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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 271 records · Page 15Linked to original sources
PubMed1987

Evaluation of the right ventricle by magnetic resonance imaging.

The ability of magnetic resonance imaging to evaluate right ventricular architecture and size was assessed in 149 subjects (26 normal volunteers and 123 patients with heart disease). The right ventricular myocardium was clearly delineated from adjacent structures in all patients. The trabeculated pattern of the right ventricle was well seen and was most evident during systole and in patients with right ventricular hypertrophy. The moderator band was discernible in 72% of the subjects, whereas smaller muscular structures such as the papillary muscles were identified less frequently. Magnetic resonance imaging provided a good image of the tricuspid valve leaflets but did not show the pulmonic leaflets well. The clear visualization of the endocardial and epicardial borders obtained with magnetic resonance imaging allowed measurement of wall thickness and of the internal dimensions of the cavity in normal subjects, in patients with moderate to severe systolic overload, and in patients with moderate to severe diastolic overload. Patients with severe systolic overload of the right ventricle had markedly thicker walls when compared with patients without this condition. The mean internal dimension at end diastole of patients with severe diastolic overload of the right ventricle was significantly increased when compared to other subgroups. Magnetic resonance imaging provides tomographic images of the right ventricle with clear distinction of the endocardial and epicardial surfaces that can be useful for quantitative and qualitative assessment of this complex structure.

Adolescent↗
PubMed1987

Influence of heart rate on metabolic and hemodynamic parameters in the Syrian hamster cardiomyopathy.

The effect of varying heart rate in 155- to 170-day-old isolated, perfused cardiomyopathic Syrian hamster hearts was evaluated by 31P nuclear magnetic resonance spectroscopy. At a low paced heart rate of 170 bpm, cardiomyopathic hearts did not differ from normal hearts except for a lower developed left ventricular pressure. As pacing rate was increased progressively to 270/min, cardiomyopathic hearts showed prolongation of contraction, which led to a pronounced rise in diastolic pressure as the interstimulus interval shortened. This was accompanied by a marked decrease in energy-rich phosphorus compounds. By contrast, increasing heart rate in normal hearts did not change left ventricular pressure and caused only a mild reduction in energy-rich phosphorus compounds. Intracellular pH of cardiomyopathic animals paced at 270 bpm was significantly lower than in normal animals. Thus, indices reflecting mitochondrial function of 155- to 170-day-old cardiomyopathic hamsters appear adequate at low heart rate. Increasing the heart rate unmasks latent mitochondrial dysfunction.

Adenosine Triphosphate↗
PubMed1987

Gated acquisition of MR images of the thorax: advantages for the study of the hila and mediastinum.

Gated and nongated magnetic resonance (MR) scans of the chest were compared in five normal volunteers and 20 patients with chest disease to determine possible advantages of gated MR for delineation of noncardiac mediastinal anatomy. In order to compare gated and nongated images of the chest using similar imaging parameters, five spin-echo sequences were obtained in each of five normal volunteers: TR: 1000 msec, TE: 30 msec; gated to every heart beat (TR approximately 1000 msec, TE: 30 msec); TR: 2000 msec, TE: 30 msec; gated to every other heart beat (TR approximately 2000 msec), TE: 30 msec; TR: 500 msec, TE: 30 msec. In the 20 patients, the gated images were gated to every heart beat and the nongated images were obtained using a TR of 2000 msec, both with a TE of 30 msec. The noise in the periphery and in the center of the gated and nongated images at the level of the carina was compared in the five normal volunteers, using the signal intensity of the posterior chest wall as a control. There was 92% +/- 44% greater noise in the central region and 63% +/- 60% greater noise in the peripheral region on the nongated studies (TR: 1000 msec), than on the studies gated to every heart beat. In three of the five volunteers, the measured noise was greater on the nongated long TR (2000 msec) images than on the images gated to every other heart beat. However, the mediastinal structures below the level of the aortic arch were much better defined on the gated images in all five subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Use of ultrafast computed tomography to quantitate regional myocardial perfusion: a preliminary report.

The purpose of this study was to assess the potential for rapid acquisition computed axial tomography (Imatron C-100) to quantify regional myocardial perfusion. Myocardial and left ventricular cavity contrast clearance curves were constructed after injecting nonionic contrast (1 ml/kg over 2 to 3 seconds) into the inferior vena cava of six anesthetized, closed chest dogs (n = 14). Independent myocardial perfusion measurements were obtained by coincident injection of radiolabeled microspheres into the left atrium during control, intermediate and maximal myocardial vasodilation with adenosine (0.5 to 1.0 mg/kg per min, intravenously, respectively). At each flow state, 40 serial short-axis scans of the left ventricle were taken near end-diastole at the midpapillary muscle level. Contrast clearance curves were generated and analyzed from the left ventricular cavity and posterior papillary muscle regions after excluding contrast recirculation and minimizing partial volume effects. The area under the curve (gamma variate function) was determined for a region of interest placed within the left ventricular cavity. Characteristics of contrast clearance data from the posterior papillary muscle region that were evaluated included the peak myocardial opacification, area under the contrast clearance curve and a contrast clearance time defined by the full width/half maximal extent of the clearance curve. Myocardial perfusion (microspheres) ranged from 35 to 450 ml/100 g per min (mean 167 +/- 125). Two flow algorithms derived from characteristics of the contrast clearance curves showed a good correlation with regional myocardial flow determined by microspheres: the ratio of the peak myocardial opacification from baseline to the area under the left ventricular cavity curve (r = 0.7, p less than 0.001, SEE = 44.4 ml/min), and the ratio of the left ventricular cavity to posterior papillary muscle curve areas divided by the full width/half maximal contrast transit time in the region of the posterior papillary muscle (r = 0.82, p less than 0.001, SEE = 52.2 ml/100 g per min). The form of these two flow algorithms was derived from classical indicator dilution theory. In conclusion, indices derived from these data correlated well with regional myocardial perfusion in the posterior papillary muscle region of the dog as assessed by microspheres. This approach offers promise for the quantitation of regional myocardial perfusion and myocardial flow reserve in patients.

Algorithms↗
PubMed1987

Measurement of ventricular volumes in the dog by nuclear magnetic resonance imaging.

Nuclear magnetic resonance (NMR) imaging is a new, noninvasive approach for imaging the cardiovascular system. Being a three-dimensional technique, NMR imaging has the capability of measuring volumes without the need for assumptions regarding ventricular geometry. In this study, the technique was validated in 19 excised dog hearts, filled with silicone-rubber, imaged using a multislice spin-echo sequence. The volume of the cavity in each slice was calculated from the number of pixels outlined for each slice multiplied by the pixel volume. Ventricular volumes measured by NMR imaging were highly correlated with cast volumes measured by water displacement: right ventricle (RV):RVNMR = 1.05 RVcast - 1.62; r = 0.99, SEE = 0.96 ml; left ventricle (LV):LVNMR = 0.98 LVcast + 0.35, r = 0.98, SEE = 1.48 ml. After validation in casts, NMR imaging volumes were measured in eight living dogs using a multiphasic gated technique to obtain images at 5, 105, 205, 305 and 405 ms after the QRS complex. Cardiac output (CO) and stroke volume (SV) measured by NMR imaging were significantly correlated with thermodilution (TD) measurements (CONMR = 0.63 COTD + 0.51 liters/min; r = 0.78, SEE = 0.57 liters/min; SVNMR = 0.67 SVTD + 1.95 ml; SEE = 5.58 ml). Right and left stroke volumes were closely related (LVSVNMR = 0.9 RVSVNMR + 1.75; r = 0.94, SEE = 4.32 ml), with the slope and intercept of the regression line showing no difference from 1 and 0, respectively. However, volumes determined by NMR imaging underestimated the thermodilution measurements, presumably reflecting the inability to obtain a true systolic image with the present sampling rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Magnetic resonance imaging evaluation of radiation-induced changes in experimentally implanted renal cell carcinoma.

The effect of radiation on the magnetic resonance imaging appearance and relaxation parameters of human renal cell tumors implanted in male white-Swiss athymic nude mice was evaluated. Twenty-three mice were treated with external beam radiation, receiving a total dose of 2,500 rads administered in a single treatment limited to subcutaneous tumor. Twenty-two tumor-bearing mice served as control animals. Experimental and control mice were studied with MRI at four (n = 9), seven (n = 20), 14 (n = 8), and 28 (n = 8) days following experimental radiotherapy. A 0.35 tesla superconductive MRI system was employed. Images were generated using spin-echo technique with repetition times (TR) of 500 and 2,000 ms and echo-delay times (TE) of 28 to 30 and 56 to 60. Relaxation time calculations were made on the basis of tumor signal-intensity measurements in assigned regions of interest. The MRI appearances and relaxation times of irradiated tumors that decreased in size following treatment, irradiated tumors that grew, and control tumors were similar, as were their histologic features. No statistically significant differences could be detected in relaxation times of the four experimental and four control groups. Statistical evaluation was performed using analysis of variance. Further investigation of MRIs potential in tissue characterization following radiotherapy is warranted, but evaluation of change in tumor dimensions remains the most reliable indicator of therapeutic response.

Animals↗
PubMed1987

Lactate accumulation in ischemic- and anoxic-isolated rat hearts assessed by H-1 spectroscopy.

Proton magnetic resonance (MR) spectroscopy with homonuclear editing was used to assess lactate accumulation in ischemic and anoxic hearts perfused according to the Langendorff method. An increase in the lactate signal was observed after 5 minutes of ischemia and after 10 to 20 minutes of anoxia. This study demonstrates that proton MR spectroscopy can be used to monitor the time course of MR-visible lactate levels in ischemic and anoxic isolated rat hearts.

Animals↗
PubMed1987

Atrial-level shunts: sensitivity and specificity of MR in diagnosis.

Gated transverse cardiac magnetic resonance (MR) images from 31 patients with proved atrial septal defect (ASD) and from 33 control subjects were reviewed retrospectively by a panel of cardiac radiologists. The panel, by consensus, determined the presence and the type of ASD and assigned a confidence level for each diagnosis. A total of 97% of ASDs were correctly identified at high levels of specificity (primum, 100%; secundum, 96%; common atrium, 100%). Sensitivity and specificity are illustrated by receiver operating characteristic curves. Pulmonary veins were demonstrated at rates exceeding those reported for echocardiography. Further, all cases of anomalous pulmonary venous connection proved by angiography were also demonstrated by MR. Thus, MR has high sensitivity and specificity in the diagnosis and location of atrial-level shunts and is at least as accurate as, and possibly more accurate than, traditional techniques for the diagnosis of anomalous pulmonary venous connection.

Adolescent↗
PubMed1987

Posttransplant renal rejection: comparison of quantitative scintigraphy, US, and MR imaging.

Accuracy of ultrasonography (US), quantitative scintigraphy, and magnetic resonance (MR) imaging in diagnosis of acute renal allograft rejection was studied in 46 patients who underwent renal biopsy. Thirty-three patients had acute rejection; six, cyclosporine nephrotoxicity, as shown by biopsy, clinical findings, and follow-up study; two, acute tubular necrosis; and five, normal biopsy findings and renal function. Accuracy in demonstrating rejection was 72% for US and 75% for scintigraphy, indicating no significant difference between the two. MR imaging was significantly more accurate, reaching a level of 98%. However, accuracy of MR in demonstrating acute tubular necrosis in a larger number of patients is not known, and its accuracy in indicating recurrent glomerulopathy or infectious disease has not been addressed. The definitive role of MR in evaluating posttransplant renal failure is currently not established, but because of its high sensitivity in detecting renal abnormality, MR can be used for cases when results of US or scintigraphy are equivocal or contradict clinical impressions or when biopsy cannot be performed for medical reasons.

Adult↗
PubMed1987

Hyperparathyroidism: comparison of MR imaging with radionuclide scanning.

Twenty-three patients with hyperparathyroidism were evaluated preoperatively with magnetic resonance (MR) imaging. Twenty patients also underwent thallium-201/technetium-99m scintigraphy. Of 22 patients with primary hyperparathyroidism, 12 had persistent or recurrent disease. One had secondary hyperparathyroidism due to end-stage renal disease. MR imaging allowed accurate localization of abnormal parathyroid glands in 64% evaluated prospectively and 82% evaluated retrospectively. Scintigraphy allowed localization of 60% evaluated prospectively and 70% retrospectively. The two imaging modalities together allowed detection of 68% evaluated prospectively and 91% retrospectively. MR imaging allowed detection of two of five mediastinal adenomas evaluated prospectively and four of five retrospectively. In patients who underwent both imaging studies, MR was more successful in those with previous neck surgery (73% evaluated prospectively and 91% retrospectively) than in those with no prior surgery (57% prospectively and 71% retrospectively). Scintigraphy allowed accurate localization in 64% evaluated prospectively and 64% retrospectively in patients with previous surgery versus 57% prospectively and 86% retrospectively in patients with no prior neck surgery. Four false-positive results were obtained with MR imaging and three with scintigraphy. MR imaging was useful for parathyroid localization in patients with hyperparathyroidism, particularly in patients requiring additional surgery.

Adult↗
PubMed1987

Measurement of right and left ventricular volumes in healthy individuals with cine MR imaging.

Cine magnetic resonance (MR) imaging is a new, rapid MR pulse sequence that acquires up to 32 images per cardiac cycle at up to four levels of the heart within 4 minutes. In this study, the whole heart was encompassed by contiguous 10-mm transverse sections. Ventricular volumes were calculated by adding luminal areas determined in each section at end-diastole and end-systole. The left ventricular volume index was 57 ml/m2 +/- 9 at end-diastole and 17 ml/m2 +/- 4 at end-systole. The right ventricular volume index was 63 ml/m2 +/- 9 at end-diastole and 22 ml/m2 +/- 6 at end-systole. The left to right ventricular stroke volume ratio was 0.97 +/- 0.06, which was not statistically different from the theoretically expected ratio of 1. Interobserver and intraobserver measurements were closely correlated. Volume measurements were validated with two-dimensional echocardiography in five volunteers. Cine MR imaging allows reproducible three-dimensional measurement of right and left ventricular volumes with short imaging time and good temporal resolution.

Adult↗
PubMed1987

Coronary artery bypass graft patency: noninvasive evaluation with MR imaging.

A noninvasive means of determining coronary artery bypass graft (CABG) patency in symptomatic patients would be an important clinical asset. The accuracy of magnetic resonance (MR) imaging was evaluated for this purpose. Multiphasic electrocardiographically gated MR imaging examinations were performed in 25 patients with a total of 72 grafts. Transverse images of the heart at ten anatomic levels were obtained at five or six phases of the cardiac cycle. The MR images were read blindly to determine CABG patency versus occlusion, and these results were compared with those of coronary angiography performed within 2 months before the MR imaging. MR imaging correctly disclosed 43 patent grafts and 13 occluded grafts (predictive accuracy, 78%). Patency and occlusion were incorrectly diagnosed from MR imaging findings in five and four CABGs, respectively. CABG status could not be determined in seven (10%) grafts because the grafts were visualized at only one anatomic level. Thus, the accuracy of a definitive MR imaging evaluation was 91% (43 of 47 grafts) for patency determination and 72% (13 of 18 grafts) for occlusion determination. MR imaging appears to be a useful method for the noninvasive evaluation of CABGs.

Adult↗
PubMed1987

Suspected intracardiac masses: evaluation with MR imaging.

Electrocardiographically gated magnetic resonance (MR) imaging was used to examine 34 patients believed or known to have intracardiac masses on the basis of results from two-dimensional (2D) echocardiography. Cardiac masses were confirmed in 15 patients on the basis of MR imaging results. In seven patients, MR imaging confirmed the absence of an intracardiac mass but demonstrated an anatomic variant or other abnormality that had been interpreted as a possible mass on the echocardiogram. In 12 patients, MR demonstrated neither an intracardiac mass nor an anatomic variant that was likely to have been misinterpreted as a mass on the echocardiogram. Clinical follow-up in these patients at 10 months to 2 years and repeat 2D echocardiography have not indicated a definite mass. In six patients tissue characterization of the mass with MR imaging added some specificity to the MR diagnosis. Thus, MR imaging can be used to verify intracardiac masses found on 2D echocardiograms and to exclude a mass as the cause of equivocal findings on 2D echocardiography.

Adolescent↗
PubMed1987

The preventive effect of verapamil on ethanol-induced cardiac depression: phosphorus-31 nuclear magnetic resonance and high-pressure liquid chromatographic studies of hamsters.

Alcoholic depression of left ventricular function was produced in normal hamsters by the administration of increasing concentrations of alcohol in drinking water (up to 50%) for 6 months. The result was assessed by phosphorus-31 nuclear magnetic resonance of isolated perfused hearts and high-pressure liquid chromatography of freeze-clamped tissues. Hemodynamic data and myocardial oxygen consumption were also monitored. Alcoholic hamsters had significantly higher inorganic phosphate and lower ATP levels, while maintaining normal intracellular pH, phosphocreatine, and creatine. Although coronary flow and oxygen consumption were maintained at normal levels, hamsters ingesting 50% ethanol had significantly lower left ventricular developed pressure and dP/dt. Treatment with verapamil during long-term ethanol consumption prevented the development of these metabolic and functional abnormalities. It is hypothesized that alcohol produces membrane abnormalities leading to adverse ion flux, and that these are largely prevented by concurrent administration of verapamil.

Adenosine Triphosphate↗
PubMed1987

Measurement of canine left ventricular mass by using MR imaging.

This study assessed the capability of ECG-gated MR imaging for quantitating left ventricular mass by means of signal intensity-based and geometric methods for measuring left ventricular mass of normal dogs and dogs with left ventricular hypertrophy. Mass was measured on transverse images encompassing the left ventricle during both diastole and late systole. Partial-volume errors were minimized by measuring the length of the left ventricle on a sagittal image and weighting the mass of end slices accordingly. The range of postmortem left ventricular mass was 61-100 g. The linear relationship between postmortem left ventricular mass and mass measured via MR images correlated closely when MR imaging measurements were done at either end diastole (r = .94) or late systole (r = .94). The standard errors of the estimate were 13.7 and 14.7 g for images gated to end diastole and late systole, respectively. Inter- and intraobserver reproducibility showed excellent agreement (r = .93 and r = .89 for end diastole and r = .99 and r = .93 for late systole, respectively). Thus, left ventricular mass can be quantified accurately and reproducibly over a wide range of masses by using ECG-gated MR imaging.

Animals↗
PubMed1987

Cine MR imaging: potential for the evaluation of cardiovascular function.

MR imaging is valuable in defining cardiac anatomy in a variety of cardiac abnormalities. However, evaluation of cardiac function by this technique has been limited by long imaging times and low temporal resolution. New, recently described pulse sequences shorten imaging time considerably and improve temporal resolution. This paper reports our early experience with cine MR imaging of the heart, a technique of gradient-recalled acquisition in the steady state (GRASS) that uses low flip angles and gradient-recalled echoes. Images were obtained in 36 subjects (14 normal volunteers and 22 patients with coronary artery or valvular heart disease) and displayed in a cinegraphic mode for assessment of cardiac function. The acquisition of 10 to 12 levels, covering the whole heart with up to 24 time frames per level, required a maximum imaging time of only 30 min. Because systole and diastole were readily identified, and the contrast between blood and surrounding structures was excellent, systolic wall thickening, wall motion, and motion of the cardiac valves were visualized easily. Regions of myocardial infarcts were clearly visible and characterized by lack of systolic wall thickening and/or diastolic wall thinning. Turbulence caused signal loss within the flowing blood, which usually had higher signal intensity than myocardium. Therefore, turbulent blood flow in valvular regurgitation and in valvular and subvalvular stenosis could be detected. Cine MR imaging is a promising new technique for the evaluation of myocardial and valvular function.

Adult↗
PubMed1987

Acute myocardial infarction: MR evaluation in 29 patients.

This study evaluated the ability of MR to identify and characterize the region of myocardial infarction in humans. Twenty-nine patients, all with ECG and enzyme rises consistent with an acute myocardial infarction, were studied by MR 3-17 days from the onset of acute chest pain. Four patients were excluded because of inability to acquire adequate MR studies. For comparison, 20 normal subjects were studied who also had gated MR examinations. The site of infarction was visualized in 23 patients as an area of high signal intensity in relation to the normal myocardium, a contrast that increased on the second-echo image. The regions of abnormal signal intensity corresponded to the anatomic site of infarction as defined by the ECG changes. The mean T2 relaxation time of the infarcted myocardium (79 +/- 22 msec) was significantly prolonged in comparison with the mean T2 (43.9 +/- 9 msec) of normal myocardium (p less than .01). The mean percentage of contrast (intensity difference) between normal and infarcted myocardium was much greater on the second-echo images (65.6 +/- 34.0%) than the first-echo images (27.5 +/- 18.7%). In the normal subjects there was no difference in T2 between the anterolateral (40.3 +/- 5.7 msec) and septal (39.5 +/- 7.4 msec) regions, and percentages of contrast between these two regions of myocardium on the first-echo (9.1 +/- 7.4%) and second-echo (15.0 +/- 13.3%) images were similar. Thus, MR can be used to directly visualize acute infarcts. However, it has several pitfalls, including the necessity to differentiate signal from slowly flowing blood in the ventricle, from increased signal from a region of infarction and artifactual variation of signal intensity in the myocardium due to respiratory motion or residual cardiac motion.

Adult↗