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Biomedical subjects

W R Webb

Publications and source records attributed to W R Webb.

At least 91 records · Page 5Linked to original sources
PubMed1990

Pediatric pulmonary disease: assessment with high-resolution ultrafast CT.

High-resolution computed tomography (HRCT) is widely used to assess pulmonary parenchymal disease in adults. The authors used ultrafast CT with 3-mm collimation and a 100-msec scan time to obtain HRCT scans in 36 children (mean age, 49.4 months). Clinical diagnoses included normal lungs (n = 6), cystic fibrosis (n = 12), obliterative bronchiolitis (n = 6), idiopathic pulmonary hemosiderosis (n = 2), and other lung diseases (n = 10). The HRCT scans and chest radiographs were reviewed separately in blinded fashion. Pulmonary parenchymal abnormalities were categorized into interstitial, airspace, and airway processes. Nine patients with normal chest radiographs had abnormal HRCT scans. In five other patients, the extent of abnormal lung parenchyma was considerably greater on HRCT scans than on chest radiographs. HRCT scans allowed accurate characterization of the type of lung process in 24 of 30 patients when compared with clinical or biopsy findings. Early HRCT findings in cystic fibrosis included lobular air trapping, bronchial wall thickening, and centrilobular nodules. The use of cine CT with high-resolution techniques is feasible in children too young or too sick to hold their breath. HRCT may enable early detection and characterization of pulmonary disease and depiction of the extent of lung abnormality.

Bronchiolitis Obliterans↗
PubMed1989

The role of magnetic resonance imaging in the assessment of patients with lung cancer: a comparison with computed tomography.

In general, computed tomography (CT) is superior to magnetic resonance imaging (MRI) as an all-around tool for imaging the wide range of thoracic abnormalities that can be present in patients with lung cancer. However, CT and MRI should not necessarily be viewed as competitive imaging modalities in this clinical setting. If MRI is used selectively as a secondary imaging study to answer specific questions raised or unanswered by CT, its value can be optimized. It can be of particular value in demonstrating chest-wall invasion in the lung apex as well as elsewhere, in defining mediastinal masses, which are hard to distinguish from vessels on CT, in detecting hilar masses, in distinguishing causes of adrenal mass, and in distinguishing recurrent tumor from fibrosis in patients who have had prior radiation.

Carcinoma, Bronchogenic↗
PubMed1989

Costal pleura: appearances at high-resolution CT.

The appearance of the costal pleura at high-resolution computed tomography (CT) was evaluated with a cadaver and 25 normal subjects. This was contrasted with the high-resolution CT appearance of the costal pleura in 15 patients with mild pleural thickening, 13 of whom had been exposed to asbestos. On high-resolution CT scans in the normal subjects, a 1-2-mm-thick line of soft-tissue attenuation at the point of contact between lung and chest wall represents the visceral and parietal pleura, pleural contents, endothoracic fascia, and innermost intercostal muscle. In a paravertebral location, the innermost intercostal muscle is lacking, and a thin line seen on high-resolution CT scans reflects pleura and endothoracic fascia. Transverse thoracic and subcostal muscles and extrapleural fat pads can be seen as tissue internal to a rib and may be confused with pleural thickening. In 13 of the 15 patients with mild pleural thickening, the 1-3-mm-thick pleura was separable from the underlying normal intercostal muscle by a layer of extrapleural fat. High-resolution CT was more sensitive than CT with 1-cm collimation in depicting this degree of pleural abnormality.

Aged↗
PubMed1989

High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs.

Asbestos-exposed persons with normal chest radiographs can demonstrate parenchymal abnormalities on high resolution computed tomography (HRCT). We reviewed the HRCT, clinical presentation, and results of pulmonary function tests in 169 asbestos-exposed workers with normal chest radiographs (ILO less than 1/0). The HRCT was normal or near normal in 76 subjects (Group 1), abnormal but indeterminate for asbestosis in 36, and abnormal and suggestive of asbestosis in 57 (Group 2). The indeterminate subjects were excluded from further analysis. The subjects in Groups 1 and 2 were not significantly different in their duration of asbestos exposure, latency, smoking history, or in measurements of airflow obstruction (FEV1/FVC% and %FEV1). Both the vital capacity percent predicted and diffusing capacity percent predicted were significantly lower in the abnormal subjects (Group 2) than in the normal subjects (Group 1) (79.0 versus 86.2, p = 0.005; 78.2 versus 87.1, p = 0.024; independent t test). We conclude that in asbestos-exposed subjects with normal chest radiographs, HRCT can identify a group of subjects with significantly reduced lung function indicative of restrictive lung disease when compared with a group with normal or near-normal HRCT.

Adult↗
PubMed1989

Leptospirosis of the lung: radiographic findings in 58 patients.

Leptospirosis is the disease produced by any of the group of spirochetes of the genus Leptospira. The main organs involved are the liver, central nervous system, kidneys, skeletal muscle, and lungs. Thirty-seven (64%) of 58 patients with leptospirosis, proved by positive serology, had pulmonary radiographic findings. Three radiographic patterns were evident: (1) 21 (57%) of the 37 patients had small nodular densities, (2) six (16%) had large confluent areas of consolidation, and (3) 10 (27%) had diffuse, ill-defined, ground-glass density. Serial radiographs showed a tendency for the nodular pattern to be followed by confluent consolidation and/or ground-glass density. Abnormalities were bilateral, nonlobar in all cases, and had a marked tendency toward peripheral predominance. Pulmonary abnormalities resolved within 15 days, except in eight patients who died because of respiratory failure (six patients) or other causes (two patients). In order to correlate pathology with the radiographic findings, Leptospira, isolated from a patient, was injected intraperitoneally into 20 guinea pigs. All lungs from the guinea pigs showed petecheal hemorrhage, which progressed to large confluent areas of hemorrhage. The typical pulmonary radiographic findings of leptospirosis are compatible with the multifocal pulmonary hemorrhage seen in the guinea pigs.

Adult↗
PubMed1989

High-resolution CT of the lung parenchyma.

High-resolution CT, a technique that optimizes the spatial resolution of lung parenchyma, uses thin collimation, reconstruction with a high-spatial frequency algorithm, image targeting, and sometimes increased kVp and mA settings. Performing a high-resolution CT study can provide information regarding lung morphology that cannot be obtained using conventional CT or plain radiographs. Alterations in anatomy can be identified at the level of the secondary pulmonary lobule, and although often nonspecific, in certain situations high-resolution CT findings can be diagnostic. High-resolution CT scanning is also helpful in identifying patients who have significant lung disease despite a normal chest radiograph, and in planning biopsy procedures.

Humans↗
PubMed1988

Intraluminal measurement of distance in the colorectal region employing rigid and flexible endoscopes.

Intraluminal measurements of distance cephalad to the anal verge in the colorectal region of 40 consecutive adult patients were performed employing rigid and flexible proctosigmoidoscopic techniques. In 2/40 (5%) patients, the measurements were identical. In 32/40 (80%) patients, measurements employing a flexible proctosigmoidoscope exceeded measurements employing a rigid instrument by at least 3 cm. The observations have relevance in the context of assessments of adequate distal margins and preservation of anal continence in patients requiring colorectal surgery via transabdominal, transsacral, transperineal, and/or transanal routes.

Colon↗
PubMed1988

Normal and diseased isolated lungs: high-resolution CT.

High-resolution computed tomography (CT) scans of 12 isolated, inflated, fresh lungs obtained at autopsy were compared with thin, paper-mounted lung sections obtained at the same levels. In six lungs considered intrinsically normal, high-resolution CT showed normal interlobular septa and pulmonary arteries in the lobular core, but lobular bronchioles were not visible. Edematous fluid resulted in thickening and increased visibility of interlobular septa. In three emphysematous lungs, high-resolution CT accurately demonstrated the degree of emphysema and suggested its centrilobular nature. In two lungs with honeycombing, cysts lined by fibrosis were easily seen on high-resolution CT scans. In less severely involved areas, septal thickening and intralobular fibrosis were seen on high-resolution CT scans, but small (1 mm) cysts were invisible. High-resolution CT was able to demonstrate some features of the normal secondary pulmonary lobule and structural alterations produced by various diseases.

Humans↗
PubMed1988

Pulmonary infections in renal transplantation patients treated with cyclosporine.

Seventeen cases of pneumonia occurring in renal transplantation patients treated with cyclosporine-prednisone immunosuppression were analyzed with regard to the organisms involved, time of occurrence after transplantation, clinical course, and radiographic findings. In a pattern similar to that encountered with conventional azathioprine-prednisone immunosuppression, opportunistic infections were most common in the period between 1 and 5 months after transplantation. All multiple-organism infections involved cytomegalovirus and carried a poor prognosis. No unexpected radiographic findings were noted.

Adult↗
PubMed1988

Hydrostatic versus increased permeability pulmonary edema: diagnosis based on radiographic criteria in critically ill patients.

To evaluate radiographic criteria recently proposed for determining causes of pulmonary edema, the authors studied 45 patients with severe pulmonary edema. Hydrostatic and increased permeability edemas were distinguished by means of the ratio of pulmonary edema fluid protein to plasma protein concentration and clinical and hemodynamic data. Chest radiographs were classified as showing hydrostatic, increased permeability, or mixed edema by three independent readers without knowledge of the clinical diagnosis. Overall, 87% of patients with hydrostatic edema but only 60% of patients with increased permeability edema were correctly identified. A patchy, peripheral distribution of edema was the single most discriminating criterion and was relatively specific for increased permeability edema, occurring in 13% of patients with hydrostatic and 50% with increased permeability edema (P less than .05). Some features considered more typical of hydrostatic edema were commonly found in patients with increased permeability, including a widened vascular pedicle (56%), pleural effusions (36%), peribronchial cuffs (72%), and septal lines (40%). The authors conclude that chest radiography is limited in the differentiation of type of pulmonary edema in severe cases.

Capillary Permeability↗
PubMed1988

CT densitometry of pulmonary nodules in a frozen human thorax.

The influence of (1) calcium concentration, (2) exposure technique, (3) reconstruction algorithm, (4) nodule size, and (5) nodule location on the CT attenuation values (CT density) of pulmonary nodules was examined in a frozen human thorax. Nodules with calcium concentrations of 0-310 mg/ml and diameters of either 0.95 or 1.59 cm were inserted into a frozen, unembalmed human thorax. The nodules were placed either at the lung apex or 4 cm below the tracheal carina. Each nodule was scanned on a GE CT 9800 scanner; five different exposure techniques were used. The slice thickness was uniformly 1.5 mm. As expected, increasing the kilovoltage caused a significant decrease in CT nodule density in all nodules with calcium concentrations greater than 80 mg/ml. The inverse relationship between kilovoltage and nodule density was exaggerated with increasing calcium concentration. A high-resolution (bone) algorithm gave a significantly higher CT number than did a smoothed (standard) algorithm, regardless of nodule size and location, but this difference could be attributed almost entirely to the edge-enhancement effect of the bone algorithm. The CT density of the larger nodules was significantly higher than that of the smaller nodules at calcium concentrations greater than 65 mg/ml for both standard and bone algorithms. Densities were significantly higher in the mid lung than in the apex with a standard algorithm, but this was not the case with a bone algorithm. The GE CT 9800 scanner had a linear response between CT density and increasing calcium concentration within the confines of a human thorax. A high-resolution (bone) reconstruction algorithm has higher spatial resolution but does show an edge-enhancing effect not found with the smoothed algorithm. Two major variables in CT densitometry for pulmonary nodules are the kilo electron voltage of the X-ray beam and the reconstruction algorithm used; these two parameters should be standardized, with a high kilovoltage and high-resolution algorithm favored on the GE CT 9800 scanner.

Absorptiometry, Photon↗
PubMed1988

MR imaging of the transverse sinus of the pericardium.

On MR images of the chest, a low-signal-intensity band is often seen between the ascending aorta and left atrium in the transverse plane, and between the right pulmonary artery and left atrium in the coronal and sagittal planes. CT and MR of cadavers, with injection of contrast media into the pericardial space, confirmed that this structure was the transverse sinus of the pericardium. Retrospective review of MR studies in 45 patients without evidence of pericardial disease showed the transverse sinus of the pericardium in 80% (32/40) of transverse ECG-gated images, 78% (7/9) of sagittal ECG-gated images, and 67% (14/21) of coronal ECG-gated images. Nongated studies showed the sinus infrequently. Knowledge of the three-dimensional anatomy of the transverse sinus of the pericardium and of its typical MR appearance should allow its recognition and preclude misinterpretation.

Adolescent↗