NEW PULSE SEQUENCE FOR INDIRECT DETECTION OF 17O IN BRAIN

在我们继续努力测量组织中的铁水平时， 已经开发了两种新的方法来测量磁 易感性 在将这些技术应用于人类之前，我们需要 进行全面的体模和动物研究 重大进展 都是朝着这个方向发展的。 在第一种称为联系人引用方法的技术中， 给一系列沙土鼠注射右旋糖酐铁溶液， 不同程度的铁超载。 然后我们测量了他们的肝脏， 离体心脏磁化率。 同时这些 样本被送到一个独立的实验室， 浓度使用原子吸收光谱法。 我们发现 样品磁化率与 铁的浓度。 我们开发的另一种磁化率测量方法是 偶极场模型 首先，将一个试管插入一个大烧瓶中 装满了水 我们获取了一个切片的相位图像， 日冕方向 然后将一个小样品（固体或液体） 在试管里。 在相同的实验条件下，我们将 再次测量。 两相图像差提供了 样品磁化产生的磁场。 我们估计 将样本转换为磁偶极子，忽略所有其他高阶 场，然后将样品的磁场建模为偶极子 场公式 这样我们就能提取出 的样本。 计算机模拟表明， 近似引入非常小的误差。 目前，我们正在寻求 将这种方法应用于绘制大脑磁化率。

During our continued effort to measure iron level in tissue, we have developed two novel methods for the measurement of magnetic susceptibility. Before applying these techniques to humans, we need to conduct thorough phantom and animal studies. Significant progress has been made in this direction. In the first technique, called the contact reference method, a series of gerbil mice were injected iron dextran solutions to induce iron overload to different levels. Then we measured their liver and heart magnetic susceptibilities ex vivo. At the same time, these samples were sent to an independent lab to measure their iron concentrations using atomic absorption spectroscopy. We have found that sample magnetic susceptibilities are linearly proportional to their iron concentrations. Another susceptibility measurement we have developed is the dipole field model. First, a test tube was inserted in a big flask filled with water. We acquired the phase image of a slice in the coronal direction. Then a small sample (solid or liquid) was placed in the test tube. Under the same experimental conditions, we took the measurement again. The two phase image difference provides the magnetic field generated by the sample magnetization. We approximated the sample to a magnetic dipole, ignoring all other higher order field, and then modelled the magnetic field of sample to the dipole field formula. This way, we could extract the magnetic susceptibility of sample. Computer simulation shows that the dipole field approximation introduces very small error. Currently we are seeking to apply this method to mapping brain magnetic susceptibility.