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Biomedical subjects

W R Webb

Publications and source records attributed to W R Webb.

At least 55 records · Page 3Linked to original sources
PubMed1995

Bronchogenic carcinoma in 13 patients infected with the human immunodeficiency virus (HIV): clinical and radiographic findings.

Bronchogenic carcinoma is a cause of parenchymal or hilar masses with or without mediastinal adenopathy in HIV-seropositive smokers. Lung cancer can occur earlier than the more commonly recognized opportunistic infections and in patients not known to be HIV seropositive. Tumor cell types do not differ markedly from those expected in HIV-seronegative young lung cancer patients, but are often poorly differentiated; patients with high-grade malignancies fare poorly independent of their degree of immunocompromise at diagnosis. Computed tomography (CT) scans not only add important information with regard to disease distribution and preferred means of diagnosis, but also result in the detection of new sites of disease with respect to the plain radiography in many patients. Because lung cancer often occurs before the diagnosis of AIDS, the association may not be suspected in some cases; poorly differentiated, rapidly growing tumors in young smokers may raise the suspicion of underlying HIV infection.

Adult↗
PubMed1995

AIDS-related Kaposi sarcoma of the lung: radiographic findings and staging system with bronchoscopic correlation.

PURPOSE: To determine the chest radiographic findings in patients with tracheobronchial Kaposi sarcoma (KS) and to develop a radiographic staging system that allows comparison of radiographic to bronchoscopic findings and allows assessment of the typical temporal progression of pulmonary KS. MATERIALS AND METHODS: The chest radiographs and medical records of 76 male patients, aged 23-60 years (mean, 36 years 4 months) with bronchoscopically proved KS were retrospectively reviewed. Tumor extent at bronchoscopy (grade 1-3) was compared with severity of parenchymal disease (radiographic stage 0-3). RESULTS: There was a statistically significant relationship between extent of tracheobronchial disease and radiographic stage (P = .01). However, in some patients, parenchymal KS of advanced stage was present with no visible endobronchial disease. CONCLUSION: The proposed staging system describes features of early, moderate, and advanced KS. Although there is a correlation between tracheobronchial and parenchymal disease, the latter can occur in the absence of endobronchial lesions.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Hydrostatic pulmonary edema: high-resolution CT findings.

Hydrostatic pulmonary edema can be defined as an abnormal increase in extravascular water secondary to elevated pressure in the pulmonary circulation, as in congestive heart failure or intravascular volume overload. The diagnosis of hydrostatic pulmonary edema is usually based on clinical information, conventional chest radiograph findings, and response to treatment and does not require high-resolution CT. However, recognizing the appearance of hydrostatic pulmonary edema on high-resolution CT can be important, as the edema can mimic other diseases or can occur as an unsuspected finding in patients having high-resolution CT for other indications, and a misdiagnosis may lead to unnecessary lung biopsy. Although the CT appearances of pulmonary edema have been described in several studies [1-3], to date, the high-resolution CT appearances of hydrostatic pulmonary edema have been described only in isolated cases [4-6] or in experimental studies of phantom or animal models [7, 8]. This essay illustrates the spectrum of high-resolution CT findings seen in adult patients with hydrostatic pulmonary edema secondary to cardiac disease.

Aged↗
PubMed1994

Pleural exudates and transudates: diagnosis with contrast-enhanced CT.

PURPOSE: To determine the accuracy of computed tomography (CT) in enabling differentiation of pleural exudates from transudates. MATERIALS AND METHODS: Eighty consecutive patients (86 effusions) underwent contrast-enhanced CT. Thoracentesis was performed to measure pleural and serum total protein and lactate dehydrogenase (LDH) values. Effusions were classified as exudates with accepted criteria. CT scans were evaluated for the presence and appearance of parietal pleural and extrapleural fat thickening. RESULTS: Fifty-nine effusions were exudates and 27 were transudates. Thirty-six of the 59 exudates (61%) were associated with parietal pleural thickening. All cases of empyema and 56% of the parapneumonic exudative effusions had pleural thickening. The specificity of this finding in diagnosing the presence of an exudate is 96%. CONCLUSION: Parietal pleural thickening at contrast-enhanced CT almost always indicates the presence of a pleural exudate. A pleural exudate in the absence of pleural thickening occurs most frequently in patients with malignancy or uncomplicated parapneumonic effusion.

Adolescent↗
PubMed1994

Idiopathic giant bullous emphysema (vanishing lung syndrome): imaging findings in nine patients.

OBJECTIVE: We reviewed the imaging findings in nine patients with idiopathic giant bullous emphysema. This progressive condition is characterized by large bullae, usually seen in association with several forms of emphysema, and usually occurs in young men, most of whom are smokers. MATERIALS AND METHODS: Nine patients with chest radiographic evidence of a bulla or bullae occupying at least one third of a hemithorax, who had also been examined with high-resolution CT, were included in this retrospective study. We examined the size, distribution, and locations of bullae. On high-resolution CT scans, bullae were categorized as predominantly subpleural or intraparenchymal. RESULTS: In eight of the nine cases, the chest radiographs showed variable asymmetry in the distribution of bullae. Bullous disease involved predominantly the upper lobes. High-resolution CT showed bullae from 1 to 20 cm in diameter, but most were 2-8 cm in diameter. Paraseptal emphysema and subpleural bullae were the predominant findings in all nine patients. Seven patients had separate centrilobular emphysema of various degrees and intraparenchymal bullae. None of the intraparenchymal bullae were larger than 2-3 cm. Additionally, two non-small-cell lung cancers were seen in our series. CONCLUSION: The dominant and consistent feature seen on high-resolution CT scans in both smokers and nonsmokers is extensive paraseptal emphysema merging into giant bullae. Associated centrilobular emphysema, seen in cigarette smokers, is the important variable finding for determining the extent of underlying parenchymal disease, which may help in the preoperative assessment of giant bullous lung disease.

Adult↗
PubMed1994

Centrilobular opacities in the lung on high-resolution CT: diagnostic considerations and pathologic correlation.

Accurate assessment of high-resolution CT scans of the lung requires a knowledge of secondary lobular anatomy. Opacity that localizes to the centrilobular region implies the presence of a disease process that primarily involves centrilobular bronchioles, lymphatics, or pulmonary arterial branches. We illustrate the high-resolution CT findings of many of these processes and provide pathologic correlation for cases in which it was available.

Humans↗
PubMed1994

High-resolution computed tomography of obstructive lung disease.

High-resolution CT (HRCT) scanning and dynamic CT techniques have significantly improved our ability to image morphologic abnormalities associated with chronic airflow obstruction. Abnormalities visible on HRCT include emphysema, lung cysts, and large airways abnormalities, such as bronchiectasis, which are accurately assessed using this technique. Also visible are small airways abnormalities, such as bronchiolar dilation and filling of bronchioles with mucus or fluid. Perfusion abnormalities resulting from abnormal lung ventilation result in regional differences in lung attenuation, so-called mosaic perfusion. Expiratory HRCT scans or dynamic scans during expiration can show areas of air trapping.

Asthma↗
PubMed1994

Dynamic quantitative computed tomography. A predictor of pulmonary function in obstructive lung diseases.

RATIONALE AND OBJECTIVES: Nine patients were examined using dynamic electron beam computed tomography to assess the utility of this technique in detecting airway obstruction and air trapping, and to compare this technique with pulmonary physiologic testing. METHODS: Dynamic computed tomography (C-100 Ultrafast CT scanner, Imatron, Inc., South San Francisco, CA) was performed, with a series of ten, 100-msec images obtained in a 6-second period during forced inhalation and exhalation. Time-attenuation curves were calculated from the observed changes in lung attenuation. Estimates of the percentage of each lung that showed air trapping were made at each level scanned, using a 5-point scale. Specific correlations were made for pulmonary function test results and air-trapping score. RESULTS: In all nine patients, dynamic computed tomography demonstrated one or more sites that failed to show a normal increase in lung attenuation during forced exhalation. Four of these 9 patients showed a paradoxical decrease in lung attenuation during exhalation in at least one region of the lung. Extent of air-trapping correlated well with forced expiratory volume in one second (r = -.92). CONCLUSIONS: Based on this small sample, the authors believe that this technique will prove sensitive for detecting abnormalities of ventilation and may be a useful adjunct to conventional diagnostic procedures in the management of disorders of airway obstruction.

Adult↗
PubMed1993

Dynamic imaging of lung morphology with ultrafast high-resolution computed tomography.

To aid in the diagnosis of lung diseases associated with airway obstruction and air-trapping, we use dynamic ultrafast high-resolution computed tomography (DUHRCT). We obtain a rapid series of ultrafast HRCT scans during a forced inspiratory and expiratory maneuver to demonstrate dynamic lung attenuation changes. Alteration in lung morphology can be seen coincident with changes in lung attenuation during different phases of the respiratory cycle. Lung attenuation changes can be evaluated qualitatively or quantitatively by using time-attenuation curves measured for specific regions of lung. In a normal population, we noted that the lingula is a common site of unsuspected and asymptomatic air-trapping. In subjects with airway obstruction, and in those with cystic lung disease, air-trapping is readily detected, even at the secondary pulmonary lobule level. In some of those cases with air-trapping, a paradoxical decrease in lung attenuation was noted during forced exhalation. Recent development of spiral CT scanners may allow more common usage of a similar dynamic technique. Simple paired inspiratory and expiratory scans, obtained during suspended respiration at the same level, may be sufficient for the detection of air-trapping in many patients.

Humans↗
PubMed1993

Dynamic pulmonary CT: findings in healthy adult men.

The authors examined 10 healthy male subjects with dynamic computed tomography to determine normal dynamic and expiratory findings. In both the supine and prone positions, the average increase in lung attenuation during exhalation was found to be significantly greater in dependent lung regions than in nondependent lung regions. In each of the lung zones studied, there was a significant correlation between the decrease in cross-sectional lung area during exhalation and the increase in lung attenuation. At the lung bases, a greater increase in lung attenuation was noted during exhalation for a given change in cross-sectional lung area than in the upper lungs. All 10 subjects showed a distinct lobar attenuation gradient in the supine position. In general, lung attenuation increased homogeneously during exhalation, but four of the 10 subjects showed regions of inhomogeneity in lung attenuation during rapid exhalation indicative of air trapping, despite normal results on pulmonary function tests.

Adult↗
PubMed1993

Normal trachea during forced expiration: dynamic CT measurements.

The purpose of this study was to define the range of normal intrathoracic tracheal diameters and cross-sectional areas during forced respiration. A report of tracheomalacia is also presented. Ten volunteers were studied in the supine position with dynamic computed tomography (CT), at a level at or between the brachiocephalic vein and the aortic arch, with 3-mm collimation and with image reconstruction by means of a high-spatial-frequency algorithm. Ten 100-msec dynamic scans were obtained at 500-msec intervals during a 6-second period as the patient performed forced inspiration and expiration vital capacity maneuvers. The mean cross-sectional area of the trachea decreased dynamically from 280 mm2 at end inspiration (standard deviation, 50.5; range, 221-388 mm2) to 178 mm2 at end expiration (standard deviation, 40.2; range, 115-236 mm2; P < .001) (mean decrease, 35% between inspiration and expiration; standard deviation, 18%; range, 11%-61%). The percentage decrease in cross-sectional area of the trachea correlates well with the decrease in the anteroposterior and coronal diameters of the trachea from maximum inspiration to maximum expiration (r = .879 and .916 and P = .0018 and .0002, respectively).

Adult↗
PubMed1993

CT gantry tilt: utility in transthoracic fine-needle aspiration biopsy. Work in progress.

The authors used a gantry tilt of 20 degrees in five patients to allow fine-needle aspiration biopsy of peripheral pulmonary lesions that were difficult to approach with a vertical alignment because of overlying ribs. This method allowed a direct approach to the lesion in all five cases, with the entire needle path visible in the scanning plane, avoidance of vital structures, and traversal of a minimal amount of normal lung parenchyma.

Adult↗
PubMed1993

Percutaneous transthoracic needle biopsy in AIDS: analysis in 32 patients.

PURPOSE: A retrospective study was performed to determine the success of percutaneous transthoracic needle biopsy (TNB) as an aid in diagnosing focal chest and mediastinal disease in patients with human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS). MATERIALS AND METHODS: The study group was composed of 32 patients seropositive for HIV; 31 of these patients had known AIDS. The subjects underwent chest radiography, computed tomography, and TNB. RESULTS: In 27 of the 32 patients a specific diagnosis was enabled by TNB. Bronchogenic carcinoma was diagnosed most frequently, although infectious agents were isolated in most patients. CONCLUSION: TNB is a safe and effective procedure for evaluation of focal thoracic disease in this patient population and provides information that is often unavailable from alternative diagnostic procedures.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Comparative effects of endothelin (ET-1) and U46619 on human saphenous vein and gastroepiploic artery, sources of human autologous grafts.

The effects of endothelin (ET-1) on smooth muscle contractile activity were investigated and compared in human saphenous vein and gastroepiploic artery, vessels frequently used in revascularization procedures. ET-1 contracted saphenous vein and gastroepiploic artery in a concentration-dependent manner. The peptide produced a greater maximal effect in the vein than in the artery and, in both preparations, ET-1 was less efficacious than U46619, an agent which mimics the actions of thromboxane A2 at the thromboxane A2/prostaglandin H2 receptor. The contractile response to ET-1 declined spontaneously at a more rapid rate in the artery than in the vein. The present data indicate that ET-1 has significant contractile activity in both vessels which are used for coronary arterial bypass surgery and suggest that although, a weaker vasoconstrictor than U46619, the peptide could induce vasospasm in both graft vessels.

Arteries↗