Intermediate frequency band digitized high dynamic range radiometer system for plasma diagnostics and real-time Tokamak control.

An intermediate frequency (IF) band digitizing radiometer system in the 100-200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the full wave information of the mm-wave signals under investigation. The system is based on directly digitizing the IF band after down conversion. The enabling technology consists of a fast multi-giga sample analog to digital converter that has recently become available. Field programmable gate arrays (FPGA) are implemented to accomplish versatile real-time data analysis. A prototype system has been developed and tested and its performance has been compared with conventional electron cyclotron emission (ECE) spectrometer systems. On the TEXTOR Tokamak a proof of principle shows that ECE, together with high power injected and scattered radiation, becomes amenable to measurement by this device. In particular, its capability to measure the phase of coherent signals in the spectrum offers important advantages in diagnostics and control. One case developed in detail employs the FPGA in real-time fast Fourier transform (FFT) and additional signal processing. The major benefit of such a FFT-based system is the real-time trade-off that can be made between frequency and time resolution. For ECE diagnostics this corresponds to a flexible spatial resolution in the plasma, with potential application in smart sensing of plasma instabilities such as the neoclassical tearing mode (NTM) and sawtooth instabilities. The flexible resolution would allow for the measurement of the full mode content of plasma instabilities contained within the system bandwidth.

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization.

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200,000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

Strong scattering of high power millimeter waves in tokamak plasmas with tearing modes.

In tokamak plasmas with a tearing mode, strong scattering of high power millimeter waves, as used for heating and noninductive current drive, is shown to occur. This new wave scattering phenomenon is shown to be related to the passage of the O point of a magnetic island through the high power heating beam. The density determines the detailed phasing of the scattered radiation relative to the O-point passage. The scattering power depends strongly nonlinearly on the heating beam power.

A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes.

An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry-Perot interferometer under an angle inside the electron cyclotron wave (ECW) beam. ECE measurements are obtained during high power ECRH operation. This demonstrates the successful operation of the diagnostic and, in particular, a sufficient suppression of the gyrotron component preventing it from interfering with ECE measurements. When integrated into a feedback system for the control of plasma instabilities this line-of-sight ECE diagnostic removes the need to localize the instabilities in absolute coordinates.

[Tako-Tsubo cardiomyopathy: a differential diagnosis of acute coronary syndrome]. / Tako-Tsubo-Kardiomyopathie: eine Differenzialdiagnose beim akuten Koronarsyndrom.

ANAMNESIS: A 68-year-old woman was admitted to the emergency unit with symptoms of an acute coronary syndrome. She complained about a feeling of chest oppression for two hours. The cardiac history was unremarkable. Her husband had died few hours before the onset of her cardiac symptoms. INVESTIGATIONS: Blood pressure was 80/40 mmHg, heart rate 110/min. Cardiac enzymes were normal. The ECG showed significant ST elevation in V2 to V6. Laevoangiocardiography revealed a severe reduction of left ventricular systolic function with an ejection fraction of 27 %. Akinesia was seen in the anterior wall region as well as apical, inferior, and poserolateral. Coronary heart disease could be excluded. DIAGNOSIS, THERAPY AND COURSE: Hemodynamic support with catecholamines was needed for one day. After two days hemodynamic recovery occurred. The creatine kinase peak level was surprisingly low (357 U/l). Echocardiographies performed in short intervals showed a continuous, rapid recovery of the ventricular function. Two weeks later the left ventricular function was normal. There was no evidence of myocarditis. In consideration of the history of emotional stress, absence of coronary lesions, a low CK peak and rapid recovery of left ventricular function, Tako-Tsubo cardiomyopathy was diagnosed. Medical treatment with beta blockers was initiated: the further clinical course was unremarkable. CONCLUSION: Tako-Tsubo cardiomypathy should be considered in patients with findings and symptoms of an acute coronary syndrome.

First-In-Man application of a miniature self-contained intracoronary magnetic resonance probe. A multi-centre safety and feasibility trial.

AIMS: To assess safety and feasibility of intracoronary Magnetic Resonance (MR) Spectroscopy in living patients, using a self-contained MR catheter. METHODS AND RESULTS: Prospective, multi-centre study in patients with stable or unstable angina that were scheduled for percutaneous coronary diagnostic or therapeutic catheterization. We assessed the feasibility of an intravascular MR catheter, capable of analysing the arterial wall without external magnets or coils, by differentiating lipid rich, intermediate and fibrotic areas of the atherosclerotic plaque on the basis of differential water diffusion.Twenty-nine patients were included at 4 centres. The intracoronary MR-spectroscopy procedure was well tolerated; no MACE and no device related serious adverse event was observed. The MR catheter was successfully advanced into the lesion in 28 patients. Introduction of the MR catheter was not possible in one patient with a tortuous proximal right coronary artery. MR data were obtained in 22 patients. According to the predominant MR pattern, lesions were classified as fibrous plaque in 4 patients, as intermediate plaque in 4 patients and as lipid-rich plaque in 8 patients. Six patients were excluded from analysis because artifacts impeded the quality of the MR signal. Plaque type did not show a correlation with angina status (p=0.552; all groups) or angiographic parameters, such as minimal lumen diameter and diameter stenosis. CONCLUSIONS: This prospective, multi-centre study demonstrates for the first time that coronary artery assessment of potentially vulnerable, non-flow limiting lesions using a dedicated intravascular MR catheter, free of external magnets or coils, is feasible in clinical practice. Assessment of the coronary wall may provide important data regarding the composition of the atherosclerotic lesion, which then could contribute to predicting the likelihood of eventual rupture and clinical instability.

[Invasive cardiac catheter procedure for thromboembolic pulmonary hypertension]. / Invasive Herzkatheterdiagnostik bei thrombembolischer pulmonaler Hypertonie.

The hemodynamic assessment and angiographic visualization of the pulmonary artery system are the mayor components for the diagnostic and therapeutical planning for patients with known or suspected pulmonary hypertension due to chronic thromboembolism. The pulmonary artery pressure and the pulmonary arterial resistance both reflect the severity of the disease. Pulmonary wave form analysis allows to some degree an etiologic differentiation of pulmonary hypertension. The typical angiographic findings of central pulmonary embolism are best identified by biplane side and lobe selected angiography of the arterial and venous phase with simultaneous consideration of the overall contrast medium exposure. Typical occasional coronary findings are residues of coronary embolism in patients with patent foramen ovale and excentric compression of the left main stem probably due to dilatation of the pulmonary artery.

[Detection of left ventricular ischemia at rest by tissue Doppler echocardiography]. / Nachweis einer linksventrikulären Ischämie in Ruhe mittels Gewebe-Doppler-Echokardiographie.

UNLABELLED: A 53-year old woman without a previous history of cardiac disease was successfully resuscitated from ventricular fibrillation. Despite a normal two dimensional echocardiogram, tissue Doppler analysis of left ventricular long-axis contraction revealed marked postsystolic contractions in the territory of the left coronary artery suggesting ischemia as the underlying pathogenetic mechanism. This was confirmed by coronary angiography which revealed a high-grade ostial stenosis of the left main stem. After coronary artery bypass surgery, the tissue Doppler findings normalized. CONCLUSION: Assessment of regional long axis function by tissue Doppler echocardiography may yield important additional findings even if two-dimensional echocardiography is apparently normal.

Impaired flow in left internal mammary artery grafts due to subclavian artery stenosis.

We report two cases of patients with left internal mammary artery (LIMA) grafts impaired by proximal stenosis of the subclavian artery. The functional impact of the subclavian lesions was investigated using flow-wire. The hemodynamic relevance of the lesions could be documented with the functional flow measurements in both instances. The relevance of preoperative evaluation of the subclavian artery is emphasized when it is planned to use the LIMA as coronary bypass. Moreover, the case reports indicate that percutaneous intervention of the subclavian artery is an effective treatment modality to restore adequate flow in the LIMA.

Effect of inhaled iloprost plus oral sildenafil in patients with primary pulmonary hypertension.

BACKGROUND: The application of iloprost, a stable prostacyclin analogue, by inhalation has been shown to improve hemodynamic variables in patients with primary pulmonary hypertension. However, repetitive inhalations are required due to its short-term effects. One potential approach to prolong and increase the vasorelaxant effects of aerosolized iloprost might be to combine use with phosphodiesterase inhibitors. METHODS AND RESULTS: The short-term effects of 8.4 to 10.5 microgram of aerosolized iloprost, the phosphodiesterase type 5 inhibitor sildenafil, and the combination thereof were compared in 5 patients with primary pulmonary hypertension. Aerosolized iloprost resulted in a more pronounced decrease in mean pulmonary arterial pressure (PAP) than sildenafil alone (9.4+/-1.3 versus 6.4+/-1.1 mm Hg; P<0.05). The reduction in mean PAP after sildenafil was maximal after the first dose (25 mg). The combination of sildenafil plus iloprost lowered mean PAP significantly more than iloprost alone (13.8+/-1.4 versus 9.4+/-1.3 mm Hg; P<0.009). No significant changes in heart rate or systemic arterial pressure were observed during any treatment. The treatments were well tolerated, without major adverse effects. CONCLUSIONS: Sildenafil caused a long-lasting reduction in mean PAP and pulmonary vascular resistance, with a further additional improvement after iloprost inhalation. These data suggest that small doses of a phosphodiesterase type 5 inhibitor may be a useful adjunct to inhaled iloprost in the management of pulmonary hypertension.

Intra-aortic counterpulsation during carotid stenting.

Postprocedural hypotension following endovascular stent placement of carotid artery disease (CAS) predicts increased in-hospital complications and long-term risk of death. Intra-aortic balloon counterpulsation (IABP) both increases mean arterial pressure and cerebral blood flow and therefore possibly reduces complications due to hemodynamic instability during and after CAS. In this study, we describe the use of IABP in a patient with severe depression of left ventricular function due to diffuse coronary artery disease undergoing CAS. Controlled studies are necessary to demonstrate a potentially protective role of IABP in high-risk CAS patients.

Do changes in blood flow in the subclavian artery affect flow volume in IMA grafts after complete arterial revascularization with the T-graft technique?

BACKGROUND: The T-graft procedure achieves complete arterial coronary revascularization with only two conduits. In this technique, all the bypass anastomoses are supplied by the left internal mammary artery (IMA). Changes in flow conditions or flow redistribution in the subclavian artery may thus sigificantly influence coronary perfusion. The objective of this study was to determine whether changes in blood flow in the subclavian artery affect the flow in IMA grafts in patients who have undergone complete arterial revascularization with T-grafts. METHODS: Quantitative flow volume and flow profiles in the IMA graft and the proximal subclavian artery were measured with a flow-wire in 20 patients one week postoperatively. Following baseline measurements, brachial artery constriction was achieved by applying a blood pressure measurement cuff to the patient's left upper arm. After 5 minutes, quantitative flow in the IMA and in the proximal subclavian artery was assessed. The cuff was then released and the measurements repeated. RESULTS: Flow in the subclavian artery changed significantly (p < 0.01) from baseline (355.4 +/- 95.2 ml/ min) to constriction (171.2 +/- 61.3 ml/min) and hyperemia (679.3 +/- 195.1 ml/min). Flow in the IMA graft remained constant irrespective of subclavian artery flow (75.4 +/- 26.2 ml/min vs. 78.0 +/- 28.9 ml/min vs. 75.5 +/- 29.3 ml/min, respectively). The flow profile in the IMA was similarily unchanged. CONCLUSION: In patients in whom the coronary bypass blood flow is dependent on the left IMA, neither the quantitative flow volume nor the flow profile are altered by changes in blood flow of the subclavian artery.

Flow wire measurements after complete arterial coronary revascularization with T-grafts.

BACKGROUND: The T-graft procedure achieves complete arterial revascularization in coronary three-vessel disease. In this technique, all bypass anastomoses are supplied by the left internal mammary artery (IMA). This prospective study explores the question of whether the quantitative flow in such grafts is influenced by the pathology in the native coronary arteries. METHODS: Eighty-two patients with coronary three-vessel disease were studied after complete arterial coronary revascularization with T-grafts. Quantitative flow and coronary flow reserve were measured in the proximal IMA with a Doppler guide wire. Three groups were compared: group 1, all native coronary arteries were stenosed but patent (n = 31); group 2, one occluded native coronary vessel (n = 33); group 3, two or more occluded native coronary arteries (n = 18). RESULTS: Quantitative flow was significantly higher in group 3 than in group 2 at 1 week (93.9 +/- 39.5 vs 75.8 +/- 27.3 mL/min, p < 0.05) and 6 months postoperatively (86.0 +/- 40.1 vs. 69.1 +/- 35.5 mL/min, p < 0.05). Flow in group 2 was significantly (p < 0.05) higher than in group 1 (1 week: 58.0 +/- 28.4 mL/min, 6 months: 55.2 +/- 29.2 mL/min) in both examinations. There were no significant differences in coronary flow reserve between the three groups (1: 2.88 +/- 0.97, 2: 2.84 +/- 0.96, 3: 2.74 +/- 0.94). CONCLUSIONS: After complete arterial revascularization with T-grafts, the quantitative flow in the IMA is influenced by the status of the native coronary arteries. As a result of competitive flow phenomena, blood flow in the bypasses is significantly lower when the coronary arteries are affected only by stenosis.