Abstract: A magnetic resonance imaging (MRI) system is provided with an interventional instrument with an indicator element which influences, for example locally disturbs, the magnetic resonance image. The position of the interventional instrument within the patient to be examined is derived from the local disturbances in the image as caused by the interventional instrument. The degree of influencing of the magnetic resonance image is adjustable notably by rotation of the interventional instrument with the indicator element relative to the direction of the steady magnetic field of the magnetic resonance imaging system. For example, the indicator element is a paramagnetic strip which may include several segments of different magnetic susceptibility.

Abstract: An image processing method includes the acquisition of a succession of low-resolution images. A succession of mask images is derived from the low-resolution images. Furthermore, a high-resolution image is acquired. The mask images are applied to the high-resolution image as bandpass filters in order to form a filtered high-resolution image. The filtered high-resolution image represents image information relating to a particular phase of a dynamic process, such as the passage of blood through the vascular system of a patient. The image processing method is used, for example in MR angiography or in X-ray angiography. An MRI system or an X-ray examination apparatus is provided with an image processor for carrying out the image processing method according to the invention.

Abstract: A magnetic resonance imaging (MRI) system is provided with an interventional instrument with an indicator element (5) which influences, for example locally disturbs, the magnetic resonance image. The position of the interventional instrument within the patient to be examined is derived from the local disturbances in the image as caused by the interventional instrument. The degree of influencing of the magnetic resonance image is adjustable notably by rotation of the interventional instrument with the indicator element relative to the direction of the steady magnetic field of the magnetic resonance imaging system. For example, the indicator element is a paramagnetic strip which may include several segments of different magnetic susceptibility.

Abstract: The invention relates to an image processing method for improving the signal-to-noise ratio for a series of MR images or CT images which are based on the projection-reconstruction method. First the pixels which reproduce the same sub-structure in the projection images are determined in the one-dimensional projection images constituting the two-dimensional MR or CT images. The image values of these pixels are subjected to noise filtering. Two-dimensional MR images or CT images are reconstructed from the noise filtered one-dimensional projection images.

Abstract: The invention relates to MR guided intervention. For biopsies and similar interventions the challenge is to align a needle or other interventional device along an anticipated trajectory which hits a target point but does not intersect sensitive structures between the target and the surface. The invention includes the following method in order to position an MR visible device: collection of pre-intervention MR-images, establishing of an anticipated trajectory and an entry point by imaging of the MR-visible device and a thick slab positioned parallel to the surface and displaying of the MR localizer in the MR-image of the slab and moving the MR visible localizer to the entry point, imaging of two mutual orthogonal slices passing through the anticipated trajectory between the entry point and the target point and establishing an angle of entry by using for example a MR-visible pen and a targeting device.

Abstract: The invention relates to a method of determining, utilizing magnetic resonance, a temperature distribution of a part of an object which is arranged in a substantially uniform steady magnetic field, the determination of the temperature distribution involving the determination of a reference image of the object, for example a part of the human body, and a phase image of the human body. Subsequently, the temperature distribution is determined from phase differences between the values of pixels of the phase image and the values of corresponding pixels of a predetermined reference phase image. In order to counteract errors in the temperature distribution which are caused by motion of the object, navigator pulse sequences are generated so as to measure navigator signals prior to the measurement of MR signals wherefrom the reference image and the phase image are reconstructed. Subsequently, a correction for correction of the temperature distribution is derived from the navigator signals.

Abstract: MR imaging apparatus includes a magnet (1) for generating in an examination zone (3) a uniform, steady magnetic field having substantially parallel lines of force extending in a first direction (Z), a gradient coil system (5) for generating a magnetic gradient field, and an RF coil system for generating RF pulses and for receiving MR signals. The apparatus also includes devices (25,27,31) for generating data from the MR signals, and a reconstruction unit (39) for reconstructing an MR image of the examination zone (3) from a set of the data. A patient support system includes a table top (7) drive means (11) configured for displacement of the table top in the first direction (Z), and a connection (43) for coupling the drive means and the control unit (29). The magnet (1) has a generally toroidal-shaped housing (15) surrounding a bore (17) and has a longitudinal axis (19) extending substantially parallel to the first direction (Z).

Abstract: An MR system for interventional procedures, includes an MR device and an invasive device. The MR device is arranged to acquire images of a part of an object. A part of the invasive device can be imaged in an MR image by providing a coil or a conductor loop which has two non-magnetic conductors which are situated at some distance from one another underneath the surface of the invasive device. A reduction of artefacts due to the movement of a patient or the invasive device can be obtained by sampling an MR signal, whereby an auxiliary magnetic field is periodically applied during the time in which the plurality of lines in k-space are scanned.

Abstract: A method of heating a target region by ultrasound radiation includes determination of a position of the target region by a magnetic resonance method. The device for carrying out this method includes an ultrasound device and an MR device. By determining movement of the target region utilizing the MR device (100) and an appropriate magnetic resonance method, and by coupling the movement information to the ultrasound device (118) by an electric signal (122, 124), it is achieved that the ultrasound device can be controlled by the movement information. Various possibilities exist for controlling the ultrasound device. According to a first possibility, the focal region is adjusted to be situated within the target region in order to generate ultrasound.

Abstract: An MR system for interventional procedures, includes an MR imaging device and an interventional instrument, for example a catheter. The MR device is arranged to acquire images of a part of an object. The entire catheter can be imaged in an MR image by providing a conductor loop which comprises two non-magnetic conductors which are situated at some distance from one another underneath the surface of the catheter, and extend along substantially the entire length of the catheter. Furthermore, the catheter may be provided with a conductor loop and a coil in a location on the catheter. By separate adjustment of the current flowing through the conductor loop and the coil, it is possible to image the location on the catheter with a contrast which deviates from that of the remainder of the catheter.

Abstract: A method of magnetic resonance imaging of a part of the body (106) arranged in a substantially uniform, static magnetic field where, in order to follow a dynamic process in the body, the temporal resolution is enhanced by successively generating MR signals which are associated with only a part of a reference set of lines in the k-space. After the generating and sampling of a series of MR signals associated with the lines of the part of the reference set, a reconstruction set is renewed and an image of the part of the body is reconstructed from the reconstruction set by a processing unit (110) executing a 2D Fourier transformation, said image subsequently being displayed on a monitor (111). In order to counteract motion artefacts, for example echo images of contours of objects in the image, the associated lines of the part of the reference set are uniformly distributed in the k-space during the generating of MR signals.

Abstract: A magnetic resonance device (1) for imaging inter alia human organs by way of magnetic resonance is provided in close proximity with an x-ray imaging device (20). When, for example, in neurosurgery interventional techniques are executed in combination with a magnetic resonance device (1), the organs are suitably visualized but the instruments guided to an organ via an opening in the body are not visible or only hardly so. Prior to the present invention, in order to carry out interventional procedures, the patient would be transported between a room housing magnetic resonance device and a room housing on x-ray device. Transporting the patient over a long distance between two rooms is objectional because of the risk of motion of the instruments lodged within the body of the patient; as such motion could be fatal to the patient. A solution consists in arranging an X-ray device (20) adjacent the MR device (1), so that the patient need be transported a short distance only.

Abstract: An off-resonance magnetization transfer contrast (MTC) RF-pulse (54, 64) is used in magnetic resonance angiography (MRA) to suppress the signal of various stationary tissues, such as brain tissue while avoiding significant suppression of signal from blood flowing in a general direction of blood flow into a slice being imaged. Application of a magnetic gradient (55, 65, 85) during the MTC RF-pulse (54, 64) directed in the general direction of blood flow increases the magnetization frequency offset (86) relative to the center frequency of the MTC RF-pulse for points within and feeding blood to the slice. The MTC RF-pulse thus causes only a small signal reduction of the blood flowing into the slice in the general direction of blood flow while producing a saturation of any blood flowing into the slice in the opposite direction. Consequently, both time and RF-power needed for a separate presaturation pulse can now be used for the MTC RF-pulse.

Abstract: An imaging system includes to a magnetic resonance device (1) for imaging inter alia human organs by way of magnetic resonance and an X-ray device for imaging by way of X-ray. When interventional techniques are applied in combination with a magnetic resonance device (1), the organs are suitably visualized, but the instruments guided to an organ via an opening in the body are not visible or only hardly so. These instruments must be imaged by means of an X-ray device (20); the patient must then be transported some distance, for example a few meters, in order to obtain distortion-free images of the instruments. Transporting the patient has some drawbacks. There is a risk of motion of the instruments within the patient and, moreover, the coordinate systems of the MR device (1) and the X-ray device (20) might deviate from one another.

Abstract: A magnetic resonance imaging method is proposed for the following of a dynamic process in a body (5), such as perfusion in the brain by means of a contrast agent such as Gd-DTPA, or the effects of a physical stimulus. The dynamic process is followed by way of a multiple-slice MR measurement through, for example, 10 slices. In accordance with the invention, before or after the injection of the contrast agent, high-resolution reference images of the slices are formed, the same slices being measured with a lower resolution during the perfusion of the contrast agent. Substitution of the low-resolution data in data matrices containing high-resolution data produces, after Fourier transformation, images of the slices in which the measured changes in image intensities due to the contrast medium are reproduced in the high-resolution images.

Abstract: In a magnetic resonance apparatus eddy current effects are compensated by measurement of the eddy current behaviour in a comparatively large measurement object on the basis of resonance signals generated therein, for example briefly after de-activation of a gradient field control signal. From these measurements a series of exponentially decreasing signals is calculated. These correction signals are generated by appropriate switching circuits which are preferably adjustable as regards decay time and amplitude. The correction can be performed for the gradient field symmetry corresponding to the switched gradient field transition as well as for eddy currents, if any, having a field symmetry which deviates therefrom.

Abstract: The method includes a critical time shift of a refocusing pulse between two (90.degree.) excitation pulses which produce multiple quantum coherence signals and which are followed by a (90.degree.) read pulse (using a critical timing a refocusing pulse serving the same purpose can also be applied between the second excitation pulse and the read pulse). With respect to the center of the time path between the excitation pulses or between the excitation pulse and the read pulse the time shift is chosen to be such that give resonances do not occur positively or negatively in the spectrum whereas other resonances do occur therein (i.e. at substantially maximum strength). The MRI method can be combined with the use of spatially selective gradients in order to obtain localized spectra or images.

Abstract: In a magnetic resonance apparatus coils of an rf coil system are incorporated for detection of magnetic resonant signals at mutually different frequencies in resonant circuits having a zero impedance for the natural frequency and an infinite impedance for a given deviating frequency. In the switching circuits a coaxial cable is used having a length which has a reactance in parallel with a second reactance to form a tuned circuit adapted to the desired frequency.

Abstract: A magnetic resonance imaging apparatus includes an r.f. coil which is comprised of a number (for example, two in the case of a surface coil and four in the case of a cylindrical coil) of coaxial cables. The outer jackets of the cables are arranged so as to form a sleeve enclosing the core or center portion at the area of a node in the electric field. By keeping lead-out portions of the cables outside the sleeve, a highly interference free coil is obtained. The total cable length amounts to, for example, 3/4.lambda., with 1/4.lambda. as a lead out portion and 0.1.lambda. as a sleeve core defining the coil circumference.

Abstract: The measurement of localized spectra by means of stimulated echoes is known per se. Using three 90.degree. pulses, stimulated echoes are then generated; these pulses are selective or not. However, this technique it is not suitable for measuring good proton spectra of metabolites because the response of the non-bound protons is much greater than the response of the bound protons. In accordance with the invention, a fourth (spatially selective) 180.degree. refocusing pulse is added to a pulse sequence consisting of a 90.degree. non-spatially selective but frequency-selective pulse and two subsequent 90.degree. spatially selective pulses. Thus, a refocused stimulated echo is generated in which the response of the non-bound protons is suppressed and which contains only signals from the chemically bound protons. The proposed methods are particularly suitable for measurements on lactate because of the excellent spectral editing properties.