CA2092406C - Thermostatically-controlled microwave cyclodestruction as a treatment for glaucoma - Google Patents
Thermostatically-controlled microwave cyclodestruction as a treatment for glaucoma Download PDFInfo
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- CA2092406C CA2092406C CA 2092406 CA2092406A CA2092406C CA 2092406 C CA2092406 C CA 2092406C CA 2092406 CA2092406 CA 2092406 CA 2092406 A CA2092406 A CA 2092406A CA 2092406 C CA2092406 C CA 2092406C
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- applicator
- waveguide
- thermocouple
- microwave
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS 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
- A61F9/00—Methods or devices for treatment of the eyes; Devices for putting-in contact lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
- A61F9/007—Methods or devices for eye surgery
- A61F9/00781—Apparatus for modifying intraocular pressure, e.g. for glaucoma treatment
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
- A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
- A61B18/1815—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using microwaves
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/02—Radiation therapy using microwaves
Abstract
A miniaturized microwave applicator comprises a thin-wall metal dielectric-filled waveguide (200) having a thermocouple (208) disposed in a groove (206) in the surface of the dielectric radiating aperture of the waveguide (200). When the aperture is placed in contact with a spot on the outer surface of the sclera overlying the ciliary body to cyclodestruct by heat generated by absorbed microwave energy radiated thereto during a given time, damage due to overheating of the scleral tissue is prevented by the thermocouple (208), which monitors the sclera surface temperature, being used to thermostatically control the microwave energy supplied to the waveguide in a manner that the scleral tissue temperature is maintained substantially constant at a value below that which would cause damage thereto. The desired operation is dependent on the fact that very little of the microwave energy is absorbed by the lower-water-content scleral tissue as it passes therethrough, but is highly absorbed by the underlying high -water-content ciliary-body tissue.
Description
wo 92/19414 Pcr/uss2/0342~
~09~40~i THERMOSTATICALLY-CONTROT T~FD MICROWAVE
CYCLODESTRUCIION
AS A TREATMENT FOR GLAUCOMA
BACKGROUND
As known in the art, several different cyclodestruction 10 procedures (i.e., procedures for destroying the ciliary body) have been developed or proposed for treating glaucoma. The clinical standard cyclodestruction procedure employs cryotherapy. Other known cyclodestruction procedures include therapeutic ultrasound and Neodymium:Yag cyclophotocoagulation. However, 15 all of these known cyclodestruction procedures have demonstrated different negative tissue reactions.
Cryotherapy has been characterized by discomfort and edema, therapeutic sound by induced scleral changes, and Neodymium:Yag cyclophotocoagulation has been shown to cause 2 0 characteristic spot-like conjunctival lesions. Other less specific morbidities have included corneal-scleral thinning, hyphema, cataract, vitritis, retinal detachment, cystoid macula edema, and hypotony. These potential complications have defined cyclodestruction procedures as a last treatment for refractory 2 5 cases.
SUMMARY OF THE INVENTION
The present invention is directed to a microwave 3 0 cyclodestruction procedure which avoids negative tissue reactions and minimi7es potential complications. The microwaves are applied to the ciliary body by a novel miniature microwave applicator placed in contact with a spot on the outer surface of the sclera. The miniature microwave applicator incorporates a 3 5 thermocouple on its anterior radiating surface, so that the thermocouple also contacts the spot on the outer surface of the sclera. The thermocouple thermostatically controls the output of SUBSTITUTE SH~ET
wo 92/19414 Pcr/uss2/o3425 ~ g~0~~ 2 the microwave generator energizing the applicator to ensure that the temperature of the scleral tissue never rises to an unsafe level. Because scleral tissue absorbs less microwave energy, while ciliary-body tissue absorbs more microwave energy, most of the 5 applied applied microwave energy penetrates through the sclera to, and is absorbed by, the underlying ciliary body. This raises the temperature of the ciliary body to the point at which some cyclodestruction occurs. This process may be repeated at several separate spots of the sclera to complete the microwave l 0 cyclodestruction procedure.
BRIEF DESCRIPTION OF THE DRAVVINGS
FIGURE 1 is a functional block diagram showing the l 5 relationship between a miniature microwave applicator incorporating a thermocouple (which may take the form shown in FIGURE 2) and a thermostatically-controlled microwave generator for energizing the applicator;
FIGURE 2 illustrates the physical form of a preferred 2 0 embodiment of the miniature microwave applicator incorporating a thermocouple that is used for microwave cyclodestruction;
FIGURE 3 is a first chart useful in explaining the principles of the present invention; and FIGURE 4 is a second chart useful in explaining the 2 5 principles of the present invention.
DESCRIPIION OF THE PREFERRED EMBODIMENT
Referring to FIGURE l, the microwave output of 3 0 thermostatically-controlled microwave generator 100 is applied as an input to miniature microwave applicator incorporating a thermocouple 102 (which may take the form shown in FIGURE 2) over a suitable microwave transmission line 104. The thermocouple of applicator 102 generates a control signal having a 3 5 value which is a function of the temperature at the microwave radiating aperture of applicator 102. This control signal, which is fed back to microwave generator 100 over connection 106 to SJBSTITUTE SHEET
wo 92/19414 pcr/uss2/o342~
3 ~09~40~
thermostatically control microwave generator 100, prevents microwave energy from being forwarded from the output of microwave generator 100 over transmission line 104 to the input of applicator 102 whenever the temperature of the thermocouple 5 rises to a certain preselected temperature.
Referring to FIGURE 2, applicator 102 comprises thin-wall metal dielectric-filled waveguide.200. In practice, waveguide 200 is fabricated from a block of ceramic material that exhibits a high dielectric constant (e.g., 85) that is machined to the proper size 1 0 and shape. The longitudinal surface of this properly sized and shaped ceramic material is first electrolessly plated with metal and then electroplated with metal to produce the thin metal wall of waveguide 200. More specifically, the length of waveguide 200 is preferably about one inch; the width of waveguide 200 is 1 5 preferably about 0.2 inch (i.e., 200 mils); and the thickness of waveguide 200 preferably tapers from about 0.1 inch (i.e., 100 mils) at at its posterior end, to which microwave input connector 202 is attached, to about 0.15 inch (i.e., 150 mils) at its anterior end, which forms dielectric radiating aperture 204. Thus, the area 2 0 of dielectric radiating aperture 204 is quite small, being only 0.03 square lnch.
As shown in FIGURE 2, the dielectric anterior surface, which is preferably flat, has a groove 206 machined therein in which thermocouple 208 is fixedly secured substantially at the center 2 5 thereof. The thickness of the thermocouple is preferably sufficient to protrude very slightly from the flat dielectric anterior surface.
Thermocouple output wires 210, connected to thermocouple 208, extend through the length of groove 206 to the outside of waveguide 200, as shown in FIGURE 2. Thermocouple output wires 30 210 constitute feedback connection 106 of FIGURE 1.
The therapeutic purpose of applicator 102 in the treatment of glaucoma is to apply sufficient microwave energy to the ciliary body to effect cyclodestruction without creating collateral eye damage. This is accomplished by first positioning 0.03 square inch 3 5 dielectric radiating aperture 204 in contact with the anterior surface of applicator 102 in contact with a 0.03 square inch spot on the outer surface of the sclera which overlies the ciliary body SUBSTITUTE ~tlEF~
wo 92/19414 Pcr/uss2/o342~
(e.g., a spot displaced about 2 millimeters beyond the outer edge of the iris). This inherently places thermocouple 208 in in contact with this spot. The applicator is energized with microwave energy having a frequency (e.g. 5,000 to 6,000 MHz) which readily 5 penetrates the thickness of the scleral tissue with little absorption and reaches a corresponding spot of the underlying ciliary body, where it is readily absorbed. The reason for this is shown by the FIGURE 3 chart, which will be discussed below.
The microwave energy is applied to the spot for a given l 0 time (e.g., one minute) which is a sufficient time for the irradiated spot of the ciliary body to be heated to a high enough temperature to cause cyclodestruction, while the sclera itself is never heated enough to raise its temperature sufficiently high to result in damage thereto. (The FIGURE 4 chart, discussed in more detail l 5 below, indicates the the relationship between temperature and time of heating duration that results in damage to different types of m~mm~lian tissue.) In any event, the thermostatic control of microwave generator lO0 is set so that the radiated microwave energy is cut off whenever the temperature of thermocouple 208 2 0 rises to a preselected therapeutic temperature which is below the temperature at which scleral damage occurs. Thus, the continuous monitoring of sclera-spot surface temperature by thermocouple 208 maintains the temperature substantially constant at the therapeutic temperature and also ensures that the operation is 2 5 fail-safe.
In order to complete the microwave cyclodestruction procedure, the above-described process is applied sequentially to each of several (e.g., five) displaced spots on the outer surface of the sclera. More specifically, after the above-described process 3 0 with respect to one of the several displaced spots is completed, the applicator is displaced by about the width of applicator 102 (200 mils) to another similar scleral spot overlying the ciliary body. Thus, the resulting several displaced spots tend to lie on the circumference of a circle having a radius about 2 millimeters 3 5 larger than that of the iris.
Referring to the FIGURE 3 chart, there is shown the penetration depth as a function of frequency at which l /e (where ~UBSTîTlJTE SHEET
wo 92/19414 Pcr/uss2/o3425 5 2~g2~0~
e is the base of natural logarithm) of incident microwave energy is absorbed by low-water-content human tissue and by high-water-content human tissue, respectively. It is apparent from this chart that low-water-content human tissue is much more microwave 5 absorbent than high-water-content human tissue. Scleral human tissue is low-water-content human tissue and ciliary-body tissue is high-water-content human tissue. Thus, most of the applied microwave energy merely passes through the thickness of the scleral tissue to be then highly absorbed by the underlying 1 0 ciliary-body tissue, thereby preferentially heating the underlying ciliary-body tissue.
Referring to the FIGURE 4 chart, there is shown temperature- time duration thresholds for damage to occur in different types of mammalian tissue. As indicated by the wide 1 5 band of the FIGURE 4 chart, for a given heating duration some types of tissue (e.g., corneal tissue) are damaged substantially less than others. It has been found that both corneal and scleral tissue are not damaged by, and tolerate well, being heated to a temperature up to about 50~ C for at least one minute. Therefore, 2 0 the aforesaid fail-safe thermostatically-controlled therapeutic temperature for a heating duration of scleral tissue for one minute certainly may be set at 50~ C, and perhaps even somewhat higher.
Returning to FIGURE 2, the high dielectric constant of the dielectric filling of waveguide 200 of applicator 102 serves two 2 5 important purposes. First, by reducing the microwave wavelength traveling therein for a given microwave frequency, the size of applicator 102 for transporting that given microwave frequency may be reduced (i.e., miniaturized). Second, the high dielectric constant of the dielectric filling of waveguide 200 more nearly 3 0 matches the high dielectric constant of the high-water content ciliary body, and, therefore, enhances microwave power transfer from dielectric radiating aperture 204 to the ciliary body. Further, for microwave power transfer purposes, the impedance at the microwave input to applicator 102 at the posterior end of 3 5 waveguide 200 should closely match that presented by transmission line 104, and the impedance at the microwave output from applicator 102 at dielectric radiating aperture 204 SUBSTITUTE SHEET
wo 92/19414 pcr/~lss2/o342s 209240~ 6 (located at the anterior end of waveguide 200) should closely match that presented by the scleral tissue with which it is in contact. The proper impedance matching at both the posterior and anterior ends of waveguide 200 is achieved by the above-discussed tapering of the thickness of waveguide 200 from 100 mils at its posterior end to 150 mils at its anterior end.
The above-described controlled microwave cyclodestruction procedure has been tested experimentally in the treatment of induced glaucoma in the eyes of rabbits. Microwave induced cyclodestruction was successful in reducing the intraocular pressure in all treated glaucomatous eyes for a 4 week duration.
Two additional glaucomatous eyes were left untreated, served as controls, and were noted to have persistently elevated intraocular pressures. Then 6 additional eyes were subjected to an equivalent treatment (50~C x 1 min. x 5 applications) which resulted in approximately 180~ of heat treatment just posterior to the corneal-scleral limbus. These specimens were evaluated by light microscopy at time 0, 24 hours, and at 7 days after treatment.
Clinical and histopathologic evaluations suggested that 2 0 microwave thermotherapy (delivered under thermometry control) allowed for chorioretinal/ciliary body destruction which resulted in reductions of intraocular pressure in glaucomatous eyes.
SuBsTlTuTE S~
~09~40~i THERMOSTATICALLY-CONTROT T~FD MICROWAVE
CYCLODESTRUCIION
AS A TREATMENT FOR GLAUCOMA
BACKGROUND
As known in the art, several different cyclodestruction 10 procedures (i.e., procedures for destroying the ciliary body) have been developed or proposed for treating glaucoma. The clinical standard cyclodestruction procedure employs cryotherapy. Other known cyclodestruction procedures include therapeutic ultrasound and Neodymium:Yag cyclophotocoagulation. However, 15 all of these known cyclodestruction procedures have demonstrated different negative tissue reactions.
Cryotherapy has been characterized by discomfort and edema, therapeutic sound by induced scleral changes, and Neodymium:Yag cyclophotocoagulation has been shown to cause 2 0 characteristic spot-like conjunctival lesions. Other less specific morbidities have included corneal-scleral thinning, hyphema, cataract, vitritis, retinal detachment, cystoid macula edema, and hypotony. These potential complications have defined cyclodestruction procedures as a last treatment for refractory 2 5 cases.
SUMMARY OF THE INVENTION
The present invention is directed to a microwave 3 0 cyclodestruction procedure which avoids negative tissue reactions and minimi7es potential complications. The microwaves are applied to the ciliary body by a novel miniature microwave applicator placed in contact with a spot on the outer surface of the sclera. The miniature microwave applicator incorporates a 3 5 thermocouple on its anterior radiating surface, so that the thermocouple also contacts the spot on the outer surface of the sclera. The thermocouple thermostatically controls the output of SUBSTITUTE SH~ET
wo 92/19414 Pcr/uss2/o3425 ~ g~0~~ 2 the microwave generator energizing the applicator to ensure that the temperature of the scleral tissue never rises to an unsafe level. Because scleral tissue absorbs less microwave energy, while ciliary-body tissue absorbs more microwave energy, most of the 5 applied applied microwave energy penetrates through the sclera to, and is absorbed by, the underlying ciliary body. This raises the temperature of the ciliary body to the point at which some cyclodestruction occurs. This process may be repeated at several separate spots of the sclera to complete the microwave l 0 cyclodestruction procedure.
BRIEF DESCRIPTION OF THE DRAVVINGS
FIGURE 1 is a functional block diagram showing the l 5 relationship between a miniature microwave applicator incorporating a thermocouple (which may take the form shown in FIGURE 2) and a thermostatically-controlled microwave generator for energizing the applicator;
FIGURE 2 illustrates the physical form of a preferred 2 0 embodiment of the miniature microwave applicator incorporating a thermocouple that is used for microwave cyclodestruction;
FIGURE 3 is a first chart useful in explaining the principles of the present invention; and FIGURE 4 is a second chart useful in explaining the 2 5 principles of the present invention.
DESCRIPIION OF THE PREFERRED EMBODIMENT
Referring to FIGURE l, the microwave output of 3 0 thermostatically-controlled microwave generator 100 is applied as an input to miniature microwave applicator incorporating a thermocouple 102 (which may take the form shown in FIGURE 2) over a suitable microwave transmission line 104. The thermocouple of applicator 102 generates a control signal having a 3 5 value which is a function of the temperature at the microwave radiating aperture of applicator 102. This control signal, which is fed back to microwave generator 100 over connection 106 to SJBSTITUTE SHEET
wo 92/19414 pcr/uss2/o342~
3 ~09~40~
thermostatically control microwave generator 100, prevents microwave energy from being forwarded from the output of microwave generator 100 over transmission line 104 to the input of applicator 102 whenever the temperature of the thermocouple 5 rises to a certain preselected temperature.
Referring to FIGURE 2, applicator 102 comprises thin-wall metal dielectric-filled waveguide.200. In practice, waveguide 200 is fabricated from a block of ceramic material that exhibits a high dielectric constant (e.g., 85) that is machined to the proper size 1 0 and shape. The longitudinal surface of this properly sized and shaped ceramic material is first electrolessly plated with metal and then electroplated with metal to produce the thin metal wall of waveguide 200. More specifically, the length of waveguide 200 is preferably about one inch; the width of waveguide 200 is 1 5 preferably about 0.2 inch (i.e., 200 mils); and the thickness of waveguide 200 preferably tapers from about 0.1 inch (i.e., 100 mils) at at its posterior end, to which microwave input connector 202 is attached, to about 0.15 inch (i.e., 150 mils) at its anterior end, which forms dielectric radiating aperture 204. Thus, the area 2 0 of dielectric radiating aperture 204 is quite small, being only 0.03 square lnch.
As shown in FIGURE 2, the dielectric anterior surface, which is preferably flat, has a groove 206 machined therein in which thermocouple 208 is fixedly secured substantially at the center 2 5 thereof. The thickness of the thermocouple is preferably sufficient to protrude very slightly from the flat dielectric anterior surface.
Thermocouple output wires 210, connected to thermocouple 208, extend through the length of groove 206 to the outside of waveguide 200, as shown in FIGURE 2. Thermocouple output wires 30 210 constitute feedback connection 106 of FIGURE 1.
The therapeutic purpose of applicator 102 in the treatment of glaucoma is to apply sufficient microwave energy to the ciliary body to effect cyclodestruction without creating collateral eye damage. This is accomplished by first positioning 0.03 square inch 3 5 dielectric radiating aperture 204 in contact with the anterior surface of applicator 102 in contact with a 0.03 square inch spot on the outer surface of the sclera which overlies the ciliary body SUBSTITUTE ~tlEF~
wo 92/19414 Pcr/uss2/o342~
(e.g., a spot displaced about 2 millimeters beyond the outer edge of the iris). This inherently places thermocouple 208 in in contact with this spot. The applicator is energized with microwave energy having a frequency (e.g. 5,000 to 6,000 MHz) which readily 5 penetrates the thickness of the scleral tissue with little absorption and reaches a corresponding spot of the underlying ciliary body, where it is readily absorbed. The reason for this is shown by the FIGURE 3 chart, which will be discussed below.
The microwave energy is applied to the spot for a given l 0 time (e.g., one minute) which is a sufficient time for the irradiated spot of the ciliary body to be heated to a high enough temperature to cause cyclodestruction, while the sclera itself is never heated enough to raise its temperature sufficiently high to result in damage thereto. (The FIGURE 4 chart, discussed in more detail l 5 below, indicates the the relationship between temperature and time of heating duration that results in damage to different types of m~mm~lian tissue.) In any event, the thermostatic control of microwave generator lO0 is set so that the radiated microwave energy is cut off whenever the temperature of thermocouple 208 2 0 rises to a preselected therapeutic temperature which is below the temperature at which scleral damage occurs. Thus, the continuous monitoring of sclera-spot surface temperature by thermocouple 208 maintains the temperature substantially constant at the therapeutic temperature and also ensures that the operation is 2 5 fail-safe.
In order to complete the microwave cyclodestruction procedure, the above-described process is applied sequentially to each of several (e.g., five) displaced spots on the outer surface of the sclera. More specifically, after the above-described process 3 0 with respect to one of the several displaced spots is completed, the applicator is displaced by about the width of applicator 102 (200 mils) to another similar scleral spot overlying the ciliary body. Thus, the resulting several displaced spots tend to lie on the circumference of a circle having a radius about 2 millimeters 3 5 larger than that of the iris.
Referring to the FIGURE 3 chart, there is shown the penetration depth as a function of frequency at which l /e (where ~UBSTîTlJTE SHEET
wo 92/19414 Pcr/uss2/o3425 5 2~g2~0~
e is the base of natural logarithm) of incident microwave energy is absorbed by low-water-content human tissue and by high-water-content human tissue, respectively. It is apparent from this chart that low-water-content human tissue is much more microwave 5 absorbent than high-water-content human tissue. Scleral human tissue is low-water-content human tissue and ciliary-body tissue is high-water-content human tissue. Thus, most of the applied microwave energy merely passes through the thickness of the scleral tissue to be then highly absorbed by the underlying 1 0 ciliary-body tissue, thereby preferentially heating the underlying ciliary-body tissue.
Referring to the FIGURE 4 chart, there is shown temperature- time duration thresholds for damage to occur in different types of mammalian tissue. As indicated by the wide 1 5 band of the FIGURE 4 chart, for a given heating duration some types of tissue (e.g., corneal tissue) are damaged substantially less than others. It has been found that both corneal and scleral tissue are not damaged by, and tolerate well, being heated to a temperature up to about 50~ C for at least one minute. Therefore, 2 0 the aforesaid fail-safe thermostatically-controlled therapeutic temperature for a heating duration of scleral tissue for one minute certainly may be set at 50~ C, and perhaps even somewhat higher.
Returning to FIGURE 2, the high dielectric constant of the dielectric filling of waveguide 200 of applicator 102 serves two 2 5 important purposes. First, by reducing the microwave wavelength traveling therein for a given microwave frequency, the size of applicator 102 for transporting that given microwave frequency may be reduced (i.e., miniaturized). Second, the high dielectric constant of the dielectric filling of waveguide 200 more nearly 3 0 matches the high dielectric constant of the high-water content ciliary body, and, therefore, enhances microwave power transfer from dielectric radiating aperture 204 to the ciliary body. Further, for microwave power transfer purposes, the impedance at the microwave input to applicator 102 at the posterior end of 3 5 waveguide 200 should closely match that presented by transmission line 104, and the impedance at the microwave output from applicator 102 at dielectric radiating aperture 204 SUBSTITUTE SHEET
wo 92/19414 pcr/~lss2/o342s 209240~ 6 (located at the anterior end of waveguide 200) should closely match that presented by the scleral tissue with which it is in contact. The proper impedance matching at both the posterior and anterior ends of waveguide 200 is achieved by the above-discussed tapering of the thickness of waveguide 200 from 100 mils at its posterior end to 150 mils at its anterior end.
The above-described controlled microwave cyclodestruction procedure has been tested experimentally in the treatment of induced glaucoma in the eyes of rabbits. Microwave induced cyclodestruction was successful in reducing the intraocular pressure in all treated glaucomatous eyes for a 4 week duration.
Two additional glaucomatous eyes were left untreated, served as controls, and were noted to have persistently elevated intraocular pressures. Then 6 additional eyes were subjected to an equivalent treatment (50~C x 1 min. x 5 applications) which resulted in approximately 180~ of heat treatment just posterior to the corneal-scleral limbus. These specimens were evaluated by light microscopy at time 0, 24 hours, and at 7 days after treatment.
Clinical and histopathologic evaluations suggested that 2 0 microwave thermotherapy (delivered under thermometry control) allowed for chorioretinal/ciliary body destruction which resulted in reductions of intraocular pressure in glaucomatous eyes.
SuBsTlTuTE S~
Claims (9)
1. A microwave applicator useful in the treatment of glaucoma by cyclodestruction; said applicator comprising a waveguide responsive to a microwave input of a given frequency supplied thereto at its posterior end for radiating microwave energy of said given frequency from the surface of an aperture situated at its anterior end; wherein:
said waveguide includes a thin. metal wall filled with solid dielectric material having a given dielectric constant that extends between said anterior and posterior ends and has a given area at said radiating aperture, whereby said radiating aperture is a dielectric radiating aperture;
said surface of said dielectric radiating aperture has a groove therein for housing a thermocouple;
said given dielectric constant of said solid dielectric material has a value that approximates the value of the dielectric constant of water; and the size of said given area is sufficiently small to permit said dielectric radiating aperture to contact only a given spot of scleral tissue of an eye that overlies substantially solely ciliary-body tissue of said eye.
said waveguide includes a thin. metal wall filled with solid dielectric material having a given dielectric constant that extends between said anterior and posterior ends and has a given area at said radiating aperture, whereby said radiating aperture is a dielectric radiating aperture;
said surface of said dielectric radiating aperture has a groove therein for housing a thermocouple;
said given dielectric constant of said solid dielectric material has a value that approximates the value of the dielectric constant of water; and the size of said given area is sufficiently small to permit said dielectric radiating aperture to contact only a given spot of scleral tissue of an eye that overlies substantially solely ciliary-body tissue of said eye.
2. The applicator defined in Claim 1, wherein:
said solid dielectric material consists of a ceramic block having said given dielectric constant.
said solid dielectric material consists of a ceramic block having said given dielectric constant.
3. The applicator defined in Claim 1 or 2, wherein:
said given dielectric constant has a value of substantially 85.
said given dielectric constant has a value of substantially 85.
4. The applicator defined in Claim 1, 2 or 3, wherein:
said thin metal wall comprises a metal plating on the surface of said ceramic block.
said thin metal wall comprises a metal plating on the surface of said ceramic block.
5. The applicator defined in any one of Claims 1 to 4, wherein:
the size of said given area is substantially 0.03 square inch.
the size of said given area is substantially 0.03 square inch.
6. The applicator defined in any one of Claims 1 to 5, wherein said microwave input is supplied to said posterior end of said waveguide by transmission means exhibiting a predetermined characteristic impedance; and wherein:
said thin metal wall filled with solid dielectric material has a second given area of a certain size at the posterior end of said waveguide, said certain size being such as to provide said waveguide with an input impedance that substantially matches said predetermined characteristic impedance exhibited by said transmission means.
said thin metal wall filled with solid dielectric material has a second given area of a certain size at the posterior end of said waveguide, said certain size being such as to provide said waveguide with an input impedance that substantially matches said predetermined characteristic impedance exhibited by said transmission means.
7. The applicator defined in Claim 6, wherein:
the size of said second given area is different from that of said first-mentioned given area, and the cross section area of said thin metal wall filled with solid dielectric material tapers in size between said second and first-mentioned given areas.
the size of said second given area is different from that of said first-mentioned given area, and the cross section area of said thin metal wall filled with solid dielectric material tapers in size between said second and first-mentioned given areas.
8. The applicator defined in Claim 7, wherein:
said first-mentioned given area has a width of substantially 200 mil and a thickness of: substantially 150 mil;
and said second given area has a width of substantially 200 mil and a thickness of substantially 100 mil.
said first-mentioned given area has a width of substantially 200 mil and a thickness of: substantially 150 mil;
and said second given area has a width of substantially 200 mil and a thickness of substantially 100 mil.
9. The applicator defined in any one of claims 1 to 8, further comprising:
a thermocouple situated within the surface groove in the dielectric radiating aperture; and thermocouple output wires adapted to deliver a signal indicative of the temperature of the thermocouple to external means for thermostatically controlling the microwave input supplied at the posterior end of the waveguide in order to prevent the thermocouple temperature from ever exceeding a temperature having a preselected value that is below that which would result in damage to scleral tissue, whereby microwave energy radiated from the dielectric aperture of the applicator may be used to effect cyclodestruction by positioning the dielectric aperture in contact with the given spot on the outer surface of scleral tissue which overlies ciliary-body tissue, thereby also situating the thermocouple in contact with the given spot.
a thermocouple situated within the surface groove in the dielectric radiating aperture; and thermocouple output wires adapted to deliver a signal indicative of the temperature of the thermocouple to external means for thermostatically controlling the microwave input supplied at the posterior end of the waveguide in order to prevent the thermocouple temperature from ever exceeding a temperature having a preselected value that is below that which would result in damage to scleral tissue, whereby microwave energy radiated from the dielectric aperture of the applicator may be used to effect cyclodestruction by positioning the dielectric aperture in contact with the given spot on the outer surface of scleral tissue which overlies ciliary-body tissue, thereby also situating the thermocouple in contact with the given spot.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US69172091A | 1991-04-26 | 1991-04-26 | |
| US691,720 | 1991-04-26 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2092406A1 CA2092406A1 (en) | 1992-10-27 |
| CA2092406C true CA2092406C (en) | 2003-07-15 |
Family
ID=24777681
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2092406 Expired - Fee Related CA2092406C (en) | 1991-04-26 | 1992-04-24 | Thermostatically-controlled microwave cyclodestruction as a treatment for glaucoma |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1893692A (en) |
| CA (1) | CA2092406C (en) |
| WO (1) | WO1992019414A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6430446B1 (en) | 1995-05-05 | 2002-08-06 | Thermage, Inc. | Apparatus for tissue remodeling |
| US5660836A (en) * | 1995-05-05 | 1997-08-26 | Knowlton; Edward W. | Method and apparatus for controlled contraction of collagen tissue |
| US6241753B1 (en) | 1995-05-05 | 2001-06-05 | Thermage, Inc. | Method for scar collagen formation and contraction |
| US5755753A (en) | 1995-05-05 | 1998-05-26 | Thermage, Inc. | Method for controlled contraction of collagen tissue |
| US6425912B1 (en) | 1995-05-05 | 2002-07-30 | Thermage, Inc. | Method and apparatus for modifying skin surface and soft tissue structure |
| US6350276B1 (en) | 1996-01-05 | 2002-02-26 | Thermage, Inc. | Tissue remodeling apparatus containing cooling fluid |
| US20170319276A1 (en) * | 2016-05-03 | 2017-11-09 | Covidien Lp | Systems and methods facilitating application of an appropriate thermal dosage in microwave ablation procedures |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4190053A (en) * | 1977-06-20 | 1980-02-26 | Rca Corporation | Apparatus and method for hyperthermia treatment |
| US4204549A (en) * | 1977-12-12 | 1980-05-27 | Rca Corporation | Coaxial applicator for microwave hyperthermia |
| US4271848A (en) * | 1979-01-11 | 1981-06-09 | Bio Systems Design, Corp. | Apparatus for electromagnetic radiation of living tissue and the like |
| US4311154A (en) * | 1979-03-23 | 1982-01-19 | Rca Corporation | Nonsymmetrical bulb applicator for hyperthermic treatment of the body |
| US4282887A (en) * | 1979-10-11 | 1981-08-11 | Rca Corporation | Ridge-waveguide applicator for treatment with electromagnetic energy |
| US4589424A (en) * | 1983-08-22 | 1986-05-20 | Varian Associates, Inc | Microwave hyperthermia applicator with variable radiation pattern |
| US4841990A (en) * | 1985-06-29 | 1989-06-27 | Tokyo Keiki Co., Ltd. | Applicator for use in hyperthermia |
-
1992
- 1992-04-24 AU AU18936/92A patent/AU1893692A/en not_active Abandoned
- 1992-04-24 WO PCT/US1992/003425 patent/WO1992019414A1/en active Application Filing
- 1992-04-24 CA CA 2092406 patent/CA2092406C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2092406A1 (en) | 1992-10-27 |
| WO1992019414A1 (en) | 1992-11-12 |
| AU1893692A (en) | 1992-12-21 |
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