ABSTRACT
Objective To measure the body surface dose under different confinations of additional filters,tube voltage and tube current and discuss the lowest amount of different additional filters,tube voltage and tube current combination for crib side X-ray radiation dose while the quality of the image is guaranteed.Methods Japan Shimadzu wireless tablet mobile DR machine and Dutch Artinis CDRAD 2.0 phantom were used.The tube voltage and tube current for children's crib side X-ray normal work were 50 kV and 1.40 mAs to get the image quality figure inverse (IQFInv),respectively.Totally four filter combinations of 1 mm A1,2 mm A1,1+2 mm A1 and 0.3 mm Cu were added to the opening of collimator system by mobile DR machine.Phantom was shot by respectively combination of 50,66,83 and 100 kV tube voltages and different tube currents.All images to get the IQFInv value,Pearson correlation and regression analysis of the influence of tube voltage and current on IQFInv value were analyzed.The IQFInv value of the additional filter corresponds to the image quality of normal work.The combination of the additional filter with the tube voltage and the tube current was also found.Swedish RTI Barracuda diagnostic level dosimeter was used to measure the entrance surface dose of these combinations after filtration,20 times for each group.Results Comparisons among different filters,tube voltage and tube current combination with quality of daily work images:the tube voltage was positively correlated with IQFInv value in the test range(r=0.49,P＜0.05),and tube current was positively correlated with IQFInv value (r=0.36,P＜0.05).As the additional filters increase,it required greater tube current to acquire the desired value of images.Meanwhile,greater additional filters would increase the difference of IQFInv of tube voltage at each level.Comparisons among different filters,tube voltage and tube current combination with daily shooting dose,and after using additional filters,entrance surface dose changed from (30.58±0.21)to (10.49±0.09) μGy.There is a significant difference between each group (t=-15.306-514.585,P＜0.05).All additional filters effectively reduced entrance surface dose.Meanwhile,as the filter and tube voltage increased,entrance surface dose showed a more significant reduction.However,when the tube voltage exceeded 83 kV,all entrance surface dose of additional filters showed an increasing trend.Conclusions Additional filter is an effective method to reduce the crib side X-ray entrance surface dose.Under the premise of ensuring image quality,additional filter with high atomic number and second high kilovolt tube voltage with paired tube current is the best condition for crib side X-ray.
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Objective To compare the differences of the spectral CT parameters between benign and malignant mediastina lymph nodes and to investigate the value of spectral imaging in the differential diagnosis. Methods According to the follow-up and pathology results, a total of 73 patients were enrolled in this study. One experienced radiologist determined the locations of lymph nodes on CT images corresponding to the surgical pathological ones. A total of 47 malignant nodes and 65 benign nodes were found. The longest and shortest diameters of lymph nodes in mediastina window were measured .The vHU, IC, WC, Zef and the CT values of normal lung, normal muscle and lymph nodes at 40, 70 and 140 keV were measured. The indices were compared between the benign nodes and malignant nodes by independent-samples t test. The Spectral HU curves were drawn. Results The long and short diameter of malignant lymph nodes were (28.8 ± 10.5),(20.3 ± 9.1)cm , while they were were (14.0 ± 4.6),(7.5 ± 1.8)cm for benign lymph nodes. Malignant nodes were significantly larger than benign nodes (t= 6.54, 7.13, respectively, P0.05). The two groups showed similar spectral HU curve slopes (1.86 values 1.73). Conclusion Spectral imaging may not be helpful in the differential diagnosis of malignant and benign lymph nodes.
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Objective To evaluate images quality and diagnostic feasibility of low-dose CT in patients with traumatic rib fractures.Methods Twenty-five patients presented with thoracic iniury were underwent 64-slice spiral CT scanning in inspiration breath-hold technique.Two scan protocols were performed.In one scan protocol noise index(NI)is 11,and in another NI is 21,but the other scan parameters were no difference.The mean value of tube current,the volume CT dose index(CTDIvol),and effective dose(ED)were recorded.Image quality was scored by 2 experienced radiologists using the 5-points scale.The numbers and degrees of rib fractures were recorded.The data were tested by using the Wilcoxon signed rank sum test.The differences of the inter-observer were determined by Kappa statistics.Results The mean CTDIvol and ED in scan protocol with NI of 11 were(13.88±5.17)mGy and(8.14±3.21)mSv,and that with NI of 21 were(3.91±1.57)mGy and(2.31±0.97)mSv.Compared the scan with NI of 11.there was 72%intrinsie dose reduction in the scan with NI of 21.The mean value of tube current in scan with NI of 11 and 21 were(195.88±69.33)mAs and(54.56±21.54)mAs.AIl patients with 11 and Ⅲ degree and most patients with I degree rib fractures that identified by the scan with NT of 11 were detected by the scan with NI of 21.There were no statistical difference between two scaus with the Wilcoxon signed rank sum test.The diagnostic acceptability and image noise score in the scan with NI of 11 were 4.9±0.2 and 4.6±0.5.and that with NI=21 were 3.5±0.5 and 3.3±0.5.There was prefect concordante in the inter-observers in diagnostic acceptability on finding of rib fractures.diagnostic acceptability and image noise(Kappa=0.876,0.820,0.792,P<0.01)between two scan protocols.Conclusion Rib fractures can be diagnosed by the low-dose CT using the scan protocol with NI of 21.
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Objective To evaluate accuracy of density measurements within coronary plaque by multi-slice spiral CT and factors that influence measurements. Methods Four adult cadaver hearts were used. Thrombus and pericardial fat which acquired from specimen (size 2.0, 1.5, 1.0 and 0.5 mm respectively) were placed into coronary artery to simulate coronary plaques. The contrast medium (three different concentrations 1: 30, 1:40, and 1:50) were injected into coronary artery. The raw date were reconstructed with two slice width ( 1. 00 and 0. 75 mm). Results When contrast medium concentrations was 1: 30, the CT values of thrombus were 109 HU ( slice width 1. 00 mm, size 2. 0 mm) , 115 HU ( slice width 1.00 mm, size 1.5 mm), 101 HU (slice width 0.75 mm, size 2.0 mm), 113 HU ( slice width 0. 75 mm,size 1. 5 mm) ; the CT values of fat were - 23 HU ( slice width 1. 00 mm, size 2. 0 mm) , -17 HU(slice width 1.00 mm, size 1.5 mm) , -9 HU(slice width 1.00 mm, size 1.0 nun), -27 HU ( slice width 0.75 mm, size 2. 0 mm) , - 19 HU (slice width 0.75 mm, size 1. 5 mm) , - 13 HU (slice width 0. 75 mm,size 1. 0 mm). When contrast medium concentrations was 1: 40, the CT values of thrombus were 79 HU( slice width 1.00 mm,size 2.0 mm) , 87 HU( slice width 1.00 mm, size 1. 5 mm) , 115 HU( slice width 1. 00 mm,size 1. 0 mm) , 73 HU(slice width 0. 75 mm,size 2. 0 mm) , 80 HU(slice width 0. 75 mm, size 1. 5 mm) , 110 HU( slice width 0. 75 mm, size 1. 0 mm) ; the CT values of fat were - 31 HU ( slice width 1. 00 mm, size 2. 0 mm) , - 22 HU ( slice width 1. 00 mm, size 1. 5 mm) , - 10 HU ( slice width 1.00 mm,size 1.0 mm) , -35 HU(slice width 0. 75 mm,size 2.0 mm) , -25 HU(slice width 0. 75 mm, size 1. 5 mm) , - 19 HU ( slice width 0. 75 mm, size 1. 0 mm). When contrast medium concentrations was 1:50, the CT values of thrombus were 53 HU ( slice width 1. 00 mm, size 2. 0 mm) , 60 HU ( slice width 1.00 mm,size 1.5 mm) ,63 HU(slice width 1.00 mm,size 1.0 mm) ,51 HU(slice width 0.75 mm,size 2. 0 mm) ,64 HU( slice width 0. 75 mm,size 1. 5 mm) ,67 HU( slice width 0. 75 mm,size 1. 0 mm) ,145 HU (slice width 0. 75 mm, size 0. 5 mm) ; the CT values of fat were - 39 HU ( slice width 1. 00 mm, size 2. 0 mm) , -28 HU( slice width 1. 00 mm,size 1. 5 mm) , - 22 HU( slice width 1. 00 mm,size 1. 0 mm) , 17 HU(slice width 1. 00 mm,size 0. 5 mm) , -41 HU(slice width 0. 75 mm,size 2. 0 mm), -36 HU(slice width 0. 75 mm, size 1. 5 mm ) , - 27 HU ( slice width 0. 75 mm, size 1. 0 mm ) , 3 HU ( slice width 0. 75 mm, size 0. 5 mm ) . The density values of thrombus were correlated with size ( t = - 6. 624, P 0. 05) not found statistically significant may be caused by both too close slice width (1.0 mm and 0. 75 mm) and few samples. The slice width(t= -2. 595,P