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Biomedical subjects

D F Cowan

Publications and source records attributed to D F Cowan.

11 recordsLinked to original sources
PubMed1992

Transitional cell carcinoma with rhabdoid features.

We discuss the light-microscopic, immunohistochemical, electron-microscopic, and flow cytometric analysis in a case of invasive transitional cell carcinoma of the renal pelvis with rhabdoid features and glandular metaplasia. This tumor demonstrated in situ rhabdoid transformation of the transitional epithelium, which has not been described before. Electron-microscopic examination of the rhabdoid cells revealed whorled aggregates of intermediate filaments. There was also evidence of mucin-filled intracellular lumina on light and electron microscopy in both in situ and invasive components of the tumor. Our findings lend support to the view that tumors with "rhabdoid" features in adults and perhaps some children represent a heterogeneous group of neoplasms, some of which may just be unusual morphologic variants of a transitional cell carcinoma, in contrast to the distinct clinicopathologic entity of childhood renal rhabdoid tumors.

Adult↗
PubMed1992

Implementing a regulation-complaint quality improvement program on a commercial laboratory information system.

Implementing a quality improvement (QI) program on an automated laboratory information system (LIS) in the current regulatory climate requires first that the QI program be defined and second that the selected LIS be able to capture important events and use flexible vendor-provided or user-defined routines to prepare reports. Reports key on specific monitors and thresholds defined in the QI program. The product of a pathology laboratory is communicated information. The QI program focuses on the accuracy, clarity and timeliness with which the whole information-generating process functions. To support peer review the LIS must be able to select reports for evaluation based on user-defined parameters, such as diagnosis keyed through Systematized Nomenclature of Medicine codes, or by random or pattern selection by accession number. Counting and review of revised reports will focus attention on accuracy and skill in communication since these indicators often reflect client satisfaction with the report. To link services--e.g., cytology with surgical pathology--the LIS must be able to gather cases from the accession lists of both services and to flag diagnostic inconsistencies. LIS transaction logging at every step in the information process allows tracking of work load, productivity and resource utilization by functional areas and by individual, thus meeting regulatory requirements. Transaction logging also provides management information, such as segmented turnaround time audits, pinpointing sources of delay by kind and location of work or individual involved. Critical data must be held on-line for at least five years.

Clinical Laboratory Information Systems↗
PubMed1991

Elastosis in the normal aging breast. A histopathologic study of 140 cases.

The incidence and pattern of elastosis of the breast was studied in tissue specimens taken at autopsy from 140 women with clinically normal breasts, ranging in age from 19 through 101 years. Elastosis, presence of excess elastic fibers, while less common in younger women, may be found in nearly half of all women over age 50 years with no breast disease. Elastosis occurs in three sites: diffusely in the stroma, around vessels, and around ducts. In the first two sites, it bears little relationship to age, while periductal elastic tissue appears to accumulate with age, probably reflecting parity, until about age 50 years. Thereafter, it is found at a more or less constant incidence and degree. While it may be associated with breast cancer, periductal elastosis by itself is not a cause for concern. Marked perivascular elastosis is, however, uncommon at any age, and its presence should suggest a special search for carcinoma, if not already evident.

Aging↗
PubMed1991

A microcomputer based system for three-dimensional reconstructions from tomographic or histologic sections.

The reconstructions of three-dimensional (3-D) objects from serial two-dimensional (2-D) images can contribute to the understanding of many biologic structures, from organelles to organs and tissues. The 3-D reconstruction of sections can be divided into several major tasks: image acquisition, alignment of slices, internal object definition, object reconstruction and rotation of the completed image. A fast, versatile, interactive system was devised for the reconstruction of 3-D objects from serial 2-D images using a low-cost microcomputer, original programs and commercial software. The system allows reconstruction from any serial images, e.g., electron micrographs, histologic sections or computed tomograms. A photographic image or a microscopic field is acquired into the computer memory using a video digitizer. Slices are superimposed and aligned to each other using an operator-interactive program. A contour-(edge-) finding algorithm isolates an object of interest from the background image by "subtraction" of the image from an overlaid, slightly shifted identical image. Contours for each slice are input to a reconstruction procedure, which calculates the x, y and z coordinates of every point in a slice and the thickness and number of slices. It then calculates the illumination for every point using a given point source of light and an intensity-fading coefficient. Finally, the points are represented by cubes to provide dimension and reflective surfaces. A cube of appropriate shade and color represents in 2-D the equivalent of a 3-D object; this results in a very effective 3-D image. The reconstruction is rotated by recalculating the positions of every point defining the object and rebuilding the image.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Quality assurance in anatomic pathology. An information system approach.

Quality assurance (QA) is the outcome-oriented process by which the performance of a complex production operation is evaluated. It is strongly focused on the use of resources and the end product, and is closely related to marketing. The pathologist's product is information, and the practice of anatomic pathology is evaluated as a system for producing and effectively communicating information. Our integrated program for QA in surgical pathology, autopsy pathology, and cytopathology recognizes that several discrete elements make up the sequence leading to communication of the diagnostic opinion. These are control and processing of the specimen, accuracy of diagnosis, timely and clear communication, efficiency in production of information, coherence with institutional programs in QA, and relation to licensing and accreditation agencies. Each of these elements may be tested separately and sources of error reduced so that the validity and cost of the pathologist's prediction will ultimately be limited only by the state of the art and not by any failure of the information system. Several components of QA, especially resource utilization by pathologists, are potentially productive areas for operations research.

Clinical Laboratory Information Systems↗
PubMed1988

A microcomputer-based algorithm for digitized image simplification and information extraction.

Spatial analysis of objects often requires significant image simplification prior to information extraction and application of a decision-making algorithm. Much decision making based on images (e.g., histologic diagnoses) requires identifying patterns in complex backgrounds (image simplification) and comparison of those patterns to other patterns (decision making). Automated extraction of information from images commonly requires the extraction system to recognize edges (contours) of structures and their internal discontinuities (such as gradations in density) and to selectively suppress irrelevant data in order to conserve memory and speed computation; data from homogeneous image areas occupy memory, but are noncontributory or redundant. This paper describes the development of a microcomputer-based algorithm that deletes all homogeneous information from overlaid digitized images, generating contours in the place of nonhomogeneities. Contours corresponding to different areas or objects depend on color differences between an object and its surroundings. Any set of contours can be deleted almost instantaneously, leaving only those of interest. Contours can be highlighted by an operator-driven interactive process if desired and can be deleted and retrieved until an appropriate image is obtained. This contour-generating and image-simplification algorithm facilitates three-dimensional reconstruction of an object from serial images by reducing the number of calculations required and yielding a cleaner final image.

Algorithms↗
PubMed1986

Invasive verrucous carcinoma of urinary bladder treated by irradiation.

A case of inoperable, invasive verrucous carcinoma of the urinary bladder treated by irradiation is presented. The incidence of anaplastic transformation of verrucous carcinoma after irradiation is lower and the coincidence of verrucous carcinoma and well-differentiated squamous carcinoma higher than is generally recognized. Radiation should be considered in inoperable cases. The pertinent literature is reviewed.

Aged↗
PubMed1976

Effects of implanted Doppler flowmeters on femoral vein autografts.

Thirteen femoral vein autografts were placed into the corresponding ipsilateral femoral arteries of 8 mongrel dogs. Cuff-type Doppler (ultrasonic) flowmeters were placed around six of the grafts. None of the vessels thrombosed. Blood flow velocities were measured in all vessels up until the time of sacrifice (mean 95 +/- 5 days after surgery) or accidental death (one dog, 49 days after surgery). The only case of graft failure was attributed to infection at the flowmeter site. With this single exception, the vein grafts exhibited uniformity in histological appearance from dog to dog. These data suggest that implantation of properly designed Doppler flow transducers may have clinical applications. This technique permits continuous or intermittent assessment of blood flow characteristics through a graft without additional trauma or cost to the patient. It is free of the many inherent disadvantages of chronically implanted electromagnetic flowmeters and may negate the need in some instances for followup angiographic studies.

Animals↗
PubMed1976

Ultrasonically-guided percutaneous nephrostomy. Report of 24 cases.

Ultrasonically-guided percutaneous nephrostomy using the Seldinger technique was attempted on 24 kidneys in 19 patients with obstructive hydronephrosis. Seventeen of the procedures were successful, 4 failed, and in 3 the catheter slipped out of the renal pelvis 1-48 hours after insertion. The procedure is simple and independent of renal function. Postrenal uremia can be relieved, infected hydronephrosis drained prior to elective surgery, and urinary parameters assessed. Injection of contrast material can define pathological anatomy in those cases where excretory urography and retrograde pyelography are unsatisfactory. No significant complications were encountered.

Fistula↗
PubMedDate not supplied

Increased collateral arterial and venous endothelial cell turnover after renal artery stenosis in the dog.

Renal artery stenosis was induced in dogs and collateral arterial formation assessed by serial angiography and histology. Endothelial cell turnover was estimated by radioautography in five normal and five collateral-forming kidneys 18-39 days following stenosis with tritiated thymidine. Normal arterial endothelial labeling was 0.1% with a highly significant (p less than 0.0005), 55-fold increase in endothelial labeling in arterial collateral vessels. A smaller but statistically significant increase in the labeling index was also found in endothelial cells of the renal vein, from a normal of 0.065% to 0.4% (p less than 0.005). An excellent correlation was found between endothelial cell labeling in small arteries and the renal veins (r = 0.97; p less than 0.01). A marked increase in epithelial cell labeling of the ureters draining the stenotic kidneys was also evident (p less than 0.005). Thus, collateral vessel development is characterized by active DNA synthesis in cellular elements, and a humoral factor is implicated in the vascular response.

Angiography↗