Koninklijke Philips Corporation N.v.

Johan Ernst Willy Vrijheid

Johannes J Van Vaals

Dirk Sinnema

In a medical MRI apparatus, it is often desirable to have devicesfor communicating with or monitoring the patientin the imaging volumeof the apparatus. Such devices need DC power or low-frequency connections with an areaoutside the imaging volume. A device cable that does not interfere with the MRI magnetic fields is known per se. The invention proposes to fix the device cable in a groovein the patient carrierin such a manner that its strip-shaped conductorsextend parallel to the field lines of the stationary field B of the apparatus. In this way, it is also possible to clip device carriersto the groove, thus supplying the devices with DC power or establishing an audio connection through the device cable in the groove.

MRI apparatus with low-frequency cable integrated into the patient carrier

An invasive device, such as a catheter, is connected to a supply and control unit via a connection conductorfor the transfer of power supply energy and/or LF signals to and from an electrical circuitin the distal partof the device. During operation the connection conductor traverses the homogeneous magnetic field and the RF field of the MRI apparatus; this may give rise to heating of the connection conductor and/or to a disturbance of said fields. In order to mitigate these drawbacks, the connection conductor in accordance with the invention is subdivided into mutually separated segments-, each of which is much shorter (for example, 1/20) than the wavelength of the RE field in the apparatus; the segments are separated from one another by separating elements-(self-inductances) that provide a high inductance for said RF frequencies and a low inductance for comparatively low frequencies.

Invasive device provided with a segmented electrical connection conductor

In medical MRI apparatus it is often desirable to maintain a connection with the patient to be examined, for example in order to observe the patient by means of a television camera or to monitor physical functions like the heart rate or blood pressure. It is often necessary to use electrically powered connection equipment which is located in or very close to the imaging area , the supply lines also being located in the imaging area so that the (precisely defined) fields required for imaging would be disturbed thereby. According to the invention the supply lines are subdivided into segments - , each of which has a length shorter than &frac14; of the wavelength of the RF field; these segments are separated from one another by inductances - . Consequently, the supply line does not present itself as an energy absorbing conductor to the RF field, so that the RF field is not disturbed thereby. Distortion of the uniform B field is avoided by twisting the conductors of the line and by winding the inductances in a bifilarr winding mode.

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Eindhoven, Netherlands

Johan Ernst Willy Vrijheid