| Objectives 1 The influence of scanning range on radiation dose and image quality of coronary computed tomography angiography.2 Preliminary study on the application value of three phase injection method in coronary angiography by 256-slice CT.Methods 1 From May 2015 to July in North China for Polytechnic University Hospital,100 patients who underwent coronary angiography by 256-slice CT were randomly divided into two groups, fifty patients of each group. In routine scan group,the scanning range was from the bifurcation of the trachea to the heart margin 1cm. And in low dose scaning group, the scanning range based on unenhanced images, was from the edge of the coronary artery tree on margin of more than 1cm to lower margin dimensions as the apical epicardial will soon disappear. The general information(Sex, age, body mass index, heart rate, and the dosage of contrast medium)、scanning range and dose length produce of each patient were recorded. The mean CT value of different sections of the cardiac artery was measured, and the coronary artery segments were evaluated. Establish Excel table, using SPSS17.0 software for statistical analysis.2 From September 2015 to November in North China for Polytechnic University Hospital, 160 patients who underwent coronary angiography by 256-slice CT and BMI in the normal range were randomly divided into tow groups, eighty patients of each group. The contrast agent injection method of dual phase group: injecting 50 ml of contrast agent in the first phase and 30 ml of injection in second phase. In triphasic injection: injecting 50 ml of contrast agent in the first phase, 20 ml of contrast agent-saline mixture(1:1) in second phase and 20 ml of physiological saline in the third phase. Recorded the general information of each patient, included sex, age, body mass index and heart rate. The mean CT value of different sections of the cardiac artery was measure, and the coronary artery segments were evaluated. Artifacts of the superior vena cava and right ventricular, and the show of coronary artery and left ventricular were assessed. Establish Excel table, using SPSS17.0 software for statistical analysis.Results 1 The mean CT value of the Right Coronary Artery proximal, Left Anterior Descending proximal, Left Circumflex Branch proximal in low dose scaning group respectively were(425.69±68.86)HU、(432.76±63.62)HU、(433.50±70.40)HU, slightly higher than( 423.06±72.19) HU 、( 428.38±67.12) HU 、(432.65±62.50)of rountine scan group. There were no significant difference between the two groups in objective image quality(P>0.05). The two groups totally showed 1303 of coronary artery segments, 669 segments of routine scan group and 634 of low dose scaning group, there was no statistical difference between the two groups in subjective image quality(P>0.05). The average scanning range, dose length product and effective dose in routine scan group respectively were:( 15.31±1.51) cm 、(1079.16±143.24)m Gy·cm、(15.10±2.00)m Sv, in low dose scaning group respectively were(13.51±1.68)cm、(858.65±100.60)m Gy·cm、(12.02±1.40)m Sv. There were no statistically difference(P<0.05).2 There were no significant difference in the mean CT value among the tow groups: dual phase group, AO( 395.15±62.82) HU 、 RCAp( 411.93±55.24) 、 LADp( 389.02±50.74) HU 、LCXp(397.42±66.58)HU; triphasic injection group, AO(382.84±61.87)HU、RCAp(404.77±53.57)、LADp(404.91±53.76)HU、 LCXp(402.77±67.40)HU. The two groups totally showed 1303 of coronary artery segments, 669 segments of dual phase group and 634 of triphasic injection group, there was no statistical difference between the two groups in subjective image quality(P>0.05). There was statistical difference in the artifact of the vena cava and right ventricle among the two groups(P< 0.05). In dual phase group: level 0 in 72 cases, level 1 in 8 cases, level 2 in 0 cases; In triphasic injection group: level 0 in 16 cases, level 1 in 64 cases, level 2 in 0 cases. There was statistical difference in ventricular septum between the two groups. In dual phase group, the patients in the display of ventricular septum from grade one to three respectively were zero cases, six cases, seventy-four cases, and respectively were thirteen cases, sixty-five cases, two cases in triphasic injection group. In the display of left ventricular wall, dual phase group: 69 patients could not completely showed left ventricular wall, 9 patients of left ventricular wall displayed fair and 2 patients showed clear; triphasic injection group: 72 patients of left ventricular wall clearly show, 7 patients showed fair and 1 patient showed a difference, the difference between the two groups was statistically significant(P< 0.05).Conclusions 1 In 256 slice CT coronary artery imaging, unenhanced images according to the optimization of the scanning range, it will not only reduce the effective radiation dose, but also get to meet the requirements of clinical diagnostic image. 2 Does not change the amount of contrast agent under the condition of using three phase injection method can not only guarantee the quality of image, meet the diagnosis, and can be a very good display compartment and the definition of left ventricular wall and for the evaluation of left heart function and morphology of lay the foundation. |
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