Robitaille P M, Merkle H, Sublett E, Hendrich K, Lew B, Path G, From A H, Bache R J, Garwood M, Uğurbil K
Department of Biochemistry, University of Minnesota, Navarre 55392.
Magn Reson Med. 1989 Apr;10(1):14-37. doi: 10.1002/mrm.1910100103.
Adiabatic pulses have been employed in spectroscopic imaging and relaxation rate measurements at 4.7 T to demonstrate the feasibility of obtaining spectroscopic data from the complete sensitive volume of a surface coil using the surface coil as a transmitter and receiver. With conventional B1 sensitive pulses, spectroscopic localization or imaging techniques, such as chemical-shift imaging, yield resonance intensities that are distorted severely as a function of space, and maximal signal is detected from a small region within the complete sensitive volume of the coil. With adiabatic pulses, however, this problem is eliminated completely. In addition, a new method of spatial localization is introduced. This method, referred to as FLAX-ISIS, is a derivative of longitudinally modulated Fourier series window and ISIS approaches and utilizes adiabatic inversion and excitation pulses. The method allows construction of localized spectra for multiple regions along the surface coil axis by postacquisition data manipulation of a single set of free induction decays. These techniques were applied to the study of the myocardium using an implanted surface coil in an instrumented closed-chest canine model and in an open-chest preparation. The results demonstrate that one-dimensional techniques are adequate for transmural detection of metabolites provided signal origin is restricted to a column perpendicular to the left ventricle wall.
绝热脉冲已用于4.7 T的光谱成像和弛豫率测量，以证明使用表面线圈作为发射器和接收器从表面线圈的整个敏感体积中获取光谱数据的可行性。使用传统的B1敏感脉冲、光谱定位或成像技术（如化学位移成像）时，共振强度会随着空间严重扭曲，并且在表面线圈的整个敏感体积内的一个小区域中检测到最大信号。然而，使用绝热脉冲时，这个问题被完全消除。此外，还引入了一种新的空间定位方法。这种方法称为FLAX-ISIS，是纵向调制傅里叶级数窗口和ISIS方法的衍生方法，并利用绝热反转和激发脉冲。该方法允许通过对一组自由感应衰减进行采集后数据处理，为沿表面线圈轴的多个区域构建局部光谱。这些技术被应用于在仪器化的闭胸犬模型和开胸准备中使用植入的表面线圈对心肌进行研究。结果表明，如果信号源限制在垂直于左心室壁的圆柱体内，一维技术足以进行代谢物的透壁检测。
