Search PubMed⌕ Search

Biomedical subjects

P T Finger

Publications and source records attributed to P T Finger.

At least 73 records · Page 4Linked to original sources
PubMed1993

A phantom system for microwave treatment of intraocular tumors.

A gel-block system was developed to illustrate heating patterns induced by ophthalmic microwave applicators. A heat-sensitive liquid crystal card was affixed as to bisect a Lucite box. The box was then filled with a clear tissue equivalent polyacrylamide gel. It was found that semicircular heating patterns were generated within the gel. These patterns were visualized by placing one of the dish-shaped ophthalmic microwave applicators on top of the polyacrylamide gel and the heat-sensitive liquid crystal card. An antenna was then placed in the gel and behind the card. Microwave energy was sent through the card and into the gel. This demonstrated the relatively homogeneous and roughly circular heating pattern produced at the applicator's surface. A combination of these profiles led to construction of a three-dimensional, dome-shaped model of heating, as provided by this microwave antenna design.

Acrylic Resins↗
PubMed1992

Long-term results of iodine 125 irradiation of uveal melanoma.

The authors report on 64 of the first 65 patients treated with iodine 125. The mean follow-up was 64.9 months. After treatment, 29 patients (45.3%) retained visual acuity of 20/100 or better, and 18 patients (28.1%) retained visual acuity within two lines of visual acuity before irradiation. Eleven patients (17.2%) died of metastasis, and 5 patients (7.8%) had local recurrence. Cataract developed in 29 (45.3%) patients; keratitis developed in only 2 (3.1%) patients, and dry eye developed in none. Neovascular glaucoma developed in 7 (10.9%) patients, and 15 (23.4%) patients had radiation retinopathy. Eleven patients (17.2%) required enucleation for either tumor growth or neovascular glaucoma. These results show the increasing number of radiation complications seen with long-term observation and the frequently seen adverse visual outcome.

Brachytherapy↗
PubMed1992

Microwave plaque thermoradiotherapy for choroidal melanoma.

Microwave thermoradiotherapy was used as a primary treatment for 44 patients with choroidal melanoma. An episcleral dish-shaped microwave antenna was placed beneath the tumour at the time of plaque brachytherapy. While temperatures were measured at the sclera, the tumour's apex was targeted to receive a minimum of 42 degrees C for 45 minutes. In addition, the patients received full or reduced doses of plaque radiotherapy. No patients have been lost to follow-up. Two eyes have been enucleated: one for rubeotic glaucoma, and one for uveitic glaucoma. Though six patients have died, only one death was due to metastatic choroidal melanoma (39 months after treatment). Clinical observations suggest that the addition of microwave heating to plaque radiation therapy of choroidal melanoma has been well tolerated. There has been a 97.7% local control rate (with a mean follow-up of 22.2 months). We have reduced the minimum tumour radiation dose (apex dose) to levels used for thermoradiotherapy of cutaneous melanomas (50 Gy/5000 rad). Within the range of this follow-up period no adverse effects which might preclude the use of this microwave heat delivery system for treatment of choroidal melanoma have been noted.

Brachytherapy↗
PubMed1991

Microwave cyclodestruction for glaucoma in a rabbit model.

Microwave thermotherapy was used to treat experimentally induced glaucoma. Microwave-induced cyclodestruction was successful in reducing intraocular pressure in all treated glaucomatous eyes for 4 weeks. Two additional glaucomatous eyes were left untreated to serve as controls, and were noted to have persistently elevated intraocular pressures. Six additional eyes were then subjected to an equivalent treatment (50 degrees C in five 1-minute applications), which resulted in approximately 180 degrees of heat treatment just posterior to the corneoscleral limbus. These specimens were evaluated with light microscopy at baseline, 24 hours, and 7 days after treatment. Our clinical and histopathologic evaluations suggested that microwave thermotherapy (delivered under thermometry control) allowed for chorioretinal/ciliary body destruction that resulted in reductions of intraocular pressure in glaucomatous eyes.

Animals↗
PubMed1991

Palladium 103 ophthalmic plaque radiotherapy.

We compared the ocular radiation distribution of palladium 103 (103Pd) vs iodine 125 (125I) ophthalmic plaques sewn to 12 human donor eyes. We then performed preoperative comparative simulations on the first seven patients to be treated with palladium 103 plaque therapy for choroidal melanoma. The in vitro experiment involved palladium 103 seeds placed into a Silastic seed holder, which was affixed into standard 14-mm gold eye plaques. Then the plaques were sewn onto 12 human donor eyes so as to approximate either the nasal (six eyes) or temporal (six eyes) equator. Three sets of two thermoluminescent dosimeters were used to quantify the amount of radiation delivered by the episcleral plaques. Thermoluminescent dosimeters were sewn to the sclera in three locations: on the center of the cornea, on the sclera beneath the macula, and at the equator in a position opposite the plaque. This experiment was then repeated with iodine 125 seeds and thermoluminescent dosimeters. After the plaques were adjusted to equalize their activity (plaque strength), the palladium 103 plaques were found to deliver less radiation to the three target points. Comparative clinical dosimetry also reflected this difference. Preoperative simulations comparing equal doses to the tumors' apex revealed that the palladium 103 ophthalmic plaques delivered more radiation to the tumor and less radiation to most normal ocular structures.

Brachytherapy↗
PubMed1991

Cis-platinum chemotherapy for ocular basal cell carcinoma.

We have used intravenous cis-platinum chemotherapy in the treatment of three patients with basal cell carcinoma of the lid extending into the orbit. Cis-platinum chemotherapy caused a reduction in tumour size and thereby delayed surgery in all cases. It allowed for local resection in one case, appeared to delay a patient's exenteration in a second case, and was used prior to radiotherapy in a third case. While not curative, cis-platinum may be useful as an adjuvant to decrease tumour mass prior to local excision and for patients who refuse or must delay exenteration.

Aged↗
PubMed1990

Vitrectomy retinotomy aspiration biopsy of choroidal tumors.

We used an investigational technique for the biopsy of intraocular tumors to aid in the diagnosis of three choroidal tumors. A three-port trans-pars plana vitrectomy was performed in conjunction with retinotomy, tumor biopsy, endophotocoagulation, and air-fluid exchange. Vitrectomy was used to decrease the amount of traction secondary to retained vitreous after intraocular surgery. Retinotomy sites were chosen under microscopic control to avoid large caliber retinal vessels. Then a modified tumor-aspiration technique, together with endophotocoagulation and aspiration of intraoperative vitreous hemorrhages, provided an opportunity to sample tumor tissue continually at varied depths. We have added standard vitreous surgery concepts, techniques, and instrumentation to produce vitrectomy retinotomy aspiration biopsy of choroidal tumors.

Adenocarcinoma↗
PubMed1990

[Sub-choroidal implanted Greene melanoma: an animal experiment model for malignant choroid melanoma].

A modified technique for subchoroidal transplantation of amelanotic Greene melanoma cells and the intraocular growth patterns of this tumor in rabbit eyes are described. Tumor fragments were implanted via a scleral tunnel in 71 rabbit eyes, with 64 successful tumor growths, producing a prominent, circumscribed choroidal mass within 12-14 days of surgery. Choroidal Greene melanoma in rabbits resembles human epithelioid uveal melanoma in both its growth patterns and morphologic characteristics. The authors' implantation technique guarantees reliable growth of choroidal tumors with easily reproducible size and location. The experimental choroidal melanoma model is particularly valuable in clinical studies where a large number of tumors, with limited variation, is necessary for different experimental groups.

Animals↗
PubMed1990

Posterior scleritis as an intraocular tumour.

Posterior scleritis rarely presents as a large 'intraocular tumour' and continues to be a challenge in diagnosis and management. We present the case of a 66-year-old male with no known rheumatic disease, pain, proptosis, or diplopia, but with progressively decreasing visual acuity and a large, discrete 'subretinal tumour', 15 X 17 mm basal diameter and 8.3 mm apical height. Histologically the tumour was shown to be grossly thickened and necrotic sclera.

Aged↗
PubMed1990

Traumatic transconjunctival orbital emphysema.

Orbital emphysema can be produced by trans-conjunctival migration of air from a high pressure airgun. In an industrial accident an 8 mm conjunctival laceration was produced in the superior fornix which acted as a portal of entry for air into the subconjunctival, subcutaneous, and retrobulbar spaces. Computed tomography revealed no evidence of orbital fracture and showed that traumatic orbital emphysema occurred without a broken orbital bone.

Accidents, Occupational↗
PubMed1990

Transscleral microwave cyclodestruction.

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.

Animals↗
PubMed1990

Intraocular radiation blocking.

Iodine-based liquid radiographic contrast agents were placed in normal and tumor-bearing (Greene strain) rabbit eyes to evaluate their ability to block iodine-125 radiation. This experiment required the procedures of tumor implantation, vitrectomy, air-fluid exchange, and 125I plaque and thermoluminescent dosimetry (TLD) chip implantation. The authors quantified the amount of radiation attenuation provided by intraocularly placed contrast agents with in vivo dosimetry. After intraocular insertion of a blocking agent or sham blocker (saline) insertion, episcleral 125I plaques were placed across the eye from episcleral TLD dosimeters. This showed that radiation attenuation occurred after blocker insertion compared with the saline controls. Then computed tomographic imaging techniques were used to describe the relatively rapid transit time of the aqueous-based iohexol compared with the slow transit time of the oil-like iophendylate. Lastly, seven nontumor-bearing eyes were primarily examined for blocking agent-related ocular toxicity. Although it was noted that iophendylate induced intraocular inflammation and retinal degeneration, all iohexol-treated eyes were similar to the control eyes at 7 and 31 days of follow-up. Although our study suggests that intraocular radiopaque materials can be used to shield normal ocular structures during 125I plaque irradiation, a mechanism to keep these materials from exiting the eye must be devised before clinical application.

Animals↗