Temperature effects on transmembrane potentials of rat ventricle.
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Action Potentials↗
Biomedical subjects
W R Webb
Publications and source records attributed to W R Webb.
Imaging evaluation of suspected pulmonary embolism.
Venous thromboembolism (VTE) is a common disorder that is difficult to diagnose clinically but carries significant morbidity and mortality if untreated. Additionally, although demonstrated to be of benefit in cases of proven deep vein thrombosis (DVT) and pulmonary embolism (PE), anticoagulation therapy is not without risk. Because the clinical exam is known to be unreliable for the detection of both DVT and PE, many imaging modalities have been used in the diagnostic imaging algorithm for the detection of VTE, including chest radiography, ventilation/perfusion (V/Q) scintigraphy, pulmonary angiography, and recently, spiral computed tomography (CT) and magnetic resonance imaging (MRI). Chest radiographic findings in acute PE include focal oligemia, vascular enlargement, atelectasis, pleural effusions, and air space opacities representing pulmonary hemorrhage or infarction. The chest radiograph can occasionally be suggestive of PE but is more often nonspecifically abnormal. The main use of the chest radiograph in the evaluation of suspected PE is to exclude entities that may simulate PE and to assist in the interpretation of V/Q scintigraphy. Lower extremity venous compression ultrasonography (CU) is both sensitive and specific for the diagnosis of femoropopliteal DVT, and the value of negative CU results has been established in outcomes studies. However, the reliability of CU for the detection of isolated calf vein thrombosis is not well established, and the clinical significance of such thrombi is debatable. Additional methods such as color and spectral Doppler analysis are also useful in the diagnostic evaluation of DVT but are best considered as adjuncts to the conventional CU examination rather than as primary diagnostic modalities themselves. Compression ultrasonography and Doppler techniques are useful in the evaluation of suspected upper extremity DVT; spectral Doppler waveform analysis is particularly useful to assess for the patency of veins that cannot be directly visualized and compressed with conventional gray-scale sonography. V/Q scintigraphy has been the initial modality obtained in patients suspected of PE for a number of years. Although many studies have investigated the role of V/Q scintigraphy in the evaluation of VTE, the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study has provided the most useful information regarding the utility of V/Q scintigraphy in this setting. A high probability scan interpretation is sufficient justification to institute anticoagulation, and a normal perfusion scan effectively excludes the diagnosis of PE. A normal/near normal scan interpretation also carries a sufficiently low prevalence of angiographically proven PE to withhold anticoagulation. Although the prevalence of PE in the setting of low probability scan interpretations is low and several outcomes studies have demonstrated a benign course in untreated patients with low probability scan results, patients with inadequate cardiopulmonary reserve do not necessarily have good outcomes. Such patients deserve more aggressive evaluation. Patients with intermediate probability scan results have a 20% to 40% prevalence of angiographically proven PE and thus require further investigation. The radionuclide investigation of DVT includes such techniques as radionuclide venography and thrombus-avid scintigraphy. Although these methods have not been as thoroughly evaluated as CU, studies thus far have indicated encouraging results, and further investigations are warranted. Pulmonary angiography has been the gold standard for the diagnosis of PE for decades. Studies have indicated that angiography has probably been underutilized by referring physicians for the evaluation of suspected PE, likely because of the perception of significant morbidity and mortality associated with the procedure. (ABSTRACT TRUNCATED)
Algorithms↗
Temporal image database design for outcome analysis of lung nodule.
This paper presents the design of a temporal image database system and its application in thoracic imaging. The design of this information system is based on the client/server architecture. The system consists of a chest imaging database server, a library of image processing modules, a link to the picture archiving and communication system (PACS) archive, and a low end client workstation with motif-based graphic user interface (GUI). The database system can be used to aid the radiologists in quantitating solitary or multiple long nodules and in assessing effectiveness of therapeutic procedures for these lung cancers. The GUI allows a user to retrieve any patient study from PACS. After a nodule is visually identified, it will be segmented automatically to obtain relevant features, such as the center of mass, volume, and surface area. Such 3D nodule information, together with the patient textual information, is subsequently organized in the chest imaging database to facilitate outcome analysis.
Breast Neoplasms↗
Artifacts in the measurement of pulmonary artery wedge pressure.
Pulmonary artery wedge pressure (PAWP) will only reflect left atrial pressure (LAP) if continuity of fluid exists from the catheter tip to the left atrium. Either increased airway pressure or decreased hydrostatic pressure may lead to discontinuity of the fluid column and midinterpretation of PAWP. Simultaneous measurements of PAWP and LAP were made in 19 anesthetized dogs. Placement of the pulmonary artery wedge catheter above the left atrium (West Zone I) in combination with the incremental addition of 5 cm H2O of PEEP caused a 5 mm Hg gradient between PAWP and LAP in the normovolemic animal. Augmenting PEEP further or hypovolemia (i.e., decrease in LAP) increased the gradient. Hypervolemia (increase in LAP) diminished the gradient. Fluid continuity between the PAW catheter and LA is a prerequisite for monitoring LAP with the Swan-Ganz catheter. Increases in PEEP, placement of the catheter above the left atrium and hypovolemia may occlude the fluid column and cause artifacts in the PAWP obtained.
Blood Pressure↗
CT of a bronchial phantom. Factors affecting appearance and size measurements.
In order to determine the most appropriate window settings for viewing CT of the bronchial tree, we performed CT of a bronchial phantom consisting of air-filled tubes measuring from 3.1 to 12.7 mm, oriented at varying angles relative to the scan plane, surrounded by water or air, and with scan collimation of 10 mm, 5 mm, and 1.5 mm. Using a computer program to graphically display CT number relative to the distance across the tube's lumen, it was found that a window mean of -150 H accurately estimated the internal diameter of tubes surrounded by water, at all angles, when collimation was 5 mm or 1.5 mm. With 10-mm collimation, tube diameter was slightly underestimated for tubes 9.5 mm or less when oriented 30 degrees or more from perpendicular to the plane of scan. At lower window settings and window widths of 500 H or less, all tube's diameters were significantly underestimated. At -150 H, with tubes parallel to and centered in the scan plane, 5-mm and 1.5-mm collimation were most accurate; with decentering of 4 mm, 10-mm collimation better showed the tube's lumen. When surrounded by air, tube wall thickness was best estimated using a window mean of -450 H.
Bronchi↗
Sagittal MR imaging of the chest: normal and abnormal.
To determine the value of sagittal magnetic resonance (MR) in diagnosing thoracic abnormality, we reviewed the multisection sagittal spin-echo MR images of 13 normal subjects and 23 patients with a variety of thoracic abnormalities. In the abnormal subjects sagittal images were compared with transaxial MR performed with repetition time values of both 0.5 and 2.0 s. Sagittal images were most helpful in the evaluation of structures lying in the sagittal plane such as the thoracic aorta. Mediastinal masses in most locations were better seen and evaluated in the transaxial plane. However, the relationship of subcarinal masses to the trachea, left atrium, and pulmonary artery was better appreciated in the sagittal plane. The relationship of hilar masses to hilar vessels, bronchi, and the mediastinum was usually better seen on transaxial images. Also, the relationship of paramediastinal masses to the mediastinum was difficult to evaluate with sagittal scans.
Adolescent↗
Computed tomography of diffuse tracheal stenosis in Wegener granulomatosis.
A patient with Wegener granulomatosis presented with diffuse tracheal narrowing and was evaluated using CT and cine-CT. The CT findings included severe laryngeal and tracheal airway narrowing, due to abnormal soft tissue within the laryngeal cartilages and tracheal rings, and enlarged abnormally calcified tracheal cartilages. Computed tomography precisely confirmed the site, level, and submucosal extent of tracheal narrowing, not obtainable on physical or bronchoscopic examination, and assisted in choosing a site for tracheostomy. Wegener granulomatosis should be considered in patients with diffuse tracheal narrowing even when the typical histology is not present.
Adult↗
Computed tomography in pulmonary sarcoidosis.
We studied the high resolution CT (HRCT) scans of 15 patients with biopsy-proven sarcoidosis and correlated the findings with pulmonary function tests (12 patients), 67Ga scans (10 patients), bronchoalveolar lavage (five patients), recent transbronchial biopsy (six patients), and recent open lung biopsy (three patients). The HRCT features included small nodules, thickened interlobular septa, patchy focal increase in lung density, honeycombing, and central conglomeration of vessels and bronchi. Active alveolitis was present by gallium scanning criteria in 5 of 10 cases. By bronchoalveolar lavage criteria, activity was present in three of five cases. Patchy increase in density may correlate with active alveolitis as seen on 67Ga scanning. High resolution CT was better than chest X-radiography for demonstration of patchy increase in density and for distinguishing nodules from septal thickening. Both nodules and patchy density were partly reversible following therapy. Nodular densities seen on CT correlated with the presence of granulomata on histology. Resting pulmonary function tests correlated poorly with presence and extent of lung disease on HRCT. The presence on HRCT of focal fine nodules, patchy focal increase in lung density, and central crowding of bronchi and vessels should suggest the diagnosis of sarcoidosis. In some patients, HRCT can identify unsuspected parenchymal lung disease and document the reversible components of sarcoid lung disease.
Bronchoalveolar Lavage Fluid↗
Interobserver variability in CT and MR staging of lung cancer.
OBJECTIVE: Our goal was to assess the interobserver variability in staging non-small cell lung cancer using CT and MRI. MATERIALS AND METHODS: As part of the Radiologic Diagnostic Oncology Group (RDOG) study of lung cancer staging, the CT and MR examinations of 40 patients suspected of having non-small cell bronchogenic carcinoma were blindly interpreted by four expert observers. The primary tumor and lymph node stages in the 40 study subjects were similar to the final proportions reported in the RDOG study. Assessed abnormalities included the presence of a lung nodule, chest wall invasion, mediastinal invasion, bronchial involvement, lymph node metastasis in specific node stations, and T and N classifications. Percent agreement and kappa-values were calculated for each of these determinations. RESULTS: Depending on the finding assessed and the method of analysis, average agreement rates ranged from 58 to 90% for CT and from 61 to 96% for MRI. Average kappa-values were largely between 0.40 and 0.60 when dichotomous analysis was used; weighted kappa-values were similar. With a single exception, no significant differences were found for kappa-values calculated for CT and MRI. CONCLUSION: Although interobserver agreement rates are good for determining T and N classification in patients with lung cancer, variability in image interpretation is frequent, even among experienced observers.
Carcinoma, Bronchogenic↗
Bronchiolitis obliterans associated with rheumatoid arthritis: findings on HRCT and dynamic expiratory CT.
OBJECTIVE: To show the CT findings of bronchiolitis obliterans (BO) associated with rheumatoid arthritis. MATERIALS AND METHODS: We used high-resolution CT (HRCT) and dynamic expiratory cine CT to evaluate two patients with rheumatoid arthritis and a clinical diagnosis of BO. Both had pulmonary function tests to correlate with the radiographic findings. RESULTS: High-resolution CT showed bronchiectasis and mosaic perfusion in both patients. Expiratory CT showed multiple scattered areas of air trapping consistent with small airway obstruction. Imaging findings correlated with pulmonary function tests, which showed severe airway obstruction and inhomogeneous lung ventilation. CONCLUSION: Pulmonary HRCT and dynamic expiratory CT are useful in verifying the clinical diagnosis of BO in patients with rheumatoid arthritis, particularly those too unstable to undergo open lung biopsy.
Adult↗
Adult-onset disseminated tracheobronchial papillomatosis: CT features.
The high resolution CT (HRCT) findings in an adult with disseminated tracheobronchial papillomatosis are discussed. In addition to polypoid masses within the trachea and main bronchi, diffuse ill-defined parenchymal centrilobular opacities were present; these reflect lesions within the small airways. Some of the nodules showed central cavitation. In a patient with centrilobular opacities, some of which cavitate, on HRCT and concomitant endobronchial or endotracheal abnormality, disseminated papillomatosis should be considered in the differential diagnosis, particularly if there is a history of hoarseness or laryngeal disease.
Adult↗
Tree-in-bud pattern: frequency and significance on thin section CT.
PURPOSE: Our goal was to describe those diseases of the airways that manifest the tree-in-bud (TIB) pattern on CT scan and to establish a differential diagnosis for this CT scan finding. METHOD: We prospectively collected cases with the TIB pattern on CT and reviewed the scans of patients with histories pertaining to small airway disease. CT scans were performed at 1 to 3 mm collimation. RESULTS: Twenty-six of 27 cases with the TIB pattern had associated bronchiectasis or proximal airway wall thickening. One case with normal proximal airways had an acute aspiration. In addition, we reviewed 141 scans of patients with emphysema, respiratory bronchiolitis (RB), bronchiolitis obliterans (BO), bronchiolitis obliterans organizing pneumonia (BOOP), extrinsic allergic alveolitis (EAA), bronchiectasis, bronchitis, and pneumonia. Of the CT scans with bronchiectasis, 25.6% had TIB, and 17.6% of CT scans with acute infectious bronchitis or pneumonia had this pattern. None of the patients with emphysema, BO, BOOP, EAA, or RB had this pattern. CONCLUSION: The TIB pattern on CT scan is mostly associated with pulmonary infections that commonly involve the large airways. This pattern was present in 17.6% of cases with acute bronchitis or pneumonia and 25.6% of cases with bronchiectasis.
Adolescent↗
Helical CT for the evaluation of suspected acute pulmonary embolism: diagnostic pitfalls.
Helical CT is being increasingly utilized for the evaluation of suspected pulmonary embolism (PE). Proper scan interpretation depends on the awareness of several diagnostic pitfalls that may simulate PE, including normal bronchovascular structures such as pulmonary veins, bronchi, and lymph nodes, technical considerations such as improper bolus timing and streak artifacts, and patient-related factors such as motion artifacts, pulmonary arterial catheters, and vascular shunts. An understanding of these pitfalls facilitates accurate diagnosis.
Acute Disease↗
Hypersensitivity pneumonitis: patterns on high-resolution CT.
Hypersensitivity pneumonitis, also known as extrinsic allergic alveolitis, is caused by inhalation of specific environmental organic antigens. This disease may have typical high-resolution CT findings that, in the appropriate clinical setting, can be sufficiently characteristic to allow a confident diagnosis without the need for a lung biopsy. In this pictorial essay, the high-resolution CT patterns of hypersensitivity pneumonitis are illustrated. The authors emphasize the correlation among the radiologic presentation, functional abnormalities, and pathologic findings.
Adult↗
Minute pulmonary meningothelial-like nodules: thin-section CT appearance.
Minute pulmonary meningothelial-like nodules are often incidentally discovered during pathologic evaluation of pulmonary parenchymal specimens. These lesions were once thought to represent pulmonary chemodectomas, but pathological studies have shown that they are not of neuroendocrine origin. Minute pulmonary meningothelial-like nodules are benign, perhaps reactive in nature, but are occasionally found in association with lung carcinoma. They may appear as randomly distributed well-defined micronodules on thin-section chest CT, and thus may simulate metastatic disease when associated with lung carcinoma.
Adenocarcinoma↗
Image interpretation session: Sunday, November 26, 2000.
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Adolescent↗
Lung thermal volume as an indicator of pulmonary extravascular water.
Double-indicator dilution methods can be used for measurement of lung water. The thermal conductivity method is based on heat as a diffusible and conductivity as a non-diffusible indicator. In the present study we correlated lung thermal volume with gravimetrical measurement of extravascular lung water after thrombin-induced microembolization in dog lungs. The embolization was accompanied by significantly increased vascular permeability and accumulation of interstitial water. Under these conditions there was a close correlation between the two methods of measuring lung water (r = 0.78, p less than 0.01).
Animals↗
A prospective randomized trial comparing the silver-impregnated collagen cuff with the bedside tunneled subclavian catheter.
A prospective study was undertaken to compare the silver-impregnated collagen cuff (Vitacuff) with the bedside tunneled catheter. Fifty patients were randomly assigned to three groups: group I received triple-lumen catheters with Vitacuff application and a semiocclusive dressing material; group II received triple-lumen tunneled catheters with a semiocclusive dressing; and group III received triple-lumen tunneled catheters with collodion as a dressing material. In patients suspected of having central venous catheter sepsis, blood cultures were obtained through the catheter, the catheter was removed, and the tip was cultured semiquantitatively. Central venous catheter sepsis was defined as a positive catheter-tip culture and blood culture for the same organism. No catheter-related sepsis was seen in either the Vitacuff or the tunneled catheters with collodion dressing. In the tunneled catheters with semiocclusive dressing, there was one case of catheter-related sepsis and one case of insertion-site infection. There was also one insertion-site infection in the Vitacuff group, but there was no statistical difference in infection rates between the three groups.
Catheterization, Central Venous↗