| Objective GE 64-slice CT was used to study CT coronary angiography scan exposure conditions, the purpose is to ensure that as quality premise, as far as possible to reduce coronary angiography scan exposure conditions, so as to reduce the radiation dose, reduce the radiation dose to patients.Method Standard according to include and exclude cases, with 120 kv GE research under the condition of noise and the tube current relationship fixed noise level 28HU. body mass index and tube current relationship, with different body mass index (BMI) corresponding numerical tube current, select 90 cases of CT coronary angiography, according to the formulation and exclusion criteria, the object of study can be divided into routine group (group 1), group (group 2) low voltage, low current group (group 3). The number of each group of 30 cases.1 set of the conventional exposure conditions (120 kv 650 mA), The second group with low kv exposure (100 kv 650 mA) scan conditions, with low mA exposure group 3 scan conditions (120 kv choose mA numerical according to body mass index), will be the image of each volume CT dose index (CTDIvol), image quality score and effective dose assessment analysis (ED). Comparative study on image quality score differences between groups of cases, and compare the differences between groups of cases effective dose value for statistical analysis, with P< 0.05 for the difference was statistically significant.Result Three groups of patients,1 and 2 group there was no statistically significant difference image quality score (P> 0.05), effective dose decrease obviously in the 2 groups, the difference was statistically significant (P< 0.05).1 group compared with 3 groups, there was no statistically significant difference image quality score (P> 0. 05). and 3 groups effective dose decrease obviously, the difference was statistically significant (P< 0.05). Three groups compared with two groups has no statistical significance of image quality evaluation of differentiation, and effective dose of two groups reduced obviously, the difference was statistically significant. The experiment of three groups of image quality score as follows, group 1 (normal group):LM (left coronary artery) 3.71 ±0.32 points, LAD, left anterior descending coronary artery) 3.81 ±0.18 points, LCX (left coronary artery from the cyclotron) 3.76±0.32 points, RCA (right coronary artery 3.76 ±0.27 points; group 2 (low voltage):LM (left coronary artery) 3.71 ±0.33 points, LAD, left anterior descending coronary artery) 3.72 ±0.31 points, LCX (left coronary artery from the cyclotron) 3.69+/-0.32 points, RCA (right coronary artery 3.74 ±0.32 points; 3 groups (low current):LM (left coronary artery) 3.66 ±0.37 points, LAD, left anterior descending coronary artery) 3.73 ±0.32 points, LCX (left coronary artery from the cyclotron) 3.70±0.33 points, RCA (right coronary artery plus or minus 0.43 points,3.64 this experiment data difference between three groups was no statistical significance (P> 0.05). The experiment of three groups of selected cases effective doses were 31.64 ±2.11 mSv (normal group).19.98 ±1.02 mSv group (low voltage) and 25.78 ±8.28 mSv group (low current), the experiment of three groups of effective dose between numerical differences have clear statistical significance (P< 0.05).Conclusion Cut tube voltage to 100 kv, and can reduce the patient radiation dose and image quality can meet the requirements of diagnosis. According to the patient’s body mass index, under the premise of image quality is not significantly reduced after the setting of lower current value can be within the scope of body mass index (BMI) in patients with certain to reduce the patient radiation dose, namely when the body mass index (BMI) of less than 23 patients, reduce the extent of the radiation dose is better than that of lower tube voltage group and normal group; Body mass index between 23 and 27 patients with is to reduce the radiation dose is better than that of normal group, but not as good as low voltage group; In patients with higher body mass index of more than 27, patients receiving radiation dose is greater than the conventional group. At fixed tube voltage and tube current numerical, CTDIvol (dose weighted index) is fixed values, or not with the patient’s body mass index (BMI) changes, the effective dose (ED) and coronary artery CTA scan along the length of axis direction of the patients, which is closely relative to both. |
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