PubMed Health⌕ Search

Biomedical subjects

D J Coleman

Publications and source records attributed to D J Coleman.

At least 19 recordsLinked to original sources
PubMed1992

Computer model of ultrasonic hyperthermia and ablation for ocular tumors using B-mode data.

Computer simulations have been conducted to examine hyperthermia and ablation for treating ocular tumors. An interactive software package has been implemented that permits relevant tissue dimensions to be determined from B-mode data. This package also permits interactive beam positioning, and it provides image displays depicting computed absorbed doses and temperature rises. Results are presented showing how hyperthermia temperature patterns are influenced by beam position, beam geometry and frequency. Images showing ablative temperature rises at various time intervals are also presented. For hyperthermia, geometric models of beam profiles showed that a non-uniform beam pattern (with a central low-intensity region) can produce more uniform heating of small ocular tumors than a beam with a uniform intensity profile. For a given tumor, the uniformity of hyperthermia temperatures was found to be a function of frequency, with 4.75 MHz providing reasonably uniform results for typical tumor heights (near 7 mm). For ablation, diffraction computations were employed to calculate beam intensity profiles; results show an initially rapid rise in temperature levels with subsequent, slower heating beyond the -3-dB limits of the focal volume. The model is now being refined, and additional phenomena, including nonlinear propagation, will be incorporated.

Body Temperature↗
PubMed1992

Computer simulations of ultrasonic heating for ocular therapy.

Computer simulations are being performed to model the temperature patterns produced during ultrasonically induced hyperthermia of ocular tumours. The software package for these simulations incorporates operator interaction and uses tissue geometry obtained from B-mode data. Previous studies used geometric approximations for the incident beams used for hyperthermia. In the current study, these beams were computed using diffraction analysis to obtain more realistic simulations of clinical exposures.

Body Temperature↗
PubMed1992

Ophthalmic ultrasonography.

Definition and differentiation of ocular structures and abnormalities necessitates the use of high-frequency, high-resolution, and high-definition ultrasound. Frequencies of 10 to 100 MHz are being employed. Color Doppler imaging, tissue characterization, parameter image staining, and three-dimensional volume rendering are new and useful adjuncts to ocular diagnosis.

Eye↗
PubMed1991

Ultrasonic tissue characterization of uveal melanoma and prediction of patient survival after enucleation and brachytherapy.

We performed survival studies on 136 patients with uveal malignant melanoma who were examined with ultrasonic tissue characterization before treatment with cobalt-60 brachytherapy (74 patients) or enucleation (62 patients). Mean follow-up time was 58.7 months for the brachytherapy group and 59.0 months for the enucleated group. The maximal follow-up time was nearly ten years. Univariate survival analysis showed that patients with small tumors (less than 250 mm3, 49 patients) had a higher five-year survival when treated with brachytherapy than when treated with enucleation. No patients in this study with tumor volumes greater than 1,500 mm3 (13 patients) were treated with brachytherapy. For tumors of intermediate size (74 patients), survival analysis did not indicate appreciable differences between the treatment options. However, multivariate models including two ultrasonic tissue characterization variables, scatterer size and concentration, showed appreciable intergroup differences in the dependence of survival on these factors. Results suggest that tissue properties detectable with ultrasonic techniques are related to differences in patient survival and may be used for treatment planning for tumors of intermediate size.

Brachytherapy↗
PubMed1991

Therapeutic ultrasound for the treatment of glaucoma.

A multicenter clinical trial of therapeutic ultrasound for the treatment of glaucoma included 20 centers in the United States in which 1,117 treatments were performed on 880 eyes. The study was limited to patients with refractory glaucoma who had not benefited from conventional medical and surgical techniques. Approximately 782 of 1,117 treatments (70%) showed an initial decrease in intraocular pressure from a pretreatment mean of 38.1 mm Hg to 22 mm Hg or less. By Kaplan-Meier survival analysis, the single treatment success rate (intraocular pressure between 6 and 22 mm Hg) was 48.7% at six months posttreatment. When retreatment was used subsequent to failure, the one-year multitreatment success rate was 79.3%. The most common complications were an immediate posttreatment intraocular pressure increase lasting a few hours and mild iritis. Other complications included scleral thinning in 28 of 1,117 treatments (2.5%) and phthisis bulbi in 12 of 1,117 treatments (1.1%).

Adolescent↗
PubMed1991

Histologic effects of contact ultrasound for the treatment of glaucoma.

The histologic effects of a contact ultrasound applicator were compared with those of the immersion applicator that is currently used clinically for the treatment of glaucoma. The applicator coupling cone uses a distensible rubber membrane that can be inflated to control stand-off distance relative to the surface of the eye. This feature allows the focal point of the therapeutic beam to be placed at selective depths. Histologic comparisons of lesions in rabbit and pig eyes showed lesions in the sclera and ciliary body that were similar to those produced by the immersion transducer when the same focal position was used. Moving the focal point to a greater depth resulted in less superficial damage, yet still produced ciliodestruction. Damage to the blood supply of the ciliary body, as found in human cadaver eyes, may be an additional mechanism of action of therapeutic ultrasound, and perhaps of other transscleral high-energy modalities.

Animals↗
PubMed1990

Correlations of acoustic tissue typing of malignant melanoma and histopathologic features as a predictor of death.

Forty-six eyes with uveal melanoma were scanned with a computerized diagnostic ultrasound system before enucleation, and light microscope sections were obtained. Tumors were characterized by ultrasonically measured dimensions and power spectrum analysis, which provided information not available in conventional A- or B-scan ultrasonography. Histopathologic features, including cell clustering pattern, cell type, pigmentation, vascularity, and necrosis, were quantified. Statistically significant correlations were found between parameters derived from the power spectrum and histologic characteristics. Patients were followed up for up to ten years with 14 deaths occurring because of metastases. Using a Cox relative risk model with histopathologic data, a risk model comprising pigmentation and cell type (P less than .0001) was obtained. Using ultrasonic characteristics, a model comprising tumor volume and scatterer concentration (P = .0062) was obtained. The results suggest that ultrasonic tissue characterization and three-dimensional biometry may provide improved in vivo prognostic indicators for uveal melanoma.

Eye Enucleation↗
PubMed1990

Production of corneal lesions using high-intensity focused ultrasound.

In order to study the potential use of ultrasound as a noninvasive system for altering corneal curvature, we used high-density focused ultrasound at a frequency of 4.8 MHz and 7.9 MHz to produce corneal lesions in the rabbit eye. Intensity and duration threshold exposure conditions were determined for the production of minimally visible lesions. Threshold lesions were initially apparent as discrete white opacities resulting from stromal edema and disruption. Light and scanning electron microscopy of higher-energy, suprathreshold lesions revealed more extensive disruption, including the formation of a superficial stromal depression and a larger zone of edema and disorganization surrounding each lesion. Posterior stromal lamellae, endothelium, and Descemet's membrane were intact. Healing and reepithelialization resulted in a smooth corneal surface with no residual opacification. Threshold determinations predict safe exposure levels to the cornea during insonification of other ocular structures. Selective heating of the peripheral cornea using focused ultrasound may be a useful technique for correcting astigmatism.

Animals↗
PubMed1988

A biologic tissue adhesive for vitreoretinal surgery.

Commercially available tissue glue was injected subretinally under mechanically induced retinal detachments in rabbit eyes resulting in chorioretinal adhesions at the injection site. After serial enucleation all eyes underwent histologic evaluation. Results were encouraging, but pooled fibrinogen is not acceptable for human use. A substitute for the pooled fibrinogen fraction, an adhesive using autologous plasma was prepared and studied after subretinal and intravitreal injection into rabbit and pig eyes. Postoperative clinical follow-up was one year for the rabbit eyes and one month for the pig eyes, after which all globes were enucleated. Histopathologic evaluation demonstrated circumscribed chorioretinal adhesions at the injection site. The autologous bioadhesive was applied as an adjunct in vitreoretinal surgery over macular holes and large retinal tears. As it is relatively short acting (ie, 4-6 days), it may be considered as a possible addition to existing techniques, facilitating difficult surgical procedures.

Adult↗
PubMed1979

Vitreous wick syndrome.

A 67-year-old man had vitreous wick syndrome after an uncomplicated intracapsular cataract extraction with a sector iridectomy in the left eye. The intraocular infection cleared with antibiotic therapy including intravitreal antibiotic injection, but a residual anterior cyclitic membrane and shallow anterior chamber persisted. An anterior vitrectomy was performed later in the course of treatment after the intraocular infection subsided, to relieve the shallow anterior chamber, prolonged hypotony, and ciliary body detachment. Final visual acuity was 6/15+(20/50+) in the left eye.

Aged↗
PubMed1979

In vivo choroidal thickness measurement.

We developed a system that permits exceptionally accurate measurements of human choroidal thickness in vivo by means of ultrasound. With minicomputer techniques, the complementary functions of the time and spectral domains of reflected sound can be used to permit measurements accurate to less than 20 mu at 10 MHz center frequency. Even more accuracy can be obtained with higher center frequencies. Choroidal thickness has been found to exceed that previously reported, with typical values of 420 mu found at the posterior pole. Even greater values are seen in regions outside the macula.

Cornea↗
PubMed1979

Ultrasonically guided needle biopsy and cytologic diagnosis of solid intraocular tumors.

Six solid intraocular tumors were reliably diagnosed by needle biopsies and cytologic examination of the aspirates. All of the tumors had an unusual clinical or diagnostic feature that raised the possibility of a non-melanomatous tumor. Two intraocular lesions that were obscured by opaque media or a retinal detachment were successfully biopsied under B-scan ultrasonographic guidance of the needle. Cytodiagnosis of narrow spindle B, plump spindle B, and eipthelioid cell types, as well as one case of Coats' disease, was possible and correlated closely with the predominant cell types comprising the lesions discovered on histopathologic examination of the globes that were enucleated. The ocular tissues were not significantly disturbed and hemorrhage was not a serious problem. Details of the biopsy and cytologic techniques, the major clinical indications, for the procedure, and the authors' belief that the procedure is not likely to produce local seeding or extraocular metastasis in cases of melanoma are presented and discussed. Considerable profit may attend the use of this technique for the diagnosis of possible metastatic lesions and tumors of the ciliary body. The technique, however, should not be routinely employed and should be restricted to extremely difficult diagnostic problems.

Adult↗
PubMed1979

Immersion ultrasonography: simultaneous A-scan and B-scan.

In eyes with opaque media, ophthalmic ultrasound provides a unique source of information that can dramatically affect the course of patient management. In addition, when an ocular abnormality can be visualized, ultrasonography provides information that supplements and complements other diagnostic testing. It provides documentation and differentiation of abnormal states, such as vitreous hemorrhage and intraocular tumor, as well as differentiation of orbital tumors from inflammatory causes of exophthalmos. Additional capabilities of ultrasound are biometric determinations for calculation of intraocular lens implant powers and drug-effectiveness studies. Maximal information is derived from ultrasonography when A-scan and B-scan techniques are employed simultaneously. Flexibility of electronics, variable-frequency transducers, and the use of several different manual scanning patterns aid in detection and interpretation of results. The immersion system of ultrasonography provides these features optimally.

Carcinoma↗
PubMed1979

A device for teaching the theory of technique.

The usefulness of comparing dream psychology and neurosis psychology is demonstrated in the teaching of a course on the theory of technique at the Pittsburgh Psychoanalytic Institute. Candidates are assigned the task of writing a five-minute segment of free associations using assigned background material, resistances to be demonstrated, and assigned current and past conflicts. The candidates then present their free associations to the class for analysis. Explication of educational and developmental issues is given.

Dreams↗
PubMed1978

A suction tip for controlled removal of nonmagnetic intraocular foreign bodies.

I used a soft-tip suction needle during a vitrectomy procedure to life glass foreign bodies away from the retina so they could be more easily and safely grasped with foreign-body extraction forceps. The use of the instrument reduces the chance of inadvertent scraping of glass fragments or instruments against the retina during the removal.

Eye Foreign Bodies↗