WO1998034564A1 - Medical ultrasound apparatus - Google Patents

Medical ultrasound apparatus Download PDF

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Publication number
WO1998034564A1
WO1998034564A1 PCT/GB1998/000241 GB9800241W WO9834564A1 WO 1998034564 A1 WO1998034564 A1 WO 1998034564A1 GB 9800241 W GB9800241 W GB 9800241W WO 9834564 A1 WO9834564 A1 WO 9834564A1
Authority
WO
WIPO (PCT)
Prior art keywords
stent
drug
shown
operating
method
Prior art date
Application number
PCT/GB1998/000241
Other languages
French (fr)
Inventor
Robert Julian Dickinson
Original Assignee
Intravascular Research Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to GB9702612.4 priority Critical
Priority to GB9702612A priority patent/GB2321853A/en
Priority to GB9710548.0 priority
Priority to GBGB9710548.0A priority patent/GB9710548D0/en
Application filed by Intravascular Research Limited filed Critical Intravascular Research Limited
Publication of WO1998034564A1 publication Critical patent/WO1998034564A1/en

Links

Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/90Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00Ultrasound therapy
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/39Markers, e.g. radio-opaque or breast lesions markers
    • A61B2090/3925Markers, e.g. radio-opaque or breast lesions markers ultrasonic
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/86Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
    • A61F2/88Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure the wire-like elements formed as helical or spiral coils
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F7/00Heating or cooling appliances for medical or therapeutic treatment of the human body
    • A61F2007/009Heating or cooling appliances for medical or therapeutic treatment of the human body with a varying magnetic field acting upon the human body, e.g. an implant therein

Abstract

In order to overcome the problem of tissue proliferation around a coronary stent, the stent is provided with means by which it can be made to radiate ultrasonic energy when in an operative position.

Description

MEDICAL ULTRASOUND APPARATUS

The present invention relates to medical ultrasound apparatus and more particularly to the use of so-called stents in the treatment of vascular disorders.

Coronary artery disease is a significant cause of death in the Western World, and a number of methods of treatment have been developed. Surgical treatment in which a vein is grafted to replace the diseased artery, known as coronary artery bypass grafts, are successful, but require the trauma of major surgery with its concomitant risks and long recovery periods, and is limited to a selected patient population.

In more recent years cardiac catheters have been increasingly used to treat the narrowing of coronary arteries, using angioplasty balloons to widen the lumen. The lumen widening in many cases is temporary and the vessel relaxes back to its original narrow lumen.

An improved treatment involves implanting metallic stents which act to hinder the remodelling of the opened vessel. A stent is essentially an elongated metallic device which can be introduced into the target area and expanded to as it were shore up the collapsed or partially collapsed arterial wall defining the lumen. A typical method of delivery employs a balloon catheter with the stent carried around the outside of the deflated balloon so that when the balloon is then inflated (at the target area) the stent is caused to expand into its operative position.

Stents do provide a longer lasting treatment for coronary artery stenosis than percutaneous coronary transluminal angioplasty (known as PCTA) but further narrowing or re-stenosis has been observed. The mechanism for this can be the formation of a thrombus around the stent, although this can be minimised by improved stent placement and appropriate use of anti-coagulation therapy. A further mechanism is a longer term proliferation around the foreign body of the stent, termed neo-intimal tissue proliferation.

A new method to reduce this tissue proliferation utilises the well known fact that ionising radiation has greater cytotoxicity on rapidly growing cells and involves radiating the coronary region, either with external radiation or via an intraluminal radiation source implanted into the coronary artery. A further technique provides the radiation to the tissue by implanting stents which are radioactive. However the use of radioactive materials has significant radiation protection implications for clinical and nursing staff, the patient and the general population, and it may be expected that these may hinder this method being more rapidly adopted.

The present invention is concerned with reducing or eliminating this problem of tissue proliferation around a coronary stent.

According to the present invention a stent is provided with means by which it can be made to radiate ultrasonic energy when in an operative position.

The principle behind the invention is to use the stent to radiate ultrasonic energy into the surrounding tissue. It is known that ultrasonic energy can affect the growth of tissue and at certain intensities is cytotoxic. The advantage of ultrasound radiation is that it is non-ionising and does not couple well to air, so there are no radiation protection issues.

Because of the small size of the stent it is very difficult to provide it with its own internal power source. Therefore the energy is coupled from outside the body via electromagnetic radiation. External coils are excited to produce a radio frequency magnetic field in the coronary area. This couples to the implanted stent and the magnetic field generates an oscillating strain in the metal stent structure, the consequent vibration couples into the tissue in contact with the stent.

The choice of frequency is limited by lower and upper bounds. The frequency has to be higher than the frequencies at which any induced currents can trigger muscle movement, typically 100kHz. At the upper end the frequency must be less than 30-40 MHz for the magnetic fields to penetrate to the coronary artery region.

The present invention is also concerned with using the ultrasound vibrations of the stent to improve the performance of drugs. These drugs are typically either anti-thrombolytic agents, or cytotoxic agents that prevent neo-intimal tissue proliferation.

How the invention may be carried out will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a perspective diagrammatic view of the overall arrangement of the present invention; Figure 2 is a perspective diagrammatic view of one construction of stent to which the present invention may be applied in the arrangement shown in Figure 1 ;

Figure 3 is a perspective diagrammatic view of a second construction of stent to which the present invention may be applied in the arrangement shown in Figure 1.

Figure 4 is a perspective diagrammatic view of a third construction of stent which may be applied in the arrangement shown in Figure 1.

Figure 5 illustrates one external arrangement for generating the magnetic field for energising the stent positioned within the patient;

Figure 6 is a view similar to Figure 5 showing a second external coil arrangement.

Figure 1 illustrates the general arrangement involved in applying the present invention.

A patient 1 is supported in a horizontal position by a known arrangement (not shown).

A metal stent 2 has been inserted into the patient so that the operative part of the stent is located in the appropriate target area within the patient, typically within one of the patients arteries.

A pair of electrical coils 3 and 4 are positioned as indicated so that the patient 1 lies substantially on the common axis X-Y of the two coils 3 and 4. The stent for use with the present invention can take a number of forms depending on the energisation frequency being used.

Three examples of constructions of stent which could be used by the present invention are shown in Figures 2, 3 and 4.

The stent 2 of Figure 2 comprises a closed coil having a plurality of windings 5 and a return portion 6 joining the two ends of the coil. The windings 5 and portion 6 are electrically insulated from one another preferably by the windings carrying an insulating layer or coating (not shown). Means may be provided to enable the coil to operate as a resonant circuit, e.g. by the incorporation of a capacitor, in order to increase the effectiveness of the coil.

Figure 3 illustrates a second possible construction in which the stent 2 comprises essentially a tubular member 7 having a plurality of slots 8, the tube 7 being made from a material which is magneto-strictive. Examples of appropriate magneto-strictive materials are nickel and stainless steel.

A third example of a possible construction is shown in Figure 4 in which again the stent 2 is of generally cylindrical configuration but each of the conductive paths of the stent comprises metal portions 9 interrupted or separated by insulation portions 10. In other words the stent is of a laminated construction. The insulation portions 10 could be in a number of configurations including helical (as illustrated), mutually parallel and extending longitudinally of the cylindrical surface or even axially spaced apart mutually parallel rings along the length of the cylinder The stent design shown in Figure 2 is suitable for operation at low frequencies.

With this construction, as indicated earlier, there is a closed coil configuration. When this stent is energised, by means of the coils 3 and 4, shown in Figure 1 , currents will be induced in the coils of the stent by means of mutual inductance which in turn will generate an electromotive force in the coil windings. The frequency of the induced force is limited to the self resonant frequency of the windings 5 of the stent.

If higher frequencies of energisation are required then the stent shown in Figure 3 is more suitable. As indicated earlier the stent 2 of Figure 3 is made of a magnetostrictive material, such as nickel or stainless steel, which will change its dimensions when energised, such that the ultrasound generated is twice that imposed by the external coils 3 and 4. Thus for input of 20 MHZ an output of 40 MHZ can be achieved. However with this construction the operating frequency is limited by the reduction in magnetic field caused by eddy currents in the metal forming the cylinder 7.

In order to overcome this limitation a stent could be constructed as indicated in Figure 4. The construction of the stent in Figure 4 is more complicated than that of either Figure 2 or Figure 3 in that it is essentially a laminated structure having both conducting materials and insulating materials 9 and 10 respectively as described earlier. As far as the energisation arrangement shown diagramatically in Figure 1 is concerned a number of other arrangements of energisation coils could be employed, two of these being shown in Figures 5 and 6 respectively.

In the arrangement of Figure 5 the radio frequency magnetic field is generated by two coils 1 1 and 12 which are substantially circular but positioned in a horizontal orientation above and below the patient 1, in contrast to the arrangement shown in Figure 1 in which the two coils 3 and 4 lie in substantially vertical planes, the patient lying along the common axis X-Y.

In the arrangement of Figure 5 the coils 1 1 and 12 are again on the same axis but in this arrangement the axis is normal to the axis in which the patient 1 is lying.

The coils 1 1 and 12 are energised by a radio frequency generator 13.

In the arrangement of Figure 6 there are three radio frequency energisation Helmholtz coils 14, 15 and 16 which are positioned as indicated in relation to patient 1 in order to generate fields in the X, Y and Z directions respectively. In particular the z coil 15 has an axis which lies substantially along the axis along which the patient 1 is lying (as with the coils of Figure 1) the x coil 14 lies substantially horizontally above the patients and the y coil 16 is positioned substantially vertically alongside the patient.

The three coils 14, 15 and 16, set on the three perpendicular axis x, y and z, allow the magnetic field vector to be controlled by sending the ratios of the currents in the coil pairs to be equal to the Cartesian components of the field vector. The coils 14, 15 and 16 are driven by three independent radio frequency generators 17, 18 and 19 respectively which are controlled by a controller 20 so that the amplitude of each generator 17, 18 and 19 is adjusted according to the desired direction of the magnetic field. The coils 14, 15 and 16 could be Helmholtz coils but this is not essential because obtaining an even field is not critical. In fact it may be advantageous to arrange the coils so that the field is concentrated at the position of the stent 2.

Although multi coil arrangements have been described and illustrated, for energising the stent 2, the invention is possible using only one energisation coil. The way in which the arrangement according to the present invention is used will now be briefly described.

In order to prevent or minimise the unwanted tissue proliferation around the coronary stent referred to earlier the stent 2, which is already embedded in the patient and is not intended to be removed, would be energised on a series of occasions in order to prevent the unwanted condition from occurring.

Because this energisation only involves placing an energisation coil or coils outside the patient, the treatment of the patient, in a series of regular doses as indicated earlier, can be carried out as an outpatient procedure.

Variations may be made to both the detailed design of the stent and to the coil arrangement for energising it from outside the patient, within the scope of the following claims. As indicated earlier the present invention also relates to employing the vibrating stent just described to improve the performance of drugs which are typically either anti-thrombolytic agents, or cytotoxic agents that prevent neo-intimal tissue proliferation.

There are a number of ways these drugs can be administered in combination with the vibrating stent three of which are described below:

Method

Systemically by intra-arterial injection as discussed in US patent 5509896.

Method 2

Systemically by intra-arterial injection, with ultrasound contrast agents which increase the effect of the ultrasound, as disclosed in US patent 538041 1.

Method 3

Encapsulated in micro-bubbles which are then systemically administered. It is known that ultrasound can burst these bubbles to release its contents ('Ultrasound

Contrast Agents', Ed. B. B. Goldberg, published by John Dean Press 1996). The use of micro-bubbles to carry therapeutic agents with external ultrasound to burst them is disclosed in US patents 5580575 and 5558092, as a coating to the stent, either as encapsulated micro-bubbles or as a chemical coating.

Methods 1 and 2 have the advantage that the effect of the anti-thrombylitic agents is locally enhanced around the stent area, thus increasing the effect without the need to increase the overall systemic dose. This differential between local dose and systemic effect is further increased in Method 3, where the drug is only activated where it is released from the micro-spheres, and so the systemic effect is smaller. Method 4 has the advantage that the effect of the drug is even further localised to the neighbourhood of the stent. Unlike using standard coated stents the application of the drug can be activated at a time independent of the stent development. Hence the time-profile of the application of the drug can be tailored to suit the development of thrombus formation or tissue formation.

Claims

1. A stent provided with means by which it can be made to radiate ultrasonic energy when in an operative position.
2. A stent as claimed in claim 1 in which the operative part of the stent comprises a helical elongated coil having its opposite ends interconnected.
3. A stent as claimed in claim 1 in which the operative part of the stent comprises a metallic cylinder provided with a pattern of apertures.
4. A stent as claimed in claim 1 or 3 made from a magnetostrictive material.
5. A stent as claimed in of claim 1 in which the operative part of the stent is made up of a laminated structure comprising metallic segments alternating with insulation segments.
6. A stent substantially as hereinbefore described with reference to and as shown in any one of Figures 2,3 or 4 of the accompanying drawings.
7. A stent as claimed in any of claims 1 to 6 in which the stent is coated with a drug.
8. A stent as claimed in claim 7 in which the drug is encapsulated in a mirror-sphere.
9. Apparatus for use with a stent as claimed in any previous claim which comprises an energisation coil arrangement substantially as hereinbefore described with reference to and as shown in any one of Figures 1 , 5 and 6 of the accompanying drawings and adapted to be located externally of a patient in which the stent is embedded.
10. A method of operating a stent which comprises inserting the stent into its operating position and then energising it by means of a magnetic coil arrangement external of and separate from the stent to cause the stent to emit ultrasonic energy.
1 1. A method of operating a stent as claimed in claim 10 which method includes the step of administering a drug systemically either with ultrasound contrast mirror-bubbles or with micro spheres containing the drug.
12. A method of operating a stent substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
PCT/GB1998/000241 1997-02-08 1998-02-05 Medical ultrasound apparatus WO1998034564A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB9702612.4 1997-02-08
GB9702612A GB2321853A (en) 1997-02-08 1997-02-08 Ultrasound Emitting Stent
GB9710548.0 1997-05-23
GBGB9710548.0A GB9710548D0 (en) 1997-05-23 1997-05-23 Medical ultrasound apparatus

Publications (1)

Publication Number Publication Date
WO1998034564A1 true WO1998034564A1 (en) 1998-08-13

Family

ID=26310956

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/000241 WO1998034564A1 (en) 1997-02-08 1998-02-05 Medical ultrasound apparatus

Country Status (2)

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GB (1) GB2321853A (en)
WO (1) WO1998034564A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999016500A3 (en) * 1997-10-01 1999-06-17 Medtronic Ave Inc Drug delivery and gene therapy delivery system
WO2001005332A1 (en) * 1999-07-16 2001-01-25 Sunnanväder, Lars A device for therapeutic treatment of a blood vessel
EP1210149A2 (en) * 1999-08-27 2002-06-05 Dan Weiss Delivery of ultrasound to percutaneous and intrabody devices
WO2002102456A1 (en) * 2001-06-15 2002-12-27 Scimed Life Systems, Inc. System for remotely actuating an implantable medical device and method of using the same
WO2004033037A2 (en) * 2002-10-04 2004-04-22 Scimed Life Systems, Inc. Induction heating for the delivery of thermal therapy

Families Citing this family (5)

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US6387116B1 (en) 1999-06-30 2002-05-14 Pharmasonics, Inc. Methods and kits for the inhibition of hyperplasia in vascular fistulas and grafts
US6361554B1 (en) * 1999-06-30 2002-03-26 Pharmasonics, Inc. Methods and apparatus for the subcutaneous delivery of acoustic vibrations
GB2352635B (en) * 1999-07-31 2002-08-07 Martin Terry Rothman Medical stents
EP1265674B1 (en) * 2000-03-24 2008-09-17 ProRhythm, Inc. Apparatus for intrabody thermal treatment
US7674256B2 (en) 2005-03-17 2010-03-09 Boston Scientific Scimed, Inc. Treating internal body tissue

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US4373532A (en) * 1980-07-07 1983-02-15 Palo Alto Medical Research Foundation Ultrasonic marker for physiologic diagnosis and method of using same
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US5380411A (en) 1987-12-02 1995-01-10 Schering Aktiengesellschaft Ultrasound or shock wave work process and preparation for carrying out same
US5405322A (en) * 1993-08-12 1995-04-11 Boston Scientific Corporation Method for treating aneurysms with a thermal source
US5509896A (en) 1994-09-09 1996-04-23 Coraje, Inc. Enhancement of thrombolysis with external ultrasound
US5558092A (en) 1995-06-06 1996-09-24 Imarx Pharmaceutical Corp. Methods and apparatus for performing diagnostic and therapeutic ultrasound simultaneously
US5580575A (en) 1989-12-22 1996-12-03 Imarx Pharmaceutical Corp. Therapeutic drug delivery systems

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US4808153A (en) * 1986-11-17 1989-02-28 Ultramed Corporation Device for removing plaque from arteries
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3570476A (en) * 1968-11-18 1971-03-16 David Paul Gregg Magnetostrictive medical instrument
US4373532A (en) * 1980-07-07 1983-02-15 Palo Alto Medical Research Foundation Ultrasonic marker for physiologic diagnosis and method of using same
US5380411A (en) 1987-12-02 1995-01-10 Schering Aktiengesellschaft Ultrasound or shock wave work process and preparation for carrying out same
US5580575A (en) 1989-12-22 1996-12-03 Imarx Pharmaceutical Corp. Therapeutic drug delivery systems
WO1994015583A1 (en) * 1993-01-08 1994-07-21 Pdt Systems, Inc. Medicament dispensing stents
US5405322A (en) * 1993-08-12 1995-04-11 Boston Scientific Corporation Method for treating aneurysms with a thermal source
US5509896A (en) 1994-09-09 1996-04-23 Coraje, Inc. Enhancement of thrombolysis with external ultrasound
US5558092A (en) 1995-06-06 1996-09-24 Imarx Pharmaceutical Corp. Methods and apparatus for performing diagnostic and therapeutic ultrasound simultaneously

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999016500A3 (en) * 1997-10-01 1999-06-17 Medtronic Ave Inc Drug delivery and gene therapy delivery system
US6129705A (en) * 1997-10-01 2000-10-10 Medtronic Ave, Inc. Drug delivery and gene therapy delivery system
WO2001005332A1 (en) * 1999-07-16 2001-01-25 Sunnanväder, Lars A device for therapeutic treatment of a blood vessel
EP1210149A2 (en) * 1999-08-27 2002-06-05 Dan Weiss Delivery of ultrasound to percutaneous and intrabody devices
EP1210149A4 (en) * 1999-08-27 2003-08-13 Dan Weiss Delivery of ultrasound to percutaneous and intrabody devices
WO2002102456A1 (en) * 2001-06-15 2002-12-27 Scimed Life Systems, Inc. System for remotely actuating an implantable medical device and method of using the same
US6626940B2 (en) 2001-06-15 2003-09-30 Scimed Life Systems, Inc. Medical device activation system
WO2004033037A2 (en) * 2002-10-04 2004-04-22 Scimed Life Systems, Inc. Induction heating for the delivery of thermal therapy
WO2004033037A3 (en) * 2002-10-04 2004-07-15 Scimed Life Systems Inc Induction heating for the delivery of thermal therapy
US6895282B2 (en) 2002-10-04 2005-05-17 Boston Scientific Scimed, Inc. Induction heating for the delivery of thermal therapy
US8412346B2 (en) 2002-10-04 2013-04-02 Medifocus, Inc Induction heating for the delivery of thermal therapy

Also Published As

Publication number Publication date
GB2321853A (en) 1998-08-12
GB9702612D0 (en) 1997-03-26

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