[Reference ranges for Doppler echocardiographic measurements within seven days of age in preterm infants].

Objective: To establish reference ranges for Doppler echocardiography in preterm infants within 7 days after birth based on different gestational age (GA), birth weight (BW) and body surface area (BSA). Methods: This retrospective study analyzed Doppler echocardiographic measurements of 489 premature infants, who were admitted to the neonatal Intensive Care Unit of Department of Pediatrics, Peking University Third Hospital from March 2017 to February 2020. These infants were divided into four groups according to GA:<28 weeks, 28-31+6 weeks, 32-33+6 weeks and 34-36+6 weeks; and five groups according to BW:<1 000 g, 1 000-1 499 g, 1 500-1 999 g, 2 000-2 499 g and ≥ 2 500 g;and 14 groups according to BSA from 0.07-0.20 m2. The Doppler values among groups were compared by independent sample KW test, and based on which, the 95%CI were established as reference ranges. Results: Among the 489 preterm infants, males were 264 and females were 225. Their GA, BW and BSA were 32.0 (30.0,33.9) weeks, 1 700 (1 260,2 040) g and 0.13 (0.11,0.15)m2, respectively. Measurements are presented charting as 95%CI with respect to GA,BW and BSA for preterm infants aged 0-7 days. Aortic valve(AV) flow rate, mitral valve E peak (MV-E), mitral valve E/A (MV-E/A) and tricuspid valve E peak (TV-E) were all correlated with GA, BW and BSA (r = 0.263, 0.256, 0.324 and 0.114 for GA; 0.292, 0.261, 0.281 and 0.135 for BW; 0.287, 0.268, 0.312 and 0.140 for BSA, all P<0.05). Within the first 7 days after birth, the greater the GA, birth weight and BSA, the greater the AV, MV-E, MV-E/A and pulmonary valve flow rate(all P<0.05). According to the above grouping of GA, the 95%CI of AV were 48-54, 52-57, 58-63 and 60-65 cm/s, respectively; and the 95%CI of MV-E were 32-37, 33-36, 39-42 and 40-45 cm/s, respectively; and the 95%CI of MV-E/A were 0.66-0.73, 0.74-0.80, 0.81-0.90 and 0.92-1.06. And according to the above grouping of BW, the 95%CI of AV were 45-53, 49-53, 59-64, 60-66 and 56-65 cm/s, respectively; 95%CI of MV-E were 29-35, 32-36, 38-41, 40-44 and 38-46 cm/s, respectively; 95%CI of MV-E/A were 0.65-0.74, 0.74-0.81, 0.81-0.99, 0.86-0.99 and 0.84-1.07. Conclusion: The 95%CI of Doppler echocardiographic measurements established based on GA, BW and BSA could provide a reference for preterm infants aged 0-7 days.

[Reference ranges for M-mode echocardiographic measurements within seven days after birth in preterm infants].

Objective: To establish reference ranges for M-mode echocardiography in preterm infants within 7 days after birth based on different gestational age (GA) and birth weight. Methods: This retrospective study analyzed M-mode echocardiographic values of 489 premature infants, who were admitted to the neonatal intensive care unit of Department of Pediatrics, Peking University Third Hospital from March 2017 to February 2020. These infants were divided into four groups according to GA:<28 weeks, 28-31+6weeks, 32-33+6weeks and 34-36+6weeks; and five groups according to birth weight:<1 000 g, 1 000-1 499 g, 1 500-1 999 g, 2 000-2 499 g and ≥2 500 g. The M-mode values among groups were compared by independent sample K-W test, and based on which, the 95% confidence interval (CI) and the Z-value reference ranges were established. Results: The gestational age of these infants was 32.0 (24.0-36.7) weeks, and the birth weight was 1 700 (650-3 180) g. The interventricular septum end-diastolic thickness (IVSd), left ventricular posterior wall end-diastolic thickness (LVPWd), left atrial diameter (LAD), left ventricular end-diastolic diameter (LVED), left ventricular end-systolic diameter (LVES), right ventricular outflow tract (RVOT) and the right ventricular end-diastolic diameter (RVED), were all correlated with GA and birth weight (r = 0.209, 0.216, 0.430, 0.608, 0.495, 0.464, 0.447; r = 0.275, 0.288, 0.445, 0.609, 0.496, 0.499, 0.464;all P<0.01). While the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) had no correlation with GA or birth weight (all P<0.05). Within the first 7 days after birth, the greater the GA and birth weight, the greater the inner diameters of the heart chambers, and the thicker the ventricular wall. The LVEF and LVFS maintained a high and stable level within the first week of life (95%CI: 67%-69%, 34%-36%). Conclusions: According to different GA and birth weight, the reference ranges for chamber diameters, interventricular septal thickness and left ventricular wall thickness within 7 days were established. The 95% CI and Z score ranges for M-mode echocardiographic measurements established based on gestational age and birth weight can provide a reliable reference for preterm infants aged 0-7 days.

The evaluation of quantitative autoradiogram processing systems for cerebrovascular research.

The development of an image processing system for quantitative autoradiography (QAR) is described, with emphasis on the evaluation of image digitization systems independent of hardware or software design. Each step of converting the autoradiographic image to a functional image of a physiological variable such as local cerebral blood flow (LCBF) or local cerebral glucose utilization rate (LCGU) is evaluated. The autoradiograms are digitized, aligned, transformed to a tissue tracer concentrations image based on the gray value (GV) of calibrated 14C standards, subtracted from each other as required in double tracer QAR, and converted to an LCBF or LCGU image using the proper tracer kinetic model. Geometric size, mean and standard deviation of the LCBF, LCGU, and tracer concentration can be measured in regions of interest. These steps are evaluated separately for their contribution to the accuracy and precision of the final, functional image. The qualities important in the final image are spatial resolution, intensity linearity, and intensity sensitivity, as well as the noise level. Techniques for evaluating the LCBF image include: (1) optimization of the input linearity and dynamic range of the video camera to maximize relative intensity sensitivity of the final functional image; (2) visual inspection of the curves used to fit various functions that are important in the conversion of the GV image to an image of physiological interest; (3) consideration of the noise introduced by the input devices and during the image conversion; and (4) above all, the integration of the various parts of the system to produce an accurate image useful in cerebrovascular research.

A technique of double-resonant operation of 19F and 1H quadrature birdcage coils.

A technique was developed to change the resonant frequency of a rotating field birdcage coil from 19F resonance (76.14 MHz) to 1H resonance (80.92 MHz). This was done by inserting an additional shield with a smaller radius on the coil which resonates at 19F. It was shown that the inhomogeneity introduced by reducing the shield radius is not significant. A working coil built with this technique produced both 19F and 1H images satisfactorily.

A mathematical description of pressures in alveolar pores of Kohn.

Small interalveolar holes within the lung are called pores of Kohn. Some researchers have correlated enlarged pore size with diseases, e.g. emphysema, that are characterized by tissue destruction. Mathematical models of the pressures generated in closed, fluid-filled and open, fluid-lined pores demonstrate that pressures capable of rupturing lung tissue can be developed in a pore due to the surface tension and shape of the air-liquid interface. Pore enlargement accompanied by tissue destruction is presented as a possible mechanism for the disease process observed during aging and the development of emphysema in the lung.