目的比较优化短反转恢复(Short TI Inversion Recovery,STIR)和三点非对称法脂肪抑制技术(Iterative Dixon of Water-fat with Echo Asymmetry and Least-squares Estimation,IDEAL)对金属植入物磁共振成像(Magnetic Resonance Imaging,...目的比较优化短反转恢复(Short TI Inversion Recovery,STIR)和三点非对称法脂肪抑制技术(Iterative Dixon of Water-fat with Echo Asymmetry and Least-squares Estimation,IDEAL)对金属植入物磁共振成像(Magnetic Resonance Imaging,MRI)图像质量的影响。方法选取腰椎金属内固定术后需行MRI检查的患者30例,行常规序列以及优化STIR、IDEAL序列扫描,通过对感兴趣区信号的强度值分别计算信噪比(Signal to Noise Ratio,SNR)和信噪比(Contrast to Noise Ratio,CNR),对数据结果做统计学分析;对脂肪抑制均匀性、金属伪影大小进行主观评价。结果优化STIR和IDEAL两种方法图像信噪比分别为:19.26±0.96、20.26±1.24(t=-2.94,P<0.01);图像噪声比分别为:7.03±0.94、8.28±0.97(t=-6.07,P<0.01);主观评分脂肪抑制的均匀性分别为:3.47±0.51、3.63±0.50(t=1.37,P>0.05);金属伪影的大小分别为:3.68±0.67,3.74±0.65(t=-0.57,P>0.05)。结论IDEAL技术在脂肪抑制均匀性、金属伪影、图像信噪比等图像质量方面和优化STIR脂肪抑制技术相当,并且可以得到更好的SNR和CNR。因此在机器条件允许的情况下,对于金属植入物的患者可以选择IDEAL脂肪抑制技术进行检查。展开更多
Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat (Triticum aestivum L.) under salt stress were studied. The results showed that several parameters associated with PSⅡ functions,...Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat (Triticum aestivum L.) under salt stress were studied. The results showed that several parameters associated with PSⅡ functions, e.g. Fv/Fo?Fv/Fm and qP were not influenced by lower salt concentration (200 mmol/L NaCl) while CO 2 assimilation rate decreased significantly. When exposed to higher salt concentration (400 mmol/L NaCl), PSⅡ functions were significantly inhibited which led to the decrease of carbon assimilation. These results suggest that different concentrations of salt stress affected photosynthesis by different modes. Salt stress made photosynthesis more sensitive to strong light and led to more serious photoinhibition. Under lower concentration of salt stress, the Q B-non-reductive PSⅡ reaction centers formed at the beginning of photoinhibition could be effectively used to compose active PSⅡ reaction center (RC) and repair the reversible inactivated PSⅡ RC. Under higher concentration of salt stress, PSⅡ reaction centers were seriously damaged during photoinhibition, the Q B-non-reductive PSⅡ RC could only be partly effective at the early time of photoinhibition, thus led to the accumulation of Q B-non-reductive PSⅡ RC in the course of restoration under dim light.展开更多
文摘目的比较优化短反转恢复(Short TI Inversion Recovery,STIR)和三点非对称法脂肪抑制技术(Iterative Dixon of Water-fat with Echo Asymmetry and Least-squares Estimation,IDEAL)对金属植入物磁共振成像(Magnetic Resonance Imaging,MRI)图像质量的影响。方法选取腰椎金属内固定术后需行MRI检查的患者30例,行常规序列以及优化STIR、IDEAL序列扫描,通过对感兴趣区信号的强度值分别计算信噪比(Signal to Noise Ratio,SNR)和信噪比(Contrast to Noise Ratio,CNR),对数据结果做统计学分析;对脂肪抑制均匀性、金属伪影大小进行主观评价。结果优化STIR和IDEAL两种方法图像信噪比分别为:19.26±0.96、20.26±1.24(t=-2.94,P<0.01);图像噪声比分别为:7.03±0.94、8.28±0.97(t=-6.07,P<0.01);主观评分脂肪抑制的均匀性分别为:3.47±0.51、3.63±0.50(t=1.37,P>0.05);金属伪影的大小分别为:3.68±0.67,3.74±0.65(t=-0.57,P>0.05)。结论IDEAL技术在脂肪抑制均匀性、金属伪影、图像信噪比等图像质量方面和优化STIR脂肪抑制技术相当,并且可以得到更好的SNR和CNR。因此在机器条件允许的情况下,对于金属植入物的患者可以选择IDEAL脂肪抑制技术进行检查。
文摘Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat (Triticum aestivum L.) under salt stress were studied. The results showed that several parameters associated with PSⅡ functions, e.g. Fv/Fo?Fv/Fm and qP were not influenced by lower salt concentration (200 mmol/L NaCl) while CO 2 assimilation rate decreased significantly. When exposed to higher salt concentration (400 mmol/L NaCl), PSⅡ functions were significantly inhibited which led to the decrease of carbon assimilation. These results suggest that different concentrations of salt stress affected photosynthesis by different modes. Salt stress made photosynthesis more sensitive to strong light and led to more serious photoinhibition. Under lower concentration of salt stress, the Q B-non-reductive PSⅡ reaction centers formed at the beginning of photoinhibition could be effectively used to compose active PSⅡ reaction center (RC) and repair the reversible inactivated PSⅡ RC. Under higher concentration of salt stress, PSⅡ reaction centers were seriously damaged during photoinhibition, the Q B-non-reductive PSⅡ RC could only be partly effective at the early time of photoinhibition, thus led to the accumulation of Q B-non-reductive PSⅡ RC in the course of restoration under dim light.
