Ultrasound biomicroscopy of anterior segment structures in normal and glaucomatous eyes.

We developed a new method of imaging the anterior segment of the eye using high-frequency ultrasound that allows structural details of the angle, iris, ciliary body, zonule, and posterior chamber to be visualized and measured at microscopic resolution in living patients. We applied the term ultrasound biomicroscopy to this technique, which we used to image anterior segment structures in a series of nine normal subjects. We provide a system of definition for anterior segment measurements that will allow reproducible measurements to be performed in the future.

Fabrication and characterization of transducer elements in two-dimensional arrays for medical ultrasound imaging.

Some of the problems of developing a two-dimensional (2-D) transducer array for medical imaging are examined. The fabrication of a 2-D array material consisting of lead zirconate titanate (PZT) elements separated by epoxy is discussed. Ultrasound pulses and transmitted radiation patterns from individual elements in the arrays are measured.

Ultrasound biomicroscopy in glaucoma.

Ultrasound Biomicroscopy is a newly developed high resolution imaging method that uses high frequency ultrasound (50-100 MHz). Tissue penetration is about 4 mm. This method allows detailed observation of anterior and posterior chamber anatomy in the living eye, and is thus a useful tool in both clinical assessment of glaucoma, and research into causes of various glaucoma types.

Destination dilemmas. Government ups the ante.

Never a simple matter, determining where to transport a patient has become increasingly difficult for EMS providers. Not only must traditional factors such as vehicle and facility availability be considered, but the increasing involvement of state and federal governments and national organizations has further clouded the decision-making process.

Clinical use of ultrasound biomicroscopy.

The authors have developed a method of obtaining images of cross-sections of the intact anterior globe at microscopic resolution. High-frequency ultrasound transducers (50-100 MHz) have been developed and incorporated into a clinical B-scan device capable of producing images in the living human eye to a depth of approximately 4 mm at an axial and lateral resolution approaching 20 microns. Clinical use of this instrument is no more difficult than conventional immersion ultrasonography.

The management of cystic fibrosis.

Cystic fibrosis is a chronic, life-threatening inherited disease which poses severe physical, psychological and social problems for the sufferer and his or her family. Frances Duncan-Skingle and Fiona Foster present an overview of recent developments in the clinical management of this distressing condition.

Characterization of lead zirconate titanate ceramics for use in miniature high-frequency (20-80 MHz) transducers.

The material properties of lead zirconate titanate (PZT) ceramics for operation in the thickness mode at frequencies as high as 80 MHz are reported. Each of the ceramics tested showed a reduction in k (t) with increasing frequency. In a fine-grained PZT, values of k(t) as high as 0.

Beam steering with pulsed two-dimensional transducer arrays.

The major problem facing the development of 2-D arrays for imaging is the complexity arising from the large number of elements anticipated in such transducers. The authors have undertaken a theoretical investigation of the focusing and steering properties of pulsed 2-D arrays to characterize the parameters required for medical imaging, such as element size, spacing, and number of elements. Details of the computational methods employed are presented, as well as a discussion of the steered beam properties of wideband 2-D arrays.

The design of protection circuitry for high-frequency ultrasound imaging systems.

Transmission line lengths in the protection circuitry of a high-frequency (>20-MHz) ultrasound imaging system have an important effect on the frequency, amplitude, and bandwidth of the pulse-echo response of the system. A model that includes the transmission line lengths between the pulser, transducer, and receiver and the electromechanical properties of high-frequency transducers is used to illustrate the importance of correctly choosing these line lengths. An iterative optimization procedure for designing the protection circuitry for a broadband system is proposed.

Measurement of the ultrasonic properties of vascular tissues and blood from 35-65 MHz.

A 50 MHz ultrasound backscatter microscope has been built to measure the acoustic properties of vascular tissues and blood over the frequency range from 35-65 MHz. High resolution (45 microns) ultrasound backscatter microscope images of nine femoral and eight common carotid human artery samples were made and compared with corresponding histological sections. Individual tissue layers were selected using these images for quantitative measurement of the frequency dependent backscatter.

Clinical applications of osseointegrated implants.

In the described seven case reports, the authors have demonstrated a number of varied applications of osseointegrated implant techniques including both removable and fixed prostheses. All patients had expressed dissatisfaction with previous prosthetic efforts to restore a satisfactory level of mastication or a desire to do away with removable oral prostheses. A high level of patient satisfaction was achieved through the application of implant techniques in these patients.

Subsurface ultrasound microscopic imaging of the intact eye.

The authors have developed a method of obtaining images of cross sections of the intact eye at microscopic resolution. High-frequency ultrasound transducers (100 MHz) have been developed and incorporated into imaging devices. These devices are capable of producing images to a depth of 4 mm at an axial and lateral resolution approaching 20 microns.

Clinical performance of a cone/annular array ultrasound breast scanner.

Ultrasound is a useful adjunctive imaging modality to x-ray mammography for the detection and management of breast disease. A high resolution (0.3 mm at -6 dB) transducer consisting of co-axially aligned cone and annular array transducers has been incorporated into a prototype breast imaging system.

Long term venous access using a totally implantable drug delivery system in patients with cystic fibrosis and bronchiectasis.

A completely implantable, subcutaneous, venous access system (Port-a-Cath) has been used for antibiotic therapy in 26 patients with cystic fibrosis or bronchiectasis over a period of 45 months. During this period there were ten complications in eight patients and in four patients all or part of the system had to be replaced. Nevertheless, the actuarial median functional survival of the implanted system exceeded 30 months.

Effect of diet on growth of M. leprae in mouse footpads.

Semipurified diets, with equal amounts of vitamins, minerals and fibre, but varied in protein and fat content from pork, barbel fish or soya beans were tested for their possible effect on the growth of M. leprae in mouse footpads. 105 BALB/c male weanling mice were randomly divided into five diet groups of 21 mice each and fed for six months.

The design and fabrication of high frequency poly(vinylidene fluoride) transducers.

Poly(vinylidene fluoride) (PVDF) transducers are well suited for use in high frequency pulse-echo ultrasound systems because of their high bandwidth. We analyze the design parameters of PVDF transducers operating in the 100 MHz range using the KLM transducer model. The effect of backing layers, electrode configuration, transducer surface area and tuning circuits on the insertion loss and pulse-echo response of the transducers are investigated.

A 100 MHz B-scan ultrasound backscatter microscope.

The construction and operation of a 100 MHz B-mode ultrasound backscatter microscope are described. The powerful B-mode technique is extended into the domain of microscopy allowing the imaging of internal structure in living specimens on a microscopic scale. A frame rate of 5 frames per second is achieved which gives rapid feedback to the operator.

A ray tracing method for calculating the speed of sound in a nonparallel layered model using pulse echo ultrasound.

A method of calculating the speed of sound in a nonparallel layered model is presented. A focussed ultrasound source and receiver are used to locate the angle and position of an incident pulse and the reflected pulses at the surface of the model. Triangulation is used to calculate the speed of sound in the first layer and points on the first interface for a number of source positions and angles.

A digital annular array prototype scanner for realtime ultrasound imaging.

The use of annular array transducers in diagnostic ultrasound applications is growing. The development of this equipment raises a number of questions concerning both the role these systems will play in the clinic and how the annular array can be best implemented in an ultrasound scanner. In this paper, we will build on the results of the previous companion paper to describe the development of a 12 element 30 mm diameter 4.

Development of a 12 element annular array transducer for realtime ultrasound imaging.

While the recent proliferation of ultrasound scanners based on annular array transducers has attracted widespread attention, very little published information is available on the physics, design criteria, and signal processing aspects of these instruments. In this paper, the first of a two part report, we describe the development and characterization of an annular array transducer for realtime medical imaging. Theoretical modeling of the pulsed fields of annular arrays is used to study and optimize array parameters.

Ultrasonic characterization of selected renal tissues.

Velocity, attenuation, and backscatter of ultrasound were measured in human renal tissues over a frequency range relevant to clinical imaging (3.5-7 MHz). Normal renal tissues, as well as three types of mass (angiomyolipoma, renal cell carcinoma, and oncocytoma) were studied, and comparisons made of the appearance of the tissues in clinical images to their ultrasonic and pathological properties.

Nutrition in leprosy: a review.

The literature relating diet to leprosy is abundant between 1900 and 1960, peaking around 1940. Dietary factors that appear to influence the etiopathogenesis of Hansen's disease include: vitamin A, vitamin B group, vitamin C, vitamin D, vitamin E, calcium, and zinc. We noted a frequent lack of detailed dietary data in much of the literature cited.

Ultrasonographically defined parenchymal patterns of the breast: relationship to mammographic patterns and other risk factors for breast cancer.

We have used ultrasound of the breast to define four parenchymal patterns in which increasing proportions of the breast are replaced by densely echogenic tissue. A series of 452 symptomatic women examined by both ultrasound and conventional X-ray mammography was reviewed to determine whether these ultrasonographic images could predict the breast parenchymal pattern defined mammographically. A very strong correlation was demonstrated between the breast pattern on ultrasound and the volume of the breast replaced by either dysplasia (Kendall's tau-b = 0.

Ultrasound backscatter microscopy images the internal structure of living tumour spheroids.

Ultrasound microscopes have the potential for imaging structure at depth in thick specimens, yet this is not possible in biological specimens using conventional ultrasound transmission or reflection methods. But, subsurfacing imaging is possible with ultrasound if a backscatter (pulse-echo) technique, similar to that used in medical imaging, is used. The central problem of extending backscatter imaging to ultrasound microscopy has been the development of high frequency (greater than 100 MHz) transducers with sufficient bandwidth and sensitivity to detect the low levels of backscatter from biological materials.

Frequency dependence of ultrasound attenuation and backscatter in breast tissue.

Attenuation and backscatter of ultrasound in human breast tissues were measured over the frequency range relevant to breast imaging (3-7 MHz). The first step in the measurement process consisted of generating an ultrasound attenuation image of a macroscopic slice of excised breast tissue. This image depicted the various tissue constituents in the samples so that a region of homogeneous tissue could be selected for further investigation.