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Biomedical subjects

D F Cowan

Publications and source records attributed to D F Cowan.

At least 37 records · Page 2Linked to original sources
PubMed1995

Thermocoagulation effect of diode laser radiation in the human prostate: acute and chronic study.

OBJECTIVES: To evaluate the safety and efficacy of low-power slow-heating diode laser-induced photocoagulation of prostatic tissue for treatment of benign prostatic hyperplasia, we conducted a series of acute and chronic studies using a diode laser (810 nm) to irradiate human prostate. METHODS: The study included 6 patients undergoing radical prostatectomy because of malignancy. Laser radiation to the prostate was given transurethrally, in a noncontact mode, at the time of the procedure in 2 patients (acute group): 10 W for 300 seconds on the right side of the prostate and 15 W for 180 seconds on the left. In the remaining 4 patients (chronic group), laser radiation was given at 1, 7, 10, and 12 weeks prior to the prostatectomy. RESULTS: In the acute group the average depth of coagulation was 8.5 and 9.0 mm for the laser regimens of 15 W for 180 seconds and the 10 W for 300 seconds, respectively. In the chronic group, the average depth of coagulation was 8.9 mm for both laser regimens studied. In the acute group, there was an ill-defined hemorrhagic ring at the periphery of the lesion. At 1 week, an intact necrotic coagulum was present. At 7 weeks, some of the coagulated tissue had already sloughed off. Longer follow-up at 10 and 12 weeks demonstrated formation of a well-defined cavity with mostly re-epithelialized surface. CONCLUSIONS: Our findings suggest that noncontact diode laser (810 nm) irradiation can induce in the human prostate significant coagulation necrosis followed by sloughing of tissue and cavitation of the prostatic urethra.

Aged↗
PubMed1995

Comparison of thermocoagulation effects of low power, slow heating versus high power, rapid heating Nd: YAG laser regimens in a canine prostate model.

We compared the thermocoagulation effects of low power, slow heating (15 W x 180 seconds) versus high power, rapid heating (50 W x 60 seconds) laser regimens in the canine prostate. The study was performed in 20 mongrel canines. On each prostate, the low power regimen was delivered at the 2 and 4 o'clock positions, and the high power at the 8 and 10 o'clock positions. The laser power was measured at the fiber tip. Seven dogs (acute group) were sacrificed 1 hour after the procedure. The other 13 dogs (chronic group) were sacrificed at different time intervals from 3 days to 9 weeks after the procedure. The average depth of coagulation was significantly greater in lesions treated at low power (acute: 10.7 mm., chronic: 13.3 mm.) than in those treated at high power (acute: 8.5 mm., chronic: 11.6 mm.). Another potential benefit of the low power regimen observed in the study was preservation of the integrity and efficiency of the laser probe.

Animals↗
PubMed1995

Amyloidosis in the bottlenose dolphin, Tursiops truncatus.

Four cases of amyloidosis were recognized in a study population of 21 (19%) bottlenose dolphins (Tursiops truncatus) examined as part of an investigation of the causes of cetacean strandings along the Texas Gulf Coast. Amyloid deposition was mainly and most prominently in the corticomedullary regions of the kidneys and less consistently in the vessels of the spleen, lung, and heart and around acini of the palatal salivary gland and the thyroid gland. Pretreatment of sections with permanganate and sulfuric acid greatly diminished Congo red staining, suggesting the dolphin amyloid is of the AA variety.

Amyloid↗
PubMed1995

Histopathological evaluation of laser thermocoagulation in the human prostate: optimization of laser irradiation for benign prostatic hyperplasia.

We have previously shown in a canine prostate model that a noncontact low power neodymium:YAG laser regimen of 15 watts for 180 seconds yields a larger volume of coagulation necrosis than the currently recommended high power regimen of 50 watts for 60 seconds. These 2 regimens have not yet been compared in humans. The objective of this study was to evaluate histopathologically the thermocoagulation effect of these 2 laser regimens in the human prostate and the effect of the spatial distribution of the laser lesions on the extent of coagulation necrosis. The study was conducted in 10 patients undergoing radical prostatectomy or cystoprostatectomy. The laser treatment was given transurethrally 1 hour before removal of the specimen. There were no fractures of the prostate. The coagulation necrosis did not reach the peripheral zone and it was minimal in areas rich in fibromuscular tissue, such as the bladder neck. At times, nodular benign prostatic hyperplasia was unaffected. A 4-quadrant treatment in the same plane often yielded small nonconfluent lesions. Confluent lesions in the same plane yielded approximately 30% greater depth of coagulation necrosis, which was achieved when 3 or 4 lesions were created on each side of the prostate (per single transverse plane). Likewise, coagulation necrosis observed with 15 watts for 180 seconds was approximately 40% greater than that noted with the 50 watts for 60 seconds regimen. Our findings suggest that noncontact laser prostatectomy is a safe procedure that can be improved by modifying the laser regimen and the spatial distribution of lesions.

Aged↗
PubMed1995

Nd: YAG laser thermocoagulation of the prostate: the barbecue effect.

OBJECTIVE: To determine systematically the depth of coagulation necrosis induced during Nd: YAG laser irradiation in the canine prostate model, and to define the correlation of laser dose with depth of the lesions. METHODS: We investigated the effect of various dosimetries on prostatic tissue of 17 mongrel canines using laser power in the range of 8 to 60 watts (W) at varying exposure times, from 20 to 300 seconds (S). Applied energy ranged from 1,000 to 5,500 Joules (J). RESULTS: Three distinct features were observed. First, deep coagulation necrosis was induced only with laser regimens of > or = 2,100J, suggesting that there is a threshold of energy that must be overcome in order to achieve significant coagulation depth. Second, the deepest coagulation necrosis was achieved with a low power slow-heating regimen (15W X 180S). Tissue surface changes appeared to be responsible for the reduced depth of coagulation necrosis seen with higher power regimens (> 20 W). Third, increasing the energy above 3,600J did not augment the depth of coagulation, suggesting that a steady state for temperature distribution is reached at that rate of heating. CONCLUSIONS: Our study suggests that in the canine prostate, a low power slow-heating regimen of 15W X 180S may yield larger volumes of coagulation necrosis than other regimens.

Animals↗
PubMed1995

Histopathologic effects of laser radiation on the human prostate.

High levels of applied laser irradiation to the prostate will carbonize or vaporize tissue, and may cause explosive expansion of superheated tissue water. Lower levels, used most often to relieve obstruction caused by benign prostatic hypertrophy, will cause coagulation necrosis. This effect is apparent within 1 h of application. In contrast to the canine, in which laser-coagulated prostate sloughs in 2 to 3 weeks leaving a smooth cavity, in the human necrotic tissue is sloughed irregularly over a period ranging up to 12 weeks. This difference is attributed to the dominantly glandular nature of the canine prostate, and the dense fibromuscular composition of the human prostate stroma. Sloughing is accomplished by surface liquefaction, cavitation of the necrotic coagulum, and to a lesser degree, formation of granulation tissue at the margins. As often occurs at the margin of spontaneous infarcts in the prostate, squamous metaplasia may be prominent at the margins of laser-induced coagulation necrosis.

Humans↗
PubMed1994

Involution and cystic transformation of the thymus in the bottlenose dolphin, Tursiops truncatus.

The thymus glands of 10 bottlenose dolphins, Tursiops truncatus, collected along the Texas Gulf coast were examined using standard histologic and immunocytochemical methods. The thymus gland of Tursiops persists into adult life, represented by medulla and progressively thinning cortex. A network of epithelial cells, including Hassal bodies, is demonstrable using polyclonal anti-cytokeratin antibody. The network condenses, with loss of lymphoid cells as involution progresses. Cysts arise within the condensed network. These cysts, found in eight of 10 animals, increase in number and size with increasing body size. Body size tends to reflect age. Thymic cysts typically have an irregular shape when small but tend to become spherical as they enlarge. They may be lined by squamous epithelium of variable thickness. Eventually, the cysts become macroscopic and filled with a colloidlike material and may largely replace the thymus, which may be identified by noncystic remnants adjacent to the cysts.

Aging↗
PubMed1993

Recurring phyllodes tumor in aberrant breast tissue of the vulva.

A 20-year-old nulligravida woman presented with bilateral cystic nodules of the vulva, diagnosed after simple excision as benign phyllodes tumor. Breast tissue, which also displayed fibrocystic changes, was also recognized. Follow-up at 2 months revealed no evidence of disease; however, 8 months after surgery she returned with a new mass in the vulva. This was excised and found to be recurrent phyllodes tumor. Although somewhat more cellular than the first lesions, it also was deemed to be benign based on histological features supported by flow cytometric DNA studies.

Adult↗
PubMed1993

Lobo's disease in a bottlenose dolphin (Tursiops truncatus) from Matagorda Bay, Texas.

Lobo's disease was diagnosed in a free-ranging male bottlenose dolphin Tursiops truncatus examined as part of a live-capture and release program conducted in Matagorda Bay, Texas, USA, during July 1992. Diagnosis was based on typical presentation of a raised skin lesion, with sub-epidermal granuloma and demonstration of typical features of the organism by light microscopy, using hematoxylin and eosin, and methenamine silver stains. This is the first instance of Lobo's disease found in a dolphin on the western coast of the Gulf of Mexico.

Animals↗
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↗
PubMed1987

The reliability of fine-needle aspiration biopsy in the diagnosis of deep lesions of the lung and mediastinum: experience with 250 cases using a modified technique.

Two-hundred and fifty discrete lesions of the lung and mediastinum were sampled by a modified fine-needle aspiration biopsy (FNAB) technique. Aspirates were collected directly into 15 ml of Saccomanno's fixative, and all preparative work was carried out in the cytopathology laboratory. Only seven aspirates were "insufficient for diagnosis," giving a productivity rate of 97%. Five insufficient aspirates later proved to be neoplasms. Of the 243 cases with a primary FNAB diagnosis, 21 had insignificant disease, 29 had benign neoplasms or nonneoplastic disease, and 193 had malignant tumors. Most malignancies could be assigned to a specific histologic type by FNAB; those that proved difficult by FNAB were usually difficult on histopathologic examination. There were no false-positive diagnoses of malignancy and only eight false-negative results. Of 12 results interpreted as "suspicious," 10 proved to be malignant on follow-up. This modified method has proven to have a low complication rate and to be both highly productive and reliable in the diagnosis of malignant and nonmalignant disease.

Aged↗