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Biomedical subjects

U Sechtem

Publications and source records attributed to U Sechtem.

At least 127 records · Page 7Linked to original sources
PubMed1989

[The value of nuclear cardiology procedures including nuclear magnetic resonance tomography in routine diagnosis].

Nuclear-cardiological diagnostic methods require close cooperation between cardiology and nuclear medicine groups. This review article summarizes the advantages (non-invasive, quantitative, effect of exercise) and the disadvantages (limited resolution, limited specificity, radiation exposure) of the methods. Methods used routinely in the clinic are radionuclide ventriculography and myocardial scintigraphy with Tl-201. The indications for and limitations of these methods are discussed. The important advantages of nuclear magnetic resonance imaging (MRI) are the large field of view which includes extra cardiac structures, choice of slice width and orientation, good resolution and the simultaneous evaluation of morphology, functional parameters, flow phenomena and some differentiation between tissues. Presently, MRI is indicated in problem cases, e.g., aortic aneurysm, dissecting aneurysm, constrictive pericarditis, cardiac and paracardiac tumors. MRI also provides useful complementary information in valvular regurgitation, congenital malformations, cardiomyopathies and intracavitary thrombi. However, magnetic resonance imaging is still under development so that its overall value in the diagnosis of cardiac diseases cannot yet be definitely assessed.

Gated Blood-Pool Imaging↗
PubMed1989

[Possibilities and limits of quantitative image analysis using magnetic resonance procedures].

Magnetic resonance imaging provides three-dimensional images of the heart with good spatial and temporal resolution. Therefore, right and left ventricular function can be assessed without assumptions regarding ventricular morphology. Depiction of intracardiac blood flow with gradient echo sequences permits estimation of the severity of valvular regurgitation. Using improved paramagnetic contrast media magnetic resonance imaging may be able to directly visualize regions of ischemic myocardium. Real-time imaging of the heart will be possible using echo planar techniques. Although quantification of cardiac parameters by MRI is still mainly a research tool, clinical applications will emerge in the near future.

Heart Diseases↗
PubMed1989

[Differentiation between dissection and a true aneurysm of the descending thoracic aorta using magnetic resonance tomography].

The case reviewed here demonstrates that magnetic resonance imaging in contrast to CT and i.v. DSA can differentiate between aortic dissection with partially thrombosed false lumen and a true aneurysm using the spin-echo and the gradient-echo technique. The gradient-echo technique was able to depict the moving intimal flap as well as the higher blood flow velocity in the true lumen.

Aged↗
PubMed1989

[Non-invasive diagnosis of atrial septal defects and anomalous pulmonary venous return using magnetic resonance tomography].

The present study was to evaluate the diagnostic information that may be obtained in patients with atrial septal defect (ASD) and/or with anomalous pulmonary venous return using spin echo and gradient echo magnetic resonance imaging (MRI). The interatrial septum and pulmonary veins were studied in 31 patients and in 16 healthy volunteers. In all patients cardiac anatomy and dilatation due to right-sided volume overload was well depicted. In 87% of the patients examined by spin echo technique and in 100% of the patients examined by gradient echo technique the defect was reliably documented. All cases of anomalous pulmonary venous return were shown. MRI diagnosis of ASD was improved by combined use of spin echo and gradient echo techniques. The new MRI sequence was particularly helpful in patients with small ASDs and anomalous pulmonary venous return.

Adolescent↗
PubMed1988

Functional evaluation of the heart with magnetic resonance imaging.

This review examines the capability of cine MRI for evaluation of cardiovascular function and shows early results in valvular, ischemic, and congenital heart disease. MR assessment of left and right ventricular volumes is independent of geometrical models; dimensional values have been defined for normal individuals. Noninvasive measurement of peak and end systolic pressure along with cine MR imaging can be used to calculate left ventricular meridional wall stress which can be used for monitoring of myocardial diseases and evaluation of therapeutic intervention. Cine MR may be more accurate than angiography for identifying regional LV dysfunction since it can measure wall thickening as well as inward wall motion. Regurgitant jets due to valvular lesions are readily seen and their characteristics may be used to define the severity of aortic or mitral regurgitation. Calculation of the regurgitant volume separates patients with mild, moderate, or severe disease. Likewise, the shunt flow across ventricular and atrial septal defects has been visualized in cine MR images and shunt flow calculated. Cine MRI serves as a three-dimensional imaging technique with high temporal resolution. It extends the capability of MRI in cardiac disease beyond the depiction of anatomy and renders a comprehensive cardiac imaging technique for quantitation of cardiac anatomy and function.

Aortic Valve Stenosis↗
PubMed1988

Nuclear magnetic resonance imaging of the heart.

NMR imaging is a noninvasive technique that has been shown to provide high-quality images of the heart. Due to the signal characteristics of flowing blood, inherent contrast between blood pool and myocardium is achieved without the use of contrast media. This paper briefly describes technical aspects of NMR imaging of the heart, normal cardiovascular anatomy, applications of the technique in patients with ischemic heart disease, and the potential of NMR imaging for functional studies in various forms of heart disease.

Coronary Disease↗
PubMed1988

Cardiac function by magnetic resonance imaging.

Gated magnetic resonance imaging of the heart displays cardiac structures with excellent resolution. This ability should be useful for assessment of cardiac physiology where acquisition of systolic and diastolic images is required. In this study, left ventricular ejection fraction was determined in 50 patients from oblique long axis views of the left ventricle using the area length formula. Angulated views were obtained by electronic gradient angulation. For comparison, all patients had monoplane angiocardiography in the RAO position. Forty-five patients were also studied by radionuclide ventriculography. Ejection fractions determined by MRI and angiocardiography were closely correlated (r = 0.90). Correlation between MRI and radionuclide ventriculography was also acceptable (r = 0.79). In addition to global left ventricular function, MR images provide information about regional wall motion. In order to acquire a three-dimensional set of images at various phases of the cardiac cycle, shorter imaging times are mandatory. A new imaging technique with potential for functional studies uses low flip angles, short repetition times and gradient refocused echoes. Up to 40 images can be obtained within one cardiac cycle. When displayed in a looped fashion, visual assessment of cardiac motion, intracardiac blood flow, and systolic wall thickening is possible. Potential advantages of functional studies by MRI are the concomitant acquisition of anatomical information and the three dimensional frame of reference.

Angiocardiography↗
PubMed1988

Mitral or aortic regurgitation: quantification of regurgitant volumes with cine MR imaging.

A new, rapid magnetic resonance (MR) imaging method, cine MR imaging, was used to determine the regurgitant fraction (RF) in patients with left-sided regurgitant lesions. Right and left ventricular stroke volumes were determined with cine MR imaging and a modified Simpson formula in ten healthy volunteers and 23 patients known to have either predominant mitral (n = 17) or aortic (n = 6) regurgitation. RFs evaluated at cine MR imaging were compared in healthy persons and patients with mild, moderate, or severe regurgitation demonstrated at angiography (n = 10) and Doppler echocardiography (n = 13). Cine MR imaging depicted regurgitant blood flow in all 29 regurgitant lesions in 23 patients as areas of low signal intensity within the regurgitant chamber. The RF was 4% +/- 7% in healthy subjects and 12% +/- 12% in those with mild, 35% +/- 14% in those with moderate, and 63% +/- 5% in those with severe regurgitation. The RFs determined by two observers were similar.

Adult↗
PubMed1988

[Noninvasive assessment of aortic and mitral valve insufficiencies with dynamic magnetic resonance tomography].

Dynamic magnetic resonance imaging (MRI) was performed in patients with aortic regurgitation (N = 14) and/or mitral regurgitation (N = 13), documented and graded for severity by angiography. Eight healthy persons were studied for comparison. Turbulent retrograde blood flow through incompetent valves causes signal loss of blood, thus permitting detection of the valvular defect. To determine the severity of regurgitation by dynamic MRI, several parameters were analyzed, including the number of slices with visible signal loss, the time course of the signal loss, and its maximal area and maximal volume. All regurgitant lesions were visualized in dynamic images. The area of signal loss correlated well with the angiographic severity of aortic and mitral regurgitation. A slightly better correlation was found for the volume of signal loss. Significant differences were also found for the other parameters. Analysis of the regurgitant jet, characterized by signal loss on dynamic MR images permits a semiquantitative assessment of the severity of regurgitant lesions of left-sided valves. Three-dimensional determination of the jet volume is a possible advantage of MRI compared to other noninvasive methods.

Adult↗
PubMed1988

[Left ventricular function and intra-cardiac blood flow: study using dynamic magnetic resonance tomography].

Cardiac function can be assessed using conventional spin-echo magnetic resonance imaging. However, long imaging times and poor temporal resolution have limited the clinical applicability of this technique. A new dynamic magnetic resonance pulse sequence avoids these shortcomings using lower flip angles, shorter repetition and echo times and gradient refocused echoes. The entire heart can thus be imaged with a temporal resolution of 60 ms within 20 min. Display of 15 images of the cardiac cycle in a movie loop allows excellent visual assessment of cardiac motion and intracardiac blood flow. Applications of this new technique include blood flow measurements, visualization of regurgitant or shunt blood flow in patients with valvular regurgitation or ventricular septal defect, assessment of regional wall thickening in patients with myocardial disease, and three-dimensional determination of ventricular and atrial volumes.

Blood Flow Velocity↗
PubMed1987

[Exercise electrocardiogram and coronary angiography after myocardial infarct].

In a prospective study the question was investigated whether the exercise ECG, in patients who had sustained a transmural myocardial infarction two to 36 months previously, provides information on perfusion of the ventricular myocardium (apart from infarct area); in other words, whether the coronary system can be assessed beyond the area of the "infarct vessel". Results obtained with the exercise ECG and coronary angiography were correlated for 81 patients with typical ECG sign of a previous anterior-wall (35) or posterior-wall infarct (46). In patients with an old posterior-wall infarct multiple-vessel disease was predicted with a 79.2% sensitivity, since ST segment depression in V3-V6 gave evidence of hemodynamically significant stenoses (stenosis of greater than 50% of vessel diameter). There was a 72.7% specificity. In patients with an old anterior-wall infarct any additional stenosis was predicted with a 78.6% sensitivity and 76.2% specificity. However, the high rate of multiple-vessel disease in symptomatic patients (63.0% after posterior-wall infarct, 62.5% after anterior-wall infarct), as well as the serious consequences of failure to miss potentially operable multiple-vessel disease in this at-risk group patients, reduce the value of this method for indicating the need of coronary angiography. In asymptomatic patients (frequency of multiple-vessel disease 36.8% after posterior-wall infarct, 21.1% after anterior-wall infarct), on the other hand, exercise ECG (predictive value of ST depression 71.4% after posterior-wall infarct, 50% after anterior-wall infarct) provides reasonable additional help in deciding whether coronary angiography is essential in at-risk patients.

Adult↗
PubMed1987

Regional left ventricular wall thickening by magnetic resonance imaging: evaluation in normal persons and patients with global and regional dysfunction.

Gated magnetic resonance imaging (MRI) provides excellent anatomic evaluation of the heart, but its capability for assessing cardiac physiology is less clear. Accordingly, regional left ventricular (LV) wall thickening was evaluated by multiphasic transverse images in 37 patients with a variety of myocardial diseases and in 9 normal subjects. Angiography and 2-dimensional echocardiography (2-D echo) were used for comparison. End-diastolic and end-systolic wall thickness, absolute systolic wall thickening and percent systolic wall thickening were determined in 7 regions. Mean systolic wall thickening in normal subjects was not significantly different among the regions. However, there was considerable individual variation in wall thickening, ranging from 18 to 100%. Patients with LV hypertrophy (n = 4), amyloid cardiomyopathy (n = 1), constrictive pericarditis (n = 5), and hypertrophic cardiomyopathy (n = 3) had absolute and percent systolic wall thickening within normal limits. Infarcted segments in patients with ischemic heart disease (n = 17) had reduced absolute and percent systolic wall thickening, often combined with diastolic wall thinning, whereas mean percent systolic wall thickening in adjacent normal myocardial regions was higher than in normal volunteers (p less than 0.001). In patients with coronary artery disease, MRI had a sensitivity and specificity of 93% in detecting regional wall motion abnormalities. Because sagittal images were not acquired, inferior wall motion abnormalities were not assessed by MRI due to parallel wall sectioning in transverse images.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomegaly↗
PubMed1987

Quantification of cardiac function by conventional and cine magnetic resonance imaging.

Magnetic resonance imaging (MRI) has been effective for depicting cardiac anatomy and is already established as a technique for the evaluation of some structural abnormalities of the heart and pericardium. With recent advances, MRI can now be used to quantitate cardiac function. Multiphasic ECG-gated spin-echo imaging has been used to quantitate right and left ventricular volumes and ejection fraction, left ventricular mass, and regional myocardial wall thickening. The new technique of cine MRI acquires frames during the cardiac cycle with a time resolution corresponding to 20 msec up to approximately 40 frames for an average cardiac cycle. This technique uses narrow flip angle (30 degrees) and gradient refocused echoes. Cine MRI has been used to measure ventricular volumes and ejection fraction and regional myocardial wall thickening. It is also sensitive to the detection of valvular regurgitation and can provide quantitation of regurgitant volume. This article reviews the current status of MRI for quantitating cardiac function.

Heart↗
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

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

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↗