MICROWAVE APPLICATOR FOR UTERINE CERVIX

Abstract

A microwave antenna apparatus comprises an electrically conductive ground element defining an aperture, an electrically conductive elongated element extending through the aperture and terminating at a distal end, and one or more dielectric elements. The one or more of the dielectric elements electrically insulate the elongated element and the ground element from one another. The microwave antenna apparatus may be configured for use in radiating microwave energy into surface tissue of a uterine cervix so as to provide a therapeutic effect in one or more regions of the uterine cervix, such as one or more regions of the cervix infected with human papillomavirus (HPV) and/or diagnosed with cervical intraepithelial neoplasia (CIN) or so as to create the correct biological response in one or more such regions. The microwave antenna apparatus may be configured for localized non-ablative hyperthermia of the surface tissue of the uterine cervix, localized ablation of the surface tissue of the uterine cervix, and/or cauterisation of the surface tissue of the uterine cervix.

Claims

1. A microwave antenna apparatus for use in radiating microwave energy into surface tissue of a uterine cervix, the microwave antenna apparatus comprising: an electrically conductive ground element defining an aperture; an electrically conductive elongated element extending through the aperture and terminating at a distal end; and one or more dielectric elements, wherein one or more of the dielectric elements electrically insulate the elongated element and the ground element from one another.

2. The microwave antenna apparatus as claimed in claim 1, wherein the ground element and the elongated element are co-axial and wherein at least one of: at least one of the microwave antenna apparatus defines an axis and the microwave antenna apparatus is cylindrically symmetrical about the axis, the elongated element is rod-like, cylindrical and/or conical or a radial extent of the ground element may be more than or less than a radial extent of the one or more dielectric elements by a predetermined radial offset; the ground element is annular or generally annular; the ground element is planar or generally planar; the ground element is curved; the ground element is shaped in the form of a cup or a bowl with an opening of the cup or the bowl directed towards the distal end of the elongated element; or the ground element is shaped in the form of an inverted cup or an inverted bowl with an opening of the inverted cup or the inverted bowl directed away from the distal end of the elongated element.

3. The microwave antenna apparatus as claimed in claim 1, wherein at least one of: one or more of the dielectric elements define an outer surface of the microwave antenna apparatus for engagement with a surface of the uterine cervix; one or more of the dielectric elements cover the distal end of the elongated element; one or more of the dielectric elements cover a distal portion of the elongated element; one or more of the dielectric elements are configured so as to prevent the elongated element from coming into contact with the surface of the uterine cervix when the microwave antenna apparatus is in use; one or more of the dielectric elements are configured to separate the ground element and/or the elongated element from the tissue of the surface of the uterine cervix by a desired predetermined distance, for example wherein one or more of the dielectric elements have a desired predetermined thickness; one or more of the dielectric elements cover at least part of the ground element; or one or more of the dielectric elements cover at least part of a distal surface of the ground element.

4. (canceled)

5. The microwave antenna apparatus as claimed in claim 1, wherein the elongated element extends axially beyond the ground element by a predetermined length and, wherein at least one of one or more of the dielectric elements cover a proportion of the predetermined length of the elongated element, or one or more of the dielectric elements cover the whole of the predetermined length of the elongated element.

6.-8. (canceled)

9. The microwave antenna apparatus as claimed in claim 1, wherein the one or more dielectric elements fill the aperture defined by the ground element.

10. The microwave antenna apparatus as claimed in claim 1, wherein the one or more dielectric elements define a central distal feature for centring the antenna with respect to an axis of a cervical os of the uterine cervix and wherein at least one of the central distal feature is configured for radiating microwave energy into a proximal section of the cervical os, or the one or more dielectric elements define a cupping feature for cupping a proximal ectocervix region of the uterine cervix and preventing excessive insertion of the central distal feature into the cervical os of the uterine cervix.

11.-18. (canceled)

19. The microwave antenna apparatus as claimed in claim 1, comprising an electrically conductive cap element at or adjacent the distal end of the elongated conductor.

20. The microwave antenna apparatus as claimed in claim 19, _p1 wherein a distal end of an outer surface of the microwave antenna apparatus is defined by one or more of the dielectric elements and the electrically conductive cap element is located between the distal end of the elongated conductor and the distal end of the outer surface of the microwave antenna apparatus; or wherein the electrically conductive cap element defines a distal end of the outer surface of the microwave antenna apparatus.

21. (canceled)

22. The microwave antenna apparatus as claimed in claim 1, wherein the microwave antenna apparatus is disposable or re-useable.

23. The microwave antenna apparatus as claimed in claim 1, wherein the microwave antenna apparatus is configured for use in radiating microwave energy into the surface tissue of the uterine cervix for at least one of: so as to provide a therapeutic effect in one or more regions, such as one or more regions of the cervix infected with human papillomavirus (HPV) and/or diagnosed with cervical intraepithelial neoplasia (CIN); so as to create the correct biological response in one or more regions, such as one or more regions of the cervix infected with human papillomavirus (HPV) and/or diagnosed with cervical intraepithelial neoplasia (CIN); localized non-ablative hyperthermia of the surface tissue of the uterine cervix; localized ablation of the surface tissue of the uterine cervix; and cauterisation of the surface tissue of the uterine cervix.

24. A plurality of microwave antenna apparatus as claimed in claim 1, wherein each microwave antenna apparatus of the plurality of microwave antenna apparatus has a different configuration selected to provide a corresponding different radiation pattern.

25. A microwave assembly for use in radiating microwave energy into surface tissue of a uterine cervix, the microwave assembly comprising the microwave antenna apparatus as claimed in claim 1 and a shaft connected to the microwave antenna apparatus.

26. The microwave assembly as claimed in claim 25, comprising a connection arrangement connecting the shaft and the microwave antenna apparatus, wherein the connection arrangement is configured to vary an angle between an axis of the microwave antenna apparatus and an axis of the shaft and wherein at least one of the connection arrangement comprises at least one of a pivot arrangement, a hinge, a flexible joint, and a ball and socket joint, or the connection arrangement is configured to detachably attach the microwave antenna apparatus to the shaft thereby allowing the fitting of a different microwave antenna apparatus to the shaft, wherein the different microwave antenna apparatus features an alternative configuration, including an alternative shape and/or size, to the microwave antenna apparatus.

27.-28. (canceled)

29. The microwave assembly as claimed in claim 25, wherein the shaft is disposable or the shaft is re-useable wherein at least one of the microwave assembly comprises a hand grip or hand piece at or adjacent a proximal end thereof, including at or adjacent a proximal end of the shaft, the hand grip or hand piece is detachably attached to the shaft, or the hand grip or hand piece is disposable or reusable.

30.-32. (canceled)

33. The microwave assembly as claimed in claim 25, comprising an electrical switch which is configurable between an on state in which the switch allows the transmission of microwave energy from a microwave generator to the microwave antenna apparatus and an off state in which the switch prevents the transmission of microwave energy from the microwave generator to the microwave antenna apparatus and, wherein the hand grip or hand piece comprises a manual control element including a button for reconfiguring the electrical switch between the on and off states.

34. (canceled)

35. A microwave system for use in radiating microwave energy into surface tissue of a uterine cervix, the system comprising: a microwave assembly as claimed in claim 25; a microwave generator; and a microwave waveguide, wherein the microwave waveguide electrically connects the microwave generator and the microwave assembly.

36. The microwave system as claimed in claim 35, wherein at least one of the microwave waveguide comprises a microwave cable such as a flexible and/or a co-axial microwave cable or the microwave waveguide is housed in the shaft.

37. (canceled)

38. A method for use in radiating microwave energy into surface tissue of a uterine cervix, the method comprising: engaging a surface of the uterine cervix with a distal surface of the microwave antenna apparatus as claimed in claim 1; and using the microwave antenna apparatus to apply microwave energy to the uterine cervix.

39. The method as claimed in claim 38, comprising selecting one or more characteristics of the microwave energy so as to: provide a desired predetermined radiation pattern when the microwave antenna apparatus is located remotely from any other object so that the desired predetermined radiation pattern is unperturbed by the proximity of any other object; or provide a desired predetermined radiation pattern when the microwave antenna apparatus is located remotely from the surface of the uterine cervix so that the desired predetermined radiation pattern is unperturbed by the proximity of the surface of the uterine cervix; and, optionally, the method comprising at least one of: selecting one or more of the frequency, frequency spectrum, power, power density, energy, energy density, intensity, strength, amount, magnitude, exposure time, dose, pulse duration, pulse repetition rate and the like of the microwave energy so as to provide the desired predetermined radiation pattern; selecting one or more characteristics of the microwave energy so as to provide a therapeutic effect when the microwave antenna apparatus is used to apply microwave energy to the uterine cervix in one or more regions, such as one or more infected regions of the cervix, such as one or more regions that are infected with human papillomavirus (HPV) and/or diagnosed with cervical intraepithelial neoplasia (CIN); selecting one or more characteristics of the microwave energy so as to cause localized non-ablative hyperthermia of the surface tissue of the uterine cervix; selecting one or more characteristics of the microwave energy so as to create a biological response in one or more regions of the surface tissue of a uterine cervix, such as one or more regions that are infected with human papillomavirus HPV and/or diagnosed with cervical intraepithelial neoplasia (CIN); selecting one or more characteristics of the microwave energy so as to cause localized ablation of the surface tissue of the uterine cervix; selecting one or more characteristics of the microwave energy so as to cauterise the surface tissue of the uterine cervix; or selecting the one or more characteristics of the microwave energy from the spatial distribution, frequency, frequency spectrum, power, power density, energy, energy density, intensity, strength, amount, magnitude, exposure time, dose, pulse duration, and pulse repetition rate of the microwave energy.

40.-46. (canceled)

47. The method as claimed in claim 38, comprising matching or substantially matching the relative permittivity of the microwave antenna apparatus to the relative permittivity of the cervix tissues for one or more given characteristics of the microwave energy, for example wherein the method comprises selecting a relative permittivity of the microwave antenna apparatus which differs by less than 50%, less than 10%, less than 1% or less than 0.1% of the relative permittivity of the cervix tissues for one or more given characteristics of the microwave energy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0146] A microwave antenna apparatus or applicator, a microwave assembly and a microwave system will now be described by way of non-limiting example only with reference to the following figures of which:

[0147] FIG. 1 is a schematic illustration of the human cervix;

[0148] FIG. 2 is a schematic illustration of a transformation zone type I of the human cervix;

[0149] FIG. 3 is a schematic illustration of a transformation zone type II of the human cervix;

[0150] FIG. 4 is a schematic illustration of a transformation zone type III of the human cervix;

[0151] FIG. 5 is a schematic illustration of a microwave system;

[0152] FIG. 6 is an illustration of the external features of a microwave antenna apparatus “type A” designed to be used for the treatment of transformation zone type I (T1) CIN;

[0153] FIG. 7 is an illustration of the external features of a microwave antenna apparatus “type B” designed to be used for the treatment of transformation zone type II (T2) CIN;

[0154] FIG. 8 is an illustration of the external features of a microwave antenna apparatus “type C” designed to be used for the treatment of transformation zone type III (T3) CIN;

[0155] FIG. 9 is an illustration of the external features of a microwave antenna apparatus “type D” which may be a variation of the antenna “type C” designed to be used when dysplasia resides only at the opening of, and continues into, the os of the cervix;

[0156] FIG. 10 is an illustration of the external features of a microwave antenna apparatus common to types A, B and C;

[0157] FIG. 11 is a cross sectional view of a microwave antenna apparatus type common to types A, B, C and D being applied on the cervix;

[0158] FIG. 12 is a cross sectional view of the internal features of a microwave antenna apparatus type common to types A, B, C and D;

[0159] FIG. 13 is a representation of the distribution of electromagnetic fields and microwave fields in particular, in a cervix in the form of SAR (surface absorption rate) using a microwave antenna apparatus common to types A, B and C;

[0160] FIG. 14 illustrates the scattering parameter S11, a mathematical construct quantifying how RF energy propagates through the microwave antenna apparatus into the tissue;

[0161] FIG. 15 is a representation of the distribution of electromagnetic fields and microwave fields in particular, in cervix in the form of SAR (surface absorption rate) using a microwave antenna apparatus common to types A, B and C where the metallic ground plane is in contact with the tissue;

[0162] FIG. 16 is a representation of the distribution of electromagnetic fields and microwave fields in particular, in cervix in the form of SAR (surface absorption rate) using a microwave antenna apparatus common to types A, B and C with the metallic ground plane is not in contact with the tissue;

[0163] FIG. 17 illustrates the effect of the critical overall length of the central conductor of a microwave antenna apparatus to achieve the overall energy distribution pattern of microwave fields in the tissue confined more towards the ground plane;

[0164] FIG. 18 illustrates the effect of the critical overall length of the central conductor of a microwave antenna apparatus to achieve the overall energy distribution pattern of microwave fields in the tissue confined more away from the ground plane;

[0165] FIG. 19 illustrates the effect of the critical radial distance from the ground plane to the external form of a microwave antenna apparatus on the overall energy distribution pattern of microwave fields in the tissue;

[0166] FIG. 20 illustrates the effect of having equal diameters of the ground plane and the external form of a microwave antenna apparatus on the overall energy distribution pattern of microwave fields in the tissue;

[0167] FIG. 21 illustrates the effect of the critical radial distance from the ground plane to the external form of a microwave antenna apparatus on the overall energy distribution pattern of microwave fields in the tissue when the length of the central conductor is extended;

[0168] FIG. 22 illustrates the effect of having equal diameters of the ground plane and the external form of a microwave antenna apparatus on the overall energy distribution pattern of microwave fields in the tissue when the length of the central conductor is extended;

[0169] FIG. 23 illustrates the effect of a conical ground plane of a microwave antenna apparatus on the overall energy distribution pattern of electromagnetic fields in the tissue;

[0170] FIG. 24 illustrates the effect of an inverted cup shaped ground plane of a microwave antenna apparatus on the overall energy distribution pattern of electromagnetic fields in the tissue;

[0171] FIG. 25 illustrates the effect of a cup shaped ground plane of a microwave antenna apparatus on the overall energy distribution pattern of electromagnetic fields in the tissue;

[0172] FIG. 26 illustrates the overall energy distribution pattern of microwave fields in the tissue with the ground plane of a microwave antenna apparatus not in contact with the tissue;

[0173] FIG. 27 illustrates the effect of a longer length of the central conductor of a microwave antenna apparatus showing non-uniform overall energy distribution pattern of microwave fields in the tissue with higher fields towards the endocervix and reduced fields towards the ectocervix;

[0174] FIG. 28 illustrates compensating the effect of the extended length of the central conductor of a microwave antenna apparatus by changing the shape of the central conductor to achieve uniform overall energy distribution pattern of microwave fields in the entire cervical region; and

[0175] FIG. 29 shows a microwave assembly of the microwave system of FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

[0176] A typical diagrammatic illustration of healthy human cervix is illustrated in the FIG. 1. The cervix 1 comprises an external part in the form of the ectocervix 2 and the endocervix 3, a canal that connects the uterine cavity 4 and the vaginal cavity 5. The opening of the cervix 1 into the vaginal cavity 5 is known as the external os 6. The area where the endocervix 3 meets the ectocervix 2 is called the transformation zone (TZ) 7. This area is the most vulnerable for CIN (cervical neoplasia) and where most abnormalities are thought to arise. FIG. 2 is a schematic illustration of the type I transformation zone (TZ) 8 which is completely ectocervical, is fully visible, and may be small or large. Type II TZ 9 which has an endocervical component but is still fully visible with a small or large ectocervical component is shown in FIG. 3. Type III TZ 10 illustrated in FIG. 4, has an endocervical component, and the upper limit is not fully visible; the ectocervical component, if present, may be small or large.

[0177] FIG. 5 illustrates a microwave system generally designated 100 for treating the cervix tissue. The microwave system 100 comprises a microwave generator 11 for providing microwave energy, a flexible interconnecting microwave cable such as a co-axial cable 12, a hand grip or hand piece 13, and a microwave antenna apparatus 14.

[0178] As shown in more detail in FIG. 29, the hand grip or hand piece 13 and the microwave antenna apparatus 14 are connected by a shaft 202. The hand grip or hand piece 13, the microwave antenna apparatus 14 and the shaft 202 together constitute a microwave assembly 200. The microwave assembly 200 is connected to the microwave generator 11 by the co-axial cable 12. The co-axial cable 12 extends through the shaft 202 between the handgrip or hand piece 13 and the microwave antenna apparatus 14. The microwave assembly 200 further comprises a connection arrangement 204 for connecting the microwave antenna apparatus 14 and the shaft 202. The connection arrangement is configured to vary an angle between an axis of the microwave antenna apparatus 14 and an axis of the shaft 202. For example, the connection arrangement 204 may comprise a pivot arrangement, a hinge, a flexible joint, a ball joint or the like. Such a connection arrangement 204 may allow the microwave antenna apparatus 14 to be adjusted or oriented for alignment with the cervix entrance or cervical os. For example, such a connection arrangement 204 may allow the angle between the axis of the microwave antenna apparatus 14 and the axis of the shaft 202 to be selected for axial alignment of the microwave antenna apparatus 14 with the cervical os. Changes to the orientation of the microwave antenna apparatus 14 may take place inside the vagina canal by adjusting the angle between the axis of the microwave antenna apparatus 14 and the axis of the shaft 202 after insertion of the microwave antenna apparatus 14 into the vagina. Alternatively, changes to the orientation of the microwave antenna apparatus 14 may take place outside the vagina canal by pre-adjusting the angle between the axis of the microwave antenna apparatus 14 and the axis of the shaft 202 before insertion of the microwave antenna apparatus 14 into the vagina. For example, the alignment angle may be a fixed angle anywhere between 1 and 90 degrees.

[0179] The microwave antenna apparatus 14 may be configured, for example, dimensioned and/or shaped, to be inserted into the vagina and manipulated within the vagina. The microwave antenna apparatus 14 may be configured to be inserted into the vagina and manipulated within the vagina to reach one or more ectocervical and/or endocervical regions of the surface tissue of the uterine cervix. The microwave antenna apparatus 14 may be configured to be inserted into the vagina and manipulated within the vagina by a colposcopist when the patient is in the dorsal lithotomy position.

[0180] The connection arrangement 204 may be configured to detachably attach the microwave antenna apparatus 14 to the shaft 202 thereby allowing the fitting of a different microwave antenna apparatus that may feature an alternative configuration, for example an alternative shape and/or size. The connection arrangement 204 may comprise an electrical connector (not shown) such as a coaxial electrical connector to allow the electrical connection/disconnection of the microwave antenna apparatus 14 and the co-axial cable 12.

[0181] The hand grip or hand piece 13 may be detachably attached to the shaft 202. This may allow the hand grip or hand piece 13 to be detached from the shaft 202. The hand grip or hand piece 13 may comprise an electrical connector (not shown) such as a coaxial electrical connector to allow the electrical connection/disconnection of the hand grip or hand piece 13 and the co-axial cable 12.

[0182] The microwave antenna apparatus 14 and the shaft 202 may be disposable such that detaching the hand grip or hand piece 13 from the shaft 202 may allow for disposal of the microwave antenna apparatus 14 and the shaft 202. Alternatively, the microwave antenna apparatus 14 and the shaft 202 may be re-useable and detaching the hand grip or hand piece 13 from the shaft 202 may allow the microwave antenna apparatus 14 and the shaft 202 to be sterilised before re-use.

[0183] The hand grip or hand piece 13 is arranged at an angle relative to an axis of the shaft 202. For example, the hand grip or hand piece 13 may be arranged at an angle of 30, 45 or 90 degrees relative to the axis of the shaft 202, much like a “pistol grip”.

[0184] The microwave assembly 200 further comprises an electrical switch 206 which is configurable between an on state in which the switch 206 allows the transmission of microwave energy from the microwave generator 11 to the microwave antenna apparatus 14 and an off state in which the switch 206 prevents the transmission of microwave energy from the microwave generator 11 to the microwave antenna apparatus 14. The hand grip or hand piece 13 comprises a manual control element such as a button 208 or the like for reconfiguring the electrical switch 206 between the on and off states.

[0185] The external form of the microwave antenna apparatus 14 may take a number of different shapes, depending on the desired TZ types and treatment zone for CIN. For the treatment of TZ I shown in FIG. 2, where only the lower outer surface of the ectocervical region is disturbed by the neoplasia 7, the microwave antenna apparatus of type A illustrated in FIG. 6 can be used. The microwave antenna apparatus of type A illustrated in FIG. 6 does not need to treat the cervix os 6. Consequently, the centre feature of the distal end 15 need not be of significant length and need not propagate microwave energy. The purpose of the centre feature 15 is to provide a centring location aid to the user, ensuring a periphery or diameter of the centre feature 15 is in contact with the ectocervix centrally/coaxially.

[0186] When treating TZ II CIN shown in FIG. 3, there is a combination of visible ectocervical and endocervical regions with neoplasia 8 thus the microwave antenna apparatus of type B illustrated in FIG. 7 features a radiating central feature 16 that serves to not only locate the microwave antenna apparatus relative to the cervix but also to deliver energy to a proximal section of the cervical os 6 for example the first 3 mm.

[0187] When treating TZ III type CIN shown in FIG. 4, there is a presence of neoplasia 9 in the visible ectocervical region along with visible or non-visible endocervical regions. Consequently, the microwave antenna apparatus of type C FIG. 8 features a radiating central feature 17 that serves to not only locate the microwave antenna apparatus relative to the cervix, but also to deliver energy to the endocervical region that is more distal than that treatable with a type B microwave antenna apparatus.

[0188] In such situations, because the patient has no or very little ectocervical CIN present and the dysplasia resides only at the opening of, and continues into, the os 6, the microwave antenna apparatus of type D illustrated in FIG. 9 may be used. The microwave antenna apparatus of type D illustrated in FIG. 9 may, for example, be a variation of the microwave antenna apparatus of type C. Here, a type D microwave antenna apparatus comprises a central feature 18 which is configured to radiate microwave energy predominantly in a radial direction.

[0189] The external features of any type of microwave antenna apparatus 14 are formed to accommodate a range of anatomy types that may vary between patients. Common to types A, B and C is a form illustrated in FIG. 10 that may be tapered or parallel along a major axis, with rounded distal end 19 for centring the antenna with respect to the cervix os 6 axis. Common to types A, B and C is the circular cupping feature 20 that prevents excessive insertion in the os of the cervix 6 and matches the form of a typical proximal ectocervix 2. Also designed to match the typical diameter of this same region is the overall diameter of the antenna 21 which should not interfere with the operation of a speculum and/or a view of the cervix through a colposcope. The approach angle of the microwave antenna apparatus 14 to the cervix is dictated by a combination of an angle of an axis of the shaft 202 of the microwave assembly 200 relative to a patient as controlled by an operator and an angle of an axis of the microwave antenna apparatus 14 as determined by a shaft 22 on which the microwave antenna apparatus 14 is mounted. The approach angle is set such that the microwave antenna apparatus axis and an axis of the os are co-linear. This may serve to ensure that a front-facing distal surface of the microwave antenna apparatus 14 engages the cervix uniformly resulting in uniform exposure to microwave energy and, therefore, uniform treatment. As will be described in more detail below, non-conductive coating 23 covers any exposed metallic components that form the microwave assembly 200. This may reduce the risk of high intensity electromagnetic fields that may lead to an inadvertent burn/deposition of energy when the microwave energy is radiated from the microwave antenna apparatus 14. This coating 23 is made from a biologically compatible substantially electromagnetically transparent material such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) or fluoroethylene polymer (FEP) or other co-polymer coating. The length and diameter of the shaft 202 is designed to allow the user ease of movement when the vagina is opened with a speculum without obscuring the user's view through a colposcope.

[0190] As cross-sectional view of the microwave antenna apparatus 14 common to types A, B and C is shown in the FIG. 11. The antenna is applied on the cervix tissue 25 through air 26.

[0191] FIG. 12 represents a cross section of a generic microwave antenna apparatus 14 across types A, B and C. The type D microwave antenna apparatus has the same feature as shown in FIG. 12 except for the cupping feature. The microwave antenna apparatus 14 comprises an electrically conductive elongated element in the form of a central conductor 30 and an electrically conductive ground element in the form of an antenna ground plane 31. The antenna ground plane 31 defines an aperture 31a through which the central conductor 30 extends. The microwave antenna apparatus 14 further comprises a dielectric element 33 which covers at least part of a distal or forward-facing surface of the antenna ground plane 31 and which defines an external distal or forward-facing surface or form of the microwave antenna apparatus 14. The dielectric element 33 also insulates the central conductor 30 from the antenna ground plane 31 where the central conductor 30 passes through the aperture of the antenna ground plane 31.

[0192] A coaxial cable 27 is formed by an outer conductor in the form of an electrically conductive outer shield 28, a further dielectric element 29, and the central conductor 30. The outer shield 28 is connected to the antenna ground plane 31 with good integrity to ensure all energy is transmitted in to the desired region. Failure to achieve this may result in lower efficiency of energy propagation and non-uniform fields that may result in non-uniform treatment zones. One of ordinary skill in the art will understand that the co-axial cable 12 may extend through the shaft 202 of the microwave assembly 200 and that the central conductor 30 and the outer shield 28 of the microwave antenna apparatus 14 may be electrically connected to a corresponding central conductor (not shown) and a corresponding shield (not shown) of the co-axial cable 12. The microwave antenna apparatus 14 further comprises an insulating support jacket 32 on an exterior surface of the outer shield 28.

[0193] A further dielectric element in the form of a dielectric support feature 34 provides additional support and serves to avoid contact between the ground plane 31 and the tissue of the cervix. A yet further dielectric element in the form of an outer jacket 35 provides additional support and insulation for the ground plane 31.

[0194] Any one or more of the dielectric elements 32, 33, 34 and 35 may comprise or be formed from any low loss biocompatible material. For example, any one or more of the dielectric elements 32, 33, 34 and 35 may comprise or be formed from at least one of acrylonitrile butadiene styrene (ABS), nylon, polyethylene terephthalate (PET), polyimide, polycarbonate, PC-ABS, polypropylene, ceramics such as alumina and FEP.

[0195] Any one or more of the dielectric elements 32, 33, 34 and 35 may comprise or be formed from the same material.

[0196] The central conductor 30 and the ground plane 31 may comprise or be formed from a metal such as copper, stainless steel, nickel or the like.

[0197] Various different microwave antenna apparatus have been simulated using a 3D simulation model. In this case, the simulation model is HFSS (Ansoft Corp) which is a Finite Element Method (FEM) based full wave electromagnetic solver. Simulations may allow the calculation of a predicted response for coupling efficiency and specific absorption rate (SAR). SAR is a measure of the rate at which energy is absorbed by the human body when exposed to a radio frequency (RF) electromagnetic field.

[0198] FIG. 13 is a representation of the distribution of the microwave fields using an microwave antenna apparatus 36 into tissue 37 such as cervix tissue. The microwave antenna apparatus 36 fits into the endocervical canal 38 of the cervix. That part of the microwave antenna apparatus 36 which is not in engagement with tissue 37 is modelled into air 39. The SAR field distribution 40 of the microwave fields is illustrated using a greyscale map 41. The scattering parameter S11 response quantifying how RF energy propagates through the microwave antenna apparatus into the tissue is shown FIG. 14. The frequency of operation for microwave fields is plotted on X-axis whereas the S11 or the return loss is shown on the Y-axis in the decibels. The plot shows more than 99% energy being delivered into the tissue at 8 GHz indicating a very good match of the antenna 36 and the tissue 37 at 8 GHz.

[0199] The operating frequency of the microwave energy plays a fundamental role in dictating the depth of penetration into the tissue and the overall treatment zone dimensions. 8 GHz is a frequency that may offer a good balance of energy penetration density for a given power. Frequencies less than 8 GHz may penetrate too deeply. Frequencies greater than 8 GHz may fail to penetrate deep enough for the correct biological response.

[0200] FIG. 15 illustrates the case when the tissue is in contact 42 with the metallic ground plane showing SAR fields 43. The high concentration of the electric fields at the metal-to-tissue interface could cause subsequent charring and burns to the tissue. Consequently, FIG. 16 shows the SAR fields 44 for a microwave antenna apparatus which includes a dielectric element 45 which covers a portion of the metal ground plane so as to avoid any metal-to-tissue interface between the tissue and the metal ground plane and providing a safer solution with SAR fields 44 spread less co-axially as compared with FIG. 15.

[0201] With reference to FIG. 17, the overall length 46 of the central conductor 47 protruding axially from the ground plane 48 is critical to achieving the overall energy transmission pattern into the tissue. In a type D microwave antenna apparatus for example, a central conductor 47 extends from the ground plane 48 for a predetermined length 46. FIG. 17 illustrates the SAR field distribution pattern 49 when the central conductor 47 protrudes axially from the ground plane 48 by 10 mm. The SAR field distribution pattern 49 shows that the fields are stronger towards the ground plane. This could be beneficial to treat the volume into the ectocervical region. In FIG. 18, when the length of the central conductor 50 is 15 mm, the fields 51 can be pulled more towards the proximal region or away from the ground plane. This could be used when treating type II or type III TZ CIN having endocervical component.

[0202] FIG. 19 shows how a radial offset distance 52 between the radial extent of the ground plane 53 and the radial extent or radially outer profile of the external form 54 is critical in achieving the overall stronger distally extended energy distribution pattern 55 into the tissue. The central conductor 56 may be of a certain length such as 10 mm. In FIG. 20, the diameter of the external form 57 and the grounding plane 58 are identical which shows the migration of the fields away from the ground plane 59 when compared to the fields 55 shown in FIG. 19. The microwave antenna apparatus of FIG. 20 could be used when treating different types of TZ CIN possessing or not possessing endocervical and ectocervical component.

[0203] FIG. 21 illustrates how the effects of the varying a radial offset distance 60 between the radial extent of a ground plane 61 and the radial extent of an external form 62 of a microwave antenna apparatus can be compensated by extending the length of the central conductor 56. Specifically, FIG. 21 shows the SAR field for a radial offset 60 between the ground plane 61 and external form 62 which is identical to the radial offset 52, and when the central conductor 63 protrudes further above the ground plane than the central conductor 56 shown in FIG. 19. The fields 64 are confined away from the ground plane 61.

[0204] FIG. 22 shows a variation of FIG. 21 without any radial gap between a ground plane 65 and an external form 66. The fields 64 and 67 are almost identical in terms of the distribution region in spite of having different radial distances. This could also mean that when the extended central conductor takes over the field distribution pattern over the radial distance differences between the external form and the ground plane.

[0205] The ground plane can have different shapes to distribute different shapes of the electromagnetic fields into the tissue which in turn could be used to treat different types of TZ neoplasia. For example, a conical shaped ground plane 68 is illustrated in FIG. 23 which may transmit more energy 69 into the endocervical component 3 of the cervix 1, whereas the inverted cup shaped ground plane 70 shown in FIG. 24 could radiate more near the ground plane i.e. radiating the SAR field 71 more into the ectocervical component of the cervix.

[0206] FIG. 25 illustrates another form of ground plane 72 with a cup shaped structure that may spread and pull the radiation 73 further into the ectocervical component of the cervix.

[0207] If the ground plane of the microwave antenna apparatus of FIG. 20 makes contact with the tissue, this may result in high electromagnetic fields which could result in charring of the tissue. Alternatively, as illustrated in FIG. 26, the antenna is pulled back away from the tissue avoiding any possibility of the contact of the ground plane 74 with the tissue 75 which shows no change in the radiation field 76 as compared to the 59.

[0208] FIG. 27 shows how the shape of the central conductor, in particular of a central conductor of an extended length, may affect the distribution of the fields. FIG. 27 shows a central conductor 77 of length 20 mm showing a non-uniform field pattern 78 which may radiate more into the endocervical component of the cervix. Similarly, with reference to FIG. 28, by thickening the central conductor 79 at the bottom and tapering it towards the top, the fields 80 may be aligned and transmitted uniformly along the entire length of the cervix in advanced cases of CIN.

[0209] One of ordinary skill in the art will understand that various modifications may be made to any of the apparatus, assemblies or systems described above. For example, in order to limit the axial propagation of energy, an electrically conductive cap element may be included at or adjacent a distal end of the microwave antenna apparatus. For example, a distal end of an outer surface of the microwave antenna apparatus may be defined by one or more of the dielectric elements and the cap element may be located between the distal end of the elongated conductor and the distal end of the outer surface of the microwave antenna apparatus. Alternatively, the cap element may define the distal end of the outer surface of the microwave antenna apparatus.

[0210] The conductive shield of the coaxial cable may comprise two components. For example, the conductive shield of the coaxial cable may comprise a mesh or weave of conductive material and a foil wrap. The foil wrap may supplement the mesh or weave.

[0211] The coaxial cable may comprise a coating. The coating may comprise any suitable insulating material, for example PTFR, PEEK, FEB, or parylene. Such a coating may increase robustness. Such a coating may reduce friction to enhance the ease with which the cable may slide relative to another object.