Biomagnetic multi-channel systems. Principles and application in cardiology.

The non-invasive measurement of the extremely weak magnetic fields generated by heart and brain is motivated by the possibility of obtaining quantitative diagnostic information about electric function. Magnetic signals (MCG, MEG) are significantly less influenced by body tissue than the corresponding electric signals (ECG, EEG). Measurement of biomagnetic signals is performed by superconducting sensors, consisting of pickup coils and SQUIDs (superconducting quantum interference device) operating in liquid Helium. For clinical investigations a biomagnetic multi-channel system (KRENIKONR) has been designed. It uses a flat array of 37 magnetic field sensors and is operated inside a shielded room. Evaluation of biomagnetic signals by use of simple source and body models and in combination with anatomical data from 3D MR- or CT-images yields sequences of locations of electrical function with a spatial resolution of some millimeters and a time resolution better than one millisecond. More than three years of clinical studies have demonstrated the value of the method primarily in cases with localized functional pathologies. In cardiology this is pathologies of the cardiac conductive pathway, ectopies, and arrhythmias. Validation has been performed by catheter stimulation in volunteers, and by catheter mapping and nuclear medical methods in patients. Extension of modelling and evaluation to cases with distributed activity, e.g. ventricular excitation, is under investigation.     

Localisation of myocardial ischaemia from the magnetocardiogram using current density reconstruction method: computer simulation study

A computer simulation study is performed to investigate the method of current density reconstruction to localise myocardial ischaemia. A computer model of the entire human heart is used to simulate the excitation and repolarisation process in eight topographically different cases of myocardial ischaemia. The associated magnetocardiogram is calculated at 37 positions of the KRENIKON^* biomagnetic measurement equipment. The method of current density reconstruction is applied at the S-point (the last discemible deviation from the ST-segment at the end of the QRS-complex) of the MCG to find characteristics of the myocardial ischaemia simulated by the model. The results show that it is possible to determine the location of the ischaemia. The current density distribution may be interpreted physiologically in terms of the so-called ‘injury current’. This indicates that magnetocardiography might be a suitable method for noninvasive ischaemia diagnosis, and further investigations of the current density reconstruction method for the injury current should be performed on patients with ischaemic heart disease.     

Renal expression of endothelial and inducible nitric oxide synthase, and formation of peroxynitrite-modified proteins and reactive oxygen species in Wegener's granulomatosis

To investigate the role of nitric oxide (NO) in glomerular inflammation, the expression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) was studied in conjunction with inflammatory cell influx, H2O2 production, and the formation of nitrotyrosines in renal biopsies from patients with Wegener's granulomatosis (WG). Renal cryostat sections from patients with WG (n=15) were stained by immunohistochemistry for eNOS, iNOS, endothelial cells (CD31), nitrotyrosines, polymorphonuclear cells (PMNs, CD15), and monocytes/macrophages (CD14, CD68). Production of H2O2 was identified by enzyme cytochemistry using diaminobenzidine. In control tissues, strong staining for eNOS was found in glomerular and interstitial tubular capillaries and cortical vessels. A significant reduction in eNOS expression was found in WG biopsies, which was associated with a reduction in CD31 expression. Expression of iNOS was found in infiltrating inflammatory cells, mainly located in the interstitium. H2O2-producing cells were detected in glomeruli and were abundantly present in the interstitium. Nitrotyrosine-positive cells, however, were almost exclusively found in the interstitium. It is concluded that renal inflammation in WG is associated with the induction of iNOS in inflammatory cells and the formation of nitrotyrosines. Expression of eNOS in glomerular capillaries is lost, most likely due to endothelial cell damage. These results suggest that decreased NO production by endothelial cells, in conjunction with increased NO production by iNOS-positive inflammatory cells, is involved in renal tissue injury in WG.     

HCV—specific cytokine induction in monocytes of patients with different oputcomes of hepatitis C

AIM：Cytokine release by macrophages critically determines the type of immune response to an antigen Therefore.we studied hepatitis C virus (HCV0-Specific induction of interleukins-1β,-10,-12(IL-1β,il-10,IL-12),and tumor necrosis factor-α(TNF-α) in monocytes.METHODS:Intracellular cytokine expression was studied by flow cytometry in 23 patients with chronic hepatitis C,14 anti-HCV seropositives without viremia and 11 controls after stimulation of peripheral blood mononuclear cells with recombinant core,NS3,NS4 NS5a and NS5b proteins .RESULTS:Patients with HCV viremia revealed greater spontaneous exprssion of IL-1β,TNF-α,and IL-10,Furthermore,greater than twofold higher IL-10 epression was induced by the HCV antigens in chronic hepatitis C than in the other two groups (P<0.05) In contrast,neither IL-12 noir TNF-α was induced preferentially.CONCLUSION:In chonic hepatitis C antigen-specific cytokine induction in monocytes is apparently shifted towards predominant IL-10 induction-not counterbalanced by antiviral type 1 cytokines,This may contribute to persistent viral replication.     

In-plane coronary arterial motion velocity: measurement with electron-beam CT

PURPOSE: To determine the speed of and changes in the speed of coronary arterial movement during the cardiac cycle with electron-beam computed tomography (CT). MATERIALS AND METHODS: With electron-beam CT, 20 consecutive cross-sectional images were acquired at the mid right coronary artery (with 50-msec acquisition time, 8-msec intersection delay, 7-mm section thickness, and intravenous administration of 40 mL of contrast agent) in 25 patients. On the basis of the displacement of the left anterior descending, left circumflex, and right coronary arterial cross sections from image to image, movement velocity in the transverse imaging plane was calculated and was correlated with the simultaneously recorded electrocardiogram. RESULTS: The velocity of in-plane coronary arterial motion varied considerably during the cardiac cycle. Peaks were caused by ventricular systole and diastole and by atrial contraction. The mean velocity was 46.6 mm/sec +/- 12. 5 (SD). The mean velocity of right coronary arterial movement (69.5 mm/sec +/- 22.5) was significantly faster than that of the left anterior descending (22.4 mm/sec +/- 4.1) or the left circumflex coronary artery (48.4 mm/sec +/- 15.0). The lowest mean velocity (27. 9 mm/sec) was at 48% of the cardiac cycle. CONCLUSION: The lowest velocity of coronary arterial movement, which displays considerable temporal variation, was at 48% of the cardiac cycle.