MRS所需的信号的激发、空间定位、探测采集等技术上均与MRI类似，但其最终的表现形式不同。MRS是将按时间域（Time domain）分布的函数转换为按频率域（Frequencydomain）分布的谱线。
·Same physical principles: Excitation, refocussing,relaxation mechanisms
·Difference: In imaging, the signal ofhydrogen nuclei in water molecules is measured, because of its very highnatural abundance. Two protons, fully equivalent to each other, give rise toone resonance frequency. In spectro, one wants to acquire signal of protonsin molecules, other than water.
·Uniqueresonance frequency, to be explained later on in this presentation
w0为拉莫尔进动频率，g为磁旋比，取决于质子本身的性质，对于某一个质子来说是常说。
ω为角频率；f为线频率。
This FID is a mixture of the variousfrequencies, transmitted by the tissue under investigation. A Fourier Transformis a mathematical technique that transforms the signal out of the time domainto a signal in the frequency domain. After FT, it’s possible to recognize thevarious frequencies that were present in the FID.
Nucleus surrounded by electrons, causingthe proton to experience a somewhat lower magnetic field. Configuration ofelectrons is different for the various molecules, so is the experienced B0,meaning that the same nucleus (1H for example) will have different resonancefrequency, depending on molecular environment.
Placing a molecule in a magnetic fieldcauses its electrons to circulate. In circulating, these electrons generatesecondary induced magnetic fields. Circulation of electrons around the protonitself always induces a field that opposes to the applied field. This processdiminishes the local field experienced by the proton, and the proton is said tobe shielded.
Conversely,circulation of electrons around nearby nuclei may generate fields that mayeither oppose or reinforce the proton's local field. If the induced fieldreinforces the applied field, however, the local field experienced by theproton is augmented, and the proton is said to be deshielded.
Consider the water molecule H2O and the ethanol, CH3-CH2-OH.The hydrogen nuclei (protons) in the water have a different chemical shift thanthose in the ethanol. But even the protons in the CH3- group have a different chemical shiftfrom those in the -CH2- group and again different from those inthe -OH group.
如果不进行水抑制的话，水的共振峰会掩盖其他浓度弱得多的分子中氢原子产生的信号。
MRS所需的信号的激发、空间定位、探测采集等技术上均与MRI类似，但其最终的表现形式不同。MRS是将按时间域（Time domain）分布的函数转换为按频率域（Frequencydomain）分布的谱线。
·Same physical principles: Excitation, refocussing,relaxation mechanisms
·Difference: In imaging, the signal ofhydrogen nuclei in water molecules is measured, because of its very highnatural abundance. Two protons, fully equivalent to each other, give rise toone resonance frequency. In spectro, one wants to acquire signal of protonsin molecules, other than water.
·Uniqueresonance frequency, to be explained later on in this presentation
w0为拉莫尔进动频率，g为磁旋比，取决于质子本身的性质，对于某一个质子来说是常说。
ω为角频率；f为线频率。
This FID is a mixture of the variousfrequencies, transmitted by the tissue under investigation. A Fourier Transformis a mathematical technique that transforms the signal out of the time domainto a signal in the frequency domain. After FT, it’s possible to recognize thevarious frequencies that were present in the FID.
Nucleus surrounded by electrons, causingthe proton to experience a somewhat lower magnetic field. Configuration ofelectrons is different for the various molecules, so is the experienced B0,meaning that the same nucleus (1H for example) will have different resonancefrequency, depending on molecular environment.
Placing a molecule in a magnetic fieldcauses its electrons to circulate. In circulating, these electrons generatesecondary induced magnetic fields. Circulation of electrons around the protonitself always induces a field that opposes to the applied field. This processdiminishes the local field experienced by the proton, and the proton is said tobe shielded.
Conversely,circulation of electrons around nearby nuclei may generate fields that mayeither oppose or reinforce the proton's local field. If the induced fieldreinforces the applied field, however, the local field experienced by theproton is augmented, and the proton is said to be deshielded.
Consider the water molecule H2O and the ethanol, CH3-CH2-OH.The hydrogen nuclei (protons) in the water have a different chemical shift thanthose in the ethanol. But even the protons in the CH3- group have a different chemical shiftfrom those in the -CH2- group and again different from those inthe -OH group.
如果不进行水抑制的话，水的共振峰会掩盖其他浓度弱得多的分子中氢原子产生的信号。