WO2003073934A1

WO2003073934A1 - Detection system

Info

Publication number: WO2003073934A1
Application number: PCT/GB2003/000945
Authority: WO
Inventors: Lee Edwards; Ara Darzi
Original assignee: Imperial College Innovations Limited
Priority date: 2002-03-06
Filing date: 2003-03-06
Publication date: 2003-09-12
Also published as: GB0205188D0; EP1538982A1; AU2003209466A1

Abstract

A method for detecting and/or locating within a body cavity a swab or surgical instrument which comprises a metal or magnetic material or other detectable material, the method comprising the step of passing a detection sensor over the wound site, wherein the detection sensor preferably comprises a multi sensor array and wherein the method does not involve the use of X-ray radiation. Two detection sensors may be used. One may be in the form of a reusable mat placed under the patient; the other may be in the form of a hand-held device or wand. The swab may comprise a thread with a metallic coating.

Description

DETECTION SYSTEM

The present invention relates to surgical swabs and methods for detecting surgical swabs and instruments during or following surgery.

The failure to remove swabs, needles and other surgical instruments from a surgical site has for many years been a major problem in all fields of surgery. A swab left in the body will result in considerable trauma or death for the patient if left unrecognised or undetected. The costs of retreatment, additional surgical time, recovery, hospital stay and subsequent litigation are considerable. Swab retention is considered a common human error in medicine.

Whilst there are strict protocols in the use of swabs in surgery, the process is exclusively human led and involves a manual count of swabs at various stages of the procedure and a final count at the end. Despite this diligence there is considerable opportunity for error.

Medical swabs are generally made of absorbent, multi-layered cotton or cotton/lint-based material with a woven in PNC thread, coated in 55 % Barium Phosphate, which is detectable under X ray. EP 0 244 992, for example, describes a process of manufacturing swabs to include a layer of X ray detectable material, allowing the detection of retained swabs under X ray control. Suture needles and instruments are most commonly made of high grade 622-625 surgical steel, and are magnetic.

However, the inefficiencies, expense and related risks of additional X ray exposure of an X-ray based detection approach make it largely impracticable and unacceptable for routine practice or as a method for preventive retained item scanning.

The present invention provides alternative detection systems suitable for routine practice or as a method for preventive retained item scanning and swabs suitable for use in such detection systems.

A first aspect of the invention provides a method for detecting and/or locating within a body cavity (or otherwise during a surgical operation) a swab or surgical instrument (which may be a needle) which comprises a metal (material with high electrical conductivity) or magnetic material (or less preferably other detectable material), the method comprising the step of passing a detection sensor over the wound site, wherein the method does not involve the use of X-ray radiation.

Preferably the detection sensor comprises a multi sensor array. A single sensor is considered sufficient to provide useful information. The multi sensor approach would allow individual sensors to be tuned at different frequencies (which may allow more detailed positional information to be obtained) and may allow wider beam spread. Multiple sensors may provide a more accurate location indication, which may be useful in larger cavities.

It will be appreciated that the detection sensor is not intended to be inserted into the body.

The method indicates the presence or possibly the number of marked swabs or other metallic items within the wound or cavity body cavity. It is preferred that the detection sensor is capable of detecting magnetic materials, for example surgical steel. The detection sensor may preferably generate and/or detect microwave radiation.

Alternatively, the detection sensor may employ ultrasonic, radio/wireless proximity, thermal, luminescence, infrared, piezoelectric or fmoroscopy methods.

It is preferred that the detection sensor has the following properties: 1. it is preferably in the form of a 'wand' which may be passed over the wound site

2. It is preferably small (for example suitable for/intended for hand-held or supported operation)

3. It preferably has an audible and/or visible and/or vibrating warning system ie provides an audible or visible signal when a metallic or magnetic material is detected.

4. It is preferably of a construction that will allow it to be fully sterilised (autoclaveable) or sheathed with a sterile covering (which may be purpose- designed for the sensor, and which may be disposable). 5. Alternatively or in addition the sensor may be fully disposable.

Suitable detection sensors may be based on metal detector instruments used in law enforcement or security operations (for example in airport security), for example adapted to be sterilisable or to have a sterile covering, as discussed above. Such instruments will be well known to those skilled in the art. WO 01/51948 relates to a hand-mounted instrument and describes other instruments, for example in the form of wands. Such instruments may be particularly suitable for use in the present invention. US 5,936,586 and US 2002/0017904 also describe non-metal and metal detection instruments embodying principles which may be useful in instruments for use in the present invention.

In a preferred embodiment the sensor comprises a (preferably battery operated and hand portable) wave guide (A) which includes a microwave oscillator for generating microwaves and (at least) two resonating slots on a wall of the wave-guide, and a microwave detector capable of detecting reflected microwaves.

Suitable detection sensors may also be based on Electronic Article Surveillance (EAS) systems used in retail environments. These have the advantage that they are designed to be substantially unaffected by the presence of steel or ferromagnetic objects such as the operating theatre bed structure. One embodiment of such a sensor system uses tags made of a soft magnetic material that is easily saturated. The detector contains a coil which generates a low (a few kHz) frequency alternating magnetic field. The tag magnetisation is a clipped waveform rich in harmonics which are detected by a receive coil in the detector. The tags can be in a number of forms, but typically can be a thin foil laminate either in a patch or in a thread about 1mm wide. Other embodiments include acousto-magnetic resonators, RF resonant circuits, microwave antenna .and RFID integrated circuits. Forms of EAS systems will be well known to those skilled in the art; examples of documents that relate to such systems include US 2003/0020613 and US 6,356,197.

In a preferred embodiment the sensor comprises a transmit coil and a receive coil, connected to a battery operated transmit and receive circuit capable of detecting harmonics in the magnetisation of the tag. A second (or further) detection sensor (which may also comprise a multi- sensor array) may be used. This may preferably be positioned on the opposite side of the patient to the first detection sensor. For example, the second detection sensor may be placed underneath the patient whilst the first detection sensor is used above (including to the side of) the patient.

The second or further detection sensor may be oriented so that its multi- sensor array is rotated relative to the multi-sensor array of the first detection sensor.

The use of two or more detection sensors, for example comprising multi- sensor arrays, may be useful in creating a constant detection zone, for example by combining the signals received from the two or more detection sensors or multi-sensor arrays, as well known to those skilled in the art.

In a preferred embodiment a re-useable mat comprising a second multi- sensor array may be placed underneath the patient (Fig 2). The array may be similar to that in the first detection sensor but constructed to be 180 degrees out-of-phase. This arrangement may create a constant 'detection zone'.

A still further aspect of the invention provides a detection sensor as defined above for use in medicine. A still further aspect of the invention provides a detection sensor as defined above for use in a method for detecting and/or locating within a body cavity (or otherwise during a surgical procedure) a swab or surgical instrument which comprises a metal or magnetic material (or other detectable material). A further aspect of the invention provides a detection sensor as defined above in the form of a mat. Thus, the invention provides a mat comprising a detection sense, preferably comprising a multi-sensor array.

A further aspect of the invention provides a swab or surgical instrument which comprises a metal or magnetic material (or other detectable material) for use in a method for detecting and/or locating within a body cavity (or otherwise during a surgical procedure) the swab or surgical instrument, the method comprising the step of passing a detection sensor over the wound site, wherein the method does not involve the use of X-ray radiation. The detection sensor preferably comprises a multi sensor array, as discussed above.

A further aspect of the invention provides a surgical swab comprising a magnetic material. The magnetic material does not comprise a noble metal, such as gold or silver as described in GB 805082.

The magnetic material preferably comprises paramagnetic atoms or ions, for example comprises Fe, Co or Ni atoms or ions (which are ferromagnetic elements). The magnetic material may preferably comprise a ferromagnetic compound, for example a ferromagnetic compound listed in the CRC Handbook of Chemistry and Physics, 82^nd Edition 2001-2002 CRC Press LLC, Ed David R Lide. Magnetic materials are discussed extensively in the CRC Handbook (supra) and in references cited therein.

It is preferred that the magnetic material is or comprises stainless steel, preferably surgical grade stainless steel, for example 622-625 stainless steel. Preferably the magnetic material or (in relation to the first aspect of the invention) metallic material or other detectable material may be incorporated in or round a thread embedded in the swab (which term includes any surgical dressing) structure. As noted above medical and surgical swabs generally have a PNC thread, coated in 55 % Barium Phosphate woven into the swab. The Barium Phosphate coating may be replaced by a metallic coating (Fig 1). This metallic coating (or other detectable material) allows detection via multi-sensor sensing devices including: a. Magnetic; b. Ultrasonic; c. Radio/wireless proximity; d. Microwave; e. Thermal; f. Luminescence; g. Infrared emission; h. Piezoelectric; i. X ray/fluoroscopy. The thread may be woven into the gauze during manufacture of the swab or it may be sewn through the finished gauze or glued or otherwise attached thereto.

The magnetic material may consist of a low-coercivity alloy such as Atalante™ (Bekaert NDS n.v.Sputtered Films, Karreweg 18,B - 9870 Zulte, Belgium, with a coercivity typically less than 1 Oersted. This is available as a thin (less than 1 micron) layer sputtered onto a flexible polymer substrate.

It is desirable that the magnetic material or metal (or other detectable material) is non-toxic, unaffected by sterilisation and by body fluids (or less preferably is coated or contained in such a material), incapable of causing abrasion or irritation, non-fraying and flexible. It is further desirable that it is easily obtainable and manipulable and is preferably cheap. In the case of steel needles and other foreign bodies, it may be necessary to coat the items with a thin layer of soft magnetic material if the harmonic magnetic field detection system is used. A further aspect of the invention provides a method for making a swab of the invention, comprising the step of incorporating a magnetic material into the swab. The magnetic material may be incorporated during formation of the material from which the swab is constructed, after formation of the material but before the swab is assembled, or after assembly of the structure of the swab. Preferably the magnetic material is incorporated on a thread on which the magnetic material is coated.

A further aspect of the invention provides a swab of the invention for use in medicine. A still further aspect of the invention provides a swab of the invention for use in a method for detecting and/or locating within a body cavity the swab or surgical instrument, the method comprising the step of passing a detection sensor over the wound site, wherein the method does not involve the use of X-ray radiation. Preferably the detection sensor comprises a multi sensor array.

The invention will now be described in more detail by reference to the following, non-limiting, Figures and Examples.

Fig 1 Cross-section of thread to be incorporated into swabs: replacement of Barium Phosphate with a metallic coating.

Fig 2 If a foreign body (metal needle/instrument) or Swab manufactured with a flexible, metal coated PNC thread, is within Zone 'C it will create interference with one of the radiating slots and result in a signal being sent from the detecting diode resulting in an alarm signal (audio/visual). If no metallic or foreign bodies are within Zone 'C the balance of A and B is maintained causing no resultant alarm signal. Example 1: Patient monitoring during surgery.

The surgeon or an assistant scans the surgical zone prior to wound closer. This may be done in conjunction with existing swab and instrument checks.

If a needle was dropped and lost an immediate scan may be made of the surgical site or surrounding drapes (most often where needles are dropped) in order to locate the missing needle.

Claims

1. A method for detecting and/or locating within a body cavity or otherwise during surgery a swab or surgical instrument which comprises a metal or magnetic material or other detectable material, the method comprising the step of passing a detection sensor over the wound site, wherein the method does not involve the use of X-ray radiation.

2. The method of claim 1 wherein the detection sensor comprises a multi sensor array.

3. The method of claim 1 or 2 wherein the detection sensor is capable of detecting magnetic materials.

4. The method of claim 1, 2 or 3 wherein the detection sensor generates and/or detects microwave radiation.

5. The method of any one of claims 1 to 3 wherein the detection sensor generates and/or detects an ultrasonic, radio/wireless proximity, thermal, luminescence, infrared, piezoelectric or fluoroscopy signal.

6. The method of any one of the preceding claims wherein the detection sensor is in the form of a 'wand' which may be passed over the wound site.

7. The method of any one of the preceding claims wherein the detection sensor is suitable for hand-held operation.

8. The method of any one of the preceding claims wherein the detection sensor has an audible and/or visible and/or vibrating warning system.

9. The method of any one of the preceding claims wherein the detection sensor is fully sterilisable or intended to be sheathed with a sterile covering.

10. The method of any one of claims 1 to 9 wherein the detection sensor is fully disposable.

11. The method of any one of the preceding claims wherein the sensor comprises a wave guide which includes a microwave oscillator for generating microwaves and at least two resonating slots on a wall of the wave- guide, and a microwave detector capable of detecting reflected microwaves.

12. The method of any one of the preceding claims wherein the detection sensor comprises a detection sensor usable as part of an Electronic Article Surveillance system.

13. The method of any one of the preceding claims wherein a second (or further) detection sensor is used in detecting and/or locating the swab or surgical instrument.

14. The method of claim 13 wherein the second or further detection sensor is positioned on the opposite side of the patient to the first detection sensor.

15. The method of claim 13 or 14 wherein the second or further detection sensor is placed underneath the patient whilst the first detection sensor is used above the patient.

16. The method of any one of claims 13 to 15 wherein the second or further detection sensor is comprised in a re-usable mat.

17. A detection sensor as defined in claim 16.

18. A detection sensor as defined in any of the preceding claims for use in medicine.

19. A detection sensor according to claim 18 for detecting and/or locating within a body cavity a swab or surgical instrument which comprises a metal or magnetic material or other detectable material.

20. A swab or surgical instrument which comprises a metal or magnetic material or other detectable material for use in a method for detecting and/or locating within a body cavity the swab or surgical instrument, the method comprising the step of passing a detection sensor over the wound site, wherein the method does not involve the use of X-ray radiation.

21. The swab or surgical instrument according to claim 20 wherein the detection sensor comprises a multi sensor array.

22. A surgical swab comprising a magnetic material.

23. The method of any one of claims 1 to 16 or swab or surgical instrument of claim 20, 21 or 22 wherein the magnetic material comprises Fe, Co or Ni atoms or ions.

24. The method of any one of claims 1 to 16 or swab or surgical instrument of claims 20 to 23 wherein the magnetic material comprises a ferromagnetic compound.

25. The method, swab or surgical instrument of claim 24 wherein the magnetic material is or comprises stainless steel.

26. The method of any one of claims 1 to 16, 23 to 25 or swab of any one of claims 20 to 25 wherein the magnetic material or metallic material is incorporated in or round a thread embedded in the swab structure.

27. A method for making a swab according to any one of claims 20 to 25, comprising the step of incorporating a magnetic material into the swab.

28. Any novel method for detecting and/or locating a swab or surgical instrument as herein described.

29. Any novel detection means for use in a method for detecting and/or locating a swab or surgical instrument as herein described.

30. Any novel swab as herein described.