metallic foreign inclusions
three identical pairs of mutually orthogonal Helmholtz coils
two pairs of identical orthogonally oriented measuring circuits
back projection algorithm with a filtration
A.A. Zhilnikov, T.A. Zhilnikov, V.I. Zhulev
The most informative method in medical practice imaging – magnetic resonance imaging is of limited use. It is caused by the fact that the nuclear magnetic resonance (NMR) tomography of biological object is placed in a magnetic field, resulting in the presence of metallic foreign bodies inside the inclusions (IVI) begin to show their magnetic properties. Moreover, the magnetic fields MRI have enough strength to pull these inclusions, slitting and squeezing the healthy tissue bioobject, resulting in serious injury or even death.
For these reasons, such patients should not be subjected to NMR tomography study. Identifying those people is not always possible because the patient may not be aware of its existing on or could not be warned about the importance of informing about them.
In connection with this an urgent problem is non-destructive testing of the biological object to detect with subse-quent visualization of possible IVI in his body.
Since IVI magnetic properties are manifested in the presence of the external magnetization, for the solution of this problem in the paper, we propose a method consisting of non-destructive bioobject measurements of vector function of the magnetic induction of the periodic in time magnetic field at any point of the investigated space for randomly selected points of time without mechanical penetration into the biological object, located within the field. To conduct magnitomeasuring, bioobject is previously placed in a rather weak compared to MRI homogeneous magnetic field with predetermined characteristics. This field is generated by three identical pairs of mutually orthogonal Helmholtz coils with independent control of x-, y-, z-component of strength. MIVs change the given uniform magnetic field, which are registered in this method. In connection with it a transducer is realized in the form of two identical orthogonally oriented relative to each other pairs of flat and curved contours, made in the form of coils with an equal number of turns and counter-switching of the windings.
During the implementation of the method investigated the space of a uniform magnetic field with biological specimens pre-partitioned into layers conventionally formed by the planes and parallel to the plane of the scan. By measuring the time intervals that are multiples of the period and consecutively in each section is two-dimensional images can be visualized as a result of MIV inside the biological object in space. And, despite the fact that the measurements significantly separated in time, they will be made for any one instantaneous state in the period.
Provided a given magnetic treatment it becomes possible to define the possible presence of IVI, since they change the original picture of magnetic distribution.
In addition, the proposed a measurement system, allowing to implement this method and basic principles implemented by the system of indirect measurements of the three components of a vector function of magnetic induction are given.
In conclusion, a synthesis of the results and discusses the main advantages of the method, namely the ease of use, noninvasive, no harm (radiation exposure), three-dimensional nature of image acquisition.