Orion-yhtyma Oy

Picker Nordstar Corporation

Koninklijke Philips Corporation N.v.

Picker International, Inc.

Instrumentarium Corporation

Instrumentarium Oy

Berggren Oy Ab

Instrumentarlum Oy

Ilmari V Kinanen

Gordon D DeMeester

Gosta J Ehnholm

Matti Rantanen

Ian R Young

Pertti Sormunen

Robert G Gylling

Raimo E Sepponen

Matti Smalen

Erkki H Tammisalo

Heikki K Kanerva

John V M McGinley

Sulo Ranne

An MRI scanner generates a temporally constant (B ) magnetic field through an examination region ( ), as well as a surrounding fringe field. The fringe field tends to decrease in strength with distance from the examination region and includes a 5 Gauss line ( &prime;) and a 1 Gauss line ( ). In a vertical field magnet, the 5 Gauss line can extend more than 3 or 4 meters above and below upper and lower pole assemblies ( ). By placing permanent magnets ( ) above and below the upper and lower pole assemblies, respectively, with an opposing magnetic polarity, the fringe field is shaped and controlled reducing a distance (d) of the 5 Gauss line above the scanner to about 2 meters and reducing an amount of ferrous material in a ferrous flux return path ( ).

MRI magnet with reduced fringe field

In an open magnetic resonance system, pole pieces ( ) on opposite sides of an imaging region ( ) are supported by a ferrous flux return path ( ). During normal operation, environmental disturbances that cause low frequency vertical vibrations in the floor cause corresponding fluctuations in the main field of the magnet. A spacing between the pole pieces ( ) expands and contracts with the vibration causing a strength of the main field to fluctuate. A force transducer ( ) under the magnet assembly measures the magnitude of the vibrations. A vibration analyzer ( ) analyzes the vibrations waveform and calculates compensation for the changes in the interpole spacing. The vibration analyzer ( ) controls one or more of a shim coil ( ) which produces a field equal and opposite to the main field fluctuations, a reconstruction processor ( ) to compensate for magnetic field resonance frequency fluctuations attributable to the main field fluctuations, and gradient magnetic fields applied by gradient field coils ( ).

MRI magnet with vibration compensation

A pair of annular magnets (,) generate a vertical magnetic flux field through an imaging volume (,). The flux is focused by a pair of Rose rings (,) of high cobalt steel. A high order shim set includes a plurality of permanently magnetized or magnetized iron rings (,) which cooperatively interact with the magnet assembly to optimize the homogeneity of the magnetic flux through the imaging volume. One of the permanent magnetic rings (,), is mounted with an opposite polarity relative to the others. The magnetized rings are mounted in a non-ferrous, electrically insulating support structure (,) such that gradient coils (,) can be positioned behind the permanent magnet rings. A flux return path (,) provides a low flux resistant path from adjacent the Rose ring at one side of the imaging volume remotely around the imaging volume to a position adjacent the Rose ring at the other side of the imaging volume.

MRI magnet with high homogeneity, patient access, and low forces on the driver coils

A magnetic resonance imaging suite is sheathed with plates (32, 34, 36) of iron or other ferrous material. The plates define projections (42, 44, 54, 54', 68) in alignment with each other on opposite ceiling and floor or wall surfaces. A pair of magnetic pole pieces (10, 10'; 50, 50'; 60, 60') are surrounded by superconducting electromagnetic coils (12, 12'; 52, 52'; 62, 62'). The pole pieces are positioned between the ferrous plates in axial alignment. When current flows through the electromagnetic coils, magnetic flux flows between the pole pieces. The ferrous wall sheathing or other ferrous constructions define a flux return path. The pole pieces are magnetically attracted toward each other and are each magnetically mirrored in and attracted toward the adjacent ferrous flux return path. The pole pieces are positioned relative to each other and the ferrous flux return path such that the attraction between the pole pieces is balanced by the attraction between each pole piece and its magnetically mirrored image in the adjacent ferrous material of the flux return path. Optionally, the magnets are selectively extinguished and one or both pole pieces are moved for better access to the patient.

Magnetic resonance imaging system with floating pole pieces

A magnetic resonance imager has a magnetically permeable core and two pole pieces, each pole piece having a face. The pole pieces are arranged on the core such that the pole piece faces are in opposed relationship forming a first gap therebetween. At least one of the pole pieces is comprised of an outer element 23 connected to the core and an inner element 24 connected between the outer element and the first gap. The outer element 23 forms a cup inside which the inner element 24 is disposed. A plurality of screws 11, 12 and 13 are disposed through the outer element 23 and engage the inner element 24 such that a second gap is formed between the inner and outer element. The homogeneity of the magnetic field in the first gap is affected by adjusting the position of the inner element relative to the outer element via screws 11, 12 and 13. The inner element being tiltable relative to the outer element by adjusting screws 12; moveable in the direction of its principal plane by adjusting screws 11; and formable into an arched surface by adjusting screws 13.

Pole piece for MR imager

Two opposite iron core pole pieces of a magnetic resonance medical imager generate a static magnetic field in a patient imaging volume disposed between the pole pieces. Gradient coils are positioned in the face of a pole piece. Thin disc shaped (42, 44) or ring shaped (41) ferromagnetic parts laminated of layers cut favorably from transformer sheet material are attached to the face of the pole piece. Each layer is electrically insulated from adjacent layers and surfaces by enamel or fixing glue. To reduce eddy currents in these layers, narrow, radially oriented slots (43, 45) are cut in these layers before lamination. The slots are oriented in the adjacent layers so as not to coincide resulting in improved conduction of the magnetic flux in the imaging volume during the production of gradient magnetic fields by the gradient coils.

Arrangement to minimize eddy currents in MR imagers

Method and apparatus for recording information from a slidable sheet of

The invention relates to a novel magnetic resonance imaging apparatus. The nuclei, protons or the paramagnetic electrons of an imaged object are cyclically polarized during a period of about one second with a permanent magnet which is then quickly shifted away from the imaged object in a permanent magnet carrier tube, so that the field of the permanent magnet would not have an interfering effect on the immediately following signal-collection for MRI-imaging. The permanent magnet can be manipulated or shifted back and forth in the tube either magnetically, pneumatically, hydraulically or mechanically. The apparatus also includes another permanent magnet or a resistive magnet coil couple, which is located in the tube near the opposite end of the tube, and which generates a homogeneous magnetic field within the imaged area. The apparatus includes a gradient coil system for generating a time-dependent magnetic field gradient necessary for imaging, as well as a coil system for producing an electromagnetic radio-frequency excitation signal to be linked with the nuclei or paramagnetic electrons of an imaged object as well as for registering the response of the nuclei or electrons to said signal. A control unit is used to control the above coils and to receive the information therefrom for producing an image or some other representation thereof.

Magnetic resonance imaging apparatus and method

The invention relates to a supporting system of a sliding plate of a magazine comprising a magazine case and a sliding plate which travels in a linear direction inside the magazine case. The system is comprised of a guide bar that is secured to the lower cover of the magazine, parallel to the longitudinal axis of the lower cover. The sliding plate rests upon the guide bar and upon support screws arranged on the end part of the magazine case against the front portion of the sliding plate.

Support for sliding radiographic plate in a magazine

A method and an apparatus for the radiographic recording of a patient's dentition, jaws, and skull regions invalues seating a patient in a patient chair (9) so as localize the patient in the coordinate system of the radiographic apparatus in an unequivocal position before taking the exposure for a radiograph (87). Furthermore, in accordance with the invention, the radiograph (87) is used for measuring the coordinates of a desired object (95) by a coordinate locator (88), after which the desired partial area (94 or 96) is selected on the basis of the coordinates, and the exposure direction is changed in relation to the first exposure in the horizontal plane and/or the vertical plane before executing the exposure program for the desired partial area (94 or 96). The apparatus in accordance with the invention comprises a coordinate locator (88) which provides for locating a desired detail (95) in the panoramic radiograph in relation to the coordinate system of the radiographic apparatus, and controllers (61, 65, 67) which steer the actuators of the radiographic apparatus in a manner which implements the recording of the desired detail. By the method, a desired detail of a radiograph can be recorded in several different projections for closer examinations.

Method and apparatus for radiography of the dental, jaw, and skull

An apparatus for the implementation of a vertical movement for a chair, especially a patient chair is disclosed. This apparatus comprises a lift column (1) with an upper end suitable for mounting a chair, a tubular shell construction (2) against which the lift column (1) is telescopically supported, a threaded member (5) whose rotation enables elevation and lowering of the lift column (1), and a motor (4) for rotating the threaded member (5). In the apparatus according the lift column (1) has a polygonal cross section, and it receives for each of its sides a support incorporating a spring action and sliding bearing contact by support braces (3) mounted to the inner surface of the shell construction (2). The apparatus achieves a vibration-free lift movement.

Apparatus for implementation of vertical movement of a chair, especially

A friction planetary transmission has a sun roller planetary roller and an elastically deformable outer periphery. The planetary rollers are attached to shafts which have a limited amount of radial movement. The outer periphery deforms to exert a frictional contact pressure on the planetary rollers such that a torque can be transmitted. The torque is adjustable by a circular disk which fits inside the outer periphery to regulate the amount of deformation. The circular disk can be moved axially to adjust the torque.

Planetary transmission based on friction

The purpose of the invention is to create a mechanically uncomplicated installation for producing radiographic layer images, making it possible to use small radiation dosages and, however, to collect sufficiently information on the object by one exposure, whereby separation of the superimposed layers from each other in a desired way for visualization can be accomplished by means of tomosynthesis. The installation includes radiation generating means (1, 2), collimating means for confining the radiation and focusing it on an object (4) to be radiographed, e.g. a patient, means (10) for detecting the radiation passed through the object and means for storing and processing the information contained in said detection. Said collimating means comprise a collimation unit (3) including at least two separate, narrow, contiguous, substantially parallel collimating slots (5) for producing narrow, fan-shaped beams, said slots being arranged preferably in alignment with the longitudinal axis of the object to be radiographed. The installation also includes means (11, 13) for displacing said collimating slots and the object to be radiographed in relation to each other at least substantially in alignment with the normal of said collimating slots, those parts of the object selected to be radiographed being arranged to be exposed to radiation by said narrow fan-shaped beams from a number of different directions. The information obtained from the object to be radiographed is stored preferably in digital form and processed for visualization.

Installation for producing radiographic layer images

A slit collimator for use in a panoramic X-ray apparatus for the collimation of X-rays into a narrow fan-like beam. The collimation is achieved by means of a collimator slit formed in a trunion which is rotatable about its longitudinal axis and by rotating the trunion the effective radiation-penetrable size of the slit is varied.

Growing community of inventors

Espoo, Finland

Ilmari V Kinanen