فهرست مطالب s. f. wang

The objective of this study was to retrospectively analyze the application of dual-energy spectral computerized tomography (DECT) to accurately diagnose breast cancer and lymph node metastasis.

Between May 2018 and December 2019, 37 patients (22 with breast cancer and 15 with normal breast cancer) who underwent spectral CT imaging were analyzed. Metastatic lymph nodes were identified in 14 patients with breast cancer. Twelve patients who underwent traditional CT were included randomly as the control group to compare the radiation dose with spectral CT. Monochromatic levels with an optimal contrast-to-noise ratio for normal breast tissue were obtained. Quantitative parameters of spectral CT were compared between normal breast and breast cancer patients. The spectral curve, histogram, and scatter plot features of metastatic lymph nodes and primary lesions were analyzed.

The monochromatic level with the optimal contrast-to-noise ratio of the breast was approximately 65keV. All quantitative parameters, including values at 40keV–140keV, the concentrations of iodine, spectral curve slope (λHU), and relative iodine concentration were increased in breast cancer compared to those in healthy breasts. Metastatic lymph nodes were more consistent with primary breast cancer lesions in the spectral curve, histogram, and scatter plot, especially in the venous phase. Additionally, the radiation of spectral CT was decreased compared to that of traditional CT.

Spectral CT can be used to identify breast cancer and metastatic lymph nodes.

In previous studies, researchers established mathematical models for predicting the pressure coefficient in simple cavities and tubed vortex reducers based on the assumptions of incompressibility and adiabatic reversibility. However, these mathematical models are not suitable for engineering design and cannot predict the internal pressure and temperature. In this study, we first derived mathematical equations for predicting the pressure drop and temperature change in a tubed vortex reducer, by considering the irreversible loss at the tube inlet. To compensate for the shortcomings of the incompressibility assumption, we developed an iterative alternating calculation method that revises the density. Subsequently, we established a coupled prediction model based on the aforementioned equations and methods. The verified Reynolds stress model results proved that the coupled prediction model and the single prediction model, which represents the incompressible case, yield similar results in predicting pressure under low-rotating-speed conditions. However, as the rotating speed was increased, the error of the single prediction model gradually increased, whereas the coupled prediction model still had good prediction accuracy. With an increase in the length and number of tubes, the pressure drop showed a decreasing trend, whereas the temperature change did not fluctuate significantly.

A novel design of cooling air supply system with dual row pre-swirl nozzles (DRPM) is promoted and investigated. Simplified theoretical analysis and numerical simulation are used to estimate the total temperature reduction and mass flow rate characteristic of DRPM and compared with single row pre-swirl nozzle model (SRPM). The results show that, both models have similar flow structure and the variation of total temperature reduction and dimensionless mass flow rate with rotational Reynolds number and pressure ratio is also similar. Which have an inflection point with the increase of rotational Reynolds number but increases monotonically with the variation of pressure ratio. The pre-swirl system has the maximum flow rate and temperature reduction when the inflow Angle equal to 0 or the swirl ratio equal to 1 at the inlet of the receiver hole. The increase in pressure ratio improves the total temperature reduction and dimensionless mass flow rate as well. In the range of rotational Reynolds number calculated, DRPM can increase the dimensionless mass flow rate by 3.0% but the total temperature reduction decreased by 37.8% in average compared with SRPM. On the other hand, the dimensionless mass flow rate increased by 2.8% and total temperature reduction decreased by 14.9% in average in the range of pressure ratio calculated. Numerical results are in good agreement with the results calculated by simplified theoretical formulas.