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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 325 records · Page 18Linked to original sources
PubMed1986

The potential of magnetic resonance imaging for the evaluation of thoracic arterial diseases.

Fifty-three patients with a variety of thoracic aortic or pulmonary arterial diseases were evaluated by magnetic resonance imaging to determine the potential of this new technique for the diagnosis of thoracic vascular disease. Direct visualization of the atherosclerotic plaques and demonstration of their precise location and extent was achieved by magnetic resonance imaging. The size and extent of the aneurysms and the presence of mural thrombus were demonstrated by magnetic resonance imaging. Magnetic resonance imaging identified the intimal flap and indicated the proximal extent of thoracic aortic dissection. Magnetic resonance imaging permitted direct visualization of thrombi and aneurysm of the pulmonary arteries. In conclusion, magnetic resonance imaging appears to be a totally noninvasive and reliable technique for demonstration of various pathologic processes involving the thoracic aorta and pulmonary arteries. Vascular imaging is achieved without the need for contrast media.

Adolescent↗
PubMed1985

Magnetic resonance imaging in pulmonary arterial hypertension.

Magnetic resonance imaging (MRI) was used to examine the right ventricle and pulmonary arteries in 17 patients with pulmonary artery (PA) hypertension documented by cardiac catheterization. The study population consisted of 7 patients with primary pulmonary hypertension, 7 with Eisenmenger's syndrome and 3 with pulmonary hypertension secondary to lung disease. The MRI studies of patients were compared with those of 10 normal volunteers. Multislice gated transaxial images encompassed the right ventricle and central pulmonary arteries, showing the severity of right ventricular (RV) hypertrophy in proportion to the elevation of PA pressure and reversal of septal curvature when PA pressure approximated systemic pressure. End-diastolic RV wall thickness and mean pulmonary pressure correlated well (r = 0.79). MRI showed enlargement of PAs in all patients with PA hypertension. A magnetic resonance signal was present in the PAs throughout the cardiac cycle in patients with severe PA hypertension (more than 90 mm Hg) and was absent during systole in normal subjects. A signal within the PAs in systole is consistent with decreased flow velocity in patients with severe PA hypertension. MRI was useful in detecting each of the congenital anatomic defects in patients with Eisenmenger's syndrome. This study indicates the potential of MRI for evaluating the severity of PA hypertension by providing direct measurements of RV wall thickness and PA diameter and by detecting abnormal intraluminal signal intensity during the cardiac cycle.

Adolescent↗
PubMed1985

Measurement of cardiac output by cine computed tomography.

High-speed computed transmission tomography (cine CT) is a new noninvasive technique that may be useful for the rapid, accurate quantitation of cardiac function. The capability of cine CT to assess cardiac output was examined 10 mongrel dogs as an initial step in validating this method. After the dogs were anesthetized, femoral arterial pressure and pulmonary artery thermodilution catheters were inserted. After intravenous injection of a bolus of contrast medium, cine CT scans were performed in the flow mode, in which 50-ms scans were triggered electrocardiographically at end-diastole at 8 levels during sequential cardiac cycles. Scans and thermodilution measurements of cardiac output were obtained at rest and during altered hemodynamic states induced by separate infusions of dobutamine and phenylephrine. Time-density analysis was performed over the left ventricular cavity and curves were fitted to the CT flow data by gamma-variate analysis. Using the Stewart-Hamilton equation established for indicator dilution techniques, the cardiac output was calculated. The results established a direct linear correlation (r = 0.92) between cine CT cardiac output and thermodilution cardiac output over a wide range of cardiac outputs (1.5 to 6.3 liters/min). This study demonstrates that cine CT can provide a reliable estimate of cardiac output noninvasively using contrast medium as an indicator in dogs.

Cardiac Output↗
PubMed1985

Magnetic resonance imaging in hypertrophic cardiomyopathy.

Gated magnetic resonance imaging (MRI) was performed using a 0.35-Tesla cryogenic system in 14 patients with hypertrophic cardiomyopathy (HC) in order to define the site and extent of abnormal wall thickness. These studies were compared with 2-dimensional (2-D) echocardiograms. Gated magnetic resonance imaging studies in 12 normal volunteers were used for comparison. In normal subjects and in patients with HC, the sharp demarcation of the myocardial wall permitted measurement of wall thickness. The thickness of the septal and posterolateral walls in normal subjects was 10.2 +/- 0.4 mm (+/- standard deviation) and 10.8 +/- 0.5 mm, respectively, whereas septal thickness in all but 1 patient with HC was 15.0 mm or greater. In patients with HC, septal and posterolateral wall thickness were 2.2 +/- 0.8 cm and 1.3 +/- 0.17 cm, respectively, by MRI. The 2-D echocardiographic measurements for septal and posterolateral walls were 2.4 +/- 0.6 cm and 1.4 +/- 0.7 cm, respectively. The severity and distribution of abnormal wall thickness were comparable on 2-D echo and MRI. Gated MRI is an effective and completely noninvasive technique for demonstrating the presence, site and extent of abnormal wall thickness in HC. The large field of view, ability to image directly in multiple planes, and discrete blood-endocardial interfaces are advantages for cardiovascular imaging.

Adult↗
PubMed1985

In vivo assessment of left ventricular wall and chamber dynamics during transient myocardial ischemia using cine computed tomography.

Using a new computed tomographic (CT) scanner design that uses a rapidly moving focused electron beam, 50-ms CT scans were obtained at 2 axial levels simultaneously through the hearts of 6 dogs in order to analyze left ventricular (LV) wall thickness and cross-sectional chamber area after acute occlusion of the left anterior descending coronary artery (LAD). Ten or fifteen 50-ms CT scans (rate of 17 scans/s through the middle of the left ventricle were performed in 1 second (cine acquisition) during intravenous administration of contrast medium at rest, 60 seconds after acute occlusion of the LAD, and 60 seconds after release of the occlusion. The percent extent of systolic wall thickening of the potentially ischemic anterior segment was 37 +/- 15% (+/- standard deviation) in the control state and -5 +/- 6.5% during LAD occlusion (p less than 0.01). There was no significant difference in the percent change in LV luminal area from end-diastole to end-systole between the control state (50 +/- 19%) compared with LAD occlusion (47 +/- 21%). There were no significant differences in the extent of systolic wall thickening or LV luminal area between the control state and 60 seconds after release of occlusion. The alterations in regional myocardial function during acute ischemia are characterized by wall thinning during systole in the jeopardized segment and no significant change in global LV function. These features can be assessed by cine computed tomography during a solitary heart cycle.

Animals↗
PubMed1985

Magnetic resonance imaging of constrictive pericardial disease.

Gated magnetic resonance imaging of 5 patients with suspected constrictive pericardial disease was performed using a superconducting magnet operating at 0.35 Tesla. Results were compared with those of echocardiography and hemodynamic measurements in all patients, with chest films in 5, computerized tomography in 2 and with histologic findings in 3. Pericardial thickness exceeded 5 mm in 4 patients and was 5 mm in 1 patient. Absence of magnetic resonance signal from the thickened pericardium was observed with extensive calcific deposits, and increased intensity of the thickened pericardium was associated with inflammatory disease. Dilatation of the right atrium, venae cavae and hepatic veins, and right ventricular narrowing was observed in all patients. The ventricular septum was straight in all patients. Magnetic resonance imaging allows both measurement of pericardial thickness and depicts internal cardiac anatomy without exposure to radiation or use of contrast medium. Satisfactory imaging with a large field of view can be performed in the presence of lung disease, thoracic deformity or surgical "hardware"--conditions that limit echocardiography and computerized tomography. The inherently 3-dimensional data permit imaging in any plane without loss of resolution. Thus, magnetic resonance appears to be the noninvasive method of choice for the diagnosis of constrictive pericardial disease.

Calcinosis↗
PubMed1985

Magnetic resonance imaging of the heart.

Magnetic resonance imaging (MRI) is a completely noninvasive technique for the evaluation of the cardiovascular system. With a multi-section technique and the spin echo pulse sequence the entire heart can be examined within six to ten minutes. All our cardiac MR studies were performed with electrocardiographic (ECG) gating, to obtain adequate resolution of the cardiac structures. With this technique, patients and animals with a variety of cardiac abnormalities were studied. The examined pathologic conditions included acute and chronic myocardial infarctions and their complications, hypertrophic and congestive cardiomyopathies, congenital heart diseases and pericardial diseases. MRI offers an enormous potential for cardiovascular diagnosis, even beyond the demonstration of pathoanatomy, because of the capability for direct tissue characterization and blood flow measurements.

Animals↗
PubMed1985

Computed axial tomography of the heart.

CT scanning provides useful cardiac imaging but has not become a routine clinical tool for heart disease due to long exposure times (2-5 seconds) and the limitation of single slice acquisition. A revolutionary high speed (Cine) CT electron beam scanner was designed at UCSF, with multilevel millisecond scanning speed at rates of 17 scans per second. Table tilt and swivel permits direct imaging in various planes including the half axis view. Images can be analysed as closed loop movies, and quantitation of wall thickening, wall mass and ejection fractions are being validated. High resolution imaging without the need for gated acquisition is a significant advantage over nuclear medicine and magnetic resonance imaging, and physiology can be studied with exercise of other interventions. Fast CT can measure vessel blood flow and has great potential for estimating myocardial perfusion using indicator dilution theory and small peripheral intravenous injection of contrast medium. Cine CT could become the noninvasive modality of choice in cardiovascular diagnosis - the scanner has universal application for all organ systems.

Cineradiography↗
PubMed1985

Nuclear magnetic resonance analysis of acute myocardial infarction in dogs: the effects of transient coronary ischemia of varying duration and reperfusion on spin lattice relaxation times.

The purposes of this study were to evaluate the effects of acute myocardial ischemia with reperfusion on T1 (spin-lattice) nuclear magnetic resonance (NMR) relaxation times in a canine model and correlate these changes with bulk myocardial water content (%H2O). In 15 dogs the left anterior descending coronary artery was occluded for either 40 minutes (n = 5), 1 hour (n = 5), or 2 hours (n = 5). In 15 additional dogs, matched occlusion periods were followed by 3 hours of reperfusion. T1 of tissue from normal and ischemic myocardium was measured in vitro with a 2.5 kg NMR spectrometer. In the reperfusion animals, the 2-hour group showed significant increases in %H2O and T1 when the ischemic segment of myocardium was evaluated (both p less than 0.01). All but one animal in the 1-hour (reperfusion) group showed increases in both %H2O or T1 in the ischemic segment of myocardium when compared to control segments. The mean values from the ischemic myocardium in the 1-hour group were significantly higher than the values from the matched control segment for %H2O (p less than 0.05) and T1 (p less than 0.05). In the group undergoing 40 minutes of ischemia followed by 3 hours of reperfusion, neither %H2O nor T1 changed significantly. In the nonreperfused animals, neither T1 nor %H2O content increased significantly after 40 minutes. Significant increases were seen in the 1-hour (p less than 0.05) and 2-hour groups (without reperfusion) (p less than 0.01). In addition, the 2-hour occlusion followed by reperfusion animals had significantly greater T1 relaxation times and %H2O than control ischemic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Computed tomography of the heart: evaluation of anatomy and function.

Diseases of the heart and blood vessels represent one of the most challenging problems for advanced diagnostic imaging systems. Computed tomographic scanning is potentially an ideal cardiac imaging modality since it is a cross-sectional imaging method with very high resolution. Currently available computed tomographic scanners have exposure speeds of 1 to 5 seconds, which are inadequate for the majority of cardiovascular imaging applications. Nevertheless, a variety of limited computed tomographic scanning techniques have been successfully performed in selected patient subgroups. These methods require the administration of contrast medium injected or infused into a peripheral vein, combined with either dynamic computed tomographic scanning or some form of electrocardiographic gated computed tomography. The newer conventional computed tomographic scanners can display anatomic structures in the heart and great vessels with considerable fidelity and provide not only cross-sectional displays but also, by means of computer manipulation, any selected reconstructed images in oblique, coronal or sagittal projections. Feasibility studies indicate improved accuracy of computed tomographic measurements of cardiac chamber volumes. Physiologic measurements include estimation of shunt flows and cardiac output and analysis of myocardial wall thickening. The full potential of computed tomography should be reached once fast, multiple slice, computed tomographic scanners using scanning electron beam techniques become available. The prototype CVCT (cine computed tomographic C-100 scanner) designed at the University of California, San Francisco, is now undergoing evaluation. This instrument images up to eight contiguous slices at the rate of 16 to 24 images/s. The computed tomographic scanner specifically designed for cardiac imaging should extend the utility of computed tomography in the evaluation of cardiac diseases and the study of cardiovascular physiology.

Heart↗
PubMed1985

Assessment of cardiac anatomy using nuclear magnetic resonance imaging.

Nuclear magnetic resonance imaging has emerged in the past few years as a completely noninvasive method for medical imaging of internal organs. Because of the loss of signal intensity by motional nuclei (hydrogen) using most proton imaging techniques, flowing blood within the cardiovascular system generates little or no signal and consequently there is high natural contrast between blood and the walls of blood vessels or cardiac chambers. However, motion during imaging also complicates cardiac imaging because signal is lost from the nuclei in the moving cardiac structures. Consequently electrocardiographic gating of data acquisition is required for nuclear magnetic resonance imaging of the heart. Distinct advantages of nuclear magnetic resonance imaging in relation to other imaging modalities are good contrast between soft tissues and the capability for characterization of specific tissues by estimation of magnetic relaxation times. Early in vitro studies measuring relaxation times of myocardial tissue samples of excised hearts indicate that nuclear magnetic resonance imaging will be capable of discriminating infarcted from normal myocardium. Recent studies using electrocardiographically gated nuclear magnetic resonance imaging of dogs with acute infarction showed the infarct as a region of high intensity on spin-echo images. Initial clinical experience with electrocardiographically gated nuclear magnetic resonance imaging (0.35 tesla) in patients has clearly defined internal cardiac anatomy without the use of contrast media. This technique has demonstrated the consequence of previous myocardial infarction such as regional wall thinning, aneurysm, thrombus and contractile dysfunction, a number of pericardial abnormalities and the morphology of hypertrophic and congestive cardiomyopathies.

Coronary Circulation↗
PubMed1985

In vivo validation of the thermal-green dye technique for measuring extravascular lung water.

Assessment of extravascular lung water (EVLW) is imprecise in vivo, yet of both clinical and investigative relevance in patients with cardiac disease. Recently, a double-indicator method using thermal-green dye has been proposed as a nondestructive technique for in vivo quantification of EVLW. In our 5-yr study, indocyanine green dye was used as the intravascular indicator and heat as the diffusible indicator in 44 control dogs, 74 dogs administered intravenous oleic acid, 63 dogs in whom left atrial pressure was altered with a left atrial balloon, and 31 dogs with low-output cardiac failure (electrical shock and complete heart block). In these animals, in vivo measures of EVLW correlated closely with standard gravimetric techniques (r = 0.87, p less than .001), although the indicator dilution technique tended to underestimate actual lung water at higher volumes. In an additional 26 dogs, fluid (lactated Ringer's solution) was administered directly into a distal pulmonary airway, producing alveolar rather than interstitial edema. In these animals, as the infused volume was increased, the thermal technique underestimated consistently the actual amount of infused fluid. Nonetheless, we conclude that in most clinical and experimental situations where moderate changes in lung water are anticipated, this technique can provide reasonable estimates of extravascular fluid accumulation.

Animals↗