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期间，我们 我开发了两种新的磁测量方法 敏感度。在将这些技术应用于人类之前，我们需要 进行彻底的幻影和动物研究。重大进展 都是朝着这个方向发展的。 在称为触点引用方法的第一种技术中， 给沙土鼠注射右旋糖苷铁溶液诱导 铁超载程度不同。然后我们测量了他们的肝脏 体外心脏磁化率。同时，这些 样本被送到一个独立的实验室来测量他们的铁 用原子吸收光谱分析测定浓度。我们发现了 样品的磁化率与磁化率成线性关系 他们的铁浓度。 我们开发的另一种磁化率测量方法是 偶极场模型。首先，将试管插入一个大烧瓶中 装满了水。我们获得了一个切片的位相图像 日冕方向。然后放入一小块样品(固体或液体) 在试管中。在相同的实验条件下，我们采取了 再测量一次。两个相位图像的差异提供了 样品磁化产生的磁场。我们近似地认为 将样品转换为磁偶极子，忽略所有其他更高阶数 场，然后将样品的磁场建模为偶极子 字段公式。这样，我们就可以提取磁化率 样品的数量。计算机模拟表明，偶极场 近似引入的误差非常小。目前我们正在寻找 将这种方法应用于绘制大脑磁化率图。

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.