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Biomedical subjects

M Seiderer

Publications and source records attributed to M Seiderer.

At least 37 records · Page 2Linked to original sources
PubMed1986

Description of flow phenomena in magnetic resonance imaging.

The magnetic resonance (MR) signal from the hydrogen nuclei of blood is not only determined by the MR parameters T1, T2 and proton density, but is strongly dependent on the movement of the protons. Magnetic resonance imaging (MRI) offers therefore the possibility to visualize the distribution of moving spins, especially blood flow, noninvasively and without contrast agents; moreover, the velocity of the moving spins can be quantified. Flow phenomena in MRI are a pretentious field because the complicated hydrodynamics of the living system is coded in the MR signal; therefore, an understanding of the underlying physical principle of the MR signal is required to interpret and extract flow information from the image. However, rather simple theoretical and experimental models of fluid transport in vessels allow to explain the main features of various effects observed in images.

Blood Circulation↗
PubMed1986

[The contrast to noise ratio as a measure of tissue contrast in nuclear magnetic resonance tomography].

The contrast-to-noise ratio, known from the theory of imaging methods, is applied to magnetic resonance imaging. This ratio is proportional to the product of relative image contrast and the signal-to-noise ratio. After predetermining all intrinsic (T1 and T2 times, proton density) and extrinsic (pulse sequence, layer thickness, number of averagings) parameters, the signal-to-noise and contrast-to-noise ratio can be computed to a proportionality constant for all possible pulse sequences. Studies in six voluntary test subjects and 11 patients with a 0.35 T-unit showed that the measured values for the signal-to-noise ratio and the contrast-to-noise ratio are in good agreement with the computed values. The contrast between gray and white brain matter was used as an example for this. The method is applied in order to gain a better understanding of tissue contrast. However, by using diagrams it can be particularly useful for determining the optimal pulse sequences for answering particular clinical questions. It should thus be possible to enhance the effectiveness of magnetic resonance imaging considerably.

Brain↗
PubMed1985

[Effect of body loading on the specific blood radioactivity following 99mTc in-vivo erythrocyte labelling. The effects on determining end-diastolic volume in equilibrium radionuclide ventriculography].

In 40 patients who underwent stress-equilibrium-radionuclide-ventriculography, we examined the stress-induced change of blood radioactivity concentration. A significant (p less than 0.025) increase of blood radioactivity concentration after peak exercise (mean +7.2%) was found. This increase was the result of a significant (p less than 0.025) increase of the hematocrit (mean +4.7%) due to a decrease of the plasma volume. The changes of radioactivity concentration and hematocrit neither show any correlation with peak exercise value, integral exercise or duration of exercise, nor with the increase of heart rate or blood pressure. The increase of end-diastolic volume appears to result largely from a stress-induced increase of blood radioactivity concentration. Thus, radioactivity concentration should be measured before and after exercise when evaluating volume changes caused by stress-equilibrium-radionuclide-ventriculography.

Cardiac Output↗
PubMed1985

[NMR tomography in urology. Principles--technics--risks--areas of use].

NMR tomography is a new imaging method based on nuclear magnetic resonance. It is possible to obtain sectional views of the human body in all three planes without ionizing radiation. NMR can differentiate soft tissue better than CT, and large blood vessels can be simultaneously evaluated without using contrast medium. The pathological process could be imaged exactly in every examination. Due to the lack of image clarity caused by breathing movement, NMR is not superior to CT when using contrast medium in the epigastrium. Calculation of relaxation times T1 and 2 shows clear differences between tumor and normal tissue. However, contrary to initial expectations. NMR did not permit a type-specific diagnosis to be made. Three-dimensional images improve the process of staging tumors, especially in the retroperitoneal space and in the pelvis. As with CT, metastatic lymph nodes can only be demonstrated when they have reached a size of at least 1 cm. Further studies will be necessary to evaluate the validity of this new imaging method.

Contrast Media↗
PubMed1984

[Course of contraction during physiological and ventricular pacemaker stimulation].

Phase imaging of gated radionuclide ventriculography was applied to the identification of cardiac activation patterns in patients with sinus rhythm (n = 14) or with ventricular (VVI)- (n = 28), atrial (AAI)- (n = 3) or AV-sequential (DDD)-pacing (n = 17). In patients with sinus rhythm, AAI- or DDD-pacing, analysis revealed homogeneous distribution of phase across both ventricles. In VVI-pacing a left bundle branch block configuration of the ventricular activation was found in 21 of 28 patients. In 7 of 28 patients phase distribution indicated a simultaneous activation of both ventricles (with or without delimitation of the apex of the right ventricle). This is of clinical importance because artificial spread of excitation and asynchronous contraction during VVI-pacing may be responsible for higher myocardial oxygen demand. Retrograde conduction in VVI-pacing was found in 9 of 28 patients. Phase analysis provides a reliable method for evaluation of pacing-induced activation patterns.

Adult↗
PubMed1984

[Clinical significance of nuclear magnetic resonance tomography in urology. Initial experiences].

NMR tomography, which is based on nuclear magnetic resonance, enables the production of sectional images of the human body without ionising radiation. In particular, the field of urology places great hopes on this new procedures, since the contrast in soft tissue is considerably better than that of computer tomography. Our first clinical results confirm the advantages of the soft tissue differentiation as well as the possibility to judge the large vessels safely and simultaneously without contrast medium, which is advantageous in the detection of tumours in the retroperitoneum and in the region of the kidneys. An improvement of the preoperative staging of urological tumours can be achieved by means of primary three-dimensional images. Only after several years of experience with NMR tomography and all its variations will it be able to evaluate properly, to what extent clinically relevant diagnostic possibilities are offered by the analysis of relaxation values.

Diagnosis, Differential↗
PubMed1984

Evaluation of left ventricular performance by radionuclide ventriculography in patients with atrioventricular versus ventricular demand pacemakers.

In 55 patients with coronary artery disease (n = 37), cardiomyopathy (n = 12), or myocarditis (n = 6) and programmable ventricular or dual-chamber atrioventricular (AV) demand pacemakers, left ventricular (LV) performance was studied by gated radionuclide ventriculography during pacing (60 or 70 to 120 bpm). Twenty-three patients were followed over 4 to 6 months. In 16 patients the findings in ventricular (VVI) and dual-chamber AV (DDD) pacing were compared. In all patients end-diastolic volume (EDV) decreased and cardiac output increased when the pacing rate was changed from 60 or 70 to 120 bpm. For instance, in the patient group with VVI pacemakers, EDV decreased by 7.53% +/- 3.5% (p less than 0.01) and cardiac output increased by 53.5% +/- 19.4% (p less than 0.01). The results were independent of the underlying heart disease. After 4 to 6 months, a reduction of both cardiac output and ejection fraction was found in 6 of the 23 patients. As compared to VVI pacing, a significantly higher cardiac output (2% to 16%) was derived from DDD pacing. The results indicate the dependence of LV performance on the pacing rate and the benefit of DDD pacing. Since gated radionuclide ventriculography provides the means to determine the effect of different pacing modes on LV performance, an optimal pacing mode may be found for each individual.

Adult↗
PubMed1984

[Nuclear magnetic resonance in the Hallervorden-Spatz syndrome].

Two patients (mother and son) with Hallervorden-Spatz's syndrome were examined both via CT and Nuclear Magnetic Resonance (NMR), using different measuring modes. In the patient with progressing disease pathological findings were seen in the right and left putamen with CT and NMR. All examinations in the mother with a less progressive syndrome were without any result. Information obtained via NMR did not yield significantly more relevant data than computed tomography.

Adolescent↗
PubMed1984

[Quantitative resting radionuclide-ventriculography for multifactorial analysis of left ventricular function].

Results from 388 patients, examined with quantitative equilibrium radionuclide ventriculography (qERNV) at rest, were stored in a data bank system and evaluated statistically. The value of time and velocity parameters [ejection time (ET), filling time (FT), time ES to peak filling rate (TpFR), mean (mER) and peak (pER) ejection rate, peak filling rate (pFR)] were evaluated in patients with coronary heart disease (CHD, with and without history of earlier myocardial infarction) or with cardiomyopathy (CMP). Significant (p less than 0.025) changes vs. normal in CHD I/II were obtained from pER, pFR, ET, in CHD III from gEF, EDV, mER, pER, pFR, in CHD IV from gEF, EDV, mER, pER, pFR, in patients with infarction or with CMP from gEF, EDV, mER, pER, pFR, ET and TpFR. Resting qERNV revealed a sensitivity in diagnosing a CHD (stages I-III) by mER of 30-59%, by pER of 40-65%, by pFR of 48-60% and by ET of 58-61%, which was higher than the sensitivity of gEF (19-56%).

Cardiac Output↗
PubMed1984

[Nuclear magnetic tomography in otorhinolaryngology. Case reports].

Magnetic resonance imaging (MRI) promises the achievement of considerable improvements in diagnostic procedures in otorhinolaryngology. In this article, the advantages of the technique are presented and their significance in diagnosis of head and neck disorders is discussed. An important advantage is the fine and detailed representation of tumours particularly in the soft tissue of the neck and the base of the tongue, which is made possible by an enhancement of contrast and by the improved spatial imaging based on the frontal and sagittal projection plane. MRI also seems to provide a new approach to the diagnosis of tumours of the glomus jugulare and the carotid body and of acoustic neurinomas. Besides, it will be possible to obtain more detailed information on the depth of infiltration of laryngeal carcinomas with the aid of surface coils.

Diagnosis, Differential↗
PubMed1984

[Quantitative equilibrium radionuclide ventriculography at rest in the evaluation of the severity of coronary disease].

The results of examining 373 patients with a quantitative equilibrium radionuclide ventriculography were stored in a data bank and evaluated statistically. The following left ventricular parameters were evaluated: global and regional ejection fractions ( gEF , rEF1 - rEF5 ) and volume parameters (EDV, ESV, stroke volume, cardiac output, heart index). It appeared that in stages I and II of coronary heart disease evaluation of gEF , EDV and ESV under resting conditions does not sufficiently discriminate diseased patients from normals. Significant changes (p less than 0.025) of these parameters (vs. normal) were found only in CHD III and IV or in patients with a history of old myocardial infarction. The additional evaluation of the regional fraction yields, however, a significant increase (CHD I and II: +25%) of the sensitivity of the equilibrium radionuclide ventriculography in the diagnosis of coronary heart disease.

Coronary Disease↗
PubMed1983

Influence of background and absorption correction on nuclear quantification of left ventricular end-diastolic volume.

Left ventricular (LV) end-diastolic volume (EDV) was determined in millilitres by equilibrium radionuclide ventriculography (MUGA) in 38 patients and in 15 normal individuals by applying corrections for background (BC), LV blood self-absorption and for absorption by the thoracic and LV walls. Volume calibration was performed by measuring a syringe containing the patient's venous blood with the gamma camera. Single plane cineventriculography (CVG) served as the reference method. Without absorption correction, LV volume values were underestimated by a factor of 3.6 on the average. Several background models (uniform, parabolic, no background) were investigated. Without BC, EDV was overestimated, and with uniform BC, EDV was underestimated. EDV calculated using a parabolic BC with a correction for absorption yielded the best correlation (r = 0.96) with volumes (VOL) obtained by CVG (VOLMUGA [ml] = -6.83 + 1.060 X VOLCVG).

Background Radiation↗
PubMed1983

[Effect of varied pacemaker stimulation on left ventricular volume data--studies with radionuclide ventriculography].

Left ventricular performance (parameters: EDV, ESV, EF, cardiac output) was studied by gated radionuclide ventriculography in 55 patients with ventricular or AV-sequential pacemakers. 23/55 patients were followed over 4-6 months. EDV and SV decreased significantly (p less than 0.01) and cardiac output increased (p less than 0.01) with changing pacing rate from 70-72 to 100/min. After 4-6 months a reduction of cardiac output was found in 15/23 patients. As compared to ventricular pacing, a significantly higher cardiac output was found during AV-sequential pacing. These nuclear data indicate the dependence of left ventricular performance on pacing mode. From non-invasive methods an individual adapted pacing mode can be derived.

Adult↗
PubMed1983

[Non-invasive determination of the enddiastolic volume of the left ventricle. A comparative angiocardiographic, two-dimensional echocardiographic, computer tomographic and radionuclide ventriculographic study].

60 patients underwent left ventricular angiography (CV) and/or two-dimensional echocardiography (2DE) and/or multiple-gated equilibrium angiography (MUGA) and/or computer-tomography (CT) for determination of the left ventricular end-diastolic volume. Estimation of the enddiastolic volume from the various measurements showed significant correlations: CV/2DE: y equal 0.839 x +6.10, r equal 0.93, SEE equal 34.2 ml; CV/CT: y equal 0.762 x +30.30, r equal 0.82, SEE equal 20.8 ml; CV/MUGA: y equal 0.992 x +20.53, r equal 0.97, SEE equal 31.4 ml; 2DE/CT: y equal 1.167 x +19.58, r equal 0.93, SEE equal 38.4 ml; 2DE/MUGA: y equal 1.068 x +37,79, r equal 0.90, SEE equal 52.1 ml. Our study demonstrates that noninvasive techniques for measurement of the enddiastolic volume give results comparable to those obtained by cardiac catheterization. In addition, it is of interest that the noninvasive techniques examined show good agreement with each other.

Angiocardiography↗