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Biomedical subjects

W Stanford

Publications and source records attributed to W Stanford.

At least 91 records · Page 5Linked to original sources
PubMed1991

Evaluation of great heart vessels and pulmonary vasculature.

This year's literature relating to imaging of the great heart vessels was devoted primarily to measurements of aortic size and to comparisons of imaging modalities in evaluating aortic aneurysms, dissections, and coarctation. The imaging modalities compared were plain chest roentgenography, conventional CT, ultrafast CT, MR imaging, transcutaneous esophageal echocardiography, and Doppler echocardiography. The pulmonary vasculature literature dealt with MR imaging of pulmonary vessels and the estimations of pulmonary pressure using echocardiography and Doppler techniques.

Aorta, Thoracic↗
PubMed1991

Aortic valve replacement with pulmonary or aortic allografts.

Limited availability of aortic valve allografts suggests consideration of pulmonary valve allografts for aortic valve replacement (AVR). From 1987 through 1990, 20 patients underwent AVR with cryopreserved aortic allografts (group 1). Five patients underwent AVR with pulmonary allografts (group 2) because no aortic allografts of the appropriate size were available. Indications for AVR in group 1 were endocarditis in five patients, aortic insufficiency in six, and aortic stenosis in nine. Indications for AVR in group 2 were endocarditis in two patients and aortic insufficiency in three. In group 1 there was one operative death and two late deaths resulting from noncardiac causes. There were no operative or late deaths in group 2. Follow-up was complete (group 1: 1-32 months [mean, 14 months]; group 2: 1-24 months [mean, 13 months]). All surviving patients remain in New York Heart Association (NYHA) class I or II. Postoperative catheterization was performed in 21 of 24 surviving patients. All patients have been followed since hospitalization with serial studies that included computerized cine tomography of the chest and echocardiograms. No false aneurysms, stenoses, or clinically significant regurgitation have occurred, although one patient in group 2 showed 2+ insufficiency at catheterization. One group 1 patient required repeat AVR for recurrent endocarditis. There were no reoperations in group 2. Although longer-term follow-up with larger numbers of patients is necessary, it seems that operative and early postoperative results for AVR have been similar with aortic and pulmonary valve allografts. In selected patients AVR with pulmonary allografts may be appropriate to consider when properly sized aortic allografts are unavailable.

Adult↗
PubMed1991

Relative accuracy of three scintigraphic methods for determination of right ventricular ejection fraction: a correlative study with ultrafast computed tomography.

The accuracy of three scintigraphic methods for determination of right ventricular ejection fraction (RVEF) was tested in 29 patients using ultrafast computed tomography (UFCT) as the gold standard. RVEF measurements by the ECG-gated first-pass approach showed excellent correlation with the UFCT results (r = 0.96, y = 0.06 + 0.91x), while both the standard gated acquisition blood-pool imaging (r = 0.71, y = 0.14 + 0.59x) and the nongated first-pass curve approach (r = 0.63, y = 0.18 + 0.37x) significantly underestimated RVEF. The error can be ascribed to partial inclusion of the atrial activity in the region assigned to the right ventricle. The tricuspid valve plane was found to move by a distance equal to 9%-33% (mean = 20%) of the right ventricular long-axis between systole and diastole. This translational motion was more pronounced with higher EFs.

Adult↗
PubMed1990

Analysis of movement of intrathoracic neoplasms using ultrafast computerized tomography.

Twenty patients with intrathoracic neoplasms were evaluated with ultrafast (cine) computerized tomography to determine the contribution of tumor motion to geographic errors. The treatment portals were setup with conventional simulation techniques and then scanned with cine computerized tomography. Eight tomographic levels were studied, 10 images per level over 7 seconds time. Major geographic misses were detected in three patients (15%), and minor geographic misses in an additional three (15%). The greatest tumor movement was noted in lesions located adjacent to the heart or aorta or near the diaphragm. Five of six hilar lesions showed significant lateral motion (average = 9.2 mm) with cardiac contraction, and three of four lower lobe lesions showed significant craniocaudal movement with respiration. Mediastinal lesions moved an average of 8.7 mm laterally. Lesions in the upper lobes showed minimal movement (average = 2.2 mm), and tumors attached to the chest wall showed no measurable movement.

Cineradiography↗
PubMed1990

Ultrafast computed tomography in the diagnosis of aortic aneurysms and dissections.

UFCT, by virtue of its 50 to 400 millisecond acquisition times, 0.75 to 1.5 mm resolution, and excellent vascular opacification, provides a rapid, minimally invasive method for assessing aortic aneurysms and dissections. During a 3.5-year period, 50 patients with suspected thoracic, thoracoabdominal, and abdominal aortic aneurysms or dissections were evaluated using the Imatron C-100 UFCT scanner. Eighteen patients had thoracic or thoracoabdominal aneurysms. 17 had thoracic or thoracoabdominal dissections, 7 had abdominal aneurysms, and in 8 no aneurysms or dissections were found. In 23 of the 35 patients with thoracic or thoracoabdominal aneurysms or dissections, the UFCT findings accurately reflected the findings at aortography, surgery, or autopsy. There was one false-positive examination. The remaining 11 patients with UFCT findings of aneurysm or dissection were followed clinically. In the 7 patients with abdominal aneurysms, 4 were confirmed by angiography or surgery, and 3 were followed clinically. Of the 8 patients with negative UFCT examinations, 2 had subsequent angiography that failed to show an aneurysm, and 6 were followed from 6 to 30 months without developing findings suggestive of aneurysm. UFCT appears to be a useful, minimally invasive technique for detecting and following aortic aneurysms and dissections.

Adolescent↗
PubMed1990

Determinants of restrictive lung function in asbestos-induced pleural fibrosis.

We evaluated whether restrictive lung function among asbestos-exposed individuals with pleural fibrosis was caused by radiographically inapparent parenchymal inflammation and/or parenchymal fibrosis. All 24 study participants were sheet metal workers who were nonsmokers with normal parenchyma on posteroanterior chest radiograph. These subjects had either normal pleura (n = 7), circumscribed plaques (n = 9), or diffuse pleural thickening (n = 8). After controlling for age, years in the trade, and pack-years of smoking, we found that sheet metal workers with diffuse pleural thickening had a lower forced vital capacity (P less than 0.001), total lung capacity (P less than 0.01), and CO-diffusing capacity of the lung (P less than 0.05) than those with normal pleura. Similarly, sheet metal workers with circumscribed plaques were found to have a reduced forced vital capacity; however, because of the small number of study subjects, this difference (regression coefficient = -11.0) was only marginally significant (P = 0.06). Although circumscribed plaque and diffuse pleural thickening were both associated with a lymphocytic alveolitis and a higher prevalence of parenchymal fibrosis on high-resolution computerized tomography (HRCT) scan, neither a lymphocytic alveolitis nor the finding of parenchymal fibrosis on HRCT scan influenced the relationship between pleural fibrosis and restrictive lung function. We conclude that pleural fibrosis is associated with restrictive lung function and abnormally low diffusion that appears to be independent of our measures of parenchymal injury (chest X-ray, bronchoalveolar lavage, and HRCT scan).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Determination of right ventricular mass in humans and dogs with ultrafast cardiac computed tomography.

There is currently no clinical approach to precisely measure right ventricular (RV) mass. We postulated that the radiological mode of ultrafast computed tomography (CT) of 3-mm-thick slices with 0.7-mm resolution would allow sufficient resolution to accurately estimate RV mass. Using this radiological mode, we serially imaged the entire right ventricle from apex to base, gated to end diastole, and applied Simpson's rule to calculate mass of the RV free wall. Thirteen mongrel dogs (weight, 6-30 kg) were studied. The free wall mass of the right ventricle was in the range of 12.0-47.5 g and averaged 35.4 +/- 3.7 g (mean +/- SEE). The correlation between RV mass estimated by ultrafast CT and actual RV mass was r equaling 0.85, SEE equaling 5.5 g, slope equaling 0.99, and gamma intercept equaling -1.8. Intraobserver and interobserver variability (r = 0.99 and r = 0.99, respectively) was excellent with a standard deviation (SD) equal to 1.5 and 1.8, respectively. The effect of variable RV preload (right atrial pressure, -5 to +20 mm Hg) on accuracy of RV mass measurements produced minimal error (SD = 3.6 g) in RV mass measurements. Seven normal young healthy men were also studied. The free wall mass of the right ventricle was in the range of 48.3-67.4 g and averaged 54.6 +/- 2.8 g (mean +/- SEE). The left ventricular to right ventricular (LV:RV) ratio averaged 3.2 +/- 0.2:1. These results are in agreement with human autopsy data in healthy males reporting mean RV mass equal to 46 g and an LV:RV ratio equal to 3.4:1. Because imaging every 3-mm slice from apex to base requires two contrast injections, we determined the accuracy of RV mass measurements if only every fourth 3-mm slice with interpolation was used. RV mass measurements using every slice or every fourth slice with interpolation were excellent (dogs, r = 0.99; humans, r = 0.97). It is concluded that high resolution CT imaging (3-mm tomograms) allows accurate measurements of RV mass. It is possible to add this stop-action mode of ultrafast CT, to previous CT studies, using every fourth tomographic slice for mass determinations and only one additional contrast injection of 40-60 ml. This should permit the study of progression and regression of RV mass in patients with various diseases.

Animals↗
PubMed1990

Comparison of two-dimensional echocardiography and ultrafast cardiac computed tomography for evaluating intracardiac thrombi in cerebral ischemia.

Two-dimensional echocardiography has a high specificity for the detection of intracardiac thrombi, but technically difficult studies are often encountered. Ultrafast cardiac computed tomography may be useful in such cases. Using transthoracic two-dimensional echocardiography and ultrafast cardiac computed tomography, we studied 36 patients with cerebral ischemia; one patient had the studies performed on two occasions, making a total of 37 sets of studies. Technical difficulties occurred in 12 echocardiographic (32%) and two ultrafast cardiac computed tomographic (5%) studies. The two techniques agreed in 29 sets of studies (78%). Among the eight discrepant sets of studies, two-dimensional echocardiography was positive for a left ventricular thrombus while ultrafast cardiac computed tomography was negative in three and equivocal in one and echocardiography was equivocal while ultrafast cardiac computed tomography was negative in two and positive in one. In the latter case, a left ventricular thrombus was confirmed at autopsy. In the other discrepant set of studies echocardiography was negative while ultrafast cardiac computed tomography revealed a left atrial and appendage thrombus. Because of its ease of performance and safety, two-dimensional echocardiography is the appropriate initial screening test for left ventricular thrombus. Ultrafast cardiac computed tomography can provide additional information in patients with technically difficult or equivocal two-dimensional echocardiographic studies or patients with cardiac disorders predisposing to atrial thrombi formation.

Adult↗
PubMed1989

Ultrafast computed tomography in the diagnosis of cardiac disease.

Ultrafast computer tomography (CT) is one of the major new imaging modalities that has become available for the evaluation of patients with heart disease. With cine CT it is possible to obtain high resolution images of the heart at 58-ms intervals. The inplane resolution is 0.7 to 1.5 mm, and the slice thickness is 3 to 9 mm. Images require the intravenous injection of nonionic contrast agents to obtain quantitative information about cardiac function. Cine CT has thus far been used in 3 general areas that relate to the evaluation of patients with heart disease: evaluation of cardiac structure and function, evaluation of vein bypass graft patency and flow reserve, and measurements of regional myocardial perfusion. Because of the outstanding spatial resolution of the images, it is possible to obtain very precise information about cardiac structure and function. The weight of the left ventricle and right ventricular walls can be measured to +/- 5%, and the stroke volumes and end-diastolic volumes of all 4 cardiac chambers can also be measured with an accuracy of +/- 5%. With this technology it is possible to determine the magnitude of aortic regurgitation within +/- 5 to 8%. This modality has also proved useful in the diagnosis of surgically resectable left ventricular aneurysm and a multitude of other cardiac disorders that involve abnormalities in cardiac structure, including congenital heart defects, aortic aneurysms and constrictive pericarditis. These diagnostic procedures use the peripheral injection of usually about 100 ml of contrast media and can ordinarily be completed in less than 15 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1989

Patterns of regional diastolic function in the normal human left ventricle: an ultrafast computed tomographic study.

The detailed evaluation of regional diastolic filling at multiple ventricular levels in the normal human left ventricle has not previously been reported. Ultrafast computed tomography was used to characterize global and regional early diastolic filling in the left ventricle of 11 normal male volunteers. Regional early diastolic filling data from six distinct ventricular levels (apex to base) were fit to a third-order polynomial curve, and the peak rate of diastolic filling and time of peak filling were determined. Peak filling rate was 259 +/- 17 ml/s (+/- SEM) as a global average, where peak filling rate referenced to end-diastolic volume and stroke volume across the levels examined was 3.78 +/- 0.17 s-1 and 4.83 +/- 0.20 s-1, respectively. Average filling fraction was 39 +/- 1%, and time to peak filling from end-systole was 145 +/- 5 ms. Regional (tomographic) peak filling rates, except for the most apical level examined, were not statistically different across the ventricle. Filling fraction and time to peak filling were remarkably constant from one level to another. However, reference of regional peak filling rate to regional end-diastolic volume demonstrated significant nonuniformity from apex (120% of average for all levels) to base (87% of average for all levels). Peak filling rate referenced to tomographic stroke volume was less variable and not statistically different across the ventricle as a whole.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The radiology of right heart dysfunction: chest roentgenogram and computed tomography.

Alterations in the right heart silhouette resulting from chamber enlargement, pericardial disease, and juxtacardiac masses can be diagnosed by plain-film radiography. On the other hand, plain films rarely reveal intracardiac masses or right ventricular hypertrophy, and to suggest these disorders it may be necessary to rely on secondary signs such as pulmonary artery enlargement. In contrast, computed tomography will show both right ventricular hypertrophy and intracardiac masses and is therefore an important adjunct in evaluating right heart abnormalities.

Heart Diseases↗
PubMed1989

Obstructive sleep apnea: diagnosis with ultrafast CT.

Patients with sleep-disordered breathing often have physiologic and anatomic abnormalities of the upper airway that are demonstrable while awake. An ultrafast computed tomographic (CT) scanner was used to measure the oropharyngeal and nasopharyngeal cross-sectional areas of 11 patients with obstructive sleep apnea. Twenty-four healthy volunteers served as control subjects. The percentage of change in cross-sectional area during quiet tidal breathing was used as a measure of airway compliance. Compared with weight-matched control subjects, patients with obstructive sleep apnea had smaller oropharyngeal airways (40.4 vs 177.8 mm2) (P less than .001) and smaller nasopharyngeal airways (31.3 vs 134.2 mm2) (P less than .001). In addition, their oropharyngeal airways were significantly more compliant (75% vs 27%) (P less than .001). Patients with obstructive sleep apnea are characterized by a small, collapsible oropharyngeal airway and by nasopharyngeal airway narrowing. These abnormalities can cause sleep-disordered breathing. Ultrafast CT scanning allows rapid, noninvasive assessment of airway variables.

Adolescent↗
PubMed1988

Patellofemoral joint motion: evaluation by ultrafast computed tomography.

Patellofemoral maltracking is a recognized cause of peripatellar pain. Measurements of the patellofemoral relationships during active motion are not available, and clinicians currently rely on observation, palpation, and static radiographic images to evaluate the symptomatic patient. Ultrafast computed tomography (ultrafast CT) offers objective observations of the dynamic influences of muscle contraction on the patellofemoral joint as the knee is actively moved through a range of motion from 90 degrees flexion to full extension. This study reports our initial observations and establishes a range of normal values so that patients with a clinical suspicion of patellar maltracking may be evaluated.

Adult↗
PubMed1988

Sensitivity and specificity of assessing coronary bypass graft patency with ultrafast computed tomography: results of a multicenter study.

Because a significant number of all patients seen by cardiologists have had coronary bypass surgery, a relatively noninvasive method of assessing coronary bypass graft patency would be very helpful. Ultrafast computed tomography, by virtue of its rapid data acquisition time and reasonable spatial resolution, may be useful in this regard. To determine the sensitivity, specificity and predictive accuracy of this imaging modality as compared with cardiac catheterization, a multicenter study was undertaken. There were two parts to the study. Part I involved the evaluation of 179 grafts in 74 patients studied in the five participating centers between March 1985 and August 1986. Twenty-nine percent of these graft studies were found to be technically inadequate and were excluded before patency determinations began. The remaining group of 127 bypass grafts in 62 patients had studies adequate for interpretation. Fifty-one grafts were to the left anterior descending coronary artery or a diagonal branch, 37 to branches of the left circumflex artery and 28 to the right coronary artery or a posterior descending vessel; in addition, there were 11 internal mammary artery bypass grafts primarily into the left anterior descending or diagonal artery distribution. The sensitivity of detecting angiographically open grafts was 93.4%, the specificity of detecting angiographically closed grafts 88.9% and the predictive accuracy was 92.1%. A subsequent study (Part 2) was performed 9 months later to assess the ability to carry out technically adequate examinations. Of the 138 consecutive graft examinations (50 patients) included in this part of the study, 94.2% of the examinations were found to be technically adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Evaluation of coronary bypass graft patency by ultrafast computed tomography.

A noninvasive technique for determining bypass graft patency is greatly needed. To determine if bypass graft patency could be accurately assessed with ultrafast computed tomography (CT) following an intravenous contrast injection, ten patients with 21 coronary bypass grafts were studied. All patients had cardiac catheterization and ultrafast computed tomographic studies within one month of each other. The sensitivity of detecting angiographically open grafts with ultrafast CT was 94.1% (16/17), specificity of detecting angiographically closed grafts was 100% (4/4), and accuracy was 95.2% (20/21). These preliminary results in a small clinical series indicate that ultrafast CT may be a useful, minimally invasive technique for evaluating coronary bypass graft patency.

Contrast Media↗
PubMed1988

Coronary artery aneurysms due to Kawasaki disease: diagnosis with ultrafast CT.

Coronary artery aneurysms are the most serious complication of Kawasaki disease, and periodic screening examinations are necessary. Two-dimensional (2D) echocardiography represents the standard screening method; however, visualization of the distal coronary arteries is often limited. This report describes the complementary role of ultrafast computed tomography (CT) with 2D echocardiography in the evaluation of coronary artery aneurysms resulting from Kawasaki disease (mucocutaneous lymph node syndrome). Six pediatric patients with coronary aneurysms were examined with 2D echocardiography and ultrafast CT. Ten of 11 lesions were detected with ultrafast CT. The one missed coronary artery aneurysm was one of two contiguous aneurysms. Because of intersection thickness these two discrete aneurysms were interpreted as a solitary aneurysm. Ultrafast CT allowed detection of one aneurysm not initially visualized with echocardiography. In conclusion, ultrafast CT was found to be an effective complementary procedure with 2D echocardiography for noninvasively evaluating coronary artery aneurysms occurring as sequelae of Kawasaki disease.

Adolescent↗
PubMed1988

Effects of awake tidal breathing, swallowing, nasal breathing, oral breathing and the Müller and Valsalva maneuvers on the dimensions of the upper airway. Evaluation by ultrafast computerized tomography.

Determinations of the size and dynamics of the upper airway during respiration are important in individuals with sleep-related breathing disorders. Ultrafast computerized tomography can acquire eight 8-mm axial-slice thicknesses of the upper airway in 224 ms. If this sequence is acquired every 0.7 second over an entire respiratory cycle and played back in movie mode, the dynamic changes in the airway's size can be evaluated and measured. This report defines the size of the upper airway during normal tidal breathing and describes the changes that occur with swallowing, isolated nasal breathing, and isolated oral breathing and with the Müller and Valsalva maneuvers.

Adult↗