GB2466935A - Methods and equipment for detecting the alignment of one object relative to another using magnetic fields - Google Patents
Methods and equipment for detecting the alignment of one object relative to another using magnetic fields Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 230000005855 radiation Effects 0.000 claims description 25
- 238000002595 magnetic resonance imaging Methods 0.000 abstract description 10
- 238000005481 NMR spectroscopy Methods 0.000 abstract description 9
- 238000003384 imaging method Methods 0.000 description 15
- 238000000926 separation method Methods 0.000 description 10
- 230000000007 visual effect Effects 0.000 description 5
- 206010009244 Claustrophobia Diseases 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
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- 229910000938 samarium–cobalt magnet Inorganic materials 0.000 description 3
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- 230000007246 mechanism Effects 0.000 description 2
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- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 230000036506 anxiety Effects 0.000 description 1
- 238000003491 array Methods 0.000 description 1
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- 238000013152 interventional procedure Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
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- 239000000725 suspension Substances 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/30—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes
- G01B7/31—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/3802—Manufacture or installation of magnet assemblies; Additional hardware for transportation or installation of the magnet assembly or for providing mechanical support to components of the magnet assembly
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
- H01F27/306—Fastening or mounting coils or windings on core, casing or other support
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F6/00—Superconducting magnets; Superconducting coils
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F6/00—Superconducting magnets; Superconducting coils
- H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
A method for detecting the alignment of one component (1) relative to another (4), comprising the steps of: placing a magnetic field generator (20) on one of the components (1) to be aligned; placing a magnetic field sensor (22) on the other component (4) to be aligned, in a position corresponding to the position of the magnetic field generator; adjusting the alignment between the two components; and detecting a magnetic field of an expected magnitude, within a predetermined tolerance, by the magnetic field sensor, thereby indicating the required alignment. The invention is suitable for the assembly of a cylindrical superconducting magnet, such as used in nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) systems, within a cryostat.
Description
METHODS AND EQUIPMENT FOR DETECTING
THE ALIGNMENT OF ONE OBJECT RELATIVE TO ANOTHER
The present invention relates to the mechanical assembly of accurately aligned components, particularly the assembly of such components where access for visual or measured alignment determination is difficult, and the components are not permitted to touch one another when aligned. The invention will be particularly described with reference to the assembly of a cylindrical superconducting magnet, such as used in nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) systems, within a cryostat. However, the invention finds application in many mechanical assemblies which require accurate alignment between components which are not permitted to touch one another when aligned.
Figs. lA-lB illustrate cross-sectional and axial sectional views, respectively, of a conventional cylindrical magnet arrangement for a nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) system. The arrangement is essentially symmetrical about axis AA, and reference to axial and radial directions are to be interpreted with reference toaxisAA.
A number of coils 34 of superconducting wire are wound onto a former 1. The resulting magnet assembly is housed inside a cryogen vessel 2 which is at least partly filled with a liquid cryogen 2a at its boiling point. The coils are thereby held at a temperature below their critical temperature, and are in a superconducting state.
The former 1 is typically constructed of aluminium, which is machined to ensure accurate dimensions of the former, in turn ensuring accurate size and position of the coils which are wound onto the former.
Such accuracy is essential in ensuring the homogeneity and reliability of
the resultant magnetic field.
Also illustrated in Figs. lA-lB are an outer vacuum container (OVC) 4 and thermal shields 3. As is well known, these serve to thermally isolate the cryogen vessel 2 from the surrounding atmosphere. The OVC is formed of a bore tube, an outer cylindrical wall and annular end plates joining the bore tube to the outer cylindrical wall. Insulation 5 may be placed inside the space between the outer vacuum container and the thermal shield. However, as can be seen in Figs. 1A-1B, these elements also reduce the available inside diameter 4a of the cylindrical magnet.
Since the available inside diameter 4a of the cylindrical magnet is required to be of a certain minimum dimension to allow patient access, the presence of the outer vacuum container 4 and the thermal shields 3 effectively increases the necessary diameter of the magnet coils and the former 1, adding to the cost of the overall arrangement.
In use, the superconducting coils 34 of the magnet produce a strong, homogeneous magnetic field in an imaging region, generally located at the axial and radial centre of the former. The magnetic field in this imaging region generally has an inhomogeneity of less than loppm. Such a homogeneous magnetic field has been found necessary to achieve quality images from the NMR or MRI imaging system.
In order to provide as large an available inside diameter 4a as possible for a given diameter of superconducting coils 34, the radial separation of the OVC, the thermal radiation shield and the cryogen vessel must be kept as small as possible, while maintaining effective thermal separation between them. The radial separations between these components are exaggerated for clarity in the drawing. The former 1 is typically mechanically attached to the cryogen vessel, so alignment between them is fixed at manufacture.
Typical radial dimensions for a current MRI magnet system are: Available inside diameter 4a: 900 mm Minimum radial separation between OVC bore tube and thermal radiation shield: 10 mm Minimum radial separation between thermal radiation shield and cryogen \ressel: 6.5 mm There is also a requirement to ensure that the bore of the OVC is as short as possible. A shorter bore has dual advantages in allowing improved access to the patient, for example for interventional procedures during imaging, and in reducing feelings of claustrophobia in a patient.
The reduction of claustrophobia has a valuable technical effect, as a relaxed patient is much less likely to move during imaging, spoiling the images achieved, than a patient suffering from claustrophobia. If a patient moves during imaging, the imaging process may need to be repeated, increasing anxiety within the patient, and increasing yet further the likelihood of spoiled images.
Accordingly, the axial spacing between the OVC 4, the thermal radiation shield 3 and the cryogen vessel 2 must be kept as small as possible, while maintaining effective thermal separation between them.
The axial separations of these components are exaggerated for clarity in the drawing.
Typical axial dimensions for a current MRI magnet system are: Length of OVC bore tube: 1400 mm Minimum axial separation between OVC bore tube and thermal radiation shield: 11 mm Minimum axial separation between thermal radiation shield and cryogen vessel: 6.5mm Minimum axial separation between cryogen vessel and magnet former: 5mm In order to maintain effective thermal isolation, it is clear that none of these components may be allowed to touch each other in the finished structure. Misalignment of the components may also introduce unwanted thermal and electromagnetic effects. This is particularly the case regarding the alignment of the bore tubes of the thermal shield with respect to the magnet. It is therefore most important to ensure that the OVC 4, the thermal radiation shield 3 and the magnet former 1 are accurately aligned. This is often a difficult task, given the size and weight of the components involved, and the fact that there is no visual line of sight or easy access for an alignment tool. The various components are typically mounted inside one another by an arrangement of several tension elements, such as fibreglass or carbon fibre rods or bands. The lengths of the rods, or mounting points of rods or bands, are adjustable in order to adjust the relative positions of the components. Access to such adjustable components may be difficult, and it may be difficult to check that the desired alignment has been achieved.
Figs. 1A and lB also show a gradient coil assembly 10. This contains resistive, electromagnetic coils which, in use, generate oscillating magnetic field in three orthogonal directions x, y, z. The position of the gradient coil assembly 10 relative to the magnet assembly 1, 34, and the position of the thermal radiation shield 3 relative to each of them are important factors in the imaging quality of an MRI system. All of these components: Gradient coil assembly 10, magnet assembly 1, 34, thermal radiation shield 3 and OVC 4 bore tube should be coaxial and axially centred for optimum image quality. At present, the location of these components relies on visual inspection and dead reckoning and has limited accuracy.
The present invention accordingly addresses the problem of aligning one component relative to another, where visual alignment checking is not possible or not desirable, and no mechanical contact is permitted or possible between the components when aligned.
The present invention accordingly provides methods and apparatus as defined in the appended claims.
The above, and further, objects, characteristics and advantages of the present invention will become more apparent from the following description of certain embodiments thereof, given by way of non-limiting examples only, in conjunction with the accompanying drawings, wherein: Figs. 1A and lB schematically show a superconducting magnet apparatus for an MRI system, suitable for improvement according to the present invention; Fig. 2 illustrates the placement of magnets according to an embodiment of the present invention; and Figs. 3 -6 show cross-sections of parts of certain embodiments of the present invention, showing certain features of the present invention in more detail.
The present invention provides methods and equipment for detecting the alignment of one component relative to another, in cases where visual or physical inspection is not possible, or not desired, and mechanical contact between the components is not permitted or not possible in the final assembly.
According to the invention, a magnetic field generator is positioned on one of the components to be aligned. A magnetic field sensor is placed on another component to be aligned. The alignment between the two components is then adjusted. When the magnetic field sensor detects a magnetic field of an expected magnitude and direction, the components are taken to be aligned as required. In preferred embodiments, several pairs of magnetic field generator and magnetic field sensor are provided.
Alignment is deemed to be achieved when all sensors detect an expected magnitude and direction of magnetic field, within a predetermined range of accuracy.
The magnetic field generator may be a permanent magnet, or may be an electromagnetic coil. The magnetic field sensor may be a flux gate or a GMR (Giant Magnetic Resistance) sensor. A GMR sensor uses the Giant Magnetic Resistance effect. Such sensors find application, for instance, in the reading heads of computers' hard disks. The magnetic field sensors need to have sufficient sensitivity and spatial resolution to achieve good spatial accuracy of alignment of the aligned components.
As mentioned above, the present invention will be particularly explained with reference to the alignment of components of a cylindrical superconducting magnet system such as shown in Figs. 1A-1B, in particular the thermal radiation shield 3, the magnet former 1 and the OVC 4.
In a preferred embodiment of the invention, and as illustrated in Fig. 2, the former 1 is fitted with an array of magnetic field generators 20, which will be referred to as localiser magnets'. Note that the former is only schematically illustrated, and the coils 34 and the arrangements for retaining the coils are not shown. In this embodiment, the localiser magnets are placed at the axial centre of the former and symmetrically disposed around the magnet centre in a radial plane at the axial centre of the former 1. In this example embodiment, four localiser magnets are arranged at 90° intervals around the circumference of the former.
The magnetisation of the localiser magnets is directed to provide a magnetic field B along a vector normal to the surface of interest. For instance, in the example illustrated in Fig. 2, to align the former 1 with the bore tube of the OVC 4, which extends axially, the localiser magnets 20 should provide magnetic fields B which are radially aligned.
Alternatively, in order to align the former 1 relative to the annular end plates of the OVC, the localiser magnets should be arranged to have axially aligned fields. This will be described in more detail below, with reference to Figs. 5 and 6.
In cases where permanent magnets are used as the localiser magnets, attention must be paid to the possible effect of the localiser magnets on the imaging performed by the system of which the magnet forms part.
If the magnetic field of a single localiser magnet is strong enough to affect the field in the imaging region of the magnet, then the localiser magnets should be arranged with their magnetic fields E directed alternately radially inwards, and radially outwards, as shown in Fig. 2.
This has been found to eliminate, or at least reduce to an acceptable level, distortion of the magnetic field of the magnet due to the localiser magnets.
In an example, permanent magnets of NbBFe or SmCo with a diameter of 10mm and a height of 5mm have been found to disturb the magnetic field in the imaging volume of a typical magnet for an MRI system by less than 0.lppm, which is presently acceptable.
Instead of such permanent magnets, other magnetic field generators can be used, such as electromagnetic coils. These will only be activated during the alignment process, and so will not interfere with the magnetic field used for imaging. Electrical connections would need to be provided to the coils, however, and this may be considered inconvenient.
Fig. 3 shows a schematic radial cross-section through components of the magnet system, provided with a localiser magnet 20 and magnetic field sensor 22 according to an embodiment of the present invention. As shown, localiser magnet 20 is positioned on the former 1. Magnetic field sensor 22 is placed on the inner surface of the OVC bore tube. Preferably, this is only a temporary placement, and the magnetic field sensor 22 is removed once alignment is achieved. The distance from the inside of the OVC 4 bore tube to the inside of the magnet former is in the order of 20 mm. If the magnets consist of NbBFe or SmCo and have a diameter of 10mm and a height of 5 mm, the resulting disruption to the magnetic field in the imaging volume will be <0.1 ppm. The fields of such magnets are strong enough to be detected by sensors 22, such as flux gates or GMR sensors.
Referring back to Fig. 2, magnetic field sensors 22 are placed on the inner surface of the bore tube of the OVC 4, at locations radially aligned with the localiser magnets 20. Adjustments are made to the suspension arrangements retaining the thermal radiation shield 3 in position, until the magnitude and direction of the magnetic fields are as expected.
Typically, and in the example of concentrically aligning a former 1 with the OVC 4 bore tube, alignment will be indicated by all detected magnetic fields from the localiser magnets being directed radially, and being of equal strength.
In some embodiments of the invention, a similar set of locating magnets 24 are placed on the bore tube of the thermal radiation shield, to assist in aligning the thermal radiation shield to the bore tube of the OVC.
In order to clearly differentiate between magnets attached to the former 1 and magnets attached to the thermal radiation shield 3, the locations of the localiser magnets on the thermal radiation shield 3 should be in offset positions compared to the localiser magnets used for aligning the former 1. For example, if the magnets 20 on the former 1 are arranged in a plane at the axial centre of the former, at circumferential positions corresponding to 0°, 90°, 180° and 270° from top dead centre, the locating magnets 24 on the thermal radiation shield may be positioned at circumferential positions corresponding to 45°, 135°, 225° and 315° from top dead centre. -10-
In alternative embodiments, the localiser magnets 22, 24 and the magnetic field sensor 22 may not be aligned in a radial plane at the axial centre of the magnet, but may be positioned in two radial planes, each displaced towards respective axial ends of the former.
In further embodiments of the present invention, axial alignment of the former 1 to the thermal radiation shield 3 and the OVC 4 may be provided by the present invention. Fig. 5 shows a partial axial cross-section of such an embodiment of the invention. A localiser magnet 26 is provided on an axial end of the former 1. It provides a magnetic fieldE, directed as shown, parallel to axis AA. A magnetic field sensor 22 is provided on the annular end plate of the OVC 4. Analogously to the arrangements described for radial alignment, a number of such arrangements may be provided around the annular end plate.
Adjustments may be made to the support mechanisms supporting the cryogen vessel and the former 1 until the magnetic fields detected by the magnetic field sensors 22 have an expected magnitude and direction.
Fig. 6 shows a similar arrangement for axially aligning the thermal radiation shield 3. A localiser magnet 28 is provided, mounted on an axial end of the thermal radiation shield 3. It provides a magnetic fieldE, directed as shown, parallel to axis AA. A magnetic field sensor 22 is provided on the annular end plate of the OVC 4. Analogously to the arrangements described for radial alignment, a number of such arrangements may be provided around the annular end plate.
Adjustments may be made to the support mechanisms supporting the thermal radiation shield 3 until the magnetic fields detected by the magnetic field sensors 22 have an expected magnitude and direction. -11 -
The method and equipment of the present invention may be applied to any situation where it is required to align components which are difficult to access. The present invention may be applied to align a specific area of one component, marked with a localiser magnet, with that of another, marked with a magnetic field sensor. The present invention may be applied to align more than two components. For example, in the arrangement discussed above, with magnets on the former 1 and on the thermal radiation shield 3, and magnetic field sensors 22 on the OVC 4 bore, three articles may be aligned: the OVC, the former and the thermal radiation shield.
In some embodiments, accurate location of non-concentric geometries may be provided. The present invention does not require that the detected magnetic field strength be the same for all sensors. If a required alignment requires that one localiser magnet should be closer to the corresponding magnetic field sensor than for another localiser magnet, then the expected detected magnetic field strength and direction for each sensor may be established accordingly, and the present invention used to achieve the required alignment.
For accurate location of a component behind a plate, it would be advantageous to use an array of magnets attached to the components, such that the location method of the invention could be used to seek a number of local maxima, or local minima. Different geometries and location requirements would necessitate different layouts of magnet and sensor arrays.
Rare earth magnets, such as the NbBFe and SmCo magnets discussed above, are unlikely to be demagnetised by the field produced by the superconducting magnet. This advantageously allows the magnetic field detector 22 to be used to inspect the locations of the former 1 and thermal radiation shield 3 after ramping and transport of the superconducting magnet arrangement.
Note that if coils are used instead of permanent magnets for the localiser magnets, the issue of disruption of the imaging field, and the advantage of alternating the magnetisation, is no longer relevant, because the coils can be switched off and will not affect the quality of the imaging field. While the magnetic field detectors have been described as detecting the magnitude and direction of a detected magnetic field, the present invention may also be performed with magnetic field sensors which detect only the magnitude of an applied magnetic field, and these sensors are used to detect a magnetic field of an expected strength.
The present invention accordingly provides methods and apparatus for aligning components relative to each other, without the need for a line-of-sight for visual aligning or an access path for mechanical alignment tools.
The invention provides an array of small magnetic field sources, "localiser magnets" at precise locations on a first object which needs to be aligned to a second object. A corresponding array of magnetic field sensors are positioned at corresponding locations on the second object, and are used to detect the magnitude and direction of the magnetic field received from the magnetic field sources, and so to determine the relative -13 -position of the locating magnets, and hence the position of the first object relative to the second object.
Once the relative positions of the former the OVC have been established, the OVC can then be used as a datum for the positioning of the gradient coil assembly 10 with respect to the former by a similar method.
By using permanent magnets as the field generators, the strength, type and position of the field generators should be selected such that image quality is not significantly affected. In embodiments of the present invention located within the magnet systems of nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) systems, the permanent magnets used as field generators must be selected and positioned so that they will not demagnetize due to changes in magnetic
field of the magnet system during ramping.
Claims (8)
- -14 -CLAIMS1. A method for detecting the alignment of one component (1) relative to another (4), comprising the steps of: placing a magnetic field generator (20) on one of the components (1) to be aligned; placing a magnetic field sensor (22) on the other component (4) to be aligned, in a position corresponding to the position of the magneticfield generator;adjusting the alignment between the two components; and detecting a magnetic field of an expected magnitude, within a predetermined tolerance, by the magnetic field sensor, thereby indicating the required alignment.
- 2. A method according to claim 1, wherein several pairs of magnetic field generator (20) and magnetic field sensor (22) are provided, and alignment is deemed to be achieved when all magnetic field sensors detect an expected magnitude of magnetic field, within a predetermined tolerance.
- 3. A method according to claim 1 wherein the magnetic field sensor is sensitive to both the magnitude and the direction of magnetic field, and the required alignment is indicated by the magnetic field sensor (22) indicating an expected magnitude and direction, within a predetermined tolerance.
- 4. A method according to claim 3, wherein several pairs of magnetic field generator (20) and magnetic field sensor (22) are provided, and alignment is deemed to be achieved when all magnetic field sensors detect an expected magnitude and direction of magnetic field, within a predetermined range of accuracy.
- 5. A method according to any preceding claim, comprising the step of energising the magnetic field generator(s).
- 6. A method according to any preceding claim for detecting the alignment of three components (1, 3, 4) relative to one another, comprising the steps of: placing a first magnetic field generator (20) on one of the components (1) to be aligned; placing a second magnetic field generator (24) on a second of the components (3) to be aligned, displaced away from the first magnetic field generator; placing a first magnetic field sensor (22) on the third component (4) to be aligned, in a position corresponding to the position of the firstmagnetic field generator;placing a second magnetic field sensor (22) on the third component (4) to be aligned, in a position corresponding to the position of the secondmagnetic field generator;adjusting the alignment between the three components; and detecting a magnetic field of an expected magnitude, within a predetermined tolerance, by each the magnetic field sensor, thereby indicating the required alignment between the three components.
- 7. A method according to any preceding claim, wherein at least someof the field generators are permanent magnets.AMENDED CLAIMS HAVE BEEN FILED AS FOLLOWS:-CLAIMS1. A method for detecting the coaxial and axial alignment of components of a cylindrical superconducting magnet arrangement, comprising an outer vacuum container (4), a thermal radiation shield (3) and a magnet assembly (1) mounted inside one another, the method comprising the steps of: placing a magnetic field generator (20) on one of the components (1) to be aligned; placing a magnetic field sensor (22) on another component (4) to be aligned, in a position corresponding to the position of the magnetic field generator; adjusting the alignment between the two components; and detecting a magnetic field of an expected magnitude, within a o predetermined tolerance, by the magnetic field sensor, thereby indicating the required alignment. c'J2. A method according to claim 1, wherein several pairs of magnetic field generator (20) and magnetic field sensor (22) are provided, on each of the components to be aligned, and alignment is deemed to be achieved when all magnetic field sensors detect an expected magnitude ofmagnetic field, within a predetermined tolerance.3. A method according to claim 1 wherein the magnetic field sensor is sensitive to both the magnitude and the direction of magnetic field, and the required alignment is indicated by the magnetic field sensor (22) indicating an expected magnitude and direction, within a predetermined tolerance.4. A method according to claim 3, wherein several pairs of magnetic field generator (20) and magnetic field sensor (22) are provided on each of the components to be aligned, and alignment is deemed to be achieved when all magnetic field sensors detect an expected magnitude and direction of magnetic field, within a predetermined range of accuracy.5. A method according to any preceding claim, comprising the step of energising the magnetic field generator(s).6. A method according to any preceding claim for detecting the alignment of three components (1, 3, 4) of a cylindrical superconducting magnet arrangement, comprising an outer vacuum container (4), a thermal radiation shield (3) and a magnet assembly (1) mounted inside one another, relative to one another, comprising the steps of: o placing a first magnetic field generator (20) on one of the (0 components (1) to be aligned; placing a second magnetic field generator (24) on a second of the components (3) to be aligned, displaced away from the first magnetic field generator; placing a first magnetic field sensor (22) on the third component (4) to be aligned, in a position corresponding to the position of the firstmagnetic field generator;placing a second magnetic field sensor (22) on the third component (4) to be aligned, in a position corresponding to the position of the secondmagnetic field generator;adjusting the alignment between the three components; and detecting a magnetic field of an expected magnitude, within a predetermined tolerance, by each the magnetic field sensor, thereby indicating the required alignment between the three components.7. A method according to any preceding claim wherein the cylindrical superconducting magnet arrangement further comprises a cylindrical gradient coil assembly (10) mounted within a central bore of the outer vacuum container (4), and the gradient coil assembly is one of the components to be aligned.
- 8. A method according to any preceding claim, wherein at least someof the field generators are permanent magnets. 0*) (0 (0 c'J
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0900480A GB2466935A (en) | 2009-01-13 | 2009-01-13 | Methods and equipment for detecting the alignment of one object relative to another using magnetic fields |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0900480A GB2466935A (en) | 2009-01-13 | 2009-01-13 | Methods and equipment for detecting the alignment of one object relative to another using magnetic fields |
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| Publication Number | Publication Date |
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| GB0900480D0 GB0900480D0 (en) | 2009-02-11 |
| GB2466935A true GB2466935A (en) | 2010-07-14 |
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| GB0900480A Withdrawn GB2466935A (en) | 2009-01-13 | 2009-01-13 | Methods and equipment for detecting the alignment of one object relative to another using magnetic fields |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2530806A (en) * | 2014-10-03 | 2016-04-06 | Siemens Healthcare Ltd | Serially bonded magnet assembly method |
Citations (7)
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|---|---|---|---|---|
| US4731579A (en) * | 1982-10-12 | 1988-03-15 | Polaroid Corporation | Magnetic position indicator and actuator using same |
| US4891589A (en) * | 1987-12-23 | 1990-01-02 | Eaton Corporation | Displacement gauge that combines vector signals |
| US5434500A (en) * | 1993-07-26 | 1995-07-18 | Hauck; Bruce | Magnetic field generator and detector position indicator |
| DE4406681A1 (en) * | 1994-03-01 | 1995-09-07 | Siemens Ag | Inspection or processing unit position determination method in esp. ferritic pipe |
| US5929757A (en) * | 1996-03-08 | 1999-07-27 | Sternal; Bernd | Method and apparatus for making through-bores |
| EP1382308A2 (en) * | 2002-07-18 | 2004-01-21 | Biosense, Inc. | Distal targeting of locking screws in intramedullary nails |
| GB2441795A (en) * | 2006-09-15 | 2008-03-19 | Siemens Magnet Technology Ltd | Tubular support system for a superconducting magnet |
-
2009
- 2009-01-13 GB GB0900480A patent/GB2466935A/en not_active Withdrawn
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4731579A (en) * | 1982-10-12 | 1988-03-15 | Polaroid Corporation | Magnetic position indicator and actuator using same |
| US4891589A (en) * | 1987-12-23 | 1990-01-02 | Eaton Corporation | Displacement gauge that combines vector signals |
| US5434500A (en) * | 1993-07-26 | 1995-07-18 | Hauck; Bruce | Magnetic field generator and detector position indicator |
| DE4406681A1 (en) * | 1994-03-01 | 1995-09-07 | Siemens Ag | Inspection or processing unit position determination method in esp. ferritic pipe |
| US5929757A (en) * | 1996-03-08 | 1999-07-27 | Sternal; Bernd | Method and apparatus for making through-bores |
| EP1382308A2 (en) * | 2002-07-18 | 2004-01-21 | Biosense, Inc. | Distal targeting of locking screws in intramedullary nails |
| GB2441795A (en) * | 2006-09-15 | 2008-03-19 | Siemens Magnet Technology Ltd | Tubular support system for a superconducting magnet |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2530806A (en) * | 2014-10-03 | 2016-04-06 | Siemens Healthcare Ltd | Serially bonded magnet assembly method |
| GB2530806B (en) * | 2014-10-03 | 2016-12-14 | Siemens Healthcare Ltd | Serially bonded magnet assembly method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0900480D0 (en) | 2009-02-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| COOA | Change in applicant's name or ownership of the application |
Owner name: SIEMENS PLC Free format text: FORMER OWNER: SIEMENS MAGNET TECHNOLOGY LIMITED |
|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |