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Biomedical subjects

F S Foster

Publications and source records attributed to F S Foster.

At least 19 recordsLinked to original sources
PubMed1996

High frequency 40-MHz ultrasound. A possible noninvasive method for the assessment of the boundary of basal cell carcinomas.

BACKGROUND: Ultrasound imaging systems operating close to 20 MHz in frequency have been used to image skin tumors. Ultrasound imaging at 20 MHz has been used to determine the boundaries of basal cell carcinomas (BCCs). An inherent shortcoming of imaging systems operating at these frequencies is their limited resolution. OBJECTIVE: We investigated whether 40-MHz ultrasound imaging could provide higher resolution compared with the lower frequency systems and thus be a superior, noninvasive method of assessing the boundaries of BCCs. METHODS: Nine BCCs from six individuals were examined clinically and ultrasonographically, and then biopsied to confirm diagnosis. The depth of BCCs measured on histological sections was compared with the corresponding value obtained using ultrasound. For this study we required a nonsurgical, nondestructive means of treating BCCs that would allow repeated ultrasound imaging, and therefore topical 5-flurouracil (5-FU) was chosen. Following 5-FU therapy a biopsy was obtained from the site of the treated BCC after ultrasound imaging had been performed. Clinical, ultrasonic and histopathologic evaluation of each BCC was carried out independently by different individuals. At the end of the study all the BCC sites were treated surgically be electrodesiccation and curettage or completely excised. RESULTS: High resolution ultrasound images of BCCs were obtained with agreement between histology and ultrasound findings in all none lesions prior to therapy and in eight of none lesions posttherapy. There was a significant correlation between the depth of BCCs measured histologically and using ultrasound (P = 0.0004, r = 0.92). CONCLUSIONS: This study suggests that 40-MHz ultrasound may provide an estimate of the boundary of a BCC in vivo. High frequency 40-MHz ultrasound imaging may be an adjunct to clinical and histologic evaluation but does not replace the need to obtain tissue for microscopic examination.

Aged↗
PubMed1996

Accommodation and iridotomy in the pigment dispersion syndrome.

BACKGROUND AND OBJECTIVE: Iris concavity has been noted in pigment dispersion syndrome, and could have a role in producing iris-zonule contact. Iris concavity is most likely caused by a relative increase in anterior chamber pressure. The method by which this occurs remains speculative. The authors used ultrasound biomicroscopy to examine the role of accommodation in producing iris concavity and to document changes that occur following iridotomy. PATIENTS AND METHODS: Thirteen patients with clinically diagnosed pigmentary dispersion and pigmentary glaucoma underwent accommodation studies while being continuously imaged with ultrasound biomicroscopy. Anterior chamber depths were measured and iris configuration noted on distance and near fixation. These studies were repeated in 6 patients following laser iridotomy. RESULTS: All patients showed a decrease in anterior chamber depth with accommodation. Ten patients had a planar iris configuration on distance fixation and 3 concave. Eleven of 13 patients showed increased concavity of the iris on near fixation as compared with distance fixation. Following iridotomy in 6 patients, the iris showed a planar configuration that remained unchanged on near fixation. CONCLUSION: Accommodation increases iris concavity in some patients with pigment dispersion syndrome. The most likely explanation is an accommodation-induced relative increase in anterior chamber pressure secondary to anterior movement of the lens surface. Iridotomy prevents change in the iris profile with accommodation.

Accommodation, Ocular↗
PubMed1996

Diagnosis of traumatic cyclodialysis by ultrasound biomicroscopy.

BACKGROUND AND OBJECTIVE: To evaluate the ability of high-frequency ultrasound biomicroscopy to diagnose traumatic cyclodialyses not evident on clinical examination. PATIENTS AND METHODS: Six eyes to six patients with posttraumatic hypotony and/or shallow anterior chamber and suspected cyclodialysis clefts were examined with slit-lamp biomicroscopy, gonioscopy, B-scan ultrasonography, and ultrasound biomicroscopy. Ultrasound biomicroscopy provided high resolution of cross-sectional images of the anterior chamber angle, posterior chamber, and anterior uveal tissue. RESULTS: Ultrasound biomicroscopy confirmed the disinsertion of the ciliary body from the scleral spur and associated ciliary body detachment in all eyes. Gonioscopy failed to demonstrate a cyclodialysis cleft in five eyes because of hyphema (two eyes) and abnormal iris architecture (related to trauma) precluding visualization of the angle recess (three eyes). Using information from ultrasound biomicroscopy imagining, one patient underwent a ciliary body reattachment procedure and repair of the cyclodialysis cleft. CONCLUSION: Ultrasound biomicroscopy is a noninvasive method that can accurately diagnose the presence of traumatic cyclodialyses and can aid in surgical management. It is particularly useful in the presence of hazy media, hypotony, and/or abnormal anterior segment anatomy.

Adolescent↗
PubMed1995

Ultrasound backscatter microscope analysis of early mouse embryonic brain development.

The history of developmental and genetic analysis in the mouse has made it the model of choice for studying mammalian embryogenesis. Presently lacking is a simple technique for efficiently analyzing early mouse mutant phenotypes in utero. We demonstrate application of a real-time imaging method called ultrasound backscatter microscopy for visualizing mouse early embryonic neural tubes and hearts. This method was used to study live embryos in utero between 9.5 and 11.5 days of embryogenesis, with a spatial resolution close to 50 microns. Ultrasound backscatter microscope images of cultured embryos made it possible to visualize the heart chambers. This noninvasive imaging method was also used for analyzing a neural tube defect. The midhindbrain deletion associated with a null mutation of the Wnt-1 protooncogene was easily recognizable on ultrasound backscatter microscope images of 10.5- and 11.5-day embryos. Computer-generated volumetric renderings of the neural tube cavities were made from three-dimensional image data. This allowed a much clearer definition of the Wnt-1 mutant phenotype. These imaging techniques should be of considerable use in studying mouse development in utero.

Animals↗
PubMed1995

Imaging of immature articular cartilage using ultrasound backscatter microscopy at 50 MHz.

A high frequency sonographic technique-ultrasound backscatter microscopy-was used to visualize the subsurface structure of immature porcine articular cartilage from the knee joint. In 20-week-old pigs, all parts that were scanned, except the weight-bearing regions of the femoral condyles, demonstrated heterogeneous ultrasound backscatter characteristics within the articular cartilage. A trilaminar pattern consisting of hypoechoic, hyperechoic, and anechoic layers ranging from superficial to deep generally was observed, except in the weight-bearing regions of the femoral condyles, where a homogeneous anechoic pattern was seen. In the younger pigs (6 and 10 weeks old), the trilaminar backscatter pattern was not observed. Small, highly echogenic structures that correlated with vascular channels in histologic assessment were observed frequently in the cartilage of younger pigs, but they were seldom present in the cartilage of 20-week-old pigs. Structural details, such as disruption of the subchondral bone and presence of a thickened fibrous layer on the articular surface at the chondrosynovial junction, also were detected with the ultrasound backscatter microscope. We concluded that high frequency ultrasound can be used to visualize the subsurface structure of immature articular cartilage and some of its developmental changes. Further research is required to explain the mechanism underlying the observed backscatter characteristics of immature articular cartilage and to study its potential for the imaging of pathologic changes.

Animals↗
PubMed1995

A 40-100 MHz B-scan ultrasound backscatter microscope for skin imaging.

There is a growing interest in high resolution, subsurface imaging of cutaneous tissues using higher frequency ultrasound, and several commercial systems have been developed recently which operate at 20 MHz. Some of the possible applications of higher frequency skin imaging include tumour staging, boundary definition, and studies of the response of tumours to therapy, investigations of inflammatory skin conditions such as psoriasis and eczema, and basic studies of skin aging, sun damage and the effects of irritants. Investigation of these areas is quite new, and the role of ultrasound skin imaging is continuing to evolve. Lateral resolution in the 20 MHz imaging systems ranges from 200 to 300 microns, which limits imaging applications to cutaneous structures which are relatively large in size. In this paper, a real-time ultrasound backscatter microscope (UBM) for skin imaging is described which operates in the 40-100 MHz range, providing axial resolution between 17 and 30 microns and lateral resolution between 33 and 94 microns. This improvement in resolution over current skin ultrasound systems should prove useful in determining the margins of small skin lesions, and in obtaining more precise, in vivo skin thickness measurements to characterize nonmalignant skin disease. Example images of normal skin, seborrhoeic keratosis and malignant melanoma illustrate the imaging potential of this system.

Analog-Digital Conversion↗
PubMed1995

Ultrasound biomicroscopic imaging of the effects of YAG laser cycloablation in postmortem eyes and living patients.

PURPOSE: The authors performed a series of experiments designed to determine if early effects of YAG laser cycloablation could be detected by ultrasound biomicroscopy in postmortem eyes and living patients. They also designed an apparatus that allowed simultaneous ultrasound biomicroscopic imaging of YAG laser cycloablation. METHODS: Treated and untreated regions of postmortem eyes treated with YAG cycloablation were imaged and compared. Treatment was placed at varying distances from the limbus in postmortem eyes and the resulting effects imaged. Histologic examinations were performed after imaging. Six living patients had ultrasound biomicroscopy before and after YAG cycloablation. An apparatus combining contact YAG laser and ultrasound biomicroscopy was used in postmortem eyes. RESULTS: Early treatment effects imaged included ciliary epithelial disruption, ciliary epithelial separation, and bubble formation. Ultrasound biomicroscopic findings varied with the distance of treatment from the limbus and were maximal below the treatment site. Results of histologic examination showed close correlation to the ultrasound biomicroscopic images. Similar findings to those found in postmortem eyes were found in living patients after treatment. The apparatus combining contact YAG and ultrasound biomicroscopy allowed realtime imaging of effects of YAG laser cycloablation. CONCLUSIONS: The ability of ultrasound biomicroscopy to detect changes associated with cyclodestructive procedures potentially could provide us with a method of improving treatment precision and correlating treatment effect with clinical response.

Cadaver↗
PubMed1995

The effect of refraction and assumed speeds of sound in tissue and blood on Doppler ultrasound blood velocity measurements.

The combined effect of three assumptions relating to refraction, the speed of sound in tissue and the speed of sound in blood on the accuracy of Doppler ultrasound blood velocity measurements has been investigated. A theoretical relationship giving the net velocity measurement error introduced by these three assumptions has derived using a model in which tissue and blood layers are separated by straight, parallel boundaries. This net error is dependent on the assumed and actual speed of sound in tissue, the assumed speed of sound in blood and the Doppler angle, but is effectively independent of the actual speed of sound in blood. For clinical blood velocity measurements, the net error is estimated to be as much as an 8% overestimation of the actual velocity, higher than previously predicted for any of the factors individually. The relationship also predicts a net velocity measurement error in experimental flow systems and string phantoms which is dependent on the speed of sound in the liquid bath. A water bath at room temperature will give an overestimation of approximately 2%. Experimental investigations using conventional and modified string phantoms and a 5-MHz linear phased array system support these conclusions. The effect of perturbing the layers from their parallel orientation has also been considered theoretically and has provided additional support for the above conclusions. These results may help more accurate Doppler velocity measurements in both experimental and clinical settings.

Blood↗
PubMed1995

Does high-frequency (40-60 MHz) ultrasound imaging play a role in the clinical management of cutaneous melanoma?

The assessment of cutaneous melanoma in the clinical setting is often difficult, and important features such as depth and width remain unknown until the pathology report is received. Access to prognostic features such as vertical height before excisional biopsy would offer a basis for guidance in defining surgical margins and early planning of treatment options. Recently developed high-frequency ultrasound imaging in the 40-to 60-MHz range is a noninvasive method that provides in vivo information about cutaneous lesions. Imaging at these frequencies provides high-resolution data within the range of the epidermis and dermis (3-4 mm in depth). Ten cutaneous melanomas and seven pigmented lesions were assessed in this fashion. Vertical height was documented and compared to histopathological findings. High-frequency ultrasound imaging determination of vertical height correlated well with the standard measurement of Breslow's thickness on histological sections only in midrange (1.0-3.0 mm) lesions. Inflammatory cells at the base of three melanomas provoked an overestimation of the depth measurement with ultrasonography. Thick keratin layers such as those found on the feet acted as a virtual block to the high-frequency scanner. The application of this new advance in noninvasive imaging technology to the clinical assessment of cutaneous melanoma provides interesting in vivo data but in its present state does not replace the need for the biopsy of pigmented lesions and histopathological diagnosis.

Humans↗
PubMed1994

Malignant glaucoma. Clinical and ultrasound biomicroscopic features.

PURPOSE: To determine conditions associated with malignant glaucoma and to assess anterior segment structures in malignant glaucoma using ultrasound biomicroscopy. METHODS: Over a 3-year period, 14 eyes from 14 patients with malignant glaucoma were evaluated. RESULTS: Of the 14 eyes, 7 received medical therapy alone and 7 required both medical and surgical intervention. Predisposing factors included trabeculectomy in 12 eyes, chronic angle-closure glaucoma in 10, sudden ocular decompression in 2 (1 from suture lysis and 1 from corneal perforation), pseudoexfoliation in 4, and cessation of aqueous suppressants and cycloplegics in 2. Ultrasound biomicroscopy of two eyes showed a shallow supraciliary fluid level, anterior rotation of ciliary processes, and obstruction of the trabeculectomy osteum. CONCLUSIONS: Malignant glaucoma is associated with glaucoma surgery, chronic angle-closure glaucoma, pseudoexfoliation, sudden ocular decompression, and cessation of aqueous suppressants. On ultrasound biomicroscopy, a low supraciliary fluid level was found in two patients.

Aged↗
PubMed1994

Ultrasound biomicroscopic analysis of haptic position in late-onset, recurrent hyphema after posterior chamber lens implantation.

Late-onset, recurrent hyphema is an uncommon complication of posterior chamber intraocular lens implantation. Pathological studies and indirect clinical evidence, including iris transillumination defects and iris tucking, have implicated haptic-iris contact. The technique of high-resolution ultrasound biomicroscopy developed in our laboratories allows imaging of intraocular lens haptics and their relationship to surrounding structures. Examination of two cases with late-onset, recurrent hyphema revealed that the margins of the superior haptics were sulcus fixated and indenting the peripheral iris. Blood could be traced beneath the peripheral iris in one case. Our findings indicate that haptic-iris contact was the source of bleeding. Capsular fixation should make this complication less likely.

Aged↗
PubMed1994

Ultrasound biomicroscopic assessment of the cornea following excimer laser photokeratectomy.

Excimer laser photokeratectomy is used as a refractive tool and in the treatment of superficial corneal disease. Ultrasound biomicroscopy is a new method of ultrasound imaging developed in our laboratories that allows subsurface imaging of ocular structures at microscopic resolution. We used this imaging method to examine 12 patients following excimer laser keratoablation. Following treatment, the normal appearance of a highly reflective Bowman's membrane below the epithelial echo was absent in the treatment zone. Corneal thinning was also noted. Postoperative scarring in the treatment area could be imaged as highly reflective regions in the superficial stroma. In therapeutic cases, corneal opacities could be imaged pretreatment and their depth assessed. The degree of opacity removal could be analyzed post-treatment. Ultrasound biomicroscopy helped assess corneal changes secondary to excimer laser photokeratectomy.

Cornea↗
PubMed1994

Ultrasound biomicroscopic features of pigmentary glaucoma.

We have developed a device capable of producing subsurface images in eyes at microscopic resolution. We call this method "ultrasound biomicroscopy." We examined 19 patients with pigmentary glaucoma or pigmentary dispersion syndrome using ultrasound biomicroscopy. Ten patients were found to have concave irides with small distances between the back of the iris and the zonule. In these patients iris-lens contact was greater than in patients without iris concavity and healthy patients. Nine patients did not show iris concavity or increased iris-lens contact. The finding of iris concavity and increased iris-lens contact is compatible with a theory of reverse pupil block producing intermittent iris-zonule touch, with a valve effect preventing posterior flow of aqueous. This theory was supported by the loss of concavity following iridotomy in three patients. The force that produces a reversal of the normal pressure gradient remains unclear, but recent evidence suggests that accommodation plays a major role. The patients who did not show iris concavity and increased iris-lens contact may have been examined at a time when these forces were not acting or had ceased to act.

Adult↗
PubMed1993

Ultrasound biomicroscopy in the assessment of anterior scleral disease.

High-frequency ultrasound biomicroscopy is a new method of examining subsurface anterior segment structures of the eye at microscopic resolution. The sclera has a high internal reflectivity and can be differentiated from the cornea, and overlying and underlying tissue. Using this modality, we examined 18 patients with various manifestations of scleral disease. Localized anterior staphyloma could be differentiated from other causes of a black spot on the scleral surface. Episcleral thickening could be differentiated from involvement of the sclera itself. Different patterns of scleral involvement could be imaged including diffuse low-reflective mottling, low-reflective nodules extending into the scleral substance, and scleral thinning. Scleral thinning could be assessed and quantified. Underlying changes in the vitreous could be detected. Ultrasound biomicroscopy was a useful adjunct to clinical examination in the assessment of anterior scleral disease.

Adult↗
PubMed1993

An ultrasound biomicroscopic analysis of angle-closure glaucoma secondary to ciliochoroidal effusion in IgA nephropathy.

Immunoglobulin A nephropathy is a common glomerulonephritis of unknown cause. Episcleritis, scleritis, anterior uveitis, and keratoconjunctivitis sicca have been associated with this disease. We diagnosed angle-closure glaucoma secondary to ciliochoroidal effusion in a patient with IgA nephropathy confirmed by biopsy. High-frequency ultrasound biomicroscopy was used to determine internal relationships of angle structures and to follow changes with treatment. Supraciliary effusion undetected by B-scan ultrasound and retinal examination was easily imaged by ultrasound biomicroscopy. Glaucoma mechanisms included forward rotation of the ciliary processes, which caused direct angle closure in a manner similar to plateau iris. Ultrasound biomicroscopy showed that cycloplegia improved this mechanism by retracting the ciliary processes, but angle closure secondary to forward iris bowing from pupil block remained. Iridectomy was performed and immediately opened the angle. Ultrasound biomicroscopy proved a useful method of defining mechanisms and a helpful guide to treatment in this type of glaucoma.

Anterior Eye Segment↗
PubMed1993

In vitro evaluation of gallstone dissolution with methyl-tert-butyl ether and ultrasound energy.

Given the large number of cholecystectomies performed annually, a nonsurgical approach to gallstone therapy is of great interest. A laboratory ultrasound system has been developed to study enhancement of methyl-tert-butyl ether (MTBE) dissolution of human gallstones in vitro. A mathematical model that quantitatively characterizes the dissolution process via a rate constant has been developed. Using this model, the kinetics of 15 gallstones from a single patient were evaluated for three dissolution methods: 1) unstirred MTBE, 2) aspirated MTBE, and 3) ultrasonically enhanced MTBE. The results showed excellent fits between the model and measured dissolution rates. 195 kHz continuous-wave (CW) ultrasonically enhanced dissolution rates exhibited a 6.2 fold gain over the manually aspirated MTBE and a 49.5 fold gain over static MTBE dissolution. Investigation of 50% duty cycle pulsed mode ultrasound revealed that total power appears to be the determinant of the observed dissolution rates. Gallstone calcification showed a strong correlation with dissolution rates measured by the model.

Cholelithiasis↗