PubMed Health⌕ Search

Biomedical subjects

M Meininger

Publications and source records attributed to M Meininger.

12 recordsLinked to original sources
PubMed2001

Detection of myocardial viability based on measurement of sodium content: A (23)Na-NMR study.

MRI of total sodium (Na) content may allow assessment of myocardial viability, but information on Na content in normal myocardium, necrotic/scar tissue, and stunned or hibernating myocardium is lacking. Thus, the aims of the study were to: 1) quantify the temporal changes in myocardial Na content post-myocardial infarction (MI) in a rat model (Protocol 1); 2) compare Na in normally perfused, hibernating, and stunned canine myocardium (Protocol 2); and 3) determine whether, in buffer-perfused rat hearts, infarct scar can be differentiated from intact myocardium by (23)Na-MRI (Protocol 3). In Protocol 1, rats were subjected to LAD ligation. Infarct/scar tissue was excised at control and 1, 3, 7, 28, 56, and 128 days post-MI (N = 6-8 each), Na content was determined by (23)Na-NMR spectroscopy (MRS) and ion chromatography. Na content was persistently increased at all time points post-MI averaging 306*-160*% of control values (*P < 0.0083 vs. control). In Protocol 2, (23)Na-MRS of control (baseline), stunned and hibernating samples revealed no difference in Na. In Protocol 3, (23)Na-MRI revealed a mean increase in signal intensity, to 142 +/- 6% of control values, in scar tissue. A threshold of 2 standard deviations of the image intensity allowed determination of infarct size, correlating with histologically determined infarct size (r = 0.91, P < 0.0001).

Animals↗
PubMed2001

In vivo 19F NMR chemical-shift imaging of Ancistrocladus species.

19F nuclear magnetic resonance (NMR) imaging and 19F NMR chemical-shift imaging (19F CSI) have been used to localize fluorinated compounds administered to stems of Ancistrocladus heyneanus and A. abbreviatus for the elucidation of biosynthetic pathways in living plants. This first application of 19F CSI on plants proved CSI to be a valuable technique for mapping fluorinated molecules in plants. Exemplarily using trifluoroacetate as a model compound allowed to select appropriate feeding methods and to optimize both concentration and duration of the application to the plant. The time course of the uptake and distribution of trifluoroacetate was monitored by both 19F imaging and 19F CSI. Fluorinated metabolites formed by uptake of 3-fluoro-3-deoxy-D-glucose were detected with 19F CSI.

Fluorine↗
PubMed2000

Microvascular reconstruction and tracheotomy are significant determinants of resource utilization in head and neck surgery.

BACKGROUND: Successful "critical pathway" design and implementation are dependent on appropriate patient stratification according to those factors that are primary determinants of resource utilization. OBJECTIVES: To test the validity of our previously reported critical pathway design and to determine whether tracheotomy and microvascular reconstruction (MR) are primary determinants of resource utilization. DESIGN: Cost-effectiveness analysis. SETTING: Tertiary referral academic institution. METHODS: Retrospective analysis of data from 133 head and neck surgery cases in which the treatment regimen was based on critical pathways over a 26-month period. OUTCOME MEASURES: Length of stay and total patient charges were used as indices of resource utilization. One-way analysis of variance and t tests were used for statistical analysis of significance. RESULTS: Ninety patients (67.7%) underwent MR; 43 (32. 3%) did not. Seventy-five patients (56.4%) underwent tracheotomy; 58 (43.6%) did not. Four patient groups were constructed in decreasing order of complexity as follows: group 1, patients who underwent both tracheotomy and MR (n = 58); group 2, patients who underwent MR alone (n = 32); group 3, patients who underwent tracheotomy alone (n = 17); and group 4, patients who did not undergo either procedure (n = 26). Both tracheotomy and MR were found to be independent determinants of resource utilization and were additive when both were present. The length of stay varied from 8.4 days (in patients who underwent both procedures) to 6.7 days (in patients who did not undergo either procedure), with intermediate values in cases in which only 1 procedure was performed. The total charges varied in a similar manner from a high of $33,371 to a low of $19,994. Subanalysis with respect to intensive care unit, ward, and operating room charges showed a similar stratification. CONCLUSION: Tracheotomy and MR are both significant determinants of charges and length of stay in head and neck surgery cases and must be considered in the design of strategies to promote efficient resource utilization.

Cost-Benefit Analysis↗
PubMed2000

[Myocardial perfusion at rest and during stress. MR signal characteristics of persistent and reversible myocardial ischemia].

AIM: Performance of combined rest/stress MR perfusion studies and the analysis of qualitative signal intensity parameters in comparison with 99mTc-SestaMIBI SPECT in patients with known coronary artery disease (CAD). METHODS: Sixteen patients with CAD underwent MR myocardial perfusion assessment at rest and after dipyridamole-induced hyperemia. Qualitative parameters (SI increase, SI upslope) of the SI time-curves were evaluated and characteristics of normal, reversible and persistent hypoperfused myocardium as assessed by 99mTc-SestaMIBI SPECT were compared. RESULTS: Compared with the rest values, normal myocardium showed a significant increase of the SI upslope during hyperemia (P < 0.001), whereas persistent (P = 0.07) and reversible (P = 0.15) hypo-perfusions showed only minor changes. SI increase over baseline also showed a significant increase only in normal myocardium (P < 0.001). At rest, reversible ischemic areas showed no significant differences from normal myocardium, whereas during hyperemia SI increase was significantly lower (P = 0.02). CONCLUSIONS: Qualitative SI parameters of a combined rest/stress MR myocardial perfusion study allow to differentiate normal from reversibly or persistently hypoperfused myocardium.

Adult↗
PubMed2000

Altered energy metabolism after myocardial infarction assessed by 31P-MR-spectroscopy in humans.

The value of 31P-magnetic resonance spectroscopy (MRS) as a possible tool to distinguish viable from non-viable tissue after myocardial infarction was analysed in humans. Fifteen patients 3 weeks after anterior myocardial infarction were studied with breath-hold cine MRI and 3D-CSI MRS (1.5 T system). 31P-spectra were obtained from infarcted as well as non-infarcted myocardium (voxel size 25 cm3 each). Gold standard for viability was recovery of regional function, as determined by a control MRI 6 months after revascularization. Ten age-matched healthy volunteers served as control group. No significant difference was found between the phosphocreatine to adenosinetriphosphate (PCr/ ATP) ratio of volunteers (SD 1.72+/-0.31) and non-infarcted septal myocardium of patients. Cine MRI demonstrated recovery of regional function in 10 patients, i. e. 10 patients showed viable and 5 non-viable myocardium. In viable myocardium, the PCr/ATP ratio was 1.47+/-0.38 (non-significant vs volunteers; p>0.05). In the 5 patients with akinetic myocardium, PCr peaks could not be detected. Therefore, calculation of PCr/ATP ratios was not possible. However, a significant reduction of the ATP signal-to-noise ratio (SNR) was observed (2.92+/-0.73 vs 6.68+/-0.80; patients vs volunteers; p<0.05). The SNR of ATP of akinetic regions may predict recovery of function after revascularization in patients with myocardial infarction.

Adenosine Triphosphate↗
PubMed1999

Concentrations of human cardiac phosphorus metabolites determined by SLOOP 31P NMR spectroscopy.

Human cardiac 31P nuclear magnetic resonance (NMR) spectra are usually quantified in relative terms, i.e., the ratio of metabolite signals is calculated. If 31P NMR spectroscopy of the heart is to emerge as a clinically relevant diagnostic modality, reliable quantification of absolute concentrations of 31P metabolites is required. We applied spectral localization with optimal point spread function (SLOOP) 31P NMR spectroscopy to measure absolute concentrations of phosphocreatine (PCr) and adenosine triphosphate (ATP) in human myocardium. The accuracy of the quantification was first validated in a phantom study. Seven healthy volunteers (aged 19-29 years) were then examined at 1.5 T using a nominal spatial resolution of 25 mL. SLOOP allowed us to obtain localized spectra from compartments anatomically matched to the left ventricular wall. The a priori knowledge of the anatomical structure was obtained from 1H images. The spatially varying effects of saturation, off-resonance, and sensitivity were considered during the reconstruction process. Metabolites were quantified with reference to an external 31P standard. Concentrations of 9.0 +/- 1.2 and 5.3 +/- 1.2 mmol/kg wet wt (mean +/- SD, n = 9) were determined for PCr and ATP in normal heart, respectively. The influence of nuclear Overhauser enhancement on metabolite quantification is discussed.

Adenosine Triphosphate↗
PubMed1999

[The quantification of energy-rich phosphates in healthy and damaged heart muscle by SLOOP 31P-MR spectroscopy. Spatial localization with optimal pointspread function].

PURPOSE: A quantitative 31P-MR-spectroscopic technique was used to assess the energy metabolism in healthy and diseased myocardium. METHODS: 31P spectra were acquired on a 1.5 T scanner using a 3D-chemical shift imaging technique. Based on the anatomical information provided by 1H images, SLOOP (Spatial Localization with Optimal Pointspread Function) allows to obtain spectra from defined compartments. With SLOOP a free voxel shape with adaption to anatomic structures, e.g. the myocardium, is possible. Absolute values for phosphocreatine (PCr) and adenosine triphosphate (ATP) were determined using an external standard. RESULTS: 31P-spectra showed only minimal contamination by surrounding tissue. The standard deviation for the determined values of healthy volunteers was low. Compared to healthy volunteers, reduced PCr and ATP concentrations were seen for dilative cardiomyopathies and coronary artery disease and unchanged concentrations were observed for hypertensive heart disease. CONCLUSION: 31P-MR spectroscopy with SLOOP allows a non-invasive, quantitative analysis of cardiac energy metabolism.

Adenosine Triphosphate↗