ABSTRACT
A 4.6-gigahertz (GHz) microwave applicator was used to ablate the ciliary body in rabbit eyes. High-frequency electromagnetic radiation provides a favorable dose distribution to induce local heating of the ciliary body. For treatment, a 3-mm diameter disc-shaped applicator was placed on the conjunctiva and over the ciliary body. Conjunctival temperatures were monitored during treatment with a built-in thermocouple thermometer located at the center of the disc-shaped antenna. This allowed direct measurement (dosimetry) of the conjunctival temperature during treatment. Using this microwave-based heat-delivery system, doses in a range of 60 degrees for 30 or 60 seconds appeared to cause ciliary body damage with relative sparing of the conjunctiva and sclera.
Subject(s)
Ciliary Body/radiation effects , Microwaves , Animals , Ciliary Body/pathology , Conjunctiva/pathology , Conjunctiva/radiation effects , Equipment Design , Microwaves/adverse effects , Necrosis , Rabbits , Sclera/pathology , Sclera/radiation effects , Technology, Radiologic , TemperatureABSTRACT
Thermoradiotherapy (TRT) was used to treat 18 patients with choroidal melanoma. Techniques and clinical observations using a plaque-type device capable of delivering microwave hyperthermia to intraocular tumors are described. Iodine-125 plaque irradiation (48-88 Gy to apex), together with microwave hyperthermia (46 degrees-52.5 degrees C to base), were given to patients during one brachytherapy session. Since October 1985, 15 medium and 3 large-sized tumors were treated. Clinical observations include partial clearing of six vitreous opacities as well as three retinal detachments noted before treatment. Objective measurements of improved visual acuity were noted in seven of the nine cases. All tumors responded to treatment, but one tumor had regrowth and the eye was enucleated. These data suggest that a microwave plaque can be used to deliver hyperthermia to human choroidal melanomas. Within the range of the follow-up period, no side effects that might preclude the use of this hyperthermia system for choroidal melanoma treatment were noted.
Subject(s)
Choroid Neoplasms/therapy , Hyperthermia, Induced , Melanoma/therapy , Choroid Neoplasms/radiotherapy , Combined Modality Therapy , Equipment Design , Fluorescein Angiography , Follow-Up Studies , Humans , Hyperthermia, Induced/instrumentation , Melanoma/radiotherapy , Microwaves/therapeutic use , UltrasonographyABSTRACT
We have developed and used a thermoradiotherapy (TRT) plaque to treat choroidal melanoma (Greene strain) in rabbits. A dual-therapy scleral plaque delivers localized hyperthermia (4.8-gigahertz microwave) and ionizing radiation (iodine I 125). Transscleral treatment involves placement of a TRT plaque on bare sclera at the base of an intraocular tumor. Therapeutic doses of ionizing and hyperthermic radiation are then simultaneously delivered to the intraocular tumor. Sparing of normal ocular structures outside the treatment area after the combined therapy has been noted on clinical, gross, and histologic examinations. Our study suggests that the TRT plaque described satisfies the requirements for dual-modality treatment of choroidal melanoma.
Subject(s)
Choroid Neoplasms/therapy , Hyperthermia, Induced , Melanoma/therapy , Animals , Body Temperature , Choroid Neoplasms/pathology , Choroid Neoplasms/radiotherapy , Combined Modality Therapy , Eye/pathology , Hyperthermia, Induced/instrumentation , Melanoma/pathology , Melanoma/rehabilitation , Neoplasm Transplantation , RabbitsABSTRACT
A 5.8-gigahertz (GHz) ophthalmic microwave applicator was used to treat choroidal melanoma (Green strain) in rabbits. High-frequency electromagnetic radiation provides a favorable dose distribution to induce local hyperthermia in the treatment of intraocular tumors. Heating of the neoplasm, while sparing normal ocular structures, is best accomplished by a transscleral approach. A hyperthermia plaque is placed on the sclera at the base of the intraocular tumor. Contact (resistive) heating and electromagnetic radiation (radiofrequency and microwave) are best suited to a plaque technique. The advantages of electromagnetic heat induction, as compared with contact heating, are twofold: the depth of hyperthermic penetration can be modulated by frequency selection, and the tissues with low water content (sclera) remain relatively unaffected by microwaves. The 5.8-GHz ophthalmic microwave applicator satisfies the requirements for local hyperthermic treatment of intraocular tumors.
