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Objective To investigate the effect of different radiation doses on the accuracy of iodine quantification and CT value of virtual monochromatic image with a muti-spectral CT iodine phantom using second-generation dual-layer detector spectral CT(DLCT).Methods The second-generation DLCT scan abdominal phantom was used,which consisted of six different concentrations of iodine rods at 4,8 and 12 g/L.The scan parameters were set at 100,120 and 140 kVp tube voltages,and six radiation exposure sequences were scanned at each tube voltage:5,10,15,20,25 and 30 mGy.Measure the iodine concentration value and the CT value at the single level of 50,70 and 100 keV,and calculate the absolute error value of iodine concentration and CT value under different radiation exposure.SPSS 22.0 software single factor analysis of variance was used to compare the difference between the io-dine concentration and the absolute error of CT value under different Radiation exposure,and LSD method was used to compare the two groups.Results The absolute error of CT value of 4 g/L iodine rod with 10～30 mGy scanning at 100 keV energy level was significantly higher than that of 12 g/L and 8 g/L(P＜0.05),and the absolute error of iodine concentration measurement of other iodine rods with different concentrations at different Radiation exposure had no statistical difference.Conclusions The second-generation double-layer detector spectral CT has high meas-urement stability for iodine concentration quantification and CT value accuracy under conditions of radiation dose greater than 5 mGy.

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<p><b>OBJECTIVE</b>To assess the value of detecting the compositional features of carotid atherosclerotic plaques by 3.0T high resolution magnetic resonance imaging (MRI) in patients with coronary artery disease (CAD).</p><p><b>METHODS</b>Consecutive 104 patients with coronary atherosclerosis confirmed by coronary angiography were prospectively recruited from January 2013 to January 2015 in Tiantan hospital. All patients were imaged with 3.0T high resolution MRI system. After exclusion patients with poor image quality, 97 patients were divided into 3 groups according to the degree of coronary artery stenosis: coronary atherosclerosis group (coronary stenosis between 1%-49%, n=16); single-vessel lesion group (single vessel lesion with stenosis between 50%-100%, n=48); multi-vessel lesion group (two or three vessel lesions with stenosis between 50%-100% or left main stem disease, n=33). The prevalence of total carotid plaque, calcified plaque, lipid-rich necrotic core, intra-plaque hemorrhage, plaque ulcer and rupture were compared among 3 groups.</p><p><b>RESULTS</b>The prevalence of total carotid plaque (81.3%(13/16), 72.9%(35/48), and 93.9%(31/33)) and calcified plaque (50.0%(8/16), 35.4%(17/48), and 42.4%(14/33)) were similar among the 3 groups (both P>0.05). The prevalence of carotid lipid-rich necrotic core in coronary atherosclerosis group was significantly lower than in single-vessel lesion group (18.8%(3/16) vs. 64.6%(31/48), P<0.01) and multi-vessel lesion group(18.8%(3/16) vs. 69.7%(23/33), P<0.01), but there was no significant difference between single-vessel lesion group and multi-vessel lesion group(P>0.05). Intra-plaque hemorrhage was detected in 2 patients of multi-vessel lesion group. There was no plaque ulcer or rupture in this cohort.</p><p><b>CONCLUSION</b>Carotid plaque features are associated with the severity of coronary atherosclerosis in CAD patients.</p>

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Objective To investigate the correlation between vertebral diffusion weigllted imaging (DWI)and dual X-ray absorptiometry(DXA),quantitative computed tomography(QCT)for the evaluation of bone mineral density(BMD).Methods A total of 152 female volunteers[aged from 30 to 80 years,mean age(58.2±14.2)years 1 were recruited in this study.All subjects underwent lateral thoracicolumbar radiographs,dual X-ray absorptiometry(DXA)and quantitative computed tomography(QCT),as well as DWI examination.Lateral spine radiographs(T4-L4)were evaluated with Genant's semiquantitative assessment.BMD was obtained by both DXA and QCT at lumbar spine(L2-L4).Axial vertebral(L2-4)DWI was performed with single shot spin-echo echo-planar imaging(SS-SE-EPI)sequenee (b value=500 s/mm2)after routine MRI examination(saginal T2 WI,T1 WI and axial T2 WI).Apparent diffusion coefficient(ADC)was measured with GE-Functool DWI software.Pearson correlation analysis was used for the statistics.Results There was a decreasing tendency in ADC value with age.A positive correlation was found between ADC(0.241×10-3 mm2/s)and BMD results measured by both DXA (1.038 S/cm3)and QCT(104.2 mg/cm3)examinations(r=0.461,0.731,respectively,P＜0.01).Conclusion DWI is an useful tool for noninvasive evaluation of the pathophysiologic changes of bone marrow in volunteers with difierent bone mineral density.

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OBJECTIVE: To study the whole body bone mineral changes in normal subjects. METHODS: Bone mineral was measured by dual X-ray absorptiometry (DXA) in 292 normal subjects aged 10-79 years, including 152 females and 140 males. They were divided into age-groups by decade. RESULTS: In males, the ages with peak value of total bone mineral content (TBMC), total bone mineral density (TBMD), anteroposterior spine BMD (L2-4 BMD) were in the 30-39, 20-39, 20-29 age-groups respectively. In females, they were all in the 30-39 age-group. Peak values of TBMC, TBMD, L2-4 BMD were higher in males than those in females. Loss of bone mineral for females was more pronounced than that for males. Loss of L2-4 BMD was more pronounced than TBMD. CONCLUSION: This study provides the normal bone mineral data of whole body for males and females, and the characteristic of changes.

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