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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 361 records · Page 20Linked to original sources
PubMed1985

Cardiac transplantations in dogs: evaluation with MR.

To assess the potential of magnetic resonance (MR) imaging as an early predictor of cardiac transplant rejection, electrocardiogram-gated (ECG-gated) MR imaging was performed in 12 dogs with heterotopic cardiac transplants. Twenty-two examinations were performed in vivo, and ten postmortem examinations were performed immediately after the dogs were killed. Examinations were performed from 3 days to 14 weeks after transplantation. A 0.35-T superconducting magnet was used with the spin-echo pulse sequence. There was a significant increase (P less than .02 to P less than .001) in T2 relaxation times and intensity values for the transplanted hearts compared with native hearts at all time intervals after transplantation. T1 relaxation times of native and transplanted hearts showed no significant difference on the in vivo ECG-gated studies. However, T1 values calculated on post-mortem studies were significantly longer (P less than .005) in the transplanted compared with the native hearts. With longer pulse repetition and echo delay times, there was an increase in the contrast between the rejecting transplanted heart and the native heart. Thus, ECG-gated MR imaging using the spin-echo technique displays cardiac allograft rejection in vivo. The rejected myocardium in vivo is characterized by a prolonged T2 relaxation time.

Animals↗
PubMed1985

MR imaging of the aorta with three-dimensional vessel reconstruction: validation by angiography.

Longitudinal vascular structures are difficult to observe on the standard abdominal transaxial magnetic resonance (MR) image sections. To display the information in a three-dimensional reconstruction, an algorithm was written to identify blood flow in a series of transaxial MR sections and was applied to reconstructing images of the aorta and iliac arteries in 12 patients with aortic aneurysm, dissection, or aortoiliac atherosclerosis. Results were validated by angiography. In all patients, the outline of the flow channel in the reconstructed image followed closely the outline of the lumen on angiograms. In aortic dissection, the MR images showed the two lumens more completely than did the angiograms, and in atherosclerosis, sites of vascular stenosis were correctly identified on MR images. The technique is valuable in providing anatomic information as well as functional information on cross-sectional areas and relative flow velocities.

Aortic Dissection↗
PubMed1985

MR imaging of blood vessels using three-dimensional reconstruction: methodology.

Multisection, dual-echo magnetic resonance (MR) transaxial images of blood vessels contain both anatomic and qualitative information about flow. Even so, the images are produced as a series of two-dimensional tomographic sections from which full visualization of connected structures is difficult. A computer algorithm was developed that automatically detects flowing blood based on pixel intensity and calculated T2 and provides reconstructed views of vessels while analyzing and displaying flow characteristics. Images of abdominal vessels, aortic aneurysms, and the heart were encoded by flow and color to demonstrate depth. In addition, these data were reconstructed to derive a more accurate assessment of patency. With this technique, transaxial images can be used to analyze flow patterns, determine patent areas, and visualize all levels of vessels in a single image.

Blood Flow Velocity↗
PubMed1985

Regional myocardial dysfunction: evaluation of patients with prior myocardial infarction with fast CT.

A prototype ultrafast cine computed tomographic (CT) scanner, designed specifically for cardiac imaging, was used to evaluate a preliminary series of patients with prior myocardial infarction (n = 21) and a control group without coronary artery disease (n = 5). Multilevel 50-msec CT scan exposures were obtained during peripheral intravenous bolus injections of contrast medium. A comparison was made between cine-CT scans and standard left ventriculographic images in assessing segmental left ventricular motion. Results indicate that cine CT, performed at sufficiently rapid speeds (20 scans per second) to allow useful analysis of regional ventricular wall motion, can provide adequate image quality. Analysis of 110 segments revealed a good correlation (90.9%) between the two techniques in characterizing normal from abnormal regional wall motion. Cine CT, based on this initial study, demonstrates considerable potential for evaluating not only cardiac chamber dimensions but also segmental wall dynamics.

Adult↗
PubMed1985

Detection and characterization of acute myocardial infarction in man with use of gated magnetic resonance.

To evaluate the capability of magnetic resonance imaging (MRI) in the detection and characterization of alterations in signal intensity and T2 relaxation time in acutely infarcted relative to normal myocardium 16 adult patients and normal volunteers were studied by electrocardiographically gated proton MRI. The seven volunteers were entirely asymptomatic and had no history of cardiovascular abnormality. The nine patients had each suffered an acute myocardial infarction within 5 to 12 days before the MRI studies. The diagnosis in each patient was confirmed by electrocardiographic (ECG) criteria and elevated levels of fractionated creatine kinase (CK) isoenzymes. Electrocardiographically gated MRI was performed with a superconducting system operating at 0.35 tesla. MRI demonstrated infarcted myocardium as a region of high signal intensity relative to that of adjacent normal myocardium; regions of high intensity corresponded anatomically to the site of infarction as defined by the ECG changes. The mean percent difference between normal and infarcted myocardium was substantially greater on 56 msec images (70.2 +/- 21.3%) compared with 28 msec images (27.1 +/- 13.6%). Region of interest analysis revealed that infarcted myocardium had a significantly (p less than .01) prolonged T2 relaxation time (mean T2 = 80.9 msec) relative to that in normal myocardium (mean T2 = 42.3 msec) and relative to the mean T2 of left ventricular myocardium in the volunteers (mean T2 = 42.4 msec). An additional finding for each patient with myocardial infarction was a high intraluminal flow signal on 56 msec images, but this was also observed in normal subjects and is therefore a nonspecific finding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Determination of left ventricular mass in dogs with rapid-acquisition cardiac computed tomographic scanning.

The development of left ventricular hypertrophy in patients with heart disease often has far-reaching clinical implications with respect to overall morbidity and mortality. Approaches used to assess left ventricular mass include electrocardiography, echocardiography, contrast ventriculography, single photon-emission tomography, and conventional computed tomography. However, all of these modalities suffer from some major draw back that precludes widespread application to all patients. In this study we assessed the accuracy of determinations of left ventricular mass in 22 dogs by rapid-acquisition (50 msec) computed axial tomography (RACAT), an ultrafast computed tomographic (CT) instrument. Electrocardiographically triggered, end-diastolic, short-axis cardiac scans were obtained from apex to base during administration of intravenous iodinated contrast. Myocardial edges were determined for each tomographic scan by two methods: the regional half-contour method (the CT density half way between that of the left ventricular myocardium and adjacent ventricular cavities or lung) and "interactive plateau thresholding" of the cardiac borders. Left ventricular mass by RACAT was calculated as the sum of the mass of each individual scan from apex to base (modified Simpson's rule). Postmortem left ventricular mass ranged from 58 to 160 g. The correlation between true left ventricular mass and tomographically determined mass was excellent (r = .99), with the slope and y intercept not statistically different from 1 and 0, respectively. The standard error of the estimate was 4.1 g. Interobserver and intraobserver variability for determining left ventricular mass demonstrated excellent agreement (r = .99 and r = .99, respectively). We conclude that quantitative assessment of left ventricular mass can be accurately and reproducibly performed in dogs by rapid acquisition CT scanning. It is likely that this technique will be readily transferable to the clinical settings and prove to be an important method for quantifying left ventricular mass in patients.

Animals↗
PubMed1985

Renal function in children after large dose contrast medium angiocardiography.

Serum creatinine and routine urinalysis were obtained and glomerular filtration rate estimated in 56 consecutive and hemodynamically stable children with congenital heart disease undergoing cardiac catheterization and angiocardiography, a day prior to, 1 and 7 days following the procedure. None had a history of renal disease. The patients were divided into 2 groups: Group I, 32 patients who received less than 3 ml/Kg of Renagrafin 60 and Group II, 24 patients who received greater than 3 ml/Kg. Despite a slight rise of creatinine on the first day, there were no statistically significant changes in serum creatinine or glomerular filtration rate for either group following the procedure. Occult blood was present in the urine of 2 in Group I and 1 in Group II prior to cardiac catheterization; this resolved in all cases after the procedure. Three patients in Group I and 1 in Group II developed transient trace proteinuria following the angiographic procedure. It is concluded that in children with congenital heart disease and normal kidney function, substantial doses of standard contrast medium administered during angiocardiography do not produce any apparent impairment of renal function.

Adolescent↗
PubMed1985

Magnetic resonance imaging in the evaluation of abscesses.

Ten patients with percutaneous biopsy or surgically proven abscesses were evaluated with magnetic resonance imaging (MRI) to describe the appearance of abscesses, define the capability of MRI to localize abscesses, and compare the capabilities of MRI and CT for the diagnosis and determination of the extent of an abscess. Comparative CT scans were available in six cases. The most common MRI finding was an abnormal area of low signal intensity, either homogeneous or heterogeneous, on the short repetition rate (500 msec TR) images with a relative increase in signal intensity on the longer repetition rate (1500 or 2000 msec TR) images. MRI demonstrated a more clear delineation of the extent of inflammatory changes than did CT, and MRI demonstrated the abscess as a collection distinct from surrounding structures on at least one repetition rate. Intravenous contrast medium was unnecessary with MRI to evaluate vasculature or to define the capsule around an abscess. With CT, unless an abscess contained air or was of low attenuation, it often blended with the surrounding structures and was difficult to differentiate from them. Surgical clips in the postoperative patient with an abscess did not degrade the MR images as often occurred with CT. This study describes the MRI appearance of abscess and indicates a potential value of the use of MRI to evaluate abscess outside the central nervous system and spine.

Abdomen↗
PubMed1985

Multiphasic cardiac magnetic resonance imaging: normal regional left ventricular wall thickening.

Magnetic resonance imaging (MRI) is a completely noninvasive method for visualizing cardiovascular anatomy but has had limited use for assessment of cardiac function. The authors evaluated the use of gated MRI for the quantification of regional myocardial contraction. Nine normal subjects underwent gated MRI of five transverse sections (7 mm thickness) through the left ventricle at five intervals in the cardiac cycle using a new technique called rotating gated sequence. All five sections were examined, and the section that best demonstrated the midportion of the left ventricle in its maximum dimension was used to obtain measurement. This technique permitted assessment of regional wall thickening of various regions of the left ventricle in different phases of the cardiac cycle. The extent and percentage of wall thickening were calculated from measurements of the septum and anterior and lateral left ventricular wall in end-diastole and end-systole. The calculated mean values for extent and percentage of wall thickening for the septum were 0.40 cm and 40%; for the anterior wall, 0.61 cm and 73%; and for the lateral wall, 0.53 cm and 57%, respectively. A limitation of the current technique in wall thickness measurements is that the transverse MR plane of section is not perpendicular to the long axis of the left ventricle. Consequently, such oblique sections through the left ventricle may give inaccurate absolute wall thickness measurements but can provide reliable estimate of regional wall thickening dynamics. The ability to define left ventricular wall thickness and function without contrast media provides a noninvasive technique for the detection of segmental left ventricular myocardial dysfunction in ischemic heart disease.

Adult↗
PubMed1985

Magnetic resonance imaging of developmental venous anomalies.

Magnetic resonance images (MRI) of nine subjects with a variety of developmental venous anomalies were studied retrospectively to assess the utility of MRI for determining the presence and type of venous abnormalities. Electrocardiogram-gated or nongated MR images were obtained in the transaxial, sagittal, and coronal planes. Venous anomalies detected with MRI were persistent left superior vena cava (three cases), total anomalous venous return (one), left inferior vena cava to left atrium (one), interrupted inferior vena cava with azygos (one) or hemiazygos (one) continuation, and retroaortic left renal vein (two). Congenital cardiac anomalies seen in conjunction with these defects were corrected transposition, coarctation of the thoracic aorta, complete transposition, and polysplenia with thoracic situs solitus and abdominal situs inversus. MRI clearly depicts developmental venous anomalies and associated congenital heart disease without the administration of contrast media, thus suggesting the potential of MRI as a noninvasive method for evaluating venous anomalies. Further experience is necessary to define the sensitivity and specificity of MRI in this regard.

Adolescent↗
PubMed1985

Pathologic blood flow in pulmonary vascular disease as shown by gated magnetic resonance imaging.

Axial, dual spin-echo magnetic resonance (MR) images, taken at the level of the pulmonary arteries and gated to the cardiac cycle, were qualitatively and quantitatively evaluated in nine patients with primary pulmonary arterial hypertension and six controls. In controls and patients, intravascular signal intensity was higher during diastole than during systole when fast flow conditions exist in the arteries; however, patients with severe pulmonary arterial hypertension showed significantly higher signals in the pulmonary arteries than did controls. A correlation between pulmonary vascular resistance and the MR signal in the right pulmonary artery in early systole (r = 0.89) showed the ability of MR images to provide information on blood flow and suggests a role for magnetic resonance in assessing the severity of this disease noninvasively. Flow-related cardiosynchronous variations in the lung parenchyma of controls were also observed; with further development, magnetic resonance may become useful to measure tissue perfusion and provide both pathoanatomic and pathophysiologic information. Furthermore, there was a significant difference between the MR signal intensity of dorsal and ventral lung regions.

Adolescent↗
PubMed1985

[Imaging of the heart using nuclear magnetic resonance tomography. I: Tomography].

Magnetic resonance (MR) is a new concept in the diagnostics of the cardiovascular system. The basic principle of MR is nuclear magnetism. MR tomography is based on induction and spatial encoding of a nuclear magnetic resonance signal. Due to the high tissue concentration and MR sensitivity, medical MR imaging chiefly uses protons of water, 1H. MR tomography of protons presents highly contrasted images of soft tissue organs with spatial resolution in millimeters. Parametric analysis of the MR signal enables quantitative assessments of physico-chemical tissue properties, blood flow and perfusion. The method is noninvasive and without serious biological side effects. Ionising radiation or traditional contrast agents are not utilized. Using conventional ECG synchronized MR tomography the cardiac and great vessels anatomy are superbly resolved, exceptions being the resolution of coronary vasculature and cardiac valve apparatus. The excellent spatial resolution and flexible spatial image orientation are important advantages of quantitative assessment of cardiac function by MR imaging. Preliminary studies demonstrated clinical utility of tomographic assessments of T1 and T2 relaxation parameters as well as phase angle analysis for definition of myocardial ischemia, blood flow rates and wall motion dynamics. The first comparative studies between imaging modalities in diagnostics of specific cardiac disorders point to a superior anatomic resolution of the heart and vascular morphology by MR tomography. The utilization of MR tomography in cardiovascular medicine is new and it would be premature to assign a definite value to this costly technique in clinical evaluations of patients with heart disease. However, there is unequivocal evidence that MR technology will play a decisive role in cardiology in the future, and MR imaging already represents significant progress in the evaluation of patients with cardiac disease.

Aortic Diseases↗
PubMed1985

Magnetic resonance imaging of acute myocardial infarction using a nitroxyl spin label (PCA).

The effects of an intravenously administered nitroxyl spin label (PCA) on the magnetic resonance imaging (MRI) appearance and relaxation times of acute canine myocardial infarctions were studied. Twenty-four hours after ligation of the left anterior descending coronary artery (LAD), animals were either sacrificed immediately (three dogs) or injected with 3.0 mmol/kg of PCA prior to sacrifice (six dogs). The PCA group dogs were sacrificed at either 5 minutes postinjection (three dogs) or 15 minutes postinjection (three dogs). Magnetic resonance imaging (0.35 T) using spin-echo techniques demonstrated high signal intensity in the infarct relative to normal myocardium in all three groups. In the control group, the T1 and T2 relaxation times were longer in infarcted compared with normal myocardium, but only the measure in T2 reached statistical significance (P less than .05). PCA produced infarct-avid T1 shortening in the six dogs that received it. Contrast in the group sacrificed at 15 minutes postcontrast administration was greater than that in the control group due to T1 shortening in the infarct. Thus, PCA produces differential effects on normal and infarcted myocardium. Between 5 and 15 minutes after IV administration, it causes greater changes in the infarct due to prolonged retention in this region.

Animals↗
PubMed1985

Magnetic resonance imaging of ischemic heart disease.

Magnetic resonance imaging (MRI) has several attributes important for evaluating ischemic heart disease. Internal cardiac anatomy is well delineated owing to inherent contrast between the blood pool and the cardiac walls. Using relaxation times and signal intensity differences, it is possible to discriminate between infarcted (acute and chronic) and normal myocardium. Gated MRI can also be used to quantitate regional myocardial infarction.

Coronary Disease↗
PubMed1984

Sensitivity and specificity of nuclear phase analysis versus ejection fraction in coronary artery disease.

Phase standard deviation (SD) and skew characteristics of the first Fourier harmonic of equilibrium radionuclide volume curves were examined and compared during rest and during supine bicycle exercise with ejection fraction (EF) changes and the development of ischemia in 17 control subjects and in 2 groups of patients (n = 57) with coronary artery disease (CAD). Group I comprised 37 patients with CAD; IA was a subgroup of 20 patients with previous myocardial infarction (MI) and IB a subgroup of 17 patients with CAD without MI (all with coronary stenosis greater than 75% diameter narrowing). Group II comprised 20 patients with CAD who had undergone coronary bypass surgery. In the Group I subjects, phase SD was the most sensitive indicator of CAD at rest (Group I, 56%; Group IA, 70%, and Group IB, 29%), and the EF was the most sensitive indicator at submaximal (Group I, 78%; Group IA, 86%, and Group IB, 64%) and maximal exercise (Group I, 70%; Group IA, 93%, and Group IB, 53%). When phase SD and skewness were combined with EF changes, little increase in sensitivity occurred in Group I (rest 61%, submaximal exercise 88% and maximal exercise 76%). The results from Group II subgroups were qualitatively similar to those observed with Group I subgroups. These data reveal a marginally improved sensitivity for detection of CAD during supine bicycle radionuclide ventriculography when phase measurements were added to changes in global EF values.

Adult↗
PubMed1984

In vivo assessment by computed tomography of the natural progression of infarct size, left ventricular muscle mass and function after acute myocardial infarction in the dog.

Quantification of myocardial infarct (MI) size is of prognostic importance in patients with acute ischemic damage. Evaluation of the efficacy of interventions for salvage of ischemic myocardium depends on the accurate estimation of the ischemic area and a knowledge of the natural progression of the infarct. Computerized transmission tomography (CTT) is a reliable in vivo technique for estimating infarct size. We serially studied 8 dogs over approximately 1 month after occlusion of the left anterior descending coronary artery using both ungated and prospectively electrocardiogram-gated CTT. Scans were obtained 20 minutes after occlusion and then several more times until the dogs were killed. Using the ungated CTT scans, infarct size increased from 0 to 4 days (+ 65 +/- 20%, mean +/- standard error of the mean, p less than 0.05), then progressively decreased. The initial perfusion defect overestimated the eventual MI size at 1 month by 33 +/- 15% (p less than 0.05). The MI size at necropsy correlated well (r = 0.98, p less than 0.001) with CTT MI size determined just before sacrifice. Non-infarcted left ventricular (LV) muscle mass increased significantly (27 +/- 7% greater at 1 month compared with day 0, p less than 0.01) over time, presumably representing compensatory LV hypertrophy. The LV muscle mass at necropsy correlated well (r = 0.94, p less than 0.001) with CTT LV muscle mass just before sacrifice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗