[en] A new nuclear stethoscope based on a matrix of small CdTe semiconductor detectors has been developed for studying the cardiac performance by gamma ventriculography at the equilibrium, in rest and stress conditions, in the early and recovery phases of the coronary disease and to follow the long-term therapy. The light-weight probe consists of an array of 64 detectors 5x5x2 mm grouped in 16 independent units in a lead shielded aluminum box including 16 preamplifiers. The probe is connected to an electronic box containing DC power supply, 16 channel amplifiers, discriminators and counters, two analog-triggering ECG channels, and interface to a PC. The left ventricle activity is, preferentially, detected by using a low-resolution matching convergent collimator. A physical evaluation of the probe has been performed, both with static tests and dynamically with a hydraulic home-built model of beating heart ventricle paced by a rhythm simulator. The sum of the 16 detectors activity provided a radiocardiogram (RCG) which well depicted the filling and ejection of the cardiac beats, allowing to compare the clinically relevant parameters of the cardiac performance, proportional variables of the stroke volume (SV), ejection fraction (EF) and ventricular flow-rate with the known absolute values programmed on the model. The portable system is now in operation for clinical assessment of cardiac patients

[en] The idea was to use the transfer function of part of the circulation system to determine the distribution of tracer molecule transit times in this system. The results obtained for the transfer function in a theoretical case with recirculation and in an actual case were compared by using the signals from a γ camera. The study of this transfer function offers an approach, independently of tracer injection conditions, to the rheological flow parameters in the haemodynamic system considered

[en] At the present time, it appears that competition exists between proton NMR imaging and CT by X-rays for anatomic description of the human body. However, NMR could offer complementary information about tissue structure by proton relaxation studies. The magnetization decay curves of the tissues appear to be complex and reflect the heterogeneity of the tissular structure. In order to interpret the complexity of decay curves, numerous and often very complicated models have been proposed for representing the mobile proton distribution. In this work a very simple model has been chosen in which water molecules are distributed into two spaces containing both free or protein bound water. In the brain a transcellular space, containing cerebrospinal fluid (CSF), has to be taken into account. However, the heterogeneity associated with the cellular metabolism has been neglected. In the best instrumental conditions of NMR imaging, because of fast exchange between spaces, the longitudinal relaxation (T₁) appears to be monoexponential in the living tissues. The transverse relaxation (T₂) appears frequently to be biexponential. The T₂ decay curves can be decomposed into two parts: a short component, assigned to intracellular water, and a long component assigned to extracellular water. The existence of two spaces was shown by previous in vitro studies. The purpose of this work is to perform an experimental study of short interpulse delays on the T₂ decay curves in tissues, in order to better define the instrumental conditions for clinical imaging

No abstract available

[en] Nuclear magnetic resonance imaging (MRI) if the brain is now known as a very sensitive tool for clearly revealing lesions in white matter, and has thus become important in the study of multiple sclerosis (MS). Since 1981, others have shown the best of MRI: we can see 6 x more lesions than CT. MRI contrast bases mainly on the spatial heterogeneity of the relaxation time of different tissues. The sensitivity depends on the longer T1 and/or T2 of the pathological tissues compared to those of normal tissues. In our series, the authors use mainly T2 weighted MR images and they evaluate their interest for the diagnosis of MS. They study the frequency of the abnormalities and their semeiology in a small number of transversal sections imaged at the level of the lateral ventricles. The authors' aim is to describe the NMR-derived morphological signs of MS and to prospect its interest in the physiopathological studies of this disease

[en] This work is based on a acquisition and pretreating Service of data and signals resulting from several types of functional explorations in cardiology. This Service, through a specialised phone-line, is connected to the Medical Centre of Informatic where the different treatments and on occasion the recording of data are carried out. This functions according to the Real Time Executive System and the clinical results are send back to the investigation unit. The main types of cardiologic analysis as studied by the system are envisaged: measure in real time of the cardiac output and analysis of the radiocardiogram, measure and display of the thoracic potentials, spectral analysis of the vectorcardiogram, quantitative cineangiocardiography and analysis of intracardiac pressures. This system is particularly interesting in that it may treat several processes which could ask for a great capacity of storing and an important calculus power, see for instance the study of thoracic potentials. This type of analysis could not be envisaged financially with isolated calculators. The set of results obtained enables us to investigate thoroughly and precisely the cardiac performance