查询词典 shimming

Magnetic Resonance Imaging, Integer Programming, Branch and Bound Method, Shimming

磁共振成像；整数规划；分支定界法；匀场

The results of experiment and computation indicate that the shimming process can be completed effectually by the reformative method.

实验与计算结果表明，改进后的方法能够快速有效地完成匀场过程。

Owing to the drawbacks of analytical shimming, this paper puts forward the concept of passive numerical shimming for searching a method of compensating Bz'easily to a high level and with a low cost. Based on the magnetic field caused by a magnetic moment, the distribution of moments in a superconducting NMR imaging megnet can be determined through some pseudoinversion algorithm directly from Bz'. The moments are used to compensate Bz'.

无源数值匀场的出发点直接是不均匀磁场的磁场偏差B〓本身；无源数值匀场的基础为磁性材料的磁矩所产生的磁场；由已知B〓，通过某种逆运算，确定磁性材料的磁矩在主磁体中的分布，实施此分布，以磁性材料的磁矩所产生的磁场直接对B〓进行补偿——这便是本文提出的无源数值匀场的概念。

By means of shimming,the filed integral and phase error can be reduced as much as possible.

磁场的垫补和测量方法由原来的整体测量改为分段进行，垫补的使用使各段积分场及位相误差都尽可能小。

Third, The author analyzed the shimming method of the existing magnet system and programmed it. Because the base field homogeneity of the open magnet is worse and only passive shimming is available, it is necessary to study more effective shimming algorithm. The ordinary shimming method is based on the disintegration of the magnetic field using spherical harmonics. It is so tedious that involved in large scaled non-linear equations.

再次，详细分析了现有磁体系统的匀场方法，并通过编程运算，发现在开放型磁体这一特殊情况下，由于基场均匀度差和只能使用水磁材料垫补进行匀场等原因，基于对磁场分布用球谐函数分解并消去球谐函数高次项的常规匀场方法在实现上相当繁琐，牵涉到大型非线性方程组的求解，所以必须采用更有效的匀场算法。

Simulation of a relatively simple process shimming of shimming algorithm validation.

仿真了比较简单的匀场过程，对匀场算法进行验证。

Thus, it is very tedious to realize passive analytical shimming. In addition, the harmonic fields above the fifth order can't be compensated by passive analytical shimming.

鉴于解析匀场的上述不足之处，本文提出了无源数值匀场的概念，目的在于寻求一种高水平、低成本、简单易行补偿B〓的方法。

It was proved through experiment that optimum passive numerical shimming can achieve a high level in superconducting NMR imaging magnets and it can be realized very easily and very economically. Field regression is not absolutely necessary in the technique of optimum passive numerical shimming, but it is useful to know the structure of the field error Bz'.

磁场回归在超导核磁共振成像主磁体的无源数值匀场技术中虽然并不是绝对必需的，但在对主磁体进行无源数值匀场时，如能知道成像空间内不均匀磁场的磁场偏差B〓的结构，也是非常有用的。

Active shimming design The magnetic field homogeneity will descend when temperature changes. Generally, active shimming is used to re-correct magnetic field.

4匀场线圈设计当外界温度发生变化时成像磁场的均匀性会随之改变，通常采用有源匀场方法对磁场进行再校正。

Active shimming designThe magnetic field homogeneity will descend when temperature changes. Generally, active shimming is used to re-correct magnetic field.

4匀场线圈设计当外界温度发生变化时成像磁场的均匀性会随之改变，通常采用有源匀场方法对磁场进行再校正。

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。