Rosell J, Casañas R, Scharfetter H
Departament d'Enginyeria Electrònica, Universitat Politènica de Catalunya, Barcelona, Spain.
Physiol Meas. 2001 Feb;22(1):121-30. doi: 10.1088/0967-3334/22/1/316.
We evaluated analytically and experimentally the performance of a planar gradiometer as a sensing element in a system for magnetic induction tomography. A system using an excitation coil and a planar gradiometer was compared against a system with two coils. We constructed one excitation coil, two different sensing elements and a high-resolution phase detector. The first sensor was a PCB square spiral coil with seven turns. The second sensor was a PCB planar gradiometer with two opposite square spirals of seven turns, with a distance between centres of 8 cm. Theoretical sensitivity maps were derived from basic equations and compared with experimental data obtained at 150 kHz. The experimental sensitivity maps were obtained measuring the perturbation produced by a brass sphere of 12 mm in empty space. The advantage of using a gradiometer is that it can be adjusted to give a minimum signal for homogeneous objects, while increasing the sensitivity to local perturbations of the conductivity. Results show that a system using a planar gradiometer as detector has less demanding requirements for the electronic system than a system using simple coils.
我们通过分析和实验评估了平面梯度仪作为磁感应断层成像系统中传感元件的性能。将使用激励线圈和平面梯度仪的系统与使用两个线圈的系统进行了比较。我们构建了一个激励线圈、两个不同的传感元件和一个高分辨率鉴相器。第一个传感器是一个有七匝的印刷电路板方形螺旋线圈。第二个传感器是一个印刷电路板平面梯度仪，由两个相对的七匝方形螺旋组成，中心间距为8厘米。理论灵敏度图由基本方程推导得出，并与在150kHz下获得的实验数据进行了比较。实验灵敏度图是通过测量在真空中一个12毫米黄铜球产生的扰动而获得的。使用梯度仪的优点在于，它可以进行调整，使均匀物体的信号最小，同时提高对电导率局部扰动的灵敏度。结果表明，与使用简单线圈的系统相比，使用平面梯度仪作为探测器的系统对电子系统的要求较低。
