Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
J Magn Reson. 2012 Feb;215:64-73. doi: 10.1016/j.jmr.2011.12.011. Epub 2011 Dec 27.
Chemical Exchange Saturation Transfer (CEST) contrast utilizes selective pre-saturation of a small pool of exchanging protons and subsequent detection of the decrease in bulk water signal. The CEST contrast is negative and requires detection of small signal change in the presence of a strong background signal. Here we develop a Positive CEST (pCEST) detection scheme utilizing the analogous nature of the CEST and off-resonance T(1)(ρ) experiments and exploring increased apparent relaxation rates in the presence of the selective pre-saturation. pCEST leads to the positive contrast, i.e., increased signal intensity as the result of the presence of the agent and RF pre-saturation. Simultaneously substantial background suppression is achieved. The contrast can be switched "ON" and "OFF", similar to the original CEST.
化学交换饱和转移（CEST）对比利用小部分交换质子的选择性预饱和，并随后检测体相水信号的减少。CEST 对比为负对比，需要在强背景信号存在的情况下检测小信号变化。在这里，我们开发了一种正 CEST（pCEST）检测方案，利用 CEST 和离共振 T(1)(ρ)实验的类似性质，并探索了在选择性预饱和存在下的表观弛豫率的增加。pCEST 导致正对比，即由于试剂和 RF 预饱和的存在而导致信号强度增加。同时实现了显著的背景抑制。该对比可以像原始 CEST 一样“开启”和“关闭”。
