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Biomedical subjects

D J Coleman

Publications and source records attributed to D J Coleman.

At least 37 records · Page 2Linked to original sources
PubMed1998

Three-dimensional ultrasound imaging. Clinical applications.

OBJECTIVE: The aim of this report is to describe the technology of three-dimensional (3-D) ultrasonic imaging and its impact on improved diagnosis and monitoring of ocular disease. DESIGN: The authors reviewed techniques for acquiring and displaying 3-D ultrasound data of the eye. PARTICIPANTS: The authors applied these techniques to representative individual cases, including a choroidal hemorrhage, a ciliary body melanoma, a ciliary body detachment, a displaced posterior chamber intraocular lens, and topographic analysis of a normal cornea. INTERVENTION: A computer-controlled motion system was used to perform very high-frequency (VHF) (50-MHz) and conventional (10-MHz) digital 3-D ultrasound data collection. The scanning system allowed digitization of ultrasound data from a series of parallel planes. The 3-D data could be manipulated interactively to obtain two-dimensional images in any plane through the scan volume. The 3-D images were constructed by volume rendering and could be positioned for viewing from a variety of perspectives. The 3-D ultrasound parameter images representing acoustic scatterer properties were generated by spectrum analysis of digitized echo data. Color maps representing the contour and thickness of the epithelium and stroma of the central corneal were generated by digital signal processing of 3-D echo data. RESULTS: Quantitative volume measurement and biometric techniques enhanced the diagnostic and treatment planning information content in 3-D ultrasound images. The location and extent of hemorrhage and clots within the suprachoroidal space were shown with solid modeling. Volume changes in ciliary body melanoma over time were documented and 3-D ultrasound parameter image changes associated with radiation therapy observed. In ciliary body detachment, the extent of the detachment was shown. Solid modeling of a posterior chamber intraocular lens showed misplacement of the haptic in relation to the lens capsule remnants. Keratopachymetric maps showed the range and variance of thickness and local radius of curvature measurements in the cornea. CONCLUSIONS: Quantitative volume measurement and biometric tools combined with segmentation of 3-D ultrasound images improve diagnostic and treatment planning informational content of 3-D ultrasound images through improved localization of tissue structures.

Choroid Hemorrhage↗
PubMed1998

Correlation of high-frequency ultrasound backscatter with tumor microstructure in iris melanoma.

OBJECTIVE: This study aimed to correlate histologic characteristics with high-frequency ultrasound backscatter spectra in malignant melanomas of the iris. DESIGN: The study design was a cohort (case series) study of patients diagnosed with iris melanoma in the authors' clinic. PARTICIPANTS: Sixteen patients with iris melanoma participated. INTERVENTION: The patients were scanned with a 50-MHz ultrasound unit equipped for digitization of raw echo data. Spectral parameter images representing the spatial distribution of size and concentration of tissue inhomogeneities were produced. MAIN OUTCOME MEASURES: The variation of spectral properties within and between tumors was determined. In the two tumors in this series for which histologic material was available, the authors compared scatterer concentration and size with histology and mathematically modeled the effect of melanocyte distribution on spectra. RESULTS: Ultrasound scattering characteristics differed considerably among tumors. Where histology was available, acoustic parameters correlated with the size and number of melanocytes present. CONCLUSIONS: Iris melanomas exhibited a wide range in acoustic backscatter properties. Whereas characteristics such as vascularity and necrosis might contribute to this, in the two cases examined here, backscatter characteristics could be largely accounted for by melanocyte distribution. A better understanding of the relationship of histology to noninvasive ultrasound data will enhance the diagnostic utility of this technique.

Adult↗
PubMed1998

Imaging and spectrum analysis of contrast agents in the in vivo rabbit eye using very-high-frequency ultrasound.

We have conducted initial studies that demonstrated the feasibility of employing ultrasonic contrast agents with very-high-frequency ultrasound (VHFU), using wideband transducers with center frequencies near 40 MHz. These studies were undertaken with an ultimate objective of quantifying perfusion in vessels in the eye and other organs. We expanded the model developed by Lizzi et al. (1983) to incorporate the scattering characteristics from encapsulated bubbles, such as contrast agents. Our analysis shows how the spectral slopes and intercepts measured from contrast agents are related to factors that include the radii and concentration of contrast-agent particles. We conducted in vitro experiments to validate the theoretical predictions and obtained excellent agreement. We obtained in vivo VHFU data from the eyes of anesthetized rabbits before and after injection of Albunex and Aerosomes. Digitally computed B-mode images demonstrated echo enhancement within the ciliary body and its processes. The magnitudes of these enhancements were quantified using calibrated spectrum-analysis techniques.

Albumins↗
PubMed1998

Ultrasonic evaluation of the vitreous and retina.

Ultrasonic evaluation of the vitreous body augments and complements visual and clinical assessment in any condition in which some form of media opacity exists, eg, cornea, lens, hemorrhage, or subretinal mass. The appearance of the eye in hypotony, the presence of foreign material, the pattern of hemorrhage, and the presence of a detached retina or choroid are all identifiable and their diagnosis may be of critical importance to patient management. Patterns of diabetic retinopathy and ocular tumors are usually characteristic using conventional 10 MHz ultrasound. The use of Very High Frequency (VHF or UBM) ultrasound can identify ciliary body detachment or other retroiridal pathology, such as tumors and cysts.

Eye Diseases↗
PubMed1997

Textured or smooth implants for breast augmentation? Three year follow-up of a prospective randomised controlled trial.

Silicone breast implant surface texturing has been shown to reduce the short-term incidence of adverse (Baker III/IV) capsular contracture in augmentation mammaplasty in double-blind randomised controlled trials. It is, however, undetermined whether the textured surface merely delays the onset of severe contracture or its effect on capsular contraction is persistent. The current study reviewed, after three years, 49 of the 53 patients who had undergone subglandular breast augmentation mammaplasty in a randomised double-blind study with textured or smooth silicone gel-filled implants in 1989. The incidence of adverse capsular contracture was 59% for smooth implants and 11% for textured ones (P = 0.001; chi 2 = 10.60). Eight patients (31%) with smooth prostheses underwent breast implant exchange for severe capsular contracture between the one and three year assessments, compared with a revisional surgery rate of only 7.4% (2/27 patients) for the textured group (P < 0.04). These adverse capsular contracture and revisional breast implant surgery rates clearly demonstrate that the effect of textured implants in reducing capsular contracture in augmentation mammaplasty found at one year is maintained at three years, and suggest that it may be long lasting.

Breast Implants↗
PubMed1997

Correlation of ultrasound parameter imaging with microcirculatory patterns in uveal melanomas.

Previous studies demonstrated a correlation between acoustic backscatter parameters and survival in ocular melanoma. The histologic presence of microvascular networks in ocular melanoma is also associated with death from metastases. This study tests the hypothesis that melanomas grouped on the basis of these microvascular patterns are separable by ultrasound spectrum analysis. We scanned 40 melanomas using a 10-MHz ultrasound unit equipped for digitization of radio frequency data. After enucleation, tumors were sectioned in planes corresponding to the ultrasonographic examination and stained to demonstrate microcirculation. Acoustic spectral parameters were compared between 14 melanomas with a nevuslike microcirculation and 26 with foci of high-risk microvascular structures. Smaller scatterer size, lower acoustic concentration and greater spatial variability were found to correlate with high-risk microvascular patterns and areas of cystic degeneration. We suggest that nonvascular extracellular matrix components associated with microvessels may be responsible for the correlation of acoustic parameters with microvascular pattern and distribution.

Choroid Neoplasms↗
PubMed1997

Ultrasonically induced hyperthermia for adjunctive treatment of intraocular malignant melanoma.

PURPOSE: This report describes results of a prospective pilot trial to evaluate the safety and efficacy of hyperthermia as an adjunct to enucleation or brachytherapy in the treatment of patients with intraocular malignant melanoma. METHODS: Twenty-five patients with intraocular malignant melanomas were treated with ultrasonically induced hyperthermia. In 14 patients, hyperthermia was administered before enucleation (median follow-up period, 44 months), and in 11 patients, hyperthermia was used as an adjunct to brachytherapy (median follow-up period, 79 months). RESULTS: Patient survival in each group was compared with that of a control group treated with enucleation or brachytherapy alone, using Kaplan-Meier and Cox analysis. Taking into account the simultaneous effects of tumor size and location, the relative risk ratios and 95% confidence bounds associated with adjunctive hyperthermia were 1.68 (range, 0.60-4.72) and 0.68 (range, 0.16-2.89) for the enucleation and brachytherapy groups, respectively. CONCLUSIONS: Patients receiving adjunctive hyperthermia with brachytherapy showed increased survival, whereas those receiving hyperthermia before enucleation showed decreased survival. Neither trend was statistically significant in this small series. The synergism of hyperthermia with radiation may offer the possibility of improved tumor management.

Brachytherapy↗
PubMed1997

Ophthalmic, ultrasonographic findings in primary central nervous system lymphoma with ocular involvement.

PURPOSE: To describe and classify ophthalmic, ultrasonographic findings in patients with primary central nervous system lymphoma with ocular involvement. METHODS: B- and A-scan ultrasonography was performed on the eyes of 13 patients with primary central nervous system lymphoma with ocular involvement. RESULTS: In seven patients, the eyes were the site of initial involvement. In the other six patients, both ocular and central nervous system disease were present at the initial evaluation. All patients had abnormal ultrasonographic findings. The most common were vitreous debris (n = 10), choroidal-scleral thickening (n = 6), and widening of the optic nerve (n = 4). Elevated chorioretinal lesions (n = 3) and retinal detachment (n = 2) were also found. CONCLUSION: Ophthalmic ultrasonography is a useful adjunctive diagnostic technique for characterizing ocular involvement in lymphoma. Ocular lymphoma may present as chorioretinitis, vitreitis and nonspecific uveitis; it produces characteristic, but nonspecific findings on ultrasonography. The diagnosis of ocular involvement is an important factor in determining treatment.

Adolescent↗
PubMed1997

Improved system for sonographic imaging and biometry of the cornea.

We developed a programmable motion system for high-frequency (50 MHz) ultrasonographic imaging of the cornea. The system permits a variety of scanning modes, including arc scans matched to the approximate radius of curvature of the cornea. This approach allows high-precision biometry (+ or - 2 microm) over a much larger region of the cornea than the 3 mm central zone obtainable with conventional rectilinear scanning. Using 60 degree wide meridional arc scans covering each clock-hour of a rabbit cornea, we obtained data over an 8 mm wide central zone and produced maps representing the thickness of the corneal epithelium.

Animals↗
PubMed1996

Iridoschisis: high frequency ultrasound imaging. Evidence for a genetic defect?

AIMS: To elucidate changes in the anatomy of the anterior chamber associated with iridoschisis, a rare form of iris atrophy, and their potential contribution to angle closure glaucoma. METHODS: Both eyes of a 71-year-old woman with bilateral iridoschisis and fibrous dysplasia and her asymptomatic 50-year-old daughter were scanned with a very high frequency (50 MHz) ultrasound system. RESULTS: The symptomatic patient exhibited diffuse changes in the iris stoma with an intact posterior iris pigmented layer in both eyes. These changes were clinically compatible with the lack of iris transillumination defects. Additionally, iris bowing with a resultant narrowing of the angle occurred. The asymptomatic daughter showed discrete, but less severe iris stromal changes. CONCLUSION: This is the first detailed study of high frequency ultrasonic imaging of the iris in iridoschisis. The observed structural changes suggest angle narrowing by forward bowing of the anterior iris stroma may be a mechanism of IOP elevation in this condition. The ultrasonic detection of iris changes in the asymptomatic daughter of the symptomatic patient and the association of iridoschisis with fibrous dysplasia suggest a possible genetic component in the pathogenesis of this condition.

Aged↗
PubMed1995

Three-dimensional high-frequency ultrasonic parameter imaging of anterior segment pathology.

PURPOSE: High-frequency ultrasound allows high-resolution imaging of anterior segment anatomy and pathology. Acoustic echo data, however, contain information relating to the microanatomic structure of the interrogated tissue which is not evident in B-mode images. The aim of this study is to develop imaging techniques to demonstrate and quantify the distribution of acoustic scattering properties in ocular tissues in three dimensions. METHODS: A tumor of the iris and a hyphema were scanned using a 50-MHz ultrasound probe mounted on a computer-controlled two-axis positioning system. Scan data from sequential parallel planes were used to make three-dimensional reconstructions. Digital signal processing and a mathematical model of acoustic backscatter then were used to represent the effective size and acoustic concentration of scattering elements using a false color representation superimposed on B-mode images. RESULTS: Three-dimensional reconstructions improved appreciation of the size and extent of pathology and allowed computation of tissue volumes. Parameter images demonstrated distinctive differences between diffuse and organized blood and allowed quantification of tumor scattering properties. CONCLUSIONS: Three-dimensional imaging of the anterior segment with high-frequency ultrasound allows construction of perspective images, which adds to the already significant clinical use of individual high-resolution B-mode images. Acoustic backscatter properties determined by tissue microstructure can be computed from echo data and represented in false color in three-dimensional reconstructions.

Anterior Eye Segment↗
PubMed1995

High frequency ultrasound evaluation of radial keratotomy incisions.

Radial keratotomy is a surgical procedure to correct myopia that involves placing corneal incisions of precise partial thickness to induce flattening. It has yielded positive but sometimes unpredictable results. Many surgical variables influence the final result. Among them, incision depth is probably the most difficult to control and evaluate. In this study, we used very high frequency (50 MHz) ultrasound (HFU) to image radial keratotomy incisions in post-radial keratotomy human corneas to obtain high definition images of the cornea. The images allowed us to measure the depth of incisions as a percentage of corneal thickness.

Adult↗
PubMed1995

The effect of transducer bandwidth on ultrasonic image characteristics.

PURPOSE: This study was conducted to determine the effect of transducer bandwidth on the characteristics of ophthalmic ultrasound images. METHODS: B-scan images produced using two transducers, one with a narrow bandwidth and the other with a broad bandwidth, both having nominal center frequencies of 10 MHz, were evaluated. Comparative scans were made of a tissue-mimicking phantom, an intraocular tumor, and a vitreous hemorrhage. RESULTS: Results showed that broadband transducers gave improved resolution and finer speckle texture, but had lower sensitivity. Broadband transducers were most suitable for situations in which resolution was more important than sensitivity, such as imaging of tumors. The greater sensitivity of the narrowband probe made it most useful for evaluation of vitreous complications, such as hemorrhage and membranes. CONCLUSION: In addition to transducer frequency, bandwidth should be taken into account when choosing a transducer for a specific ophthalmic imaging application. Both broad- and narrowband transducers have relative advantages in particular applications.

Ciliary Body↗
PubMed1995

Evaluation of ciliary body detachment in hypotony.

PURPOSE: This article describes an anatomic classification for the hypotonous eye and links this classification with approaches to the surgical treatment of this condition. The classification is based on very-high-resolution ultrasound scans and three-dimensional reconstruction of planar ultrasound scans. METHODS: Standard 10-MHz B-scans and very-high-resolution (40-60 MHz) scans were performed with a planar motor system using the immersion method. The anatomic changes in the hypotonous eye were classified and correlated with clinical and ultrasonographic findings at the time of therapeutic intervention and after resolution of the hypotonous condition. RESULTS: Hypotony is defined as low intraocular pressure most commonly due to ciliary body detachment or ciliary body dysfunction. With ciliary body detachment, three anatomically related causative types were identified: tractional hypotony, which has ultrasonographically demonstrable proliferative vitreociliopathy with membrane attachments between the ciliary body, iris, and formed vitreous; dehiscence hypotony, which has a modification in the scleral acoustic architecture consistent with a scleral break or wound dehiscence; and primary type hypotony, which has ciliary body detachment but no ultrasonographically demonstrable tractional component or scleral anatomic modification, but may have an iris scleral separation. CONCLUSIONS: Each type of ciliary body detachment hypotony may have a different management approach, so high-resolution ultrasound, particularly when shown with sequencing or three-dimensional displays to demonstrate the extent of detachment, can aid in the selection and implementation of appropriate therapy.

Ciliary Body↗
PubMed1995

An evaluation of immunomagnetic separation for the detection of salmonellas in raw chicken carcasses.

Immunomagnetic separation techniques were used in the isolation of salmonella from raw chicken carcasses. Improved isolation rates were achieved with increased specificity and decreased processing time, although several technical difficulties remain to be addressed. Immunomagnetic separation offers significant potential for improvement on existing microbiological systems for the isolation of salmonella.

Animals↗
PubMed1995

A comparison of immunomagnetic separation plus enrichment with conventional Salmonella culture in the examination of raw sausages.

Immunomagnetic separation with additional enrichment was used in conjunction with improved selective media to improve the isolation of salmonellae from raw sausages. The isolation rate achieved was almost double that of conventional culture with no increase in processing time. The selective media gave an overall specificity of approximately 74%; all false-positive pickoffs being identified as Citrobacter freundii. It is believed that this method represents a significant advance in the isolation of salmonellae from foods, although the ideal media both for enrichment and selection have yet to be found.

Bacteriological Techniques↗