Abstract: The invention relates to a method of and a device for exciting the nuclear magnetization in a limited volume of an object to be examined, utilizing a microcoil (L) which is present in the volume and is attached, for example, to an interventional instrument during the formation of a magnetic resonance image of the object to be examined. The excitation of the nuclear magnetization is performed by at least one RF pulse whose frequency spectrum does not overlap the range of the spin resonance spectrum, so that no nuclear magnetization is excited outside the close range of the microcoil in the object to be examined. The microcoil, however, is provided with an active or passive circuit (for example, it is wired together with at least one capacitance (C) and a non-linear component (D1, D2) so as to form a non-linear resonant circuit) which locally generates an RF signal from the RF pulse.

Abstract: The invention sets forth an RF-safe invasive device which is intended to cooperate with a magnetic resonance imaging apparatus and which contains at least one long conductor for a specific purpose, e.g., the localization of the RF-safe device in an object under test. It is known that in such devices with long conductors during RF transmission of the magnetic resonance apparatus a standing RF wave along the conductors may build up which causes dangerous heating of the device and surrounding tissue. It is the object of the invention to provide a construction applicable to such devices such that the heating of the conductor and surrounding tissue is avoided.

Abstract: The invention relates to an MR method which utilizes a microcoil without connection leads which causes an increase of or a change in phase of an external RF magnetic field in its direct vicinity within an object to be examined. This increase can be used to localize the coil, to image the direct vicinity, or to track the propagation of a liquid flow passing through the direct vicinity.

Abstract: The invention relates to a magnetic resonance (MR) device which is provided with a medical instrument (10) which is to be introduced into an object (1) to be examined, and also with a coil system (11) which is arranged in or on the instrument (10) and includes at least one coil for receiving and/or transmitting an RF signal, to a medical instrument (10) of this kind and also to a method of determining the position of such a medical instrument (10) that can be introduced into an object (1) to be examined. According to the invention the coil system (11) in an MR device of this kind forms a resonant circuit (20) in conjunction with a capacitor (19) and a modulation unit (12) is provided in order to modulate an RF signal coupled into the coil system (11).

Abstract: The position of an object, for example a catheter, in a body to be examined is determined so as to enable monitoring of its movement through the body at the same time that information concerning the anatomy in the surroundings of the object is to be acquired. An as high as possible temporal and spatial resolution should be achieved for this purpose. To this end, the nuclear magnetization in the surrounding region of the object is determined by means of a micro-coil which is mounted on the inserted object, it being possible to determine the position of the object from the nuclear magnetization. Subsequently, an RF coil system is used to perform a line scan around this position in order to determine the nuclear magnetization in a line-shaped region.

Abstract: An image synthesizing method and apparatus for forming a composite image from basic images with complex image values acquired by sensors having sensitivities which vary differently across the area to be imaged, includes the deviation of complex image values of the composite image from the image values of the basic images which have been weighted in dependence on the complex values of the sensitivity of the sensors. The complex sensitivity values are determined according to the invention in that the sensitivities of the sensors are estimated on the basis of the basic images themselves by determining the sensitivity of each sensor from the basic image acquired thereby.

Abstract: A shielding sleeve (19) for SQUID-magnetometers which serves to shield from electromagnetic interference fields, consists of an electrically conductive shielding material so as to obtain adequate RF shielding in conjunction with a low noise contribution, completely envelops a non-shielding cryostat (10), has a predetermined sheet resistance and consists of at least one layer of the shielding material in order to avoid an increase of the magnetometer overall noise.

Abstract: A miniaturized SQUID module (10), notably for multi-channel magnetometers, for measurement of varying magnetic fields in a field strength range below 10.sup.-10 T, includes superconducting and shielded connections between a SQUID chip (19) and a gradiometer (12). The module can be mounted in the lower part of a cryostat and enables a large number of measurement points per unit of surface area. The SQUID chip (19) is arranged on a fully shielded supporting plate (18) which has a width of only a few millimeters and which is provided with electronic circuitry (23), the SQUID chip (19) being connected in a superconducting manner, at least by soldering, to the wires (11) of the gradiometer (12) via a superconducting, solderable and bondable intermediate support (27).

Abstract: A method of suppressing current distribution noise in a DC SQUID comprising two Josephson junctions (12) in a superconducting current. This current distribution noise is caused by individual fluctuations of the critical currents of the two Josephson junctions used for measuring weak magnetic fields. A DC SQUID is connected to a device which comprises a control device (14) for generating a periodic bias current (I.sub.b), a modulation device (15) for generating a flux modulation via an induced AC current in the loop (11), and a signal detection device (17) for forming a mean output voltage (V.sub.ges). The polarity of the bias current (I.sub.B) is reversed by the control device (14) with the modulation frequency and a time shift of one quarter of the period duration of the modulation frequency, so that the SQUID assumes different bias states.