GB2384564A - Detecting metal fragments - Google Patents
Detecting metal fragments Download PDFInfo
- Publication number
- GB2384564A GB2384564A GB0210971A GB0210971A GB2384564A GB 2384564 A GB2384564 A GB 2384564A GB 0210971 A GB0210971 A GB 0210971A GB 0210971 A GB0210971 A GB 0210971A GB 2384564 A GB2384564 A GB 2384564A
- Authority
- GB
- United Kingdom
- Prior art keywords
- loop
- signal
- detector
- ferromagnetic
- metal fragments
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
- G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
- G01V3/104—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils
- G01V3/105—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops
- G01V3/107—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops using compensating coil or loop arrangements
Abstract
A detector to detect metal fragments (especially in pre MRI scanning) comprising: a first loop (1) of conducting material, means to feed an rf signal to the first loop, a second loop (2) of conducting material, and means to detect an induced rf signal consequent to said rf signal in said first loop, said second loop being geometrically symmetrically arranged with said first loop such that the rf signal induced therein is substantially zero when there are no metal fragments in the close proximity of the sensor. Preferably the second loop comprises two halves arranged in anti-phase, such as in the form of a figure of eight. The loops are arranged to be substantially co-planar, such as on a PCB. The detector may distinguish between ferromagnetic and non-ferromagnetic materials.
Description
<Desc/Clms Page number 1>
METHOD AND APPARATUS OF TO DETECT METAL
FRAGMENT IN PATIENTS
This invention relates to a method and apparatus of detecting metal fragments in patients, particularly pre-MRI patients.
If there are ferromagnetic fragments located in patients and these are undetected prior to undergoing a MRI scan, the scanner's magnetic field will cause the fragment to move, causing injury. The problem is generally not with medical implants as these are known to the patient and doctor, but it is with unsuspected objects such as shrapnel or splinters in people who have previously worked with metal.
The current method of determining is to CT-scan the patients who are suspected of having metal fragments. The problems result in delays to the MRI scan schedule. Further the CT method cannot distinguish between materials. Another problem is that it means the patents are exposed to X-rays. As a consequence radiologists have to err on the side of caution and assume that all metal objects detected are ferromagnetic so denying MRI scanning to many patients.
It is an object of the invention to overcome these problems and provide a device and method to detect small subcutaneous objects so as to reduce injury during MRI scanning.
The invention comprises a detector to detect metal fragments comprising: a first loop of conducting material, means to feed an rf signal to the first loop, a second loop of conducting material, and means to detect an induced rf signal consequent to said rf signal in said first loop, said second loop being geometrically symmetrically arranged with said first loop such that the rf signal induced is therein is substantially zero when there are no metal fragments in the close proximity of the sensor.
<Desc/Clms Page number 2>
Preferably the second loop comprises two halves arranged in antiphase, such-in the form of a figure of eight. The loops are arranged to be substantially co-planar, such as on a PCB.
The invention will now be described with by means of example only.
Figure 1 shows a schematic representation of one embodiment of the invention. The figure shows a first copper loop 1 and a second copper loop 2. These are laid out flat on a printed circuit board (not shown). The second loop is in the form of a figure of"8". In operation a very low power radio frequency is applied to one loop. The signal consequently induced in the second (figure of eight) loop cancels the and so no signal is detected in the output signal (the two halves of the loop are connected in anti-phase)
If the antenna system and the electrical characteristics of the material underneath are symmetrical, the radio frequency signal fed to the first loop produces no resultant signal from the figure of eight loop. If however there is a metal fragment under one half (side) of the figure of eight loop that will effect its rf characteristics relative to that of the other half of the loop, the system is then unbalanced and a net signal is produced. This is detected, amplified and signalled to an operator. The level of the signal peaks either side of a fragment when the antenna is moved from side to side over the area to be scanned. The sharp null in the middle of the scan can be used to accurately locate the object even if the antenna is very much larger than the object.
In a refined embodiment of the invention, the detector can also discriminate between ferromagnetic and non-ferromagnetic materials by measuring the phase of the detected signal. Ferromagnetic materials produce an output signal which is in phase with the energising waveform,
<Desc/Clms Page number 3>
whereas the output from ferromagnetic materials is at phase-quadrature with the energising signal.
Figure 2 shows a schematic representation of a deployable device according to the invention in the form of a small hand held version and includes LED indicators 3, a lid 4 enclosing electronics and battery space 5 and search head 6 which comprises a PCP with the loops on it. An onoff button is 6 also provided. Detection of a metal fragment is indicated by LED's. which would also indicate ferrous or non-ferrous material.
Alternatively an audible tone may be used (or in addition to) the LED's.
A detector such as this can used to scan e. g. the patients eyes, where the danger of metallic fragments is the greatest, and detect fragments smaller than 0.1 cu mm.
Such a device may be used for other purposes such a detecting metal fragments such as shrapnel in people. For a battlefield device, a detector head size of 20 x 16 cm gives good coverage, and detects metal objects such as a 9mmm diameter bullet at a range of 30 cm.
In fabrication of the loops on a PCB for example, it is sometimes difficult to get perfect symmetry in the layout so that a small offset signal is obtained when no metal fragment is under the detector. The inventor has determined that the fine balance of the loops to produce nominal zero output can be effected by placing metal"balancing"fragments at suitable position (s) on the PCB itself. This may even be adjustable, such as having two or more screw means 7 (inserted on or through the PCB 8 which carries the loops 1 and 2) on each side of the line of symmetry of the "figure of 8"loop, shown in figure 3.
Claims (11)
- CLAIMS 1. A detector to detect metal fragments comprising : a first loop of conducting material, means to feed an rf signal to the first loop, a second loop of conducting material, and means to detect an induced rf signal consequent to said rf signal in said first loop, said second loop being geometrically symmetrically arranged with said first loop such that the rf signal induced is therein is substantially zero when there are no metal fragments in the close proximity of the sensor.
- 2. A detector as claimed in claim I wherein said second loop comprises two halves arranged in anti-phase.
- 3. A detector as claimed in claim 2 wherein said second loop is in the form of a figure of eight.
- 4. A detector as claimed in claim s 1 to 3 wherein said loops are arranged to be substantially co-planar.
- 5. A detector as claimed in claims 1 to 4 wherein said loops are fabricated onto a flat surface.
- 6. A detector as claimed in claim 1 to 5 wherein said flat surface includes adjustable means to zero output from the second loop.
- 7. A detector as claimed in any preceding claims having means to determine if the induced signal in the second loop is in phase or quadrature to the signal in the first loop.<Desc/Clms Page number 5>
- 8. A detector as claimed in claim 7 which includes means to indicate whether a detected metal fragment is ferromagnetic or non-ferromagnetic.
- 9. A method of detecting metal fragments in patients comprising using a detector as claimed in any of claims 1 to 8.
- 10. A method of detecting metal fragments as claimed in claim 9 which includes determining whether any metal fragment is ferromagnetic or non-ferromagnetic.
- 11. A method as claimed in claims 9 or 10 wherein the rf signal applied to the first coil has a frequency of less than 0.5 MHz.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03075200A EP1332719A1 (en) | 2002-01-23 | 2003-01-20 | Method and apparatus to detect metal fragments in patients |
US10/348,350 US20030227282A1 (en) | 2002-01-23 | 2003-01-22 | Method and apparatus of to detect metal fragment in patients |
CNA031198597A CN1473546A (en) | 2002-01-23 | 2003-01-23 | Method and device for detecting metal debris in human body |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0201465A GB0201465D0 (en) | 2002-01-23 | 2002-01-23 | Pre-mri metal detector |
Publications (2)
Publication Number | Publication Date |
---|---|
GB0210971D0 GB0210971D0 (en) | 2002-06-19 |
GB2384564A true GB2384564A (en) | 2003-07-30 |
Family
ID=9929565
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB0201465A Ceased GB0201465D0 (en) | 2002-01-23 | 2002-01-23 | Pre-mri metal detector |
GB0210971A Withdrawn GB2384564A (en) | 2002-01-23 | 2002-05-14 | Detecting metal fragments |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB0201465A Ceased GB0201465D0 (en) | 2002-01-23 | 2002-01-23 | Pre-mri metal detector |
Country Status (1)
Country | Link |
---|---|
GB (2) | GB0201465D0 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2492872A (en) * | 2008-08-29 | 2013-01-16 | Cambridge Silicon Radio Ltd | An integrated circuit inductor structure |
GB2462885B (en) * | 2008-08-29 | 2013-03-27 | Cambridge Silicon Radio Ltd | Inductor structure |
WO2013079844A1 (en) * | 2011-12-02 | 2013-06-06 | Perin Ambroise Jean-Pierre | Vibration sensor device for musical instruments |
EP2730950A3 (en) * | 2012-11-09 | 2017-03-29 | Elmos Semiconductor Aktiengesellschaft | Coil for an inductive sensor and circuit for controlling the same |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3882374A (en) * | 1974-04-18 | 1975-05-06 | Us Army | Transmitting-receiving coil configuration |
US4024468A (en) * | 1975-06-18 | 1977-05-17 | White's Electronics, Inc. | Induction balance metal detector with inverse discrimination |
EP0058076A2 (en) * | 1981-02-09 | 1982-08-18 | Goring Kerr Limited | Metal detection apparatus |
WO1993006433A1 (en) * | 1991-09-24 | 1993-04-01 | Industrial Contractors Holland B.V. | Position measurement by radio frequency transponders |
GB2278199A (en) * | 1993-05-08 | 1994-11-23 | Roke Manor Research | Apparatus for detecting and estimating length of hidden elongated conductive objects |
WO1997049334A1 (en) * | 1996-06-25 | 1997-12-31 | Quantum Magnetics, Inc. | Ferromagnetic foreign body screening method and apparatus |
GB2339288A (en) * | 1998-07-06 | 2000-01-19 | Roke Manor Research | Buried object detector apparatus |
-
2002
- 2002-01-23 GB GB0201465A patent/GB0201465D0/en not_active Ceased
- 2002-05-14 GB GB0210971A patent/GB2384564A/en not_active Withdrawn
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3882374A (en) * | 1974-04-18 | 1975-05-06 | Us Army | Transmitting-receiving coil configuration |
US4024468A (en) * | 1975-06-18 | 1977-05-17 | White's Electronics, Inc. | Induction balance metal detector with inverse discrimination |
EP0058076A2 (en) * | 1981-02-09 | 1982-08-18 | Goring Kerr Limited | Metal detection apparatus |
WO1993006433A1 (en) * | 1991-09-24 | 1993-04-01 | Industrial Contractors Holland B.V. | Position measurement by radio frequency transponders |
GB2278199A (en) * | 1993-05-08 | 1994-11-23 | Roke Manor Research | Apparatus for detecting and estimating length of hidden elongated conductive objects |
WO1997049334A1 (en) * | 1996-06-25 | 1997-12-31 | Quantum Magnetics, Inc. | Ferromagnetic foreign body screening method and apparatus |
GB2339288A (en) * | 1998-07-06 | 2000-01-19 | Roke Manor Research | Buried object detector apparatus |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2492872A (en) * | 2008-08-29 | 2013-01-16 | Cambridge Silicon Radio Ltd | An integrated circuit inductor structure |
GB2462885B (en) * | 2008-08-29 | 2013-03-27 | Cambridge Silicon Radio Ltd | Inductor structure |
GB2492872B (en) * | 2008-08-29 | 2013-05-01 | Cambridge Silicon Radio Ltd | Inductor structure |
US8841983B2 (en) | 2008-08-29 | 2014-09-23 | Cambridge Silicon Radio Limited | Inductor structure |
WO2013079844A1 (en) * | 2011-12-02 | 2013-06-06 | Perin Ambroise Jean-Pierre | Vibration sensor device for musical instruments |
FR2983621A1 (en) * | 2011-12-02 | 2013-06-07 | Ambroise Jean Pierre Perin | VIBRATION SENSOR DEVICE FOR MUSICAL INSTRUMENTS |
US9286873B2 (en) | 2011-12-02 | 2016-03-15 | Jean-Pierre Ambroise Perin | Vibration sensor device for musical instruments |
EP2730950A3 (en) * | 2012-11-09 | 2017-03-29 | Elmos Semiconductor Aktiengesellschaft | Coil for an inductive sensor and circuit for controlling the same |
EP3594724A1 (en) * | 2012-11-09 | 2020-01-15 | Elmos Semiconductor Aktiengesellschaft | Coil for an inductive sensor and circuit for controlling the same |
Also Published As
Publication number | Publication date |
---|---|
GB0210971D0 (en) | 2002-06-19 |
GB0201465D0 (en) | 2002-03-13 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |