1、Hyperpolarized Instruments

The principle that enables researchers to generate hyperpolarization in gases (e.g. hyperpolarized ¹²⁹Xe or ³He) via spin exchange collisions. The collisions are mainly binary collisions that depend on thermal velocity at high pressures and also short-lived van der Waals interactions or three-body collisions that depend on the partial pressure at low pressure.

The basic structure diagram of the ¹²⁹Xe hyperpolarizer is shown above.  It features an optical cell used for optical pumping and spin-exchange collisions, collection system, gas supply system, vacuum system.  A computer is used for monitoring and controlling the process.

2、MRI Methods and Techniques for the Lung

Left image shows conventional proton MR image of lung.  The signal originates from the lung's H₂O content (about 10^22 hydrogen atoms).

Right image shows a hyperpolarized MR image of lung.  The signal originates from helium (³He) gas (about 10^10 atoms).

Lung diseases, especially lung cancer, are a major cause of human death.Thus, imaging techniques that can help identify the onset, type and grade of disease at an early stage is critical.  Lungs are normally imaged by x-ray techniques (2D and CT).  However, these techniques rely on ionizing radiation, which represents an additional health risk, and do not provide any information that can help assess the function of the lung. The latter is important because an accurate diagnosis should interrogate not only its structure, but whether or not the lung functions (e.g. ventilates) well.

Conventional MRI, based on the use of proton signal, can depict structure and function of brain and other organs, but cannot image lung.  This is because the lung consists of:

    1) much void space filled with air, which does not yield detectable signal, and

    2) its tissue is made of alveolae, which have a very low proton density and short relaxation times due to their porous structure.

In recent years, the technique of hyperpolarized nobles gas MRI has enabled amplifications of the NMR signal by orders of magnitude compared to that of thermal equilibrium.  This technique is an excellent tool for the study of lung by MRI and has excellent potential for the diagnosis of lung diseases by measuring associated changes in the lung's structure and function.

Our team develops NMR and MRI techniques based on hyperpolarized noble gases to quantify the changes in lung structure and function associated with various lung diseases.  This will, in turn, benefit the medical profession and public health by offering new possibilities for early and accurate diagnosis.

3、Hyperploarized Xenon Molecular Sensors and Molecular Imaging

Hyperpolarized ¹²⁹Xe MRI has emerged in recent years as one of the most powerful methods for molecular imaging with the development of molecular sensors based on xenon. Hyperpolarized 129Xe nuclei offer unprecedented sensitivity enhancement, along with excellent chemical shift sensitivity for detection of molecular events and chemical substances.   This offers new possibilities for molecular imaging.

Our lab is developing various 129Xe-cryptophane biosensors targeted to cancer cells, proteins, and ions.  We are also developing pH- and temperature-sensitive biosensors for in vivo sensing, thereby expanding the capabilities of Xe biosensors.

Another research direction exploits the rapid and reversible encapsulation of Xe between "bound" (i.e., cryptophane) and "free" (i.e., bulk water) states to report additional information for in vitro and in vivo studies of local chemical environments. Our xenon biosensor developments, which include high detection sensitivity, improve medical diagnostic imaging technology while targeting a broad range of biomedical applications.

4、Atomic Magnetometry and Laser-Detected NMR

Nuclear magnetic resonance (NMR) is a powerful analytical technique that has been used not only in fundamental physics, chemistry and biology research, but also in applications such as medical imaging and oil well logging. However, the detection sensitivity of conventional NMR techniques is poor, especially in low magnetic fields. The conventional method of detection is Faraday induction. Low field NMR and MRI are attractive from the point of view of developing simpler (e.g. smaller), more mobile and less costly instrumentation that does not rely on cryogenic superconducting magnet technology.    Thus, much effort is devoted toward improving detection sensitivity. Our group is developing novel NMR detection technology based on optical atomic magnetometry. Optical magnetometers are usually operated at low magnetic fields and become significantly cheaper and more portable than conventional NMR instruments. This provides an interesting alternative approach for low-field NMR.

Our recent work includes a Cs atomic magnetometer with a sensitivity of 150 fT/Hz1/2 operating near room temperature. The NMR signal of a 125 uL water sample was detected in magnetic fields as low as 47 nT, with a signal-to-noise ratio close to 50 after only eight signal averages. To demonstrate the magnetometer's ability to measure spin-lattice relaxation times, relaxivity experiments using a Gd(DTPA) MRI contrast agent were performed near zero field.

In contrast with Faraday induction detection, our zero-field atomic magnetometer is particularly sensitive in the frequency range from DC to a few kilohertz. NMR in low fields does not require the cryogenics needed to operate superconducting magnets. Cryogens are also needed to operate magnetic sensors based on a superconducting quantum interference devices.

Moreover, because magnetic-field gradients are proportional to the magnetic field, operation in ultra low fields implies that the "external field" can be made extremely homogenous. Homogeneous fields lead to very narrow resonance lines, permitting the measurement of ultra weak spin interactions. The prospect of "pure J coupling" NMR in ultra low fields, where chemical shifts are much weaker, has been recognized by several leading research groups.

As a result, this kind of magnetometer makes NMR increasingly more powerful and accessible to a wider range of applications that involve chemical analysis. Our is focusing its research efforts on the development a new class of SERF magnetometers based on Cs vapor and the understanding spectra in low fields for purposes of ultra sensitive chemical detection.

   

070302-分析化学
070208-无线电物理
083100-生物医学工程

生物医学分子影像
肺部磁共振成像仪器与技术
激光探测磁共振

1999-09--2004-06   中国科学院武汉物理与数学研究所   博士

-- 研究生

-- 博士

   

2009-10~现在, 中国科学院精密测量科学与技术创新研究院, 研究员
2007-09~2009-09,美国加州大学伯克利分校；美国劳伦斯国家实验室, 研究助理
2005-01~2007-09,美国哈佛大学，美国Brigham Women's Hospital, 博士后
2004-07~2004-12,中国科学院武汉物理与数学研究所, 助理研究员

Harvard University;
UC Berkeley;
Lawrence Berkeley National Lab;

已指导学生

张继  硕士研究生  070302-分析化学  

朱筱磊  博士研究生  070302-分析化学  

王琦  硕士研究生  085238-生物工程  

任莉莉  博士研究生  070302-分析化学  

张智颖  博士研究生  070208-无线电物理  

曾庆斌  博士研究生  070302-分析化学  

阮伟伟  博士研究生  070208-无线电物理  

李海东  博士研究生  070208-无线电物理  

肖洒  博士研究生  070302-分析化学  

王崇武  硕士研究生  070302-分析化学  

李莎  博士研究生  070302-分析化学  

谢军帅  博士研究生  070208-无线电物理  

肖康达  博士研究生  070208-无线电物理  

现指导学生

张旭  博士研究生  070302-分析化学  

赵龙辉  博士研究生  070302-分析化学  

单海威  博士研究生  070302-分析化学  

刘小玲  博士研究生  070302-分析化学  

陈小明  硕士研究生  085208-电子与通信工程  

肖忠宇  硕士研究生  070302-分析化学  

乐曲儿  博士研究生  070302-分析化学  

岳森  硕士研究生  070302-分析化学  

隋美菊  博士研究生  070302-分析化学