Necessary and sufficient conditions for equalities between a 2 y′(I-P Xx)y and minimum norm quadratic unbiased estimator of variance under the general linear model, where a 2 is a known positive number, are...Necessary and sufficient conditions for equalities between a 2 y′(I-P Xx)y and minimum norm quadratic unbiased estimator of variance under the general linear model, where a 2 is a known positive number, are derived. Further, when the Gauss? Markov estimators and the ordinary least squares estimator are identical, a relative simply equivalent condition is obtained. At last, this condition is applied to an interesting example.展开更多
Objective To measure volume and other parameters of normal adrenal glands in Chinese adults with 64-slice multidetector CT, to evaluate the relationship of volume result with age, sex and body size, and to explore the...Objective To measure volume and other parameters of normal adrenal glands in Chinese adults with 64-slice multidetector CT, to evaluate the relationship of volume result with age, sex and body size, and to explore the correlations between adrenal volume and other measurements. Methods This study was based on 125 acquired contrast-enhanced upper abdominal CT scans performed with a 64-slice CT. The final study group consisted of 81 patients (49 males, 32 females). Portal venous phase images were studied for the measurements. Both the reconstruction interval and thickness were 1.5 mm. Each adrenal gland was outlined manually with computer-assistant technology to calculate its volume. The maximal sectional area, length, width and thickness of each adrenal gland were also measured. Results The mean age of total population was 47.9±13.0 (range: 20-76) years. The left, right, and total adrenal gland volumes were 4.23±0.74 (range: 2.85-5.83) cm 3 , 4.26±0.86 (2.59-6.56) cm 3 , and 8.50±1.40 (5.80-11.39) cm 3 , respectively. These volumes increased with weight (r=0.381, 0.389, and 0.437 respectively, all P<0.001), height (r=0.386, P<0.001; r=0.297, P=0.007; r=0.384, P<0.001) and body surface area (r=0.406, 0.392, and 0.452, all P<0.001). There was no significant difference in left, right or total adrenal volume with regard to sex after applying General Linear Model procedure to reduce the impact of weight (F=1.304, 0.064, and 0.597, all P>0.05), nor did volume change significantly with age (r=-0.033, -0.014, and -0.026, all P>0.05). Nearly all descriptors of bilateral adrenal glands correlated with ipsilateral volume except thickness (r=-0.027, P=0.814) and width (r=0.166, P=0.138) in the left side. Among these parameters, length had a stronger correlation with volume than others in the both left (r=0.412, P<0.001) and right (r=0.516, P<0.001) adrenal glands. Conclusion Our study has defined the volume distribution and other parameters of normal adrenal glands in Chinese adults, which provide a baseline for future studies.展开更多
文摘Necessary and sufficient conditions for equalities between a 2 y′(I-P Xx)y and minimum norm quadratic unbiased estimator of variance under the general linear model, where a 2 is a known positive number, are derived. Further, when the Gauss? Markov estimators and the ordinary least squares estimator are identical, a relative simply equivalent condition is obtained. At last, this condition is applied to an interesting example.
文摘Objective To measure volume and other parameters of normal adrenal glands in Chinese adults with 64-slice multidetector CT, to evaluate the relationship of volume result with age, sex and body size, and to explore the correlations between adrenal volume and other measurements. Methods This study was based on 125 acquired contrast-enhanced upper abdominal CT scans performed with a 64-slice CT. The final study group consisted of 81 patients (49 males, 32 females). Portal venous phase images were studied for the measurements. Both the reconstruction interval and thickness were 1.5 mm. Each adrenal gland was outlined manually with computer-assistant technology to calculate its volume. The maximal sectional area, length, width and thickness of each adrenal gland were also measured. Results The mean age of total population was 47.9±13.0 (range: 20-76) years. The left, right, and total adrenal gland volumes were 4.23±0.74 (range: 2.85-5.83) cm 3 , 4.26±0.86 (2.59-6.56) cm 3 , and 8.50±1.40 (5.80-11.39) cm 3 , respectively. These volumes increased with weight (r=0.381, 0.389, and 0.437 respectively, all P<0.001), height (r=0.386, P<0.001; r=0.297, P=0.007; r=0.384, P<0.001) and body surface area (r=0.406, 0.392, and 0.452, all P<0.001). There was no significant difference in left, right or total adrenal volume with regard to sex after applying General Linear Model procedure to reduce the impact of weight (F=1.304, 0.064, and 0.597, all P>0.05), nor did volume change significantly with age (r=-0.033, -0.014, and -0.026, all P>0.05). Nearly all descriptors of bilateral adrenal glands correlated with ipsilateral volume except thickness (r=-0.027, P=0.814) and width (r=0.166, P=0.138) in the left side. Among these parameters, length had a stronger correlation with volume than others in the both left (r=0.412, P<0.001) and right (r=0.516, P<0.001) adrenal glands. Conclusion Our study has defined the volume distribution and other parameters of normal adrenal glands in Chinese adults, which provide a baseline for future studies.
