Biomedical subjects

J C Watts

Publications and source records attributed to J C Watts.

At least 55 records · Page 3Linked to original sources

PubMed1986

Contiguous thin multisection MR imaging by two-dimensional Fourier transform techniques.

Section thickness in two-dimensional Fourier transform (FT) imaging is dependent on gradient strength and the shape of the radio-frequency pulses used to excite the nuclei. By manipulation of these parameters, it is possible to obtain 2.5-mm-thick sections in contiguous, multisection imaging. Because this method is efficient in imaging with long repetition times (TR), it effectively complements three-dimensional FT thin-section imaging techniques, which require imaging with short TRs. Fifteen double-echo, contiguous images of 0.9 X 0.9 X 2.5-mm resolution were obtained in 17.1 minutes for a TR of 2 seconds.

Fourier Analysis↗

PubMed1986

Halving MR imaging time by conjugation: demonstration at 3.5 kG.

Conjugation can be used to synthesize half of the data acquired during a conventional two-dimensional Fourier transform imaging procedure, thus reducing imaging time by nearly half. The images acquired by this process have the same object contrast and spatial resolution as conventional images do, but with a 40% reduction in the signal-to-noise ratio (S/N). Conjugation can be used to advantage in magnetic resonance imaging units in which S/N levels are higher than needed to permit imaging with a single acquisition of each projection.

Fourier Analysis↗

PubMed1986

Mucinous carcinoid tumor of the appendix presenting as bilateral ovarian tumors.

Mucinous carcinoid tumor of the vermiform appendix, an uncommon variant of appendiceal carcinoid, may present clinically with ovarian metastases. We studied a tumor by immunohistochemistry and electron microscopy and reviewed eight similar cases from the literature. The primary and metastatic tumors in our case were composed of mucin-producing cells and small argyrophilic cells arranged in cords and acini. Tumor cells in both primary and metastatic sites exhibited identical patterns of immunoreactivity for epithelial antigens (epithelial membrane antigen, carcinoembryonic antigen) and neuroendocrine antigens (serotonin, vasoactive intestinal polypeptide, adrenocorticotropic hormone). Ultrastructurally, the cells contained either mucin vacuoles or dense-core neurosecretory granules; rare individual cells contained both types of inclusions. When bilateral solid mucinous ovarian tumors are discovered at laparotomy, diagnostic appendectomy is indicated if no obvious extraovarian primary tumor can be found.

Adrenocorticotropic Hormone↗

PubMed1985

Zygomycosis. Report of four cases with formation of chlamydoconidia in tissue.

The authors describe spheric to ovoid chlamydoconidia and mucoraceous hyphae in tissues from four patients, two with cutaneous and two with pulmonary zygomycosis. The diagnosis in each case was confirmed by immunofluorescence staining and the presence of characteristic hyphae in tissue. It is important that these conidia be recognized, because they can easily be mistaken for other fungi, nematode ova, or other microorganisms in tissue sections, thereby resulting in the potential for misdiagnosis.

Adult↗

PubMed1985

A comparison of saddle-shaped and solenoidal coils for magnetic resonance imaging.

Differences in magnetic resonance (MR) imaging signal-to-noise (S/N) performance between saddle-shaped and solenoidal coils have been postulated. Each coil shape is tied to a particular magnetic field configuration, so that they are not typically interchangeable except in special situations. The solenoidal coil is predicted to have a two- to three-fold advantage over the saddle-shaped coil. Simple basic arguments raise a dispute with this assertion. Experiments show that both coils produce essentially equivalent S/N levels.

Animals↗

PubMed1985

Multiple spin-echo magnetic resonance imaging.

Spin-echo magnetic resonance (MR) imaging detects a variety of pathologic states with great sensitivity. A technique for producing multiple spin-echo images in multisection operation is presented. This method of intensity-image acquisition is compared with retrospective intensity-image synthesis from routine data sets. Both yield long echo time (TE) images with similar image contrast and comparable and often increased diagnostic utility. Technical and clinical considerations are addressed, including signal-to-noise levels, flow effects, and patient throughput.

Brain Diseases↗

PubMed1985

Variable magnetic resonance imaging parameters: effect on detection and characterization of lesions.

With change in the imaging technique and magnetic field strength used in magnetic resonance imaging, wide variations in the delineation of pathologic features occur. Using imaging data from patients with known pathologic conditions, we evaluated the intensity images in spin-echo and inversion-recovery imaging at varying repetition times, echo times, and inversion times over broad ranges and changing magnetic field strengths. Differences in conspicuity and the apparent size of the lesions are important to consider in diagnosing and evaluating pathologic conditions, especially when different imagers and techniques are employed.

Brain Diseases↗

PubMed1985

Magnetic resonance imaging performance: a comparison of sodium and hydrogen.

Although many nuclei can be used to produce magnetic resonance (MR) images, technical considerations dictate the choice of certain of these. Hydrogen is the most favorable, followed by sodium. We present an evaluation of the imaging performance of sodium MR imaging based on imager performance and biologic factors. Because it is hampered by high operating fields, low signal-to-noise levels, and radiofrequency power deposition constraints, careful clinical comparisons will be needed to identify a diagnostic niche that could take advantage of the large sodium differences known to exist within biologic systems.

Brain Neoplasms↗

PubMed1985

Inner volume MR imaging: technical concepts and their application.

Although cross-sectional magnetic resonance examination of the head and body is useful for screening large regions of tissue, subsectional regions of the head and body often need to be examined. Orthogonally directed, selectively irradiated planes with different flip angles produce a spatially limited signal region from which two- or three-dimensional volume images can be reconstructed. Images with limited fields-of-view can be acquired in reduced imaging time. We present a general description of this technique. These subsectional or "inner volume" images eliminate respiratory motion artifacts by excluding moving tissues from the imaged volume. A result of this technique is a high signal from rapid pulsatile blood flow, produced without cardiac gating the pulse sequence.

Blood Flow Velocity↗

PubMed1985

Hydrogen MR imaging of the head at 0.35 T and 0.7 T: effects of magnetic field strength.

To determine whether hydrogen magnetic resonance imaging at 0.7 T provides added clinical value over imaging at 0.35 T, images of the heads of patients with various intracranial disorders were obtained at these field strengths. Measurements of tissue contrast (C), signal-to-noise (S/N) ratio, and T1 and T2 relaxation times were determined. For a given spin-echo sequence with equal imaging time, resolution, and data sampling window, the product C X S/N was somewhat lower for the lower field strength. Under conditions of imaging with equal chemical shift artifact, C X S/N at 0.35 T was equal to or greater than that measured at 0.7 T. With an increase in field strength, T1 of pathologic areas and surrounding normal tissues increased, resulting in a corresponding loss of absolute signal level and decrease in contrast. Lesions were equally well seen at both 0.35 T and 0.7 T. The increased T1 and decreased C X S/N for higher magnetic fields--when measured with a fixed imaging time, resolution, chemical shift, and sequence--suggest that such field strengths may not improve tissue contrast, diagnostic ability, or clinical throughput when compared with lower field strength systems.

Brain↗

PubMed1985

MR imaging of blood vessels using three-dimensional reconstruction: methodology.

Multisection, dual-echo magnetic resonance (MR) transaxial images of blood vessels contain both anatomic and qualitative information about flow. Even so, the images are produced as a series of two-dimensional tomographic sections from which full visualization of connected structures is difficult. A computer algorithm was developed that automatically detects flowing blood based on pixel intensity and calculated T2 and provides reconstructed views of vessels while analyzing and displaying flow characteristics. Images of abdominal vessels, aortic aneurysms, and the heart were encoded by flow and color to demonstrate depth. In addition, these data were reconstructed to derive a more accurate assessment of patency. With this technique, transaxial images can be used to analyze flow patterns, determine patent areas, and visualize all levels of vessels in a single image.

Blood Flow Velocity↗

PubMed1985

Pneumocystis carinii pneumonitis. The nature and diagnostic significance of the methenamine silver-positive "intracystic bodies".

The cyst forms of Pneumocystis carinii in specimens stained with methenamine silver contain single or paired discrete foci of enhanced staining that measure 1-2 micron in maximum size. The nature of these foci and their location within the cysts have been disputed. We demonstrate by electron microscopy of silver-stained sections that the darkly stained foci correspond to a focal thickening of the cyst wall and are unrelated to sporozoites and other intracystic organelles. The morphology of these structures by light microscopy is characteristic, and their recognition is helpful in identifying P. carinii cysts and in differentiating them from yeast-form fungi and argyrophilic tissue elements in histologic sections and cytology specimens.

Acquired Immunodeficiency Syndrome↗

PubMed1984

Isolated ischemic necrosis of the cecum in patients with chronic heart disease.

Isolated ischemic necrosis of the cecum is an infrequently described entity. We report three cases seen at our institution within a three-year period. All three patients had been hospitalized for congestive heart failure in the past, but none was in failure at the time of the most recent hospitalization. All three patients presented with clinical and laboratory findings consistent with acute appendicitis. At surgery the cecum was ischemic in each case, while the appendix and the remainder of the intestine appeared normal. There was no evidence of major vascular occlusion or embolization at the time of original operation. We propose that the cecum, like the splenic flexure, is a "watershed area," with poor blood supply relative to that of the adjacent intestine. While cecal ischemia has been described in association with a variety of clinical entities, we propose a newly recognized association with poor myocardial function. In such patients, isolated ischemic necrosis of the cecum should be considered in the differential diagnosis of right lower quadrant pain.

Aged↗

PubMed1984

Analytical tools for magnetic resonance imaging.

The response of different magnetic resonance (MR) techniques to tissue parameters - T1, T2, and N(H) - is a determinant of clinical efficacy. The large possible number of imaging techniques and range of variable parameters for each make it difficult to perform exhaustive evaluations in a single patient or even in animal models. In addition, changes in operating magnetic field strength change the relaxation times sufficiently so that the efficacy of a technique at a given field does not imply similar results at another field value. Tools are demonstrated that permit the evaluation of the efficacy of any model of response to tissue parameters, and also allow the investigation of the effects of changing magnetic field. Global maps of signal difference between tissues as well as calculated images are obtainable from a minimally sufficient data set. These tools serve as an important adjunct to experimental work.

Electron Spin Resonance Spectroscopy↗

PubMed1984

Magnetic resonance imaging strategies for heart studies.

Given a suitable trigger signal, cardiac synchronized magnetic resonance (MR) imaging is simple to implement; however, single section techniques are not efficacious, especially when the heart rate sets the repetition interval. We demonstrate multi-section, double, and single-echo imaging, any of which rapidly covers the cardiac volume; 3-D modes capable of achieving very thin sections; and cycled multi-section imaging capable of efficaciously providing dynamic data on heart motion. These modes form a complementary, powerful set of options for clinical work.

Heart↗

PubMed1983

Nuclear magnetic resonance imaging of a fibrosarcoma tumor implanted in the rat.

Fibrosarcoma tumor cells were implanted in the hind legs of 25 rats and studied from the first to the sixth week postimplantation. Nuclear magnetic resonance imaging detected all tumors and did not yield any false-positives in five control rats. The T1 relaxation values of tumors overlapped those of muscle, and the T2 values overlapped those of fat, but the combination of the two values allowed discrimination of each of the three tissues with no overlap. The difference in relaxation time between tumor and muscle could be accounted for on the basis of water content, which was approximately 14% higher in the tumors. This study confirms data from previous studies suggesting that nuclear magnetic resonance imaging is a highly sensitive modality, but that T1 and T2 values are not specific for individual pathologic conditions.

Adipose Tissue↗

PubMed1980

Idiopathic infarction of intraabdominal lymph nodes. A cause of fever of unknown origin.

Infarcted peribiliary lymph nodes were found at laparotomy in a 56-year-old man who had a fever of unknown origin and transient abdominal pain. Despite thorough clinical and laboratory investigation, a cause was not demonstrated. A review of the reported cases of idiopathic or spontaneous lymph node infarction revealed a clinical presentation characterized by the sudden appearance of a painful mass, often associated with otherwise unexplained fever. Most clinical laboratory test results were negative. Although the pathogenesis is not known, histologic changes in involved lymph nodes are indistinguishable from those produced experimentally by occlusion of the vascular supply of lymph nodes. The histologic differential diagnosis includes lymphoma, metastatic carcinoma, vasculitis, and infection.

Abdomen↗

PubMed1980

Fatal pneumonia caused by Legionella pneumophila, serogroup 3: demonstration of the bacilli in extrathoracic organs.

An immunosuppressed patient with malignant lymphoma died of acute pneumonia caused by Legionella pneumophila. Bacilli of serogroup 3 were detected in areas of pnemonia, in a mediastinal lymph node, and in the liver and spleen by direct immunofluorescence done on tissue obtained at autopsy. That the extrathoracic fluorescent material represented intact bacteria rather than antigenic fragments or antigen-antibody complexes was confirmed by finding intracellular bacilli in the liver by electron microscopy. To our knowledge, this case represents the first example of fatal disease attributed to serogroup 3 L. pneumophila and the first case in which L. pneumophila has been demonstrated in extrathoracic organs.

Bacteria↗