Conductive Member For Use In Radiofrequency Ablation

Abstract

A conductive member such as conductive pad (1) for use in radiofrequency ablation, the conductive member being flexible so as to conform to a subject's skin, the conductive member comprising a conductive skin contact layer (5) arranged for contact with the subject's skin and a conductive layer (4) over the conductive skin contact layer, in which the conductive skin contact layer (5) and the conductive layer (4) are both conductive to DC electrical signals.

Claims

1. A conductive member for use in radiofrequency ablation, the conductive member being flexible so as to conform to a subject's skin, the conductive member comprising a conductive skin contact layer arranged for contact with the subject's skin and a conductive layer over the conductive skin contact layer, in which the conductive skin contact layer and the conductive layer are both conductive to DC electrical signals.

2. The conductive member of claim 1, being a conductive pad.

3. The conductive member of claim 1, which is arranged to adhere, typically by means of the conductive skin contact layer, to the subject's skin.

4. The conductive member of claim 1, in which the conductive member is not adhesive to a user's skin.

5. The conductive member of claim 1, comprising attachment means by means of which the conductive member (typically the conductive skin contact layer) can be held in use against the subject's skin.

6. The conductive member of claim 1, arranged so as to be wearable, and comprising a compression member which is wearable on a part of the subject and which is placed in tension by being worn, tension in the compression member acting to hold the conductive member, and in particular the conductive skin contact layer, against the subject's skin.

7. The conductive member of claim 1, in which the conductive skin contact layer has a volume resistivity at a frequency less than 5 Hz, or at zero frequency (i.e. DC) of a maximum of 2500 ohm cm, or 2000 ohm cm, or 1500 ohm cm, or 1000 ohm cm.

8. The conductive member of claim 1, in which the conductive skin contact layer comprises a gel layer.

9. The conductive member of claim 8, in which the gel layer comprises a hydrogel which is conductive to DC signals.

10. The conductive member of claim 1, in which the conductive layer comprises a conductive plastic material, such as carbon-loaded polymer mix.

11. The conductive member of claim 1, comprising a removable release layer on the conductive skin contact layer.

12. The conductive member of claim 1, comprising a foam layer over the conductive layer on the side of the conductive layer opposite to the conductive skin contact layer.

13. The conductive member of claim 12, in which the foam layer is attached to the conductive layer by means of an intervening adhesive layer.

14. The conductive member of claim 13, in which the adhesive layer comprises two layers of a conductive adhesive over a non-woven fabric core.

15. A radiofrequency ablation system, comprising a conductive member in accordance with claim 1, an electrode and a radiofrequency source arranged to generate a signal with a radiofrequency component, and coupled to the electrode and the conductive member to apply the signal between the electrode and the conductive member.

16. The system of claim 15, in which the signal has a DC component.

17. The system of claim 15, in which the electrode comprises a pointed needle.

18. A method of ablating a subject's tissue using the radiofrequency ablation system of claim 15, the method comprising applying the conductive member to the subject's skin, positioning the electrode adjacent to the tissue to be ablated and passing the signal from the electrode through the tissue to be ablated, the signal returning to the conducting pad through the subject.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 shows an exploded view of a conductive member in accordance with an embodiment of the disclosure;

[0025] FIG. 2 shows a plan view of the conductive member of FIG. 1, showing the internal arrangement of the components forming the conductive member;

[0026] FIG. 3 shows a side elevation of the conductive member of FIG. 1;

[0027] FIG. 4 shows an enlargement of area A of FIG. 3;

[0028] FIG. 5 shows a plan view of the foam layer of the conductive member of FIG. 1;

[0029] FIG. 6 shows a plan view of the adhesive layer of the conductive member of FIG. 1;

[0030] FIG. 7 shows a plan view of the conductive layer of the conductive member of FIG. 1;

[0031] FIG. 8 shows a plan view of the gel layer of the conductive member of FIG. 1;

[0032] FIG. 9 shows a plan view of the release layer of the conductive member of FIG. 1;

[0033] FIG. 10 shows schematically a radiofrequency ablation system in accordance with the present disclosure, using the conductive member of FIG. 1.

DETAILED DESCRIPTION

[0034] A conductive member of the form of a conductive pad 1 for use in radiofrequency ablation is shown in FIGS. 1 to 9 of the accompanying drawings; it is shown as part of a radiofrequency ablation system in FIG. 10 of the accompanying drawings. The conductive pad 1 comprises a number of layers built into a flexible pad.

[0035] Taking the layers in turn, from the bottom of FIG. 1 upwards: [0036] a foam layer 2; [0037] an adhesive layer 3; [0038] a conductive layer 4; [0039] a conductive skin contact layer, of the form of a gel layer 5; and [0040] a release layer 6.

[0041] The foam layer 2 provides structure to the conductive pad 1. It comprises a single-sided medical closed cell polyethylene foam, such as product 9776 from 3M Medical Specialities of St Paul, Minn., USA. The foam layer is 0.7 mm thick. It is shaped as a rounded rectangle, with a tail portion 7 extending parallel to one side of the rectangle.

[0042] On the foam layer is provided the adhesive layer 3. This is provided as a layer of conductive non-woven fabric with conductive adhesive on both sides, such as the tape sold as HB350 from Hi-Bond Tapes Ltd of Corby, United Kingdom. Again, this is formed of rounded rectangular body, smaller than the foam layer 2, with a tail portion 8 that fits within tail portion 7 of the foam layer 2. The area around tail portion 7 connection needs to be fully covered by an insulating material (typically the backing layer) to avoid any risk of short circuit to the patient or operator. The adhesive layer is 0.1 mm thick.

[0043] On top of the adhesive layer is the conductive layer 4. This comprises a polyethylene film loaded with carbon, such as the film available as LINQSTAT XVCF from Caplinq, Heemskirk, Netherlands. It is again of the form of a rounded rectangle, with a tab 9 for the connection to a signal generator (discussed below). The conductive layer 4 is larger than the adhesive layer, but smaller than the foam layer 2. The conductive layer 4 is 0.2 mm thick.

[0044] On top of the conductive layer 4 is the gel layer 5. This comprises a hydrogel, such as that sold as AG625 from Axelgaard Manufacturing Co, Ltd of Fallbrook, Calif., USA. This allows the conductive pad 1 to conform to a subject's skin, and provides some adhesion to the subject's skin. The gel layer is provided as a rounded rectangle, larger than the conductive layer 4 but smaller than the foam layer 2. The gel layer is 0.7 mm thick.

[0045] The conductive layer 4 and the gel layer 5 are together conductive to a range of frequencies from DC (zero frequency) up to at least 1 MHz.

[0046] On top of the gel layer 5 is provided a release layer 6 of the form of silicone-coated polyethylene terephthalate. This protects and retains the gel layer 5 until it is ready to be used. The silicone coating allows for the easy removal of the release layer 6.

[0047] The use of the conductive pad 1 is shown in FIG. 10 of the accompanying drawings. The conductive pad 1 is used as part of a radiofrequency ablation system along with a radiofrequency source 11 and a needle electrode 12.

[0048] The conductive pad 1 (with the release layer 6 removed) is applied to a subject's skin 10, so that the gel layer 5 adheres to the subject's skin 10. It is connected to the radiofrequency source 11, as is the needle electrode 12. The radiofrequency source 11 is used to create a signal applied as a voltage between the needle electrode 12 and the conductive pad 1. The signal has a radiofrequency component at around 460 kHz supplying between 20 and 200 W. It also has a DC component of between 0 and 40 volts (with the conductive pad 1 as the anode), which will be transmitted by the conductive layer 4 and the gel layer 5 as they transmit DC signals.

[0049] Typically the resistance measured through the patient as a result of using the hydrogel will be less than 500 ohm the resistance is largely driven by the impedance of the stratum corneum which can be greater 1 megaohm per cm2. A sufficient area of hydrogel is used to overcome this.

[0050] As such, the needle electrode 12 can be introduced into an incision 13 in the user's skin 10 and used to ablate a tissue 14 of interest. The DC component will reduce the dehydrating effect of the tissue ablation.