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Biomedical subjects

W Stanford

Publications and source records attributed to W Stanford.

At least 19 recordsLinked to original sources
PubMed1992

Ultrafast computed tomography in experimental pulmonary embolism.

Computed tomography (CT) has proven useful in the diagnosis of central pulmonary embolism; however, its ability to detect peripheral emboli has not been established. The authors evaluate the usefulness of ultrafast CT (UFCT) in detecting experimental peripheral pulmonary emboli. Three Gelfoam emboli measuring 0.7 x 1.5 cm were introduced into the pulmonary arteries of each of seven dogs, and contiguous, 3-mm, axial UFCT images from the lung apex to the base were obtained after the administration of a contrast bolus. After scanning, the dogs were killed, and the locations of the emboli were determined by a pulmonary pathologist blinded to the imaging results. Concomitantly, the locations of the emboli on the UFCT images were determined by consensus of three chest radiologists blinded to the autopsy results. All 21 emboli were identified on UFCT images; the locations of the emboli corresponded exactly with the autopsy findings. The authors conclude that UFCT can reliably detect Gelfoam emboli in second- to fourth-division pulmonary vessels. Further studies are needed to determine if in vivo blood clots can be similarly visualized.

Animals↗
PubMed1992

Cardiac anatomy instruction by ultrafast computed tomography versus cadaver dissection.

RATIONALE AND OBJECTIVES: This prospective study was designed to determine to what extent an ultrafast computed tomography (UFCT) videotape of the heart could enhance or substitute for cadaver dissection in teaching anatomy to first-year medical students. METHODS: A student population (n = 180) was randomized into four groups. Group 1 (control) received no instruction, group 2 viewed the videotape, group 3 participated in cardiac dissection, and group 4 performed cardiac dissection and viewed the videotape. After randomized instruction, each group was tested with 10 UFCT static cardiac images and 8 cardiac cadaver specimens. A different population consisting of nonrandomized fourth-year medical students also was tested. RESULTS: The results point to an interaction between instruction and the manner in which it was assessed. There was more carryover from the videotape-acquired knowledge to specimens than from dissection-acquired knowledge to UFCT images. CONCLUSIONS: Cardiac UFCT instruction resulted in dramatically improved image testing performance. This image-acquired knowledge was not sufficiently transferred to cardiac specimen identification; thus, videotape instruction should not replace dissection for teaching cardiac anatomy. Video provided instruction benefits beyond that gained through general clinical experience.

Audiovisual Aids↗
PubMed1992

Minimum scan speeds for suppression of motion artifacts in CT.

Cardiac and ventilatory motions cause artifacts at chest computed tomography (CT). To determine how short the scan times on third-generation units must be to avoid such artifacts, motion was measured with fast and ultrafast CT scans. Minimum detectable motion was then determined. The longest scan time that avoided a barely perceptible artifact was calculated by dividing the minimum detectable motion by the peak physiologic velocity. The posterior left ventricular wall moved at a maximum velocity of 52.5 mm/sec, necessitating a scan time of 19.1 msec or less to avoid artifact. Lung vessels near the heart moved at 40.5 mm/sec for a scan time of 24.7 msec or less. During quiet breathing, pulmonary vessels moved at 10.7 mm/sec for a scan time of 93.5 msec or less. The authors conclude that the shortest scan time on third-generation units (0.6 second) cannot prevent all artifacts arising from motion in the chest. Even ultrafast scan times (50 msec) are not short enough to eliminate artifacts on these units. Thus, reduction of motion artifacts will require techniques other than fast scanning.

Artifacts↗
PubMed1991

Fungal pulmonary infections after bone marrow transplantation: evaluation with radiography and CT.

The authors reviewed 55 pairs of chest radiographs and computed tomographic (CT) studies obtained in 33 febrile bone marrow transplant (BMT) recipients. The images were read separately, without knowledge of the clinical diagnosis. Twenty-one episodes of fungal infection were documented. One chest radiograph showed a pneumonia-like opacity, and 17 showed nodular opacities, five with cavitation. In 20 of 21 episodes, CT showed nodules with cavitation (n = 7), halo (n = 4), hazy margin (n = 5), air bronchogram (n = 2), cluster of fluffy nodules (n = 1), or sharp margin (n = 1). In none of the nine bacteremic episodes, however, were there opacities on chest radiographs or CT studies. CT studies demonstrating complicated nodules in febrile BMT patients strongly suggest a fungal infection, whereas negative CT studies suggest bacteremia or non-filamentous fungal infection of nonpulmonary origin. CT appears to add useful information to radiographic analysis during the assessment of febrile episodes in BMT patients, especially when invasive diagnostic procedures pose a high risk.

Adult↗
PubMed1991

High-resolution ultrafast chest CT in the clinical management of febrile bone marrow transplant patients with normal or nonspecific chest roentgenograms.

Plain chest roentgenograms may be normal or show nonspecific abnormalities during the frequent febrile episodes that occur in patients after bone marrow transplantation. In this group, ultrafast 10-mm and 3-mm high-resolution CT scans were prospectively performed in 33 patients to determine if useful information was provided that either changed the patient's clinical management or added confidence to the clinical diagnosis. The 36 symptomatic episodes that occurred in 33 patients included fever in 20 episodes and fever combined with cough, dyspnea, chest pain, or rales in 16. Fourteen chest roentgenograms were interpreted as normal, and 22 were interpreted as demonstrating nonspecific changes; however, none of the roentgenograms was considered helpful in that they did not provide sufficient information for further management. In 2 of 14 episodes in patients with normal chest roentgenograms and in 9 of 22 episodes in patients with nonspecific chest roentgenograms, CT scanning resulted in a change in clinical management that included performing bronchoscopy, increasing or changing antibiotic coverage, starting white blood cell transfusions, requesting surgical biopsy, or a combination of these. In 1 of 14 episodes in patients with normal chest roentgenograms and in 8 of 22 episodes in patients with nonspecific roentgenograms, CT added confidence to the diagnosis. In the remaining 16 episodes, CT scans provided no additional information. We conclude that in many instances, noncontrast ultrafast chest CT scans can provide information that may either change a patient's clinical management or more clearly establish the extent of pulmonary disease.

Adult↗
PubMed1991

The evaluation of coronary bypass graft patency: direct and indirect techniques other than coronary arteriography.

Patients having one or more coronary artery bypass graft operations constitute an important part of the practice of cardiac radiology. Bypass graft patency can be determined by indirect and direct methods. The indirect imaging methods include radionuclide ventriculography, thallium-201 scintigraphy, and positron emission tomography. The direct methods include conventional CT, ultrafast CT, MR imaging, digital subtraction angiography, and Doppler sonography. This review discusses the advantages and limitations of these methods and attempts to define the relative importance of each of these techniques in the evaluation of bypass graft patency.

Coronary Angiography↗
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↗