Seven patients with arrhythmogenic right ventricular dysplasia were explored by magnetic resonance imaging (MRI), using the spin-echo technique (TR = the patient's own RR cycle; TE = 28 ms, 56 ms, 84 ...ms) with multiple, contiguous, 7 to 10 mm thick sections performed in two planes: axial plus sagittal or frontal planes. In 5 out of 7 patients, MRI showed dysplastic lesions in the right ventricular wall presenting typically as fat-like high signals contrasting with the normal myocardium. In 2 patients, no lesion was clearly visualized. The parietal lesions were located in the anterior wall of the right ventricle and conus arteriosus in 5 cases and in the lower wall of the right ventricle in one patient who had two dysplastic areas. In 3 patients the lesions extended up to the tip of the interventricular septum and of the left ventricle. In the 2 patients whose lesions were most extensive, their predominance in the subepicardial region and the concordance between the sites of abnormalities at MRI and angiography were clearly observed. Thus, despite its present technical limitations MRI seems to be one of the first techniques capable of visualizing the parietal lesions in patients with arrhythmogenic right ventricular dysplasia.
The entire dataset of the GRANAT/SIGMA observations of Cyg X-1 and 1E1740.7-2942 in 1990-1994 was analyzed in order to search for correlations between primary observational characteristics of the ...hard X-ray (40-200 keV) emission - hard X-ray luminosity, hardness of the spectrum (quantified in terms of the best-fit thermal bremsstrahlung temperature kT) and the RMS of short-term flux variations. Although no strict point-to-point correlations were detected certain general tendencies are evident. It was found that for Cyg X-1 the spectral hardness is in general positively correlated with relative amplitude of short-term variability. The correlation of similar kind was found for X-ray transient GRO J0422+32 (X-ray Nova Persei 1992) and recently for GX339-4. For both sources approximate correlation between kT and L_X was found. At low hard X-ray luminosity - below 10E37 erg/sec - the kT increases with increase of L_X. At higher luminosity the spectral hardness depends weaker or does not depend at all on the hard X-ray luminosity. The low luminosity end of these approximate correlations (low kT and low RMS) corresponds to extended episodes of very low hard X-ray flux occurred for both sources during SIGMA observations.
The entire dataset of the GRANAT/SIGMA observations of Cyg X-1 and 1E1740.7-294 in 1990-1994 was analyzed in order to search for correlations between primary observational characteristics of the hard ...X-ray emission - hard X-ray luminosity L_X, hardness of the spectrum (quantified in terms of the best fit thermal bremsstrahlung temperature kT) and the RMS of short term flux variations. Two distinct modes of the kT vs. L_X dependence were found for both sources. At low luminosity - below the level corresponding approximately to the gamma_1 state of Cyg X-1 - the kT increases as the L_X increases. Above the luminosity level of ~1.2L_gamma_1 the spectrum hardness is nearly constant (kT ~150 keV) and does not depend on the luminosity. In the case of Cyg X-1 the correlation of similar kind was found between the spectrum hardness and RMS of the short term flux variations. The increase of the kT, corresponding to the increasing branch on the kT vs. L_X diagram, is accompanied with increase of the RMS from few percent level to ~10-15%. Further increase of the RMS is not accompanied with change of the kT and does not correlate with changes in the luminosity.
