Sex differences and age-related changes in vertebral body volume and volumetric bone mineral density at the thoracolumbar spine using opportunistic QCT

ObjectivesTo quantitatively investigate the age- and sex-related longitudinal changes in trabecular volumetric bone mineral density (vBMD) and vertebral body volume at the thoracolumbar spine in adults.MethodsWe retrospectively included 168 adults (mean age 58.7 ± 9.8 years, 51 women) who received ≥7 MDCT scans over a period of ≥6.5 years (mean follow-up 9.0 ± 2.1 years) for clinical reasons. Level-wise vBMD and vertebral body volume were extracted from 22720 thoracolumbar vertebrae using a convolutional neural network (CNN)-based framework with asynchronous calibration and correction of the contrast media phase. Human readers conducted semiquantitative assessment of fracture status and bony degenerations.ResultsIn the 40-60 years age group, women had a significantly higher trabecular vBMD than men at all thoracolumbar levels (p<0.05 to p<0.001). Conversely, men, on average, had larger vertebrae with lower vBMD. This sex difference in vBMD did not persist in the 60-80 years age group. While the lumbar (T12-L5) vBMD slopes in women only showed a non-significant trend of accelerated decline with age, vertebrae T1-11 displayed a distinct pattern, with women demonstrating a significantly accelerated decline compared to men (p<0.01 to p<0.0001). Between baseline and last follow-up examinations, the vertebral body volume slightly increased in women (T1-12: 1.1 ± 1.0 cm3; L1-5: 1.0 ± 1.4 cm3) and men (T1-12: 1.2 ± 1.3 cm3; L1-5: 1.5 ± 1.6 cm3). After excluding vertebrae with bony degenerations, the residual increase was only small in women (T1-12: 0.6 ± 0.6 cm3; L1-5: 0.7 ± 0.7 cm3) and men (T1-12: 0.7 ± 0.6 cm3; L1-5: 1.2 ± 0.8 cm3). In non-degenerated vertebrae, the mean change in volume was <5% of the respective vertebral body volumes.ConclusionSex differences in thoracolumbar vBMD were apparent before menopause, and disappeared after menopause, likely attributable to an accelerated and more profound vBMD decline in women at the thoracic spine. In patients without advanced spine degeneration, the overall volumetric changes in the vertebral body appeared subtle

Messung der räumlichen Polarisationsverteilung in polymeren Elektreten mit der Laser-Intensitäts-Modulations-Methode

Detn. of the spatial polarization distribution in thermally poled poly(vinylidene fluoride) electrets by the laser intensity modulations method (LIMM) is discussed. The resulting curves were normalized with the aid of the quasistatic detd. pyroelec. coeff. and exhibited a dependence on the field strength.status: publishe

Latest design trends in modal accelerometers for aircraft ground vibration testing

Accelerometers are widely encountered in structural analysis applications such as modal analysis with vibrational or impact input excitation and operational modal analysis. This paper aims to outline design trends and requirements for acceleration sensors in order to insure optimal structural analysis measurement results. Key parameters for a performing modal sensor are: sensitivity, mass, noise level, amplitude and phase frequency response, as well as thermal transient response, thermal sensitivity response, transverse sensitivity (cross axis), base strain and survivability which will be taken into detailed consideration in this paper. Nowadays three IEPE (Integrated Electronic Piezo Electric) sensor designs can be considered: piezo-ceramic shear, piezobending beam and piezo-crystal shear mode sensing elements. Unfortunately, none of the sensor technologies available on the market today will allow for the best of all parameters mentioned earlier. Advantages and disadvantages have to be considered in order to make the optimal choice. Even though Variable Capacitive (VC) MEMS sensors can be used in cases of operational modal analysis at ultra-low frequencies, such as Bridge Structural Testing or Monitoring, only IEPE technology will be in this study. Besides the technical properties of an accelerometer, the handling qualities during installation and removal are extremely important for high channel count systems. Installation time, error rate and reliability for more than 10 years during several tests a year are of special interest for the user. Among the considerations made here, easy monitoring and sensitive axis alignment compared to the overall coordinate system will be examined. The German Aerospace Center (DLR) will illustrate the applicability of accelerometers in context of industrial testing such as Ground Vibration Testing (GVT) of aircraft structures or structural and modal testing of wind turbine blades where innovative methods such as allowing one free adjustable degree of freedom around one rotational axis in order to freely orient the sensitive axis