Polarization enhancement technique for nuclear quadrupole resonance detection.

We demonstrate a dramatic increase in the signal-to-noise ratio (SNR) of a nuclear quadrupole resonance (NQR) signal by using a polarization enhancement technique. By first applying a static magnetic field to pre-polarize one spin subsystem of a material, and then allowing that net polarization to be transferred to the quadrupole subsystem, we increased the SNR of a sample of ammonium nitrate by one-order of magnitude.

MRI with an atomic magnetometer suitable for practical imaging applications.

Conventionally implemented MRI is performed in a strong magnetic field, typically >1T. The high fields, however, can lead to many limitations. To overcome these limitations, ultra-low field (ULF) [or microtesla] MRI systems have been proposed and implemented. To-date such systems rely on low-Tc Superconducting Quantum Interference Devices (SQUIDs) leading to the requirement of cryogens. In this letter, we report ULF-MRI obtained with a non-cryogenic atomic magnetometer. This demonstration creates opportunities for developing inexpensive and widely applicable MRI scanners.

[Use of a Soviet-made device for recording late ventricular potentials]. / Ispol'zovanie otechestvennoi ustanovki dlia registratsii pozdnikh potentsialov zheludochkov.

Late ventricular potentials (LVP) were detected with an ECG signal-averaging installation developed at the Institute of Radio Engineering and Electronics, USSR Academy of Sciences. A total of 103 patients were examined: 33 with sustained ventricular tachycardia (VT), 30 with unsustained VT and high-grade ventricular premature contraction, 20 with coronary heart disease, postinfarction cardiosclerosis without arrhythmias and 20 apparently healthy subjects (controls). LVPs are the most susceptible to sustained VT in the presence of postinfarction cardiosclerosis (77%), their specificity is lower (70%). LVPs are a low sensitive marker (35%) for sustained idiopathic VT. In unsustained VT and high-grade premature ventricular contraction, LVPs were recorded infrequently in 1 (3%) of the 30 patients.

Tikhonov regularisation approach to dynamic biomagnetic imaging.

We describe a method of identifying the distributed sources associated with biomagnetic data sets. The technique is based on Tikhonov regularisation. An algorithm has been implemented in FORTRAN on a PC/AT computer. Its predictions are stable with respect to measurement noise.

[An experimental unit for high-resolution electrocardiography and the method of recording of late ventricular potentials]. / Eksperimental'nyi kompleks dlia élektrokardiografii vysokogo razresheniia i sposob registratsii pozdnikh potentsialov zheludochkov.

One of the methods of recording late ventricular potentials, markers of decelerated depolarization of the heart ventricles, is depicted. The complex suggested by the authors consists of an interface connected to the personal computer, a block for cardiosignal processing, and an analog-to-digital converter. The averaging is realized after preliminary signal processing, which results in the computation of the mean period of the QRS. The mode of automatic amplification is provided as are alterations of the lower frequency of the section of the band-pass filters as well as the switching on of the rejection filter.

[The first experience using a Soviet-made device for recording late ventricular potentials]. / Pervyi opyt primeneniia otechestvennoi ustanovki dlia registratsii pozdnikh potentsialov zheludochkov.

Late potentials (high-frequency oscillation of the initial part of ST-segment) reflect decelerated ventricular depolarization and predispose onset of reentry arrhythmias. Investigators are keenly interested in their possible exact registration. The article describes the experience of realization of late potentials registration method based on the method of Simson et al, with the use of a USSR-produced electronic apparatus. The first experience of clinical application of the late potentials registration method in patients with IHD is analysed. Presence of late potentials is correlated with spontaneous ventricular arrhythmias and possible disturbances of left ventricular contractility. The obtained data as well as analysis of technical possibilities of the developed system allow evaluation of the proposed technique as acceptable for late potentials registration.

[Methodologic problems in the use of dynamic magnetic mapping of the heart]. / Metodicheskie voprosy ispol'zovaniia dinamicheskogo magnitnogo kartografirovaniia serdtsa.

Dynamic magnetic maps have been constructed with the help of a magnetocardiograph, based on a superconductive quantum interferometric transducer, for 19 normal subjects, 12 patients with postinfarction cardiosclerosis, 5 patients with ventricular extrasystoles, and 1 patient with left-ventricular hypertrophy. A correlation between general patterns and ventricular depolarization phases of normal subjects' maps was demonstrated, using a biophysical myocardial excitation wave model as an even layer of current dipoles. Methods are proposed for the localization of ectopic pacemaker, postinfarction scars and hypertrophic myocardial areas within the same model.