Biomedical subjects

R H Knapp

Publications and source records attributed to R H Knapp.

At least 19 recordsLinked to original sources

PubMed2001

In situ complement activation by polyethylene wear debris.

A frequent long-term complication of total joint arthroplasty is aseptic loosening, the end result of wear debris accumulation, synovitis, and osteolysis about the implant-bone or cement-bone interface. Complement, an effector system in plasma, synovial fluid, and tissue, has powerful chemotactic, inflammatory, and osteoclast-activating potentials. This study explored the complement-activating ability of polyethylene, a material used in joint implants. In vitro hemolytic assays using sheep red blood cells (E(sh)), human serum, and particulate polyethylene suggested alternative pathway complement activation, as well as polyethylene adsorption of activated complement components. These results were confirmed by enzyme-linked immunosorbent assay (ELISA) quantification of activated complement factors Bb and C3b. In situ double antibody immunoperoxidase staining for factors Bb, C3a, iC3b, and SC5-9 in synovial tissue from revision hip specimens showed localized alternative pathway activation and component adsorption. These results introduce a likely role for complement activation in particle-mediated recruitment, proliferation, and activation of macrophages during early events in osteolysis and implant loosening.

Biocompatible Materials↗

PubMed1997

Three-dimensional dental imaging by spiral CT. A progress report.

OBJECTIVE: To demonstrate the feasibility of using spiral computed tomographic data for three-dimensional image acquisition, display, and segmentation of dental structures and lesions and to demonstrate the feasibility of metal artifact suppression. STUDY DESIGN: Isolated extracted teeth, a dry mandible, cadaver mandible, and cadaver head were scanned and reconstructed using spiral computed tomography data. Algorithms for metal artifact reduction including extended attenuation range and interpolation of missing projections were applied. Volumetric rendering was performed to synthesize images comparable to conventional intraoral dental radiographs. Serial examinations were obtained by spiral computed tomographic tomography, registered by surface matching, and interval change determined by three-dimensional subtraction. RESULTS: Metal artifact reduction was successful in markedly reducing the streaks and star patterns that usually accompany metallic restorations and intraoral appliances. Voxel sum images were comparable to dental radiographs. Image segmentation could successfully isolate dental structures, and simulated lesions could be detected through three-dimensional subtraction. CONCLUSION: The results demonstrate the feasibility of spiral volumetric computed tomography for quantitative study of oral hard tissues in the presence of metal restorations.

Algorithms↗

PubMed1992

Digital dental image processing of alveolar bone: Macintosh II personal computer software.

Dental radiographs are amenable to digital image processing and analysis for both subjective interpretation and quantification of scene features. Four general-purpose image processing programs for the Apple Macintosh II computer (NIH Image, Enhance, IP Lab and DIP Station) were applied to digital analysis of dental radiographs. These programs can manipulate and quantitatively analyse the gray scale and spatial data of dental images and improve their subjective quality. They can interactively make geometric measurements of features. The programs were evaluated for their versatility and applicability in the quantification of alveolar bone. Overall, NIH Image was judged most suitable for current dental imaging needs. Each of the other programs offered unique features that may be valuable in specific applications.

Alveolar Process↗

PubMed1992

Live and carcass values from different cattle types.

Slaughter steers and heifers (n = 345) were selected representing the following cattle types: English steers and heifers, Exotic steers and heifers, less than 50% Bos indicus steers and heifers, greater than or equal to 50% Bos indicus steers, and Holstein steers. Thirty sides representing 30 carcasses from each cattle type were fabricated into boneless subprimals and trimmed to three fat-trim levels: 2.54, 1.27, and .64 cm. Yields of cuts to each trim level were used to calculate values for each carcass component. Live values were calculated after slaughter and fabrication costs and drop credits were considered. Values were calculated for U.S. Choice and U.S. Select grades and the weighted average value accounting for the Choice/Select mix for each cattle type. At a constant quality level, fatter cattle types were more valuable at the 2.54 cm of fat-trim level. As fat was trimmed, the leaner cattle types became more valuable and the fatter types became less valuable. Cattle types with higher percentages of Choice carcasses were more valuable at the 2.54 cm of fat-trim level, but when subprimals were trimmed to .64 cm, the lower-grading carcasses became closer in value due to cutability advantages.

Adipose Tissue↗

PubMed1990

Validation study of skull three-dimensional computerized tomography measurements.

Recent advances in imaging have led to high-resolution computerized tomography (CT) scanning with exquisitely detailed slice images of the skull and three-dimensional (3-D) surface reconstructions using computer software. It is possible to use CT scans to acquire morphologic information about the skull in a convenient digital form and to derive 3-D measurements from surface reconstruction images. Unfortunately, no effort has been made to date to test the validity of these measurements on laboratory specimens, and no compelling evidence is available from phantom studies to indicate the nature and magnitude of the errors inherent in the measurement technique. We have performed a pilot study to quantify the morphology of the skull based on surface features that can be found in CT scans and 3-D reconstructions. Comparative measurements were obtained from five skulls (two normal and three with dysmorphology) with calipers and a 3-D electromagnetic digitizer. These measurements were statistically compared with those based on original CT scan slices and reformatted 3-D images. It is concluded that 3D-CT measurement techniques are superior to those in which measurements are obtained directly from the original CT slices; 3-D CT methods, however, must be significantly improved before measurements based on these techniques can be used in studies that require a high degree of precision. The results are used to indicate the most fruitful areas of future study.

Cephalometry↗

PubMed1990

Yields of by-products from different cattle types.

Slaughter cattle (n = 360), selected and allocated to types according to their phenotypic breed type characteristics, were slaughtered in lots of 15 head at a large commercial packing plant. By-product weights were obtained for these lots of 15 head after plant personnel had separated the by-products according to plant procedures. Percentage of slaughter weight in each by-product was calculated. The trait most influenced by cattle type was the hide; Bos indicus cattle generally had the greatest percentage of their live weights as hide (green, trimmed, fleshed or cured), and Holstein cattle generally had the lowest. For edible by-products, the liver differed significantly among cattle types, with Holstein cattle having the higher percentage of their live weight as liver. Other items studied were not significantly or economically different among cattle types.

Animals↗

PubMed1989

Electrodiagnostic evolution of carcinomatous sensory neuronopathy.

Sensory neuronopathy is a well-recognized remote effect of carcinoma. We report the clinical and electrodiagnostic evolution of a sensory neuronopathy in a patient with carcinoma of the lung. Serial electrophysiologic studies suggest transformation from normal peripheral nerve function through early posterior root involvement to absent sensory nerve function. Diffuse motor conduction abnormalities occurred late in the disease, perhaps reflecting motor axon changes associated with disuse.

Carcinoma, Small Cell↗

PubMed1989

Craniosynostosis: diagnostic value of three-dimensional CT reconstruction.

Three-dimensional computed tomography (CT) has an important role in determining the presence and extent of congenital and acquired craniofacial deformities. The authors compared the sensitivity and specificity of three-dimensional CT in the detection and characterization of craniosynostosis with that of planar CT and skull radiography. Eighty-two patients with isolated and syndromal synostoses were imaged with CT and three-dimensional CT, and 42 with skull radiography. Three-dimensional CT scan processing was performed by shaded-surface reconstruction, volumetric, and depth-coded methods. Two trained observers read each scan series in a blinded fashion. Diagnostic utility of the images was determined with receiver operating characteristic analysis. The observers ranked three-dimensional shaded images higher than the other types, with three-dimensional volumetric images second and three-dimensional surface images ranked third. Results of this study demonstrate that three-dimensional shaded-surface reconstruction from CT scans is superior to conventional plain radiographs and CT scans in diagnosing craniosynostosis.

Adolescent↗

PubMed1989

Craniosynostosis: image quality, confidence, and correctness in diagnosis.

The authors used the diagnosis of craniosynostosis to compare subjective evaluation of image quality with objective diagnostic utility. They studied in detail the responses of one observer, who read plain radiographs, computed tomographic (CT) scans, and three-dimensional reconstructions of CT scans (obtained with three different methods) for 82 patients with this diagnosis. The observer rated image quality and certainty in diagnosis made from each image. Subjective and objective performances were found to be strongly linked. High-quality images served as the basis for more accurate diagnoses than low-quality images. The increase in diagnostic performance results primarily from increased specificity, a fact that suggests that specificity and the concomitant diagnosis of normalcy are the focus of attention when image quality is evaluated.

Adolescent↗

PubMed1988

Three-dimensional magnetic resonance imaging of congenital heart disease.

Three-dimensional surface reconstruction images of the heart and great vessels have been produced from contiguous sequences of EKG-triggered MRI scans in more than 35 patients with congenital heart disease and 5 normal subjects. The scan data was semiautomatically processed to separate the epi- and endocardial surfaces and to define the outlines of the enclosed blood volumes on a slice by slice basis. Surface reconstruction images aid communication with clinicians, establish the size and location of intracardiac defects, and image the pulmonary venous drainage. The method is practical for use in the evaluation of cardiac morphologic abnormalities, especially for planning cardiac surgery.

Adult↗

PubMed1985

Three-dimensional cranial surface reconstructions using high-resolution computed tomography.

Until recently, there has been no satisfactory way for anthropologists to visualize intracranial morphology in more than two dimensions without actually "invading" the skull in some manner. Images provided by conventional x-ray and computed tomography (CT) scans are often abstract, flat, two-dimensional representations that fail to reveal three-dimensional relationships. We describe new computer-imaging techniques that reconstruct three-dimensional images from sequential series of narrowly collimated (1-2 mm), high-resolution CT scans of the skull. These computed images represent three-dimensional surface data and can be viewed from any direction. Depth information is encoded in gray scale. In addition, selected portions of the anatomy can be "removed", i.e., made transparent, to allow visualization of previously hidden intracranial morphology. Since the geometric data obtained with the CT scanner are precise, parameters such as linear distances, angles, areas, and volumes can be accurately (and instantaneously) generated. The power and versatility of these computer-imaging techniques are demonstrated by examining living subjects with major craniofacial dysmorphology (Treacher-Collins syndrome and unilateral coronal synostosis); an anthropoid osteological specimen (Gorilla); and a fossil mammal skull.

Cephalometry↗

PubMed1985

Cytogenetic studies in 174 consecutive patients with preleukemic or myelodysplastic syndromes.

Routine cytogenetic studies were done in 174 consecutive patients with preleukemic or myelodysplastic syndromes (PL/MDS): 5 had the 5q - syndrome, 2 had refractory cytopenia, 43 had refractory anemia, 38 had refractory anemia with ringed sideroblasts, 69 had refractory anemia with excess blasts, 6 had refractory anemia with excess blasts in transition, and 11 had chronic myelomonocytic leukemia. Successful chromosome studies were accomplished in 167 patients (96%); 64 (37%) had a chromosomally abnormal clone. Abnormal clones were most common among patients who had refractory anemia with excess blasts (45%), refractory anemia with excess blasts in transition (60%), and chronic myelomonocytic leukemia (45%); they were least common among patients with refractory anemia (32%) and refractory anemia with ringed sideroblasts (21%). The two patients with refractory cytopenia had normal cytogenetic results. Each patient with the 5q - syndrome had a 5q-chromosome, as this is a prerequisite for the diagnosis. The two most common structural abnormalities were deletion of part of a chromosome 5 long arm (17 patients) and deletion of part of a chromosome 20 long arm (8 patients). Nonspecific structural abnormalities of chromosomes 1, 3, 6, and 17 were also common. The most common numeric abnormalities were monosomy 5 (7 patients), monosomy 7 (4 patients), loss of the Y chromosome (9 patients), and trisomy 8 (20 patients). No chromosome abnormalities were specifically associated with any PL/MDS classification.

Adult↗

PubMed1985

Malignant germ cell tumors of the mediastinum.

A review of 56 cases of primary malignant germ cell tumors of the mediastinum revealed that, as with benign teratomas, the tumors occurred in young adults (mean age 29 years) but that the sex distribution differed (86% male and 14% female). A single germ cell element was found in 37 (66%) of the tumors, and various combinations were present in the remaining 19 (34%). The tumors were classified among five recognized types of germ cell tissues. There were 24 seminomas (22 pure and two with mature teratomas), 17 embryonal carcinomas (nine pure and eight with mixtures), five teratomas, seven choriocarcinomas (three pure and four with mixtures), and three pure yolk sac tumors. Most (86%) of the patients were symptomatic at the initial examination, with chest pain, cough, and loss of weight being the most frequent presenting symptoms. The standard posteroanterior and lateral roentgenograms were the most helpful diagnostic tool, showing evidence of an anterior mediastinal mass in 53 patients. The diagnosis was established by surgical exploration of the mediastinum or by biopsy of a lymph node in 55 patients. Of the 55, 24 (43.6%) had complete resection of the tumor and 31 (56.4%) had incomplete resection or biopsy alone. The overall prognosis for mediastinal germ cell tumors is poor, partly because the tumors are far advanced at the time of diagnosis but also because some of the tumors that contain embryonal cell carcinoma, choriocarcinoma, and yolk sac elements are very aggressive. Factors that were prognostic in patients with seminoma--such as age, presence of the superior vena caval syndrome, lymphadenopathy, evidence of hilar disease on the chest roentgenogram, and resectability--were not predictive in patients with other types of malignant germ cell tumors. Although aggressive combination chemotherapy may represent a significant treatment modality for nonseminomatous mediastinal tumors, the present study spanned many years in which no chemotherapy was available. Patients in the later years of the study received combination chemotherapy with various treatment regimens. No conclusions concerning specific chemotherapy, therefore, can be derived from this study.

Adolescent↗

PubMed1985

Musculoskeletal applications of three-dimensional surface reconstructions.

We have applied computer programs originally developed for craniofacial surgical planning and evaluation to complex musculoskeletal problems. These computer programs reformat ordinary CT scans into black and white images of the three-dimensional osseous surfaces found in the scanned volume. These reformatted three-dimensional CT scan images increase the utility of CT scan examinations of complex osseous structures, such as the wrist, spine, hip, knee, and shoulder. The software, which operates on an unmodified commercially available CT scanner, can produce high-quality surface reconstructions from CT scan slices without operator intervention. No special knowledge of the principles used in the reconstruction methods is needed to successfully use the programs.

Adolescent↗

PubMed1984

Leiomyoblastomas and their relationship to other smooth-muscle tumors of the gastrointestinal tract. An electron-microscopic study.

Twelve cases of gastrointestinal leiomyoblastoma were studied by electron microscopy, and the findings were compared with those in 12 cases of leiomyoma and nine cases of leiomyosarcoma of the gastrointestinal tract. All of the "classic" ultrastructural features of smooth-muscle tumors, including subplasmalemmal dense patches, pinocytotic vesicles, cytoplasmic microfilaments and dense bodies, and focal basement membrane formation, were present in the leiomyoblastomas ; however, extensive sampling was commonly necessary to demonstrate such findings. In contrast, these features were more prominent in leiomyomas and leiomyosarcomas.

Adult↗

PubMed1983

Benign teratomas of the mediastinum.

Approximately 8% of all mediastinal tumors are benign teratomas. We reviewed 86 cases of benign teratoma seen at the Mayo Clinic from 1930 through 1981. The mean age of the patients was 28 years and the sex distribution was approximately equal. The most common symptoms were chest, back, or shoulder pain, dyspnea, and cough, but 36% were asymptomatic at the time of presentation. Chest roentgenograms showed a well-circumscribed anterior mediastinal mass which often protruded into one lung field. Detectable calcification was observed in 22 patients: a calcified tumor wall in seven, bone or teeth in the mediastinum of seven, and nonspecific calcifications in eight. Surgical excision remains the best means of diagnosing and treating this benign tumor. Though the tumors are histologically benign, they may present difficult surgical problems because of the vital structures involved. Since 1952 there has been a change in the clinical presentation of patients with this entity: More patients are asymptomatic and have smaller tumors and fewer complications than prior to 1952.

Adolescent↗

PubMed1982

Adamantinoma of bone. An electron microscopic and immunohistochemical study.

Adamantinoma of bone is a rare tumor, and fine structural analysis has been done in only a few cases. We report four cases studied by electron microscopy and immunohistochemical methods. Ultrastructural evaluation revealed a characteristic constellation of features, including intracellular bundles of type I microfilaments, moderate numbers of evenly dispersed mitochondria, scattered profiles of rough endoplasmic reticulum, occasional Golgi bodies and lysosomes, and scattered glycogen particles. Microvillous processes and desmosomes were identified in all tumors. Well-formed basement membranes enveloped cell clusters but did not surround individual cells. Intercellular basement membrane-like material also was found focally in pools. Ultrastructural features of endothelial differentiation, including Weibel-Palade bodies, micropinocytotic vesicles, and tight junctions, were not identified. Immunoperoxidase stains for coagulation factor VIII (von Willebrand factor) and blood group antigens were negative, whereas similar stains for keratin were positive. Our findings strongly suggest that adamantinoma is a neoplasm expressing definite epithelial, rather than endothelial, characteristics.

Adolescent↗

PubMed1982

Primary embryonal carcinoma and choriocarcinoma of the mediastinum. A case report.

Primary germinal tumors of the mediastinum are very rare. We studied a 67-year-old man with a primary embryonal carcinoma and choriocarcinoma of the mediastinum. To our knowledge, this is the oldest patient described as having this lesion. The diagnosis of primary germinal tumor of the mediastinum should not be made unless the possibility of a primary testicular lesion has been eliminated by thorough clinical evaluation. The prognosis is very poor for patients with teratocarcinoma, embryonal carcinoma, or choriocarcinoma, despite aggressive therapy.

Aged↗