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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 217 records · Page 12Linked to original sources
PubMed1990

Fat-saturation MR imaging of the upper abdomen.

The fat-saturation (fatsat) MR technique decreases the signal intensity of fat, thereby enhancing the definition of upper abdominal organs and reducing artifacts while maintaining the T1 and T2 information available on spin-echo sequences. To evaluate the potential of fatsat in examining the abdomen, we conducted a prospective study involving 30 subjects, including four normal volunteers, 18 patients investigated for liver disease, and eight patients studied for miscellaneous abdominal disease. Short TR, 300-600/15-20 (TR/TE), and long TR, 2000-2500/20-30, 70-80, spin-echo images with and without fatsat were compared. The images were evaluated both qualitatively and quantitatively. Qualitative assessment was made with receiver-operating-characteristic (ROC) curve analysis of the confidence level of observers to detect the presence of disease, comparing fatsat with standard spin-echo sequences. ROC analysis showed greater interpreter confidence and accuracy for fatsat sequences than for standard spin-echo sequences. The measured signal-difference-to-noise (SD/N) ratio comparing upper abdominal organs with surrounding tissue revealed the highest values for short TR/TE regular spin echo, followed by short TR/TE fatsat. The highest SD/N ratio for hepatic masses was with long TR/TE fatsat followed by short TR/TE fatsat. The results of this study suggest that the fatsat technique may improve abdominal MR imaging.

Abdomen↗
PubMed1990

[Three-dimensional analysis of the regional contractility of the normal and the cardiomyopathic left ventricle using cine-magnetic resonance imaging].

The left ventricular regional contractile pattern, global function and mass of normal subjects and patients with idiopathic dilated cardiomyopathy was compared using cine magnetic resonance imaging (MRI) in a short-axis imaging plane. Left ventricular ejection fraction and mass were 64.3 +/- 2.5% and 115 +/- 10 g in normal hearts and 23.5 +/- 3.1% and 194 +/- 20 g in dilated cardiomyopathic hearts (p less than 0.001 and p less than 0.002). Left ventricular end-diastolic wall thickness was homogeneous in normal hearts except for the posterior wall at the basal level, which was significantly thinner compared to the anterolateral wall and the septum (p less than 0.02). End-diastolic wall thickness in the cardiomyopathic group was significantly more heterogeneous and was thinner at the apical compared to the basal level (p less than 0.02) as well as in the segment of the posterior compared to the anterolateral and septal wall (p less than 0.005 and p less than 0.03). In normal hearts, left ventricular end-systolic wall thickness was progressively greater from base to apex for the anterolateral (p less than 0.01) and posterior wall (p less than 0.02) and the septum (p less than 0.02). Such a uniform gradient of end-systolic wall thickness was not present in hearts with dilated cardiomyopathy. It was even reversed for the anterolateral wall with decreasing thickness from base to apex (p less than 0.03). Left ventricular mean systolic wall thickening increased progressively from base to apex (p less than 0.005) in normal hearts, whereas there was no significant gradient from base to apex in hearts with dilated cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Reversibility of chronic alcohol cardiac depression: 31P magnetic resonance spectroscopy in hamsters.

In order to investigate the reversibility of chronic alcohol cardiac depression, hamsters were fed with 50% ethanol for 3 1/2 months, reaching serum alcohol levels of 0.13 +/- 0.11 g/dl (mean +/- SD). Alcohol was then withdrawn for 2 days. Isolated hearts were perfused according to a modified Langendorff method. Energy metabolites were studied using 31P magnetic resonance spectroscopy of isolated perfused hearts standardized by HPLC analysis of freeze-clamped tissue. Total intracellular calcium [Ca2+]i was measured with atomic absorption spectrophotometry, marking the extracellular space in vivo with K(CoEDTA). In alcohol-treated hamster hearts developed pressure was significantly depressed compared to controls. End-diastolic pressure was significantly increased. Coronary flow was not changed, whereas oxygen consumption and high-energy phosphate levels were significantly depressed. Intracellular pH was significantly decreased. [Ca2+]i was significantly increased. Heart weights were significantly lower. After alcohol withdrawal ventricular function, high-energy phosphate levels, and [Ca2+]i were not significantly different from control. The results indicate that chronic alcohol consumption depresses ventricular function and energy levels and also leads to myocardial acidosis. The increase in intracellular calcium likely causes mitochondrial dysfunction. Withdrawal of alcohol is associated with reversibility of functional and energetic cardiac depression.

Animals↗
PubMed1989

The effect of dobutamine on myocardial performance and high-energy phosphate metabolism at different stages of heart failure in cardiomyopathic hamsters: a 31P MRS study.

Dobutamine has been shown to exert disparate clinical effects in patients with cardiomyopathy and heart failure. This study evaluated the effects of dobutamine on hemodynamics and energetics in isolated, perfused myopathic hamster hearts at a moderate and advanced stage of heart failure. Biochemical changes were correlated with left ventricular developed pressure, coronary flow, and myocardial oxygen consumption. During dobutamine treatment left ventricular developed pressure increased in the control and moderate heart failure group 28.0 +/- 1.0% and 114.2 +/- 11.6%, respectively. Myocardial oxygen consumption increased 50.1 +/- 9.1% and 45.5 +/- 16.0%, respectively. There were no significant changes of left ventricular developed pressure and myocardial oxygen consumption in the advanced heart failure group. Inorganic phosphate (Pi) increased in the control group from 6.8 +/- 0.5 to 11.4 +/- 1.2 mmol (p less than 0.005) and in the advanced heart failure group from 10.4 +/- 1.1 to 15.3 +/- 1.2 mmol (p less than 0.01). Phosphocreatine (PCr) and beta-ATP (adenosine triphosphate) decreased in the control group from 12.2 +/- 0.4 to 8.7 +/- 0.7 mmol (p less than 0.001) and 10.4 +/- 0.8 to 7.7 +/- 0.7 mmol (p less than 0.02), respectively. PCr/Pi ratio, reflecting mitochondrial function, fell in the control and advanced heart failure group from 1.84 +/- 0.14 to 0.84 +/- 0.14 (p less than 0.02) and 0.81 +/- 0.16 to 0.37 +/- 0.08 (p less than 0.03), respectively. Thus in cardiomyopathic hamsters dobutamine improved mechanical performance and thermodynamic efficiency in moderate stages of heart failure by improving mitochondrial activity, but did not improve mechanical performance in an advanced stage of heart failure. These experiments provide into the disparate clinical effects of dobutamine at various stages of heart failure.

Adenosine Triphosphate↗
PubMed1989

Magnetic resonance imaging of congenital heart disease: sensitivity and specificity using receiver operating characteristic curve analysis.

MRI has shown promise for the evaluation of various congenital heart lesions. The current study was designed to assess the sensitivity and specificity of the technique for the evaluation of all major anatomic elements of the heart affected in simple and complex congenital heart disease. MR images of 51 patients (31 males and 20 females, ages 3 to 69 years) with a total of 110 congenital heart lesions were reviewed by a panel of two cardiac radiologists and one pediatric cardiologist, who assessed the cardiac pathoanatomy without knowledge of clinical details and assigned a confidence level to each diagnosis. The true diagnosis was established independently by the findings of angiocardiography and catheterization as well as by surgery, where applicable. ROC curves were generated from the responses, and the sensitivity at a specificity level of 90% was determined. MRI was shown to have a high sensitivity in evaluating great vessel relationships (100%), thoracic aorta abnormalities (94%), ASDs (91%) and VSDs (100%), visceroatrial situs (100%), and loop (100%). Three of five anomalies of the pulmonary and systemic veins were diagnosed by MRI. Right ventricular outflow obstructions (95%) were detected with a much higher sensitivity than lesions of the other valves (aortic valve 52%, mitral valve 62%, tricuspid valve 76%). Spin-echo MRI is a sensitive and specific method for the noninvasive assessment of congenital heart disease, with limitations in the evaluation of some valvular anomalies.

Adolescent↗
PubMed1989

Diagnostic accuracy and estimation of the severity of valvular regurgitation from the signal void on cine magnetic resonance images.

Anomalous blood flow caused by valvular regurgitation can be visualized as a narrowly defined area of signal loss in contrast to the high intensity of the blood pool on repetitive gradient refocused magnetic resonance (MRI) (cine MRI) views. In order to assess the accuracy of identification and measurements of the signal void in the evaluation of mitral (MR) and aortic regurgitation (AR), the cine MRI studies of 62 patients with regurgitation and of 20 normal volunteers were retrospectively analyzed in a blinded study of three independent reviewers. Accuracy for detection of MR was greater than 0.96 and for AR was greater than 0.91 for all three reviewers. The total volume of the signal void associated with regurgitation was measured on cine MRI images of 58 patients by two independent observers. The patients were divided into three groups of severity based upon assessment of severity of regurgitation by two-dimensional echocardiography and/or angiography. The total volume of signal loss was 9.0 ml (+/- 0.94 SEE; n = 18) for mild MR, 30.7 ml (+/- 5.3 SEE; n = 11) for moderate MR, and 83.4 ml (+/- 17.4 SEE; n = 5) for severe MR. In patients with AR, the calculated signal void was 27.3 ml (+/- 3.2 SEE; n = 24) in mild, 49.7 ml (+/- 2.9 SEE; n = 7) in moderate, and 75.8 ml (+/- 5.7; n = 6) in severe cases. The differences in the volume of the signal void were significant among the three groups of severity (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve Insufficiency↗
PubMed1989

Noninvasive evaluation of mitral regurgitation by analysis of left atrial signal loss in cine magnetic resonance.

Magnetic resonance imaging that uses shallow flip angles, short repetition times, and gradient refocused echoes results in multiple images throughout the cardiac cycle in which the blood pool has high signal intensity. In cine magnetic resonance images, disturbed (high velocity) blood flow produces a loss of signal intensity within the intracavitary blood pool, which makes this technique potentially useful for evaluating valvular disease. Multilevel cine magnetic resonance imaging was performed in 26 patients with mitral regurgitation (MR) documented and graded for severity by Doppler echocardiography or contrast ventriculography. Intracavitary left atrial signal intensity was analyzed in order to derive parameters that reflect the severity of the lesion. Seven normal volunteers were studied for comparison. All regurgitant lesions were visualized in cine magnetic resonance images as discrete regions of systolic signal loss extending from the mitral valve into the left atrium. The extent and degree of signal loss correlated well with severity. In patients with mild MR, signal loss was seen in 3.3 +/- 1.2 (+/- SD) anatomic levels compared to 4.9 +/- 1.4 levels in patients with moderate MR (p = NS), and in 7.0 +/- 1.4 levels in patients with severe MR (p less than 0.001 versus mild MR). The total area of maximal systolic left atrial signal loss seen in all levels was 10 +/- 6 cm2 in mild versus 31 +/- 17 cm2 in moderate (p less than 0.001) and 96 +/- 30 cm2 in severe MR (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Noninvasive evaluation of global left ventricular function with use of cine nuclear magnetic resonance.

Previous reports have validated the accuracy of nuclear magnetic resonance (NMR) imaging for quantitating ventricular volumes and myocardial mass. In this study, a new rapid NMR imaging method, cine NMR imaging, was used to compare left ventricular volumes determined from the transverse plane and short-axis plane in healthy volunteers and patients with dilated cardiomyopathy. With use of the short-axis plane, left ventricular mass at end-systole and end-diastole were determined and left ventricular systolic wall thickening at three different levels was assessed. For validation in the current study, cine NMR imaging and two-dimensional echocardiographic measurements of left ventricular volumes were correlated. Left ventricular volumes of the normal volunteers (end-systolic volume = 34 +/- 3.8 ml, end-diastolic volume = 90.4 +/- 7.2 ml) and patients with cardiomyopathy (end-systolic volume = 173 +/- 28.3 ml, end-diastolic volume = 219.5 +/- 29.6 ml) obtained in the transverse plane were nearly identical to those obtained in the short-axis plane (normal volunteers, end-systolic volume = 30.3 +/- 3.5 ml, end-diastolic volume = 84.7 +/- 7.0 ml and patients with cardiomyopathy, end-systolic volume = 179.1 +/- 27.8 ml, end-diastolic volume = 227 +/- 30.9 ml) and correlated highly (r = 0.91) with volumes obtained by two-dimensional echocardiography. Assessment of left ventricular mass over a broad range using cine NMR imaging in a short-axis plane was identical at end-systole (normal volunteers, 117 +/- 10 g; patients with cardiomyopathy, 202 +/- 20 g) and end-diastole (normal volunteers, 115 +/- 10 g; patients with cardiomyopathy, 194 +/- 21 g).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Magnetic resonance imaging of acute myocardial ischemia using a manganese chelate, Mn-DPDP.

Nine adult rats underwent occlusion of the left coronary artery (LCA) to assess the ability of a manganese chelate of N, N'-Bis (pyridoxal-5-phosphate) ethylenediamine-N, N'-diacetic acid (Mn-DPDP), to delineate acute myocardial ischemia. Hemodynamic effects of the contrast medium were tested in the isolated rat heart. Gated transaxial images of the heart at the mid-ventricular level were obtained using a 2 Tesla magnet. A TE of 20 msec and a TR of 1 R-R interval (approximately 250 msec) were used. Images were taken prior to injection of 400 mumol/kg of Mn-DPDP, 2 minutes after injection, and then at 15 minute intervals for one hour. The time between LCA occlusion and injection of contrast averaged 95 minutes. The signal intensity (SI) of normal myocardium was increased by 125 +/- 9% immediately after injection, and did not significantly vary over one hour. SI of ischemic myocardium increased by only 16 +/- 14% immediately after injection, gradually rising to 44 +/- 13% after one hour. Visual discrimination between normal and ischemic myocardium was obtained throughout the study. The percent contrast between normal and ischemic myocardium was 47.2 +/- 6% at 2 minutes after injection, gradually decreasing to a final value of 31.3 +/- 4%. No hemodynamic effects were produced in the isolated heart using concentrations in the perfusate several-fold higher than those expected to be produced by the intravenous injection of 400 mumol/kg Mn-DPDP. Mn-DPDP shows the potential for delineation of the jeopardy area resulting from coronary occlusion for at least one hour after injection of the agent.

Animals↗
PubMed1989

Magnetic resonance spectroscopy of the heart. Overview of studies in animals and man.

Magnetic resonance spectroscopy (MRS) has been used effectively in the evaluation of cardiac physiology. Studies have been done at various levels of complexity extending from isolated hearts to man. Correlation of high-energy phosphate compounds with contractile function is achieved by simultaneous or immediate sequential measurement of ventricular contractile function and the phosphorus-31 MR spectra. Studies in isolated hearts have monitored the response to ischemia of normal and hypertrophic hearts and the preservation of myocardial function and high- energy phosphate stores by drugs administered prior to the ischemic event. Regional myocardial ischemia has been evaluated by simultaneous monitoring of myocardial regional segment length by sonomicrometry and regional myocardial 31P MRS in the intact heart of larger animal models. Function and metabolism have been assessed in man by the combined application of cine MRI and 31P MRS acquired with a surface coil.

Animals↗
PubMed1989

Magnetic resonance imaging of thoracic vascular disease.

Magnetic resonance imaging (MRI) appears to provide at least as much diagnostic information as angiography in the evaluation of acquired and congenital forms of disease of the great arteries. Since it can also be used to assess the tissues adjacent to the great arteries, MRI often provides a distinct diagnostic advantage over angiography. In addition, the recently introduced dynamic MRI techniques may provide valuable information regarding hemodynamic abnormalities associated with diseases of the thoracic aorta and the pulmonary arterial system.

Humans↗
PubMed1989

Magnetic resonance imaging of cardiac and paracardiac masses.

Magnetic resonance imaging (MRI) with ECG-gated acquisition displays the blood pool as a signal void and thereby provides high contrast differentiation between cardiovascular structures and soft-tissue masses. The role of MRI for the detection and definition of the extent of paracardiac and intracardiac masses is reviewed. The extension of mediastinal, lung, and upper abdominal tumors to the heart and pericardium is depicted favorably by MRI and this attribute is also demonstrated. It is anticipated that MRI will have an increasing role in the evaluation of primary and secondary masses of the heart and pericardium.

Electrocardiography↗
PubMed1989

Occlusive and reperfused myocardial infarcts: differentiation with Mn-DPDP--enhanced MR imaging.

To assess whether the administration of manganese N,N'-bis(pyridoxal-5-phosphate)ethylenediamine-N,N'-diacetic acid (DPDP) permits differentiation between occlusive and reperfused infarcts, the authors subjected rats to either 6 hours of left coronary artery occlusion (n = 13) or 2 hours of occlusion followed by 4 hours of reperfusion (n = 10) before magnetic resonance (MR) imaging. Electrocardiographic-gated T1-weighted images were obtained before and for 1 hour after injection of 400 mumol/kg of Mn-DPDP. On T1-weighted images obtained before injection of Mn-DPDP. no significant differences in signal intensity were observed between normal and infarcted regions. Use of Mn-DPDP permitted delineation of the area of infarction. The pattern of enhancement in the injured zone was different for occlusive and reperfused myocardial infarcts. In rats with occlusive infarcts, In rats with occlusive infarcts, three well-defined zones were seen. Epicardium and endocardium were enhanced, while the midmyocardial zone was hypointense. The midmyocardial signal intensity gradually increased during the 60 minutes after injection. In rats with reperfused infarcts, the injured area was uniformly and intensely enhanced. Histologic examination confirmed the presence and location of myocardial infarct. Mn-DPDP may improve the detection and delineation of acute myocardial infarcts, demonstrate perfusion of the infarct, and permit discrimination between reperfused and occlusive infarcts.

Animals↗
PubMed1989

Incorporation versus infection of retroperitoneal aortic grafts: MR imaging features.

The magnetic resonance (MR) imaging characteristics of normal aortic graft healing were compared with those of perigraft infection in 57 patients after aortic graft implantation. Thirty-three patients without postoperative complications underwent MR imaging in a 0.35-T unit 1 week after graft implantation, and 13 of those patients were reexamined 2-3 months after graft implantation. Twenty-four patients with clinically suspected perigraft infection underwent MR imaging 6 weeks to 18 years after graft implantation. Early normal postoperative changes were characterized by a perigraft collar of low to medium signal intensity on T1-weighted images and of high intensity on T2-weighted images in all 33 cases, consistent with perigraft fluid collection. In 10 of 13 patients reexamined 2-3 months postoperatively, the MR images demonstrated a collar of tissue consistent with perigraft fibrosis. In cases of clinical suspicion of retroperitoneal graft infection, MR imaging showed eccentric fluid collections of low to medium signal intensity on T1-weighted images and high intensity on T2-weighted images at more than 3 months after surgery. The MR findings were diagnostic of retroperitoneal perigraft infection in 17 of 20 patients shown to be infected at surgery. Retroperitoneal infection was correctly excluded on the basis of MR findings in four patients. Thus, MR imaging is an accurate imaging method for the diagnosis of aortic graft infection. In the early postoperative phase, resolving perigraft fluid cannot be differentiated from perigraft infection.

Adult↗