Device for monitoring a living object during a magnetic resonance experiment
A device for monitoring a living object during a magnetic resonance (MRI) experiment in an MRI tomograph, wherein the device comprises one or more individual electrodes which are connected in an electrically conducting fashion to the living object to be examined, and are connected to a monitoring device via signal lines, wherein each signal line comprises individual parts that are electrically connected to each other via impedances. The eigenfrequencies of these parts are higher than the NMR measuring frequency, preferably more than twice as high, and the parts are electrically connected to each other via frequency-dependent impedances Z n . The electro-magnetic coupling from the RF antenna and the gradient coils to the signal lines can thereby also be minimized in a simple fashion.
1. A device for monitoring a living object during a magnetic resonance (MRI) experiment in an MRI tomograph, the device comprising:
one or more individual electrodes which are connected in an electrically conducting fashion to the living object to be examined;
a monitoring device; and
signal lines disposed between and connecting said electrodes to said monitoring device, each signal line comprising individual parts that are electrically connected to each other via impedances, wherein eigenfrequencies of said parts are higher than an NMR measuring frequency, said parts being electrically connected to each other via frequency-dependent impedances (Z n ).
2. The device of claim 1 , wherein said eigenfrequencies of said parts are more than twice as high as said NMR measuring frequency.
3. The device of claim 1 , wherein reactances of said frequency-dependent impedances Z n are larger than ohmic resistances thereof.
4. The device of claim 3 , wherein said reactances at least twice as large or more than ten times as large as said ohmic resistances thereof.
5. The device of claim 1 , wherein, for said impedance |Z n | of said frequency-dependent impedances Z n , |Z n |>500 ohms for the NMR resonance frequency and |Z n |<50 ohms for frequencies smaller than 100 kHz.
6. The device of claim 1 , wherein rejector circuits are used for at least one part of said impedances Z n , said rejector circuits having resonance frequencies which are adjusted to said NMR measuring frequency.
7. The device of claim 1 , wherein at least one part of said impedances Z n have inductances.
8. The device of claim 1 , wherein at least one part of said impedances Z n comprises Bazooka Baluns which are disposed one behind an other and contain said signal lines to said electrodes in interiors thereof.
9. The device of claim 1 , wherein said signal lines are mechanically mounted to a carrier of an RF antenna in an area of said RF antenna of an MRI receiving system.
10. The device of claim 9 , wherein positions of said signal lines on said carrier of said RF antenna are selected by means of experiments such that an electromagnetic coupling between said RF antenna and said signal lines is minimized.
11. The device of claim 1 , wherein several signal lines with a same distribution of parts are provided, said signal lines being positioned in such a fashion that corresponding parts are disposed next to each other.