Object. The purpose of this work is to reveal the possibilities of low-field 23Na MRI. It was supposed to obtain images of various human organs using the 3D-scanning method, and to do this with minimal hardware modifications of a typical clinical 0,5T scanner. Materials and methods. The proprietary receiving coils, originally intended for registering proton signals (21,1 MHz), were transformed to transceiver ones and tuned to the sodium Larmor frequency of 5,6 MHz. The scanning was carried out by the 3D-gradient echo method with the parameters: TR/TE=44,7/12 ms, FA=45° and isotropic resolution of 6 mm. To increase SNR, apodization in k-space was applied during data processing. Results. 23Na MRI (including volumetric reconstructions) of several human organs – head, breast, heart, joints were obtained with SNR up to 15. Discussion. When developing low-field 23Na MRI, it is advisable to focus on recording only the T2long component (>15 ms). In this case, it is possible to narrow the receiver bandwidth as much as possible and thereby minimize noise. In addition, the requirements for the transmission path are reduced. As a result, for debugging MRI methods, the equipment of a typical clinical scanner, which is supplemented by coils tuned to the sodium NMR frequency only, can be used.

Experiments on proton and sodium MRI at 0.5 T are described to assess the sensitivity of various types of coils, namely solenoidal, surface, volumetric, and with specific complex geometry. Each type of coil, characterized by its geometric specificity, was built to record MR signal of protons (1H) and sodium (23Na) at 21.1 MHz and 5.6 MHz, respectively. Sodium coils were initially built for 1H MRI and modified for 23Na MRI. Measurements in a container phantom filled with a 12% salt solution showed that the quality factor and sensitivity of various type coils approximately coincide at both sodium and proton resonance frequencies. The possibility of using data on SNR for a highly concentrated sample and Q-factor measurements to predict MRI results for a weakly concentrated sample is considered. These measurements represent a guide for extension to multinuclear whole body low field MRI clinical platform that is usually designed to operate in proton mode only.

Background. One promising direction in development of contactless techniques for assessment of the human psychoemotional slate (PES) is elucidation of the relationships between psychophysiological indices and electromagnetic radiation in the IR and THz ranges. Objective. To present a complex approach to assessing PESs based on combining psychological testing and psychophysiological diagnostics with measurements of radiation in the IR-THz range from face areas. Methods. Stressful psychoemotional states were provoked by physical or cognitive stressors. The PES was monitored by psychological testing and registration of heart rate, photoplethysmogram, galvanic skin response, and respiration rate. The facial images in the IR-THz range were extracted by an IRIV-T0831C detector (NEC, Japan). Results and Discussion. Different PESs are characterized by different specific patterns of psychophysiological parameters. Scores on the anxiety test are highly correlated with scores on the chronic stress questionnaire, but there are no reliable links between the data of psychological tests and the psychophysiological indicators. This discrepancy allows us to assume that for reliable identification of PESs, it is necessary to combine these technologies into one diagnostic complex. We found statistically significant correlations between the intensity of the IR-THz image in the forehead and the galvanic skin response. Conclusion. For the effective diagnosis and forecast of changes in the PES, it is important to consider both the psychological and physiological data. Despite the relatively low signal-to-noise ratio and low frequency of image recording, it is possible to extract informative THz parameters of the broadband IR-THz signal and associate them with psychophysiological reactions. The improvement of IR-THz detectors and the development of new processing methods will allow wide use of the THz range for remote assessment of human PESs in real time.

We propose a new approach to non-contact recording of respiratory function based on the analysis of a sequence of Infrared-terahertz images of the human face, allowing the processes that occur during breathing to be visualized. To obtain quantitative estimates of the respiratory function, two methods are proposed. The first one utilizes a probe which implements the function of spatial differentiation and provides high sensitivity, but requires an increased accuracy of positioning the probe at the nasal opening and scaling in accordance with the camera angle. The other one is a histogram method for obtaining quantitative estimates of the external respiratory function, which is scale invariant and does not require precise positioning, but has a lower sensitivity compared to the first one. The methods proposed have made it possible to remotely evaluate the respiratory rate, which correlates well with the data obtained by a contact method of respiratory function registration.

A new approach to terahertz (THz) diagnostics of the human psychoemotional state is proposed, based on the analysis of the THz contribution to the total signal while simultaneously recording the IR and THz emissions from the human body (hereinafter referred to as the IR – THz image). The developed image-processing algorithm allows extraction of the informative contribution determined by the THz radiation from the total signal perceived by the recording system. Simultaneous registration of the IR – THz images of the human face and the psychophysiological indicators are carried out in situations of physical stress (short-term intense physical exercise – squats functional test), electrical stimulation, and information stress (cognitive load – simple arithmetic mental calculations). The obtained data are compared with those of similar measurements at rest. It is shown that using cluster analysis of IR – THz images it is possible to divide the test subjects into classes according to the type of reaction of the circulatory system under stressful conditions.

Variations of psychophysiological characteristics, biochemical parameters and terahertz images of a human face were studied during the special test pass which modeled stress situations.

Human and rat skin reflection spectra and the effect of glucose and glycerol on these spectra are studied in vivo by terahertz time-domain spectroscopy in the frequency range of 0.1–2.0 THz. Variations in skin optical properties proved to correlate with changes in the blood glucose level.

В работе приведены результаты исследования методом импульсной терагерцевой спектроскопии кожи человека и животных in vivo в диапазоне частот 0.1–2.0 ТГц. Показано, что уровень глюкозы в крови оказывает влияние на спектры отражения кожи.

Deviations of the ortho/para ratio from its normal value (3: 1) were observed by spectral selective detection of ortho and para water molecules when water vapor passed through a column with a nanoporous polymeric adsorbent. The effect was suggested to be related to the nonstationary dynamics of sorption, that is, nonequilibrium character of chromatography. In terms of this model, the factor of spin ortho/para selectivity is slow and unequal diffusion of the spin isomers of water molecules inside the adsorbent, a process spurious for ideal equilibrium chromatography.

Методом спектрально-селективного детектирования орто- и пара-молекул воды при пропускании водяного пара через колонку с нанопористым полимерным адсорбентом зарегистрировано отклонение орто/пара-отношения от нормального значения (3:1). Предположено, что эффект связан с нестационарностью динамики сорбции, т.е. с неравновесностью хроматографии. В рамках этой модели показано, что фактором спиновой орто/пара-селективности является паразитный для идеальной равновесной хроматографии процесс медленной и неодинаковой диффузии спин-изомеров водных молекул внутри адсорбента.

A diode laser spectrometer, which is ment for recording ortho-and paracomposition of water vapor in gas mixtures, is described. The studied mixture is probed by infrared radiation at frequencies of the resonance absorptions of ortho-and paramolecules of water (λ ≈ 1.85 μ m). The recording rate of spectral ortho-and paralines is 2 Hz, and the ortho/para composition is calculated in real time with respect to their integrated intensities. An accuracy of 1% is ensured in a 0.01- to 20-Torr partial pressure range for water vapor and in a 0- to 700-Torr partial pressure range for the buffer gas.

Описан спектрометр на диодном лазере, предназначенный для регистрации орто/пара-состава водяного пара в газовой смеси. Исследуемая смесь зондируется инфракрасным излучением на частотах резонансного поглощения орто- и пара-молекул воды ( 1.85 мкм). С частотой 2 Гц регистрируются спектральные орто- и пара-линии, по отношению интегральных интенсивностей которых в реальном масштабе времени рассчитывается орто/пара-состав. Точность 1% обеспечивается в диапазоне парциальных давлений водяного пара от 0.01 до 20 Торр и буферного газа от 0 до 700 Торр.

Violation of the normal spin 3:1 ortho/para ratio in saturated water vapor above a 0.5% water-glycerol solution was detected using the BWO spectroscopy method. The solution was prepared by pumping the initial solution out at room temperature. The effect is supposed to be due to increased fugacity of ortho water molecules from the solution and the corresponding para enrichment of residual water.

Sorption experiments with water/glycerol solution were performed by measuring the ortho/para content in saturated water vapor using the 1-THz BWO spectral method. The results were interpreted as detection (i) of preferential fugacity of ortho molecules from the glycerol surface and (ii) the ability of glycerol to keep the deviation from 3:1 normal ortho/para water ratio for unexpectedly long time (several weeks for 0.5 % water concentration).

It is an intriguing challenge for researchers to separate water into its spin isomeric modifications -paramagnetic ortho-water and nonmagnetic para-water. Accessibility of these new forms of water could stimulate the research in many branches of science. We report on the application to this problem of the terahertz BWO-based technique as a diagnostic method.