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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 397 records · Page 22Linked to original sources
PubMed1984

Acute myocardial ischemia: magnetic resonance contrast enhancement with gadolinium-DTPA.

Gadolinium-DTPA (Gd-DTPA) was used to improve the diagnostic utility of magnetic resonance (MR) in detecting early ischemia, before the onset of infarction. Following one minute of left anterior descending coronary artery occlusion, 9 dogs were intravenously injected with either 0.5 mM/kg of Gd-DTPA (6 dogs) or normal saline (3 dogs). One more minute was allowed for perfusion of injectate prior to cardiectomy and MR imaging of the ex situ heart. There was no visible difference in intensity or alterations in magnetic relaxation times between normal and ischemic myocardium in the control (saline-injected) animals. The Gd-DTPA-injected dogs had a well-defined segment of high intensity representing the ischemic myocardium in the anterior wall of the left ventricle, due to significant T2 relaxation rate enhancement in the adjacent normal myocardium. Both T1 and T2 were significantly (p less than 0.01) shortened in the normal myocardium of the Gd-DTPA animals, but relatively greater T2 relaxation rate enhancement resulted in reduced intensity of normal myocardium, thus increasing contrast with ischemic myocardium. As a result of the significant shortening of T1 and T2 in the normal myocardium relative to the ischemic myocardium, improved delineation of the ischemic segment could be obtained using calculated T1 and T2 images. It is concluded that Gd-DTPA has the potential to expand the sensitivity and diagnostic utility of MR in the study of occlusive coronary artery disease.

Animals↗
PubMed1984

Effect of gadolinium-DTPA on the magnetic relaxation times of normal and infarcted myocardium.

Acute myocardial infarctions were produced in 11 dogs by ligation of the left anterior descending coronary artery. Twenty-four hours after ligation, 0.35 millimoles per kilogram of Gd-DTPA was injected intravenously, followed by cardiectomy either 90 seconds (3 dogs) or 5 minutes (5 dogs) later. The remaining 3 dogs had cardiectomy without injection of Gd-DTPA at 24 hours after coronary occlusion. The 3 dogs that did not receive Gd-DTPA had longer T1 and T2 relaxation times in infarcted myocardium than in normal myocardium, as measured by a 10.7-MHz magnetic resonance (MR) spectrometer. The T1 and T2 relaxation times of normal myocardium at 90 seconds postinjection of Gd-DTPA were significantly shorter (p less than 0.05) than those of the normal myocardium of animals that did not receive Gd-DTPA. At five minutes postinjection, significantly (p less than 0.01) greater T1 shortening was exhibited in the infarcted myocardium compared with adjacent normal myocardium in the dogs injected with Gd-DTPA. Thus, Gd-DTPA has differential and time-varying effects on relaxation times of normal and infarcted myocardium.

Animals↗
PubMed1984

Magnetic resonance imaging of the lymph nodes: comparison with CT.

This retrospective study of 144 patients was made to (a) assess the potential of magnetic resonance (MR) for demonstrating lymph nodes using spin-echo technique, (b) compare the MR results with those of CT, and (c) determine the optimal pulse-sequence interval (TR) and echo-delay time (TE) for imaging lymph nodes. The reported CT findings on normal lymph nodes were compared with MR findings in 60 patients who underwent MR imaging of the neck (20 patients), chest (20 patients), abdomen (10 patients), and pelvis (10 patients) for conditions other than lymph node disease. The results showed that CT is presently better than MR for imaging neck and abdominal lymph nodes less than 13 mm in diameter. The ability of MR to demonstrate normal-size (less than 10 mm) lymph nodes in the chest was comparable to that of CT. In addition, MR scans of 84 patients with proven abnormal lymph nodes (8 neck, 49 chest, and 27 abdomen and pelvis) were assessed: in 72 patients, these nodes had also been imaged by CT. MR and CT gave similar results with abnormal lymph nodes (greater than 13 or 15 mm), but MR displayed these nodes better because of its excellent soft-tissue contrast resolution. MR can clearly differentiate abnormal lymph nodes from normal fat, muscle, vessels, adult thymus, thyroid, and diaphragmatic crura, as well as from primary tumor and lymphoceles. Optimal demonstration of lymph nodes with MR required two sequences: one with a short TR and one with a long TR and long TE. Preliminary results indicate that MR holds great promise for the demonstration of lymph nodes in every part of the body.

Adolescent↗
PubMed1984

Imaging and characterization of acute myocardial infarction in vivo by gated nuclear magnetic resonance.

Imaging by nuclear magnetic resonance (NMR) techniques has been shown to provide high-contrast resolution between soft tissues and characterization of normal and pathologic tissues by differences in magnetic relaxation times. The current study was designed to determine whether electrocardiogram (ECG)-gated NMR imaging of the canine heart in vivo could distinguish normal from infarcted myocardium without the use of intravenous paramagnetic contrast agents. Seven dogs were studied by ECG-gated NMR imaging in vivo (spin-echo technique) with a 0.35 Tesla superconducting magnet at 2 to 7 days after ligation of the left anterior descending coronary artery. In six of the seven dogs, signal intensity was increased in the anterior wall compared with the remainder of the left ventricle; this region of high signal intensity corresponded to the area of myocardial infarction demonstrated at postmortem examination. The signal intensity of the infarcted region was 66 +/- 27% greater than that of normal myocardium (p less than .01). The T2 (spin-spin) relaxation time was 69 +/- 3% longer in the infarcted myocardium as compared with normal myocardium (p less than .01). The NMR images from the seventh dog had uniform signal intensity throughout the myocardium of the left ventricle. An infarct was not evident on postmortem examination in this dog. Thus gated NMR imaging in vivo by the spin-echo technique displays acute myocardial infarctions as regions of high signal intensity without the use of contrast media. The infarct is characterized by a prolonged T2 relaxation time.

Animals↗
PubMed1984

Imaging by nuclear magnetic resonance in patients with chronic ischemic heart disease.

Cardiac anatomy was defined by gated nuclear magnetic resonance (NMR) imaging at a magnetic field strength of 3.5 kGauss in eight normal subjects and 10 patients with chronic myocardial infarctions. Multisectional imaging was performed with the spin-echo technique and encompassed most of the left ventricle in an imaging time of 5 to 12 min. In all subjects internal cardiac structure was well delineated without the use of any type of contrast medium. The myocardial wall-blood interface was sharply defined, resulting in visualization of trabeculations, papillary muscle, and chordal structures in both ventricles. In patients with ischemic heart disease, the extent of postinfarctional wall thinning, aneurysms, and mural thrombi were depicted on NMR images. Images obtained with the second spin-echo (delay time = 56 msec) demonstrated high signal intensity in regions of the left ventricular chamber adjacent to the site of aneurysms or infarctions; this finding suggested stasis of blood in a region of akinesis or dyskinesis. The results of this study show that gated NMR is feasible as a technique for imaging the human heart and is capable of demonstrating a variety of left ventricular abnormalities associated with chronic myocardial infarction. NMR is a completely noninvasive technique for clinical imaging of the cardiovascular system.

Adult↗
PubMed1984

Magnetic resonance imaging in patients with congenital heart disease.

Magnetic resonance imaging (MRI) was conducted with use of the spin-echo technique (0.35 Tesla) in 22 patients with a variety of congenital and cardiovascular anomalies and in 16 normal volunteers. Electrocardiographic (ECG) synchronization of the data acquisition produced transverse, parasagittal, and coronal tomograms that were used to define size and relationship of the great vessels and internal cardiac structures. MRI findings were corroborated by angiography and sector-scan echocardiography. In most patients the diagnosis had been established before the MRI study. MRI detected all of 11 abnormalities at the level of the great vessels, all of six atrial septal abnormalities, and 10 of 11 ventricular septal defects. Images of poor quality resulting from patient motion were obtained in the one instance in which a small ventricular septal defect was not imaged. Of two patients with Ebstein's anomaly, the displacement of the tricuspid leaflets was shown in one patient but was not evident in another. Complex anomalies such as double-outlet right ventricle, uncorrected L-transposition, single atrioventricular valve, single ventricle, and common ventricle were clearly shown by MRI. Initial experience with MRI has indicated the effectiveness of this technique for defining great vessel and internal cardiac anatomy in patients with congenital heart disease. This is accomplished without the use of contrast media and is thus a completely noninvasive technique for cardiovascular diagnosis.

Abnormalities, Multiple↗
PubMed1984

Hypoplastic pulmonary arteries and aorta with obstructive uropathy in 2 siblings.

Two sisters who presented with diffuse hypoplasia of pulmonary arteries, relative hypoplasia of ascending aorta, obstructive uropathy, bilateral ureteral reflux, and hydronephrosis, are described. The subsequent course was characterized by progressive and gradual onset of right heart failure, failure to thrive, chronic malabsorption and systemic hypertension. The syndrome which appears to be transmitted by autosomal recessive inheritance can possibly represent a generalized hypoplasia and growth failure of a part or the entire arterial system. Peripheral pulmonary stenosis can occur as an isolated lesion or in association with other congenital cardiac anomalies, as well as in rubella syndrome and the syndrome of supravalvular aortic stenosis. This communication reports two siblings with a hitherto unreported combination of hypoplastic pulmonary arteries, and aorta with identical genito-urinary tract abnormalities.

Abnormalities, Multiple↗
PubMed1984

Multiplane magnetic resonance imaging of the heart and major vessels: studies in normal volunteers.

The feasibility of magnetic resonance imaging for defining anatomy of internal cardiac structures and major blood vessels was assessed in 14 normal subjects. Both electrocardiogram-gated and standard spin-echo images were obtained. The R-R interval determined the pulse repetition times in gated sequences. Gated images provided better visualization of internal cardiac morphology and of upper mediastinal vessels than did nongated images. Trabecular detail and components of the mitral valve could be resolved. All segments of the left ventricular wall could be evaluated by combining axial, coronal, and sagittal images. Gated acquisition of magnetic resonance images did not increase imaging time; five transverse slices of the left ventricle were obtained in 6.0-8.5 min. The good image quality, ease of gated acquisition, large field of view, capability of direct imaging in multiple planes, and noninvasiveness of the technique suggest that it will be an important imaging method in cardiovascular disease.

Adult↗
PubMed1984

Progressive thoracic aortic dilatation after aortic valve replacement.

Aneurysms of the ascending aorta developed after aortic valve replacement for chronic aortic insufficiency in four cases. Two of the aneurysms were complicated by dissection; one patient died. Rheumatic disease has become a less common cause of pure aortic regurgitation, and a number of etiologies primarily involving the wall of the aorta are now recognized. Although appropriately timed aortic valve replacement can prevent the irreversible left ventricular depression associated with chronic aortic insufficiency, careful evaluation of the thoracic aorta on serial postoperative chest radiographs is warranted, because the underlying pathologic process may proceed in the aortic wall with eventual aneurysm formation.

Aged↗
PubMed1984

Heart size in newborn infants with birth asphyxia.

Cardiomegaly is believed to be an important and relatively common radiographic finding in infants asphyxiated at birth. However, the true incidence of cardiomegaly in such infants has not been previously assessed. Accordingly, heart size was estimated using the cardiothoracic ratio (CTR) in 67 consecutive neonates with birth asphyxia (Apgar score below 6 at 1 and 5 min). The average CTR on the first postnatal film was 52.8%, significantly higher than that of unasphyxiated infants published previously. Subsequent CTR values did not differ significantly from the initial value. Of the 67 patients studied, 13 (19%) had significant cardiomegaly (CTR more than 2 SD above normal). Of these, 10 had conditions other than asphyxia that probably contributed to the cardiomegaly observed. Although relative heart enlargement is common in asphyxiated infants, absolute cardiomegaly is relatively uncommon, and in such infants causes other than asphyxia should be sought.

Asphyxia Neonatorum↗
PubMed1984

Gated MRI of cardiac and paracardiac masses: initial experience.

Ten cardiac and paracardiac masses were studied with magnetic resonance imaging (MRI) to evaluate the utility of this new method for determining the nature, location, and extent of such masses. The masses were intramural lesions (two cases), left atrial thrombus (one case), pericardial cysts (three cases), and mediastinal masses deforming and displacing the left atrium (two cases). ECG-gated images were obtained in all patients. In each of nine cases, MRI determined the location of the mass as intracavitary, intramural, or paracardiac, without the need for exogenous contrast material. It excluded the clinical diagnosis of cardiac tumor in one case. A combination of multislice transaxial, coronal, and sagittal images established the extent of the masses and the degree of impingement on cardiac structures. This initial experience suggests that MRI can provide as much information as echocardiography, computed tomography, and angiography combined in the evaluation of cardiac and paracardiac masses.

Adolescent↗
PubMed1984

Magnetic resonance imaging with respiratory gating: techniques and advantages.

Respiratory motion is an important problem in magnetic resonance imaging (MRI) of the thorax and upper abdomen. This study assessed several approaches for practical respiratory gating. Methods of acquiring respiratory signals, gated sequencing methods, duration of examination, strategies for reducing examination time, diagnostic quality of gated images, and the influence of respiratory gating on relaxation time measurements were evaluated. Of three different devices for acquiring the respiratory signal, a belt containing a displacement transducer placed around the upper abdomen was found to be most effective and practical. Two pulse-gating modes were implemented, as well as a method for combining cardiac and respiratory gating. Gating methods were tested using phantoms and human volunteers. A spin-conditioned mode of respiratory gating was found to be superior to a more simply implemented triggered mode in which spin-echo (SE) sequencing was interrupted. The time penalty for respiratory gating is technique-dependent. Gated studies with uncontrolled tidal breathing took two to four times longer than nongated studies. When the time between respirations was voluntarily prolonged, gated studies could be only 30%-50% longer than nongated. The standard deviation of relaxation-time measurements for organs that are displaced during respirations was substantially reduced by respiratory gating. Gating acquisition without spin-conditioning gating. Respiratory gating is a practical and useful technique for improving the contrast and spatial resolution of SE images of the upper abdomen and chest. SE images produced with short repetition times were particularly improved by respiratory gating.

Humans↗
PubMed1984

Magnetic resonance imaging of aortic disease: preliminary results.

Fourteen patients with a variety of aortic diseases were evaluated with magnetic resonance imaging (MRI). These included abdominal aortic aneurysms (eight cases), aortoiliac aneurysm (one), thoracoabdominal aneurysm (one), aortic dissections (four), and Takayasu arteritis (one). The size and extent of aneurysms, the presence of thrombus or atherosclerotic debris, the relation to renal and iliac arteries, and the effect of aneurysms on adjacent structures were readily demonstrated by MRI. The size of the residual lumen in a variety of vascular diseases and abnormal blood flow patterns could be assessed. In aortic dissection, MRI permitted identification of intimal flaps and determination of the origin of aortic branches from either of two lumina. Thickening of the wall and luminal narrowing of the aorta and arch vessels in Takayasu arteritis were clearly defined. These early results indicated that MRI achieved precise and complete assessment of a number of aortic abnormalities without the administration of any type of contrast material. Thus, early experience suggests that an important application of MRI will be as a totally noninvasive and reliable method for evaluating aortic disease.

Adult↗
PubMed1984

Thallium scintigraphy in experimental toxic pulmonary edema: relationship to extravascular pulmonary fluid.

Pulmonary fluid volumes (PBV = lung blood volume; EVLW = extravascular lung water) were examined to define the effects of oleic acid injury and then to examine the relationship between edema formation and accumulation of pulmonary thallium. In six dogs, pulmonary fluid compartments were monitored during the induction of pulmonary injury by oleic acid (0.15 cc/kg i.v.). By 30 min after the injection, EVLW had doubled (p less than 0.01); it continued to increase slowly for 180 min, whereas PBV declined. In six anesthetized dogs, we made similar measurements in an identical preparation and compared pulmonary fluid volumes with pulmonary counts derived from sequential thallium (1-1.3 mCi) scintigrams obtained after the injection of oleic acid (0.12-0.15 ml/kg). Measures of EVLW and PBV were obtained sequentially along with thallium scintigrams. There was a linear relationship between EVLW and pulmonary counts alone, or when pulmonary counts were normalized to myocardial activity. We conclude that sequential thallium scintigrams provide useful information about the degree of change of EVLW over time in a model of noncardiogenic pulmonary edema.

Animals↗
PubMed1983

Comparison of digital intravenous ventriculography with direct left ventriculography for quantitation of left ventricular volumes and ejection fractions.

Digital images of the left ventricle obtained at 30 frames/second from continuous fluoroscopy after intravenous injection of contrast medium (digital intravenous ventriculography) were used to estimate left ventricular (LV) volumes and ejection fraction with use of several techniques for identifying the ventriculographic silhouette. The digital technique was compared with direct contrast left ventriculography in 26 patients undergoing diagnostic cardiac catheterization. End-diastolic and end-systolic volumes calculated from digital intravenous and direct left ventriculograms were obtained with use of a standard area-length formula. Both end-diastolic volume (EDV) (r = 0.88, y = 1.06x - 17.1 ml) and end-systolic volume (ESV) (r = 0.89, y = 0.96x + 0.43 ml) determined from digital intravenous ventriculography (mask mode images) correlated closely with those obtained by direct left ventriculography. Combining the EDV and ESV to define the relation between the 2 techniques yielded an even closer correlation (r = 0.96). There was also good correlation between the 2 techniques for measurement of ejection fraction (r = 0.81, standard error of the estimate 6.7%). Measurements from direct left ventriculography were frequently invalidated by ventricular arrhythmias during the time of opacification of the left ventricle; this was rarely the case for digital intravenous ventriculography. It is concluded that area-length estimates of LV volumes and ejection fraction can be accurately obtained from digital processing of fluoroscopic LV images after intravenous injection of contrast medium.

Arrhythmias, Cardiac↗