Search PubMed⌕ Search

Biomedical subjects

W R Webb

Publications and source records attributed to W R Webb.

At least 127 records · Page 7Linked to original sources
PubMed1986

Evaluation of a chest phantom for CT nodule densitometry.

The characteristics of a chest phantom used for CT nodule densitometry were determined by use of a GE CT 9800 scanner (General Electric, Milwaukee, WI). The supplied reference rods were scanned in different positions within the lung fields of the phantom and with varied chest wall thicknesses. The liver/spleen inserts were added. The CT attenuation values of different-size rods and their mineral content were also tested. The size of the standard rod is the major determinant of its CT number, which varied from 1 to 83 H. The standard rods contained no measurable calcium or other mineral. Position-dependent variability in CT numbers was relatively small with the GE CT 9800 scanner. The simulated chest wall additions and liver/spleen inserts produced only small increases in CT density. We conclude that the GE CT 9800 scanner, as an example of one of the newer CT scanners, shows improved operating characteristics for pulmonary nodule densitometry. Nodule densitometry should be further evaluated with simplified phantoms.

Densitometry↗
PubMed1986

Routine intraoperative cholangiogram.

The value of a routine intraoperative cholangiogram is controversial. We reviewed 352 consecutive instances of cholecystectomy for nonmalignant disease during a period of three years to assess the diagnostic accuracy and additional cost of the roentgenographic technique. Intraoperative cholangiogram was done in all except 11 patients. Forty-nine of 341 patients underwent exploration of the common bile duct. The diagnosis was determined by the cholangiogram and was correct in 46 patients with three false-positive results. The other 292 patients did well without exploration of the common bile duct. The cholangiocatheter and a special cholangioclamp made the procedure easy and minimized additional operation time (five minutes with no mortality and negligible morbidity). Clinical indications for exploration of the common bile duct correlated poorly with abnormal findings in the bile duct. Unsuspected common duct stones were detected by cholangiogram in 17 (5 per cent) patients. Possible iatrogenic trauma to the common duct was prevented when significant abnormal findings were demonstrated by cholangiogram. The results of this study indicate that routine intraoperative cholangiogram is: accurate for diagnosis of common bile duct stones; useful in identification of bile duct anomalies and, thus, aids in preventing injury to the common bile duct; safe with negligible risk, and neither expensive nor time consuming if done correctly as a routine procedure.

Adult↗
PubMed1986

MR characteristics of benign lymph node enlargement in sarcoidosis and Castleman's disease.

The magnetic resonance characteristics of mediastinal and hilar lymphadenopathy were reviewed in five patients with sarcoidosis and one with Castleman's disease. Although the T1 values of 26 nodes measured in patients with sarcoidosis ranged from 390 to 786 msec (mean 549 msec; SD 88 msec), the mean values recorded for each patient were quite similar (range 501-616 msec). T2 values ranged from 40 to 68 msec (mean 49 msec; SD 7 msec). In the patient with Castleman's disease T1 and T2 values measured 838 msec and 45 msec respectively. In comparison to T1 and T2 values we have recently measured in patients with proven mediastinal lymph node metastases from bronchogenic carcinoma, lymph nodes in the patients with sarcoidosis have significantly lower T1 (p less than .001) and T2 (p less than .05) values. However, because of significant overlap between the values recorded in these two groups, their differentiation may be difficult in individual cases.

Adult↗
PubMed1985

Coronary bypass surgery in patients with circulating lupus anticoagulant.

Clinical and laboratory experience with circulating lupus anticoagulant in 3 patients undergoing coronary artery bypass procedures is reported. This circulatory anticoagulant inhibits activation of prothrombin by the prothrombin activator complex (factor Xa, factor V, and phospholipid). The presence of lupus anticoagulant was initially detected because of a prolonged activated partial thromboplastin time and a normal or mildly prolonged prothrombin time. The 3 patients underwent uncomplicated coronary artery bypass grafting and experienced no abnormal bleeding postoperatively. The lupus anticoagulant is a rare cause of bleeding after open-heart surgery. It appears to be a problem only when an additional coagulation defect is present.

Adult↗
PubMed1985

Management of airway trauma. I: Tracheobronchial injuries.

One hundred six consecutive patients with injuries to the tracheobronchial tree who were admitted to the emergency room of the Tulane Medical Center Hospital or the Charity Hospital of Louisiana at New Orleans over a period of almost 20 years were analyzed retrospectively. Penetrating trauma of the neck or chest was reported in 100 of the patients, and only 6 had blunt trauma to the neck or thorax as the cause of injury. There were 18 deaths among the 106 patients (16.98%), including 11 (13.75%) of 80 with injuries of the cervical trachea. Seven (53.8%) of 13 with principal injuries of the thoracic trachea died; all 13 patients with major bronchial injuries survived. On admission to the emergency room, all patients had signs of airway compromise such as tachypnea, dyspnea, cyanosis, subcutaneous emphysema, or an abnormal respiratory pattern. Severe airway compromise was evident in 46 patients; 24 (23%) were treated with oral or nasal intubation, 19 (18%) with emergency tracheostomy, and 3 (2%) with intubation of a tracheal injury. Hemoptysis was an unreliable signal of serious injury, being present in only 28 of the patients. Patients who had major vascular injuries combined with trachea involvement were generally not salvageable. In regard to morbidity and mortality, the most common preventable errors were delay in diagnosis and treatment of tracheobronchial injuries, missed esophageal injuries, massive aspiration of blood, and abdominal vascular injuries.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Radiographic imaging of the pulmonary hila.

Evaluation of the pulmonary hila is an important but difficult aspect of chest radiology. The posteroanterior (PA) and lateral chest radiographs are useful in screening patients, but further evaluation of questionable abnormalities is often required. We review the strengths and weaknesses of each of the different imaging modalities used to assess the hila, including conventional tomograms, computed tomography (CT), and magnetic resonance imaging (MRI).

Bronchial Diseases↗
PubMed1985

Magnetic resonance imaging of the mediastinum, hila, and lungs.

Magnetic resonance imaging (MRI) takes advantage of physical properties of matter that are radically different from those that result in radiographic contrast, and therefore, has the potential to provide unique diagnostic information. During the last three years, the author's experience with MRI has suggested that this technique can be advantageous in evaluating some patients with chest disease. Although results to date remain somewhat preliminary, they serve to illustrate some of the strengths as well as weaknesses of this technique.

Blood Flow Velocity↗
PubMed1985

Differentiation of volume averaging and mass on magnetic resonance images of the mediastinum.

Volume averaging of high intensity mediastinal fat and low intensity flowing blood in mediastinal vessels can mimic a mediastinal mass on magnetic resonance (MR) images of the chest. However, when different repetition times (TR) are used to perform two imaging sequences, volume averaging can be distinguished from true disease, since the ratio of intensities of mediastinal fat, which is volume averaged, to nonvolume-averaged fat will remain relatively constant on a pair of images obtained using different TR times. Mediastinal masses, on the other hand, will exhibit predictable alterations in intensity relative to fat with changing TR.

Humans↗
PubMed1985

Pulmonary nodules: detection using magnetic resonance and computed tomography.

Detection of pulmonary nodules using spin-echo magnetic resonance (MR) imaging was compared with detection using computed tomography (CT). Of the 25 patients studied independently by two radiologists, no lung nodules were detected in 11 (CT or MR), ten had a single nodule, and four had multiple nodules. The lesions not seen using CT or MR were less than 1.3 cm in diameter. The greater spatial resolution of CT enabled better detection of nodules close to the diaphragm, the pleura, or to each other, whereas the better contrast resolution of MR enabled the detection of several nodules close to blood vessels. With MR, nodules were best seen on images with long repetition times (2.0 sec). Most pulmonary nodules are seen using both CT and MR. CT generally enables the detection of more small nodules than MR does, and some low-density nodules near blood vessels are better displayed using MR.

Adolescent↗
PubMed1985

Bronchogenic carcinoma: staging with MR compared with staging with CT and surgery.

Thirty-three patients suspected of having bronchogenic carcinoma were studied prospectively using magnetic resonance (MR). In this group, 30 underwent examination with computed tomography (CT), 15 underwent thoracotomy, six had mediastinal biopsy procedures performed, and eight underwent bronchoscopy. MR studies, which included transaxial spin-echo imaging (TR, 0.5 and 2.0 sec; TE, 28 and 56 msec) of all patients and sagittal or coronal imaging of 18, were performed without knowledge of CT findings, using only plain radiographs as a guide. CT and MR studies were interpreted separately. CT and MR provided comparable information regarding the presence and size of mediastinal lymph nodes. MR better discriminated mediastinal nodes from vascular structures. However, in two of 11 patients who had multiple mediastinal lymph nodes that were normal in size at CT examination and surgery, MR suggested a confluent abnormal mass, probably because of its poorer spatial resolution. MR was superior to CT in showing enlarged hilar lymph nodes, but CT was better for demonstrating bronchial abnormalities. In three of four patients who had a proved hilar mass with distal obstructive pneumonia, MR (TR, 2.0 sec) helped distinguish between the mass and collapsed lung.

Adult↗
PubMed1985

Paratracheal lymphadenopathy: radiographic findings and correlation with CT.

Possible signs of paratracheal lymphadenopathy on the posteroanterior (PA) chest radiograph were assessed in 98 patients and correlated with computed tomography (CT). The nodes were normal in size in 62 patients and enlarged (greater than 15 mm) in 36. Among the latter group, widening of the right paratracheal stripe was seen in 11 (31%) and enlargement of the azygos node in 15 (42%). While the lateral contour of the superior vena cava (SVC) was convex in 46 patients (47%), 81 (83%) had an increased density in the region of the SVC. When all four parameters were combined, lymphadenopathy could be detected on the PA view in 87 patients (89%). CT demonstrated that the enlarged nodes were anterolateral rather than directly lateral to the trachea and also immediately posterior to the SVC, explaining the findings on the PA radiograph.

Adolescent↗
PubMed1985

Subcarinal lymph node enlargement: radiographic findings and CT correlation.

Detection of subcarinal lymph node enlargement on the posteroanterior chest radiograph was assessed in 90 patients who also had computed tomography (CT). Sixty of the 90 patients had normal-sized and 30 had enlarged (greater than 15 mm diameter) subcarinal lymph nodes on CT. An abnormality in the contour of the azygoesophageal recess interface was present on plain radiographs in only 23% of patients with lymphadenopathy; increased subcarinal opacity was present in 40%. The external surface of the medial wall of the right main-stem bronchus and bronchus intermedius was visible in 87% of patients with normal-sized lymph nodes but in only 27% of patients with lymphadenopathy. CT showed that the medial wall of the right main-stem and intermediate bronchi normally is delineated laterally by air within the bronchus and medially by lung or subcarinal fat. Nonvisualization may be due to replacement of lung or fat by enlarged nodes or tumor and may be helpful in assessing patients with suspected subcarinal adenopathy.

Adult↗
PubMed1985

Magnetic resonance imaging of the superior pericardial recesses.

The potential of magnetic resonance imaging (MRI) of the superior pericardial space was evaluated in a retrospective review of MR images of 46 subjects. The superior pericardial space and its two recesses had low signal intensity. The preaortic recess was demonstrated on 82% of nongated transverse scans. The retroaortic recess was demonstrated on 67% of nongated transverse scans. Generally, both recesses were shown with an even higher frequency on ECG-gated and ECG-permutation-gated scans. Knowledge of the location and typical appearance of these pericardial recesses should preclude mistaking them on MRI for a vascular structure, aortic dissection, or an atherosclerotic plaque or mural thrombus within the ascending aorta.

Adolescent↗
PubMed1984

Early biochemical alterations induced by 2-acetylaminofluorene in rat liver.

Livers from rats fed the carcinogen 2-acetylaminofluorene (AAF) were analyzed at weekly or semiweekly intervals to correlate appearance of enzymatic markers in total liver homogenates with histochemical events accompanying formation of hyperplastic liver nodules. gamma-Glutamyltranspeptidase (gamma-GT)-positive foci appeared by day 11 and visible nodules were present by days 28-35. Specific activity of homogenate gamma-GT increased in parallel to formation of hyperplastic foci and nodules, declined and then rose again to 20-fold that of controls by day 77. Specific activity of ornithine decarboxylase increased in advance of that of gamma-GT, to a level of 8-fold above control during the period of formation of hyperplastic foci. An early response was a 2-fold rise in the specific activity of nucleoside diphosphate phosphatase during the first week of carcinogen administration. The specific activity of 5'-nucleotidase, known to increase during liver regeneration, declined as the animals aged and was not increased by the dietary AAF. The enzymatic alterations induced by AAF could not be mimicked by cell proliferation, diet stress or the hepatotoxicity induced by feeding 1.87% 4-acetamidophenol.

2-Acetylaminofluorene↗