Objective To study the difference of image quality which based on different reconstruction in head dual‐energy computed tomography angiography (DECTA) scanning ,and evaluate the radiation dose which using different tube voltage in DEC‐TA .Methods An anthropomorphic head phantom with simulated arteries was used for DECTA scanning by different scan parame‐ters (tube voltage 80/140 kV and tube voltage 100/140 kV) ,the data was reconstructed with filtered back projection (FBP) and Si‐nogram Affirmed Iterative Reconstruction (SAFIRE) .The CT values with SD were measured and calculate to SNR and CNR ,the dose length product (DLP) was recorded and invert to effective dose .The image quality and radiation dose were evaluated in differ‐ent imaging condition .Results The image noise of SAFIRE reconstruction was lower than FBP reconstruction in same san parame‐ters .The increase of tube current‐time product from 100 mAs to 300 mAs ,it shows the characteristics of linear tendency .When it was on 260 mAs ,the image quality become stable .The difference between the two groups(80/140 kV ,100/140 kV)of SD of CT value by SAFIRE was significant (P< 0 .05) ,the difference of SNR and CNR between the two groups was not significant (P>0 .05) .The effective doses of group A (80/140 kV) was significantly lower than group B(100/140 kV) .Conclusion Using tube voltage of 80/140 kV combine with SAFIRE algorithm in head DECTA can ensure the image quality ,which can significantly reduce radiation dose .

Objective To evaluate the radiation dose to patients using radial and femoral artery access in coronary angiography (CAG) and intracoronary stenting (IS) ,provide basis for clinical intervention path .Methods The data of 190 samples (43 by femo-ral and 147 by radial) underwent CAG and 54 samples (17 by femoral and 37 by radial) underwent CAG+IS were analyzed retro-spectively .All samples were divided into two groups (radial group and femoral group) by different approach ,and radiation dose in different approach were analyzed .Results There was no significant difference of Dose Area Product (DAP) and Cumulative Dose (CD) using femoral and radial access in CAG (P>0 .05) .Separating two samples which CD were much higher than others ,the mean DAP was 23 .93 Gy · cm2 and the mean CD was 358 .85 mGy using radial vs .27 .06 Gy · cm2 and 369 .57 mGy using femoral , not distinctive either(P=0 .734 ,P=0 .834) .In CAG+IS ,the mean DAP was 82 .64 Gy · cm2 using radial and it was 78 .11 Gy · cm2 using femoral ,and the mean CD was 1 286 .41 mGy using radial and it was 1 267 .76 mGy using femoral .There were no signifi-cant difference in both DAP and CD (P=0 .705 ,P= 0 .919) .Conclusion The radiation dose of DAP and CD were not different when using radial access and using femoral access in CAG and CAG +IS .

Objective To assess the effectiveness of iterative metal artifact reduction (IMAR) on metal artifacts reduction in thorax scan.Methods Thoracic phantom with two pedicle screws implanted in both sides of the T5 vertebrae was used,with the scan parameters of 130 kV and CARE Dose 4D,the phantom was scanned with and without the screws respectively.Images without screws were reconstructed with FBP.Images with screws were reconstructed with FBP and IMAR respectively.Three ROIs were selected on tissues including aorta,pulmonary and paravertebral soft tissue on image slice adjacent to the screws.The CT value and standard deviations (noise) of ROIs were measured,and the deviation of CT value (△HU) was calculated as the difference between CT values in images with and without screws.Twenty-six cases who received chest CT examination and with pedicle screw implant in scanning range were collected.The scanning parameters and image reconstruction methods were the same as phantom scan.The CT value (HU) of metal artifacts adjacent to vertebrae and dorsal soft tissue was measured,and the image quality of reconstructed image by two skilled radiologists independently was evaluated.Results In the phantom after implanted screws,the noise were significantly reduced by IMAR compared to FBP in all the three ROIs of aorta,pulmonary and paravertebral soft tissue (P＜0.05),and the △HU was significantly smaller in IMAR compared to that with FBP (P＜0.01).In 26 patients,there were significant differences in CT value of vertebral bone tissue and dorsal soft tissue between FBP and IMAR (P＜0.05),and the subjective evaluation scores of the two image reconstruction methods showed a statistically significant difference (P＜0.05).Conclusion IMAR can significantly reduce streak artifacts of metal implant and adjuste the CT values of artifact affected tissues to make it more close to the true value without metal implant.

Objective To investigate the influence of acquisition time of C-arm cone-beam CT on image quality and radiation dose of cerebral angiography.Methods C-arm cone-beam CT of cerebral angiography was performed on the male anthropomorphic head phantom,with DynaCT imaging mode and the acquisition time of 5 s,8 s and 20 s were used.Scanning was performed with each acquisition time for three times,and VR,MIP and MPR images were reconstructed.The attenuation values and their standard deviations of intracranial segment of the internal carotid artery (ICA),middle cerebral artery(MCA),anterior cerebral artery(ACA) and uniformed brain tissues were measured to calculate the image noise,signal to noise ratio (SNR) and contrast to noise ratio (CNR).We used the image noise,SNR and CNR as the objective standard to evaluate the image quality,and One-way ANOVA analysis of variance was used to assess the difference among them.A scale with scores 1 to 5 was used to rate the quality of the reconstructed image of ICA,MCA,ACA as a subjective evaluation,the difference among the evaluation scores were analyzed using Kruskal-wallis.We recorded the dose area product (DAP) of each acquisition time and the effective dose(ED) was calculated to assess the radiation dose,the difference among them were analyzed using One-way ANOVA analysis of variance.Results In C-arm cone beam CT 20 s imaging,the SNR of intracranial segment of the ICA,M CA,ACA were 22.29± 1.41,29.36 ±0.11 and 23.13 ±2.10 respectively,in 5 s imaging13.83 ±0.61,14.65 ±0.16 and 12.79±0.19 respectively,in 8 s imaging 14.92±0.96,18.97 ± 1.24 and 16.65 ±0.46 respectively,all the results showed a significant difference (F valued 58.19,327.29,52.74 respectively,all P valued＜0.01),the CNR of 20 s imaging were higher than that of 5 s and 8 s imaging,the Noise of ICA,MCA,ACA and the uniformed brain tissues of 20 s imaging were lower than that of 5 s and 8 s imaging,all the results showed significant difference (all P valued＜0.01).The subjective evaluation scores of VR imaging of 5 s,8 s and 20 s were 3.61 ±0.49,4.06±0.53,4.72±0.45 respectively,the scores of MIP imaging were 3.42±0.50,3.83±0.65 and 4.50±0.51 respectively,the scores of MPR imaging were 2.83±0.45,3.14±0.35 and 3.67±0.49 respectively,all the results showed significant difference (x2 valued 51.29,42.25 and 43.56 respectively,all P valued ＜0.01).The DAP values in C-arm cone beam CT 5 s,8 s and 20 s imaging were (9.11 ±0.18),(13.81±0.75)and(58.62±0.62)Gy· cm2,ED values were (0.91 ±0.02),(1.38±0.75)and(5.84± 0.11) mSv,all the results showed significant difference (F valued 3 720.30 and 3 654.85 respectively,all P valued＜0.01).Conclusion The image quality and radiation dose of C-arm cone-beam computed tomography are closely correlated with acquisition time.

Objective To investigate the clinical significance of the ST segment changing in treadmill exercise test positive for the diagnosis of coronary heart disease. Methods 133 patients (hospitalized from January 2014 to January 2015) with the ST segment depression≥0.1 mm in treadmill exercise test were retrospectively analyzed. Patients were divided into the observation group and the control group according to the coronary angiography (the dividing line is artery stenosis is more than 50% or not ). ST-segment depression margin and recovery time of the two groups were compared. ST-segment depression margin and recovery time of patients with different vascular lesion number were also analyzed. Results In 133 cases, 79 cases of coronary angiography were positive(59.4%). Positive rate of ST segment recovery time(> 90 s) was 76.9% in. The maximal ST-segment depression margin and recovery time in the observation group were more than the control group, the difference was statistically significant (P<0.05). Compared with the maximal ST segment depression margin in single-vessel stenosis group , the difference in the double-vessel and multi-vessel stenosis group was not statistically significant(P > 0.05). But in terms of ST-segment recovery time, the double-vessel and multivessel stenosis group were higher than the single-vessel stenosis group , and the difference was statistically significant (P< 0.05). Conclusion Clinically, patients with TET positive combined the ST segment depression and ST-segment recovery time are important hints for the diagnosis of coronary artery disease , and is worthy of promotion.

Objective To compare the differences of pulmonary nodule detection rates between iterative reconstruction (sinogram affirmed iterative reconstruction,SAFIRE)algorithm and filtered back projection (FBP) algorithm in chest CT, and to evaluate the detection accuracy.Methods Three groups of tube voltage values of 80,100,and 120 kV were defaulted on the new dual-source CT,with automatic mAs care dose 4D technology, the chest phantom with simulated pulmonary nodules was scanned, then the images were reconstructed with FBP and SAFIRE (grade 1-5 ),respectively. The detection rates of simulated pulmonary nodules in the chest CT images reconstructed of SAFIRE (grade 1-5 )and FBP were compared, and their diameters and CT values were measured.Results With the same tube voltage, no significant difference was found in the detection rate of simulated pulmonary nodules between SAFIRE (grade 1-5 )and FBP (P>0.05 ), the diameter deviation of simulated nodules of SAFIRE (grade 3 )was less than FBP, and the difference in the average CT value of the simulated nodules between SAFIRE (grade 3)and FBP was not statistically significant (P>0.05);the simulated nodule detection rate of 100 kV was equivalent to the detection rate of 120 kV,the simulated nodule (-800 HU and 3 mm )detection rate of 80 kV was less than that of 120 kV;as the tube voltage reduced,or simulated nodule diameter decreased,or the density of simulated nodule reduced,the nodule’s diameter deviation was increased. Conclusion Compared with FBP,the capabilities of SAFIRE in pulmonary nodule detection in different densities and different sizes are same,and SAFIRE algorithm is helpful for accurate displaying of pulmonary nodules,and it can be used for low-dose CT lung cancer screening program.

Objective To analyze serum 25(OH)D level and the influence factors in preterm infants. Methods The data of serum 25(OH)D level in preterm infants born from July 2012 to June 2014 were retrospectively analyzed along with gestational age, gender, parity, delivery mode, birth season, birth weight, age of the mother and pregnancy complications. Results Totally 325 cases were included and their average gestational age was 33.41±2.29 week, the ratio of male to female was 1.32?1 and average serum 25(OH)D level was 37.34±16.17 nmol/L. The incidence of vitamin D deficiency and insufficiency in preterm infants was 37.8% and 41.8% respectively. Serum 25 (OH) D levels in preterm infants born in summer and autumn were higher than those born in winter and spring, and there was statistical difference (P<0.05). Logistic regression analysis showed that birth season and the mother's age may be the risk factors that influence serum 25 (OH) D levels in preterm infants. Conclusion The incidence of vitamin D deficiency and insufficiency in preterm infants is high, and the factors affecting the level of vitamin D need to be further studied.

Objective To evaluate the accuracy and efficiency of the Monte Carlo software in measuring the radiation dose to the patients who received the CCTA (Coronary Computed Tomography Angiography) examination.Methods A anthropomorphic chest phantom underwent CCTA using three scan parameters (tube voltage 80 kV,100 kV and 120 kV).Computer Software ImpactDose 2.0 was used to compute the chest organ dose on the basis of the three groups tube voltage CT scan characteristic,and the stimulation results of ImpactDose 2.0 software was verified by use of anthropomorphic phantom thermoluminescence dosimeter experiment method.Results For all the measured organs except for lung,the absorbed organ dose and effective dose of three groups of tube voltages of CCTA measured by the InpactDose 2.0 was lower than those as measured by anthropomorphic phantom study.The relative error of both methods was within ± 50％.Conclusions Monte Carlo software can be used to estimate the levels of radiation dose during CCTA examination with a tolerable error within the acceptable range.

Objective To analyze the distribution of image noise in low-dose chest CT scan and optimize the relative scanning parameters.Methods The CT images of the Chinese anthropomorphic chest phantom( CDP-1 C) were simulated into six groups of low-dose images with different noise indexs by using an image noise addition tool.The difference between the preset noise index and analog noise value was compared.The CT images of 20 volunteers were also simulated into nine groups of low dose scans with the tube currents of 10,30,50,80,100,120,150,180 and 240 mA.The noise values of images were recorded and analyzed.Results There was no statistical difference between the analog noise value and the noise index.The image noise of low-dose chest scan was increased with the decrease of tube current.The noise was increased quickly when the current was decreased from 50 to 30 mA ( F =24.09 - 40.79,P ＜ 0.05),but the noise increased slowly when the current decreased from 240 to 80 mA.There was no statistical difference between the noise of 80 mA group and that of 120 mA(P ＞ 0.05).Conclusions The noise addition tool can be used to evaluate the image noise of low-dose chest CT scan.Adoption of 80 mA in chest CT scan would result in low radiation dose without adding image noise.

Objective Using the Chinese anthropomorphic chest phantom to measure the absorbed dose of various tissues and organs under different noise index, and to assess the radiation dose of MSCT chest scanning with the effective dose(ED). Methods The equivalence of the Chinese anthropomorphic chest phantom(CDP-1C) and the adult chest on CT sectional anatomy and X-ray attenuation was demonstrated. The absorbed doses of various tissues and organs under different noise index were measured by laying thermoluminescent dosimeters(TLD) inside the phantom, and the corresponding dose-length products(DLP) were recorded. Both of them were later converted into ED and comparison was conducted to analyze the dose levels of chest CT scanning with automatic tube current modulation (ATCM) under different noise index. Student t-test was applied using SPSS 12.0 statistical software. Results The Phantom was similar to the human body on CT sectional anatomy. The average CT value of phantom are -788.04 HU in lung,45.64 HU in heart,65.84 HU in liver,254.32 HU in spine and the deviations are 0.10%,3.04%, 4.49% and 4.36% respectively compared to humans. The difference of average CT value of liver was statistically significant(t=-8.705,P＜0.05),while the differences of average CT values of lung, heart and spine were not significant(t value were -0.752,-1.219,-1.138,respectively and P＞0.05).As the noise index increased from 8.5 to 22.5, the DLP decreased from 393.57 mGy·cm to 78.75 mGy·cm and the organs dose declined. For example, the average absorbed dose decreased from 22.38 mGy to 3.66 mGy in lung. Compared to ED calculating by absorbed dose, the ED calculating by DLP was lower. The ED values of the two methods were 6.69 mSv and 8.77 mSv when the noise index was set at 8.5. Conclusions Application of the Chinese anthropomorphic chest phantom to carry out CT dose assessment is more accurate. The noise index should be set more than 8.5 during the chest CT scanning based on ATCM technique.