, allowing direct spatial encoding and image formation in the time domain. In this work, we show that Fourier decoding or least square fitting in combination with frequency sweep spatial encoding schemes can generate high fidelity images and we also extend spatial encoding to include nonlinear frequency sweep. Application to in vivo multiscan susceptibility-weighted imaging is demonstrated. Our results show that Fourier-decoded, spatially encoded images compare favorably with conventional high resolution images while preserving the unique features of sequential excitation.
Shen
Jun
J
Molecular Imaging Branch, National Institute of Mental Health Intramural Research Program, NIH, Bethedsa, MD 20892-1527, USA. shenj@intra.nimh.nih.gov
Xiang
Yun
Y
D000465:Algorithms; D000818:Animals; D001921:Brain / Q000033:anatomy & histology*; D005583:Fourier Analysis; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted