| Objective:To study the feasibility of low tube voltage and low dose of contrast agent for prospective electrocardiography-triggered coronary computed tomography(CCTA) in overweight patients.Methods: 90 overweight patients( 30kg/m2 ≥ BMI ≥ 25.0kg/m2) with clinically suspected coronary disease underwent 640-slice CT angiography using prospective electrocardiography-triggered scan protocol were randomly divided into A, B, C three groups equally, each group 30 cases, consisted of a voltage 100 kv, 120 kv, 120 kv, and contrast medium of 51, 61, 51 ml, respectively. Data acquisition was set at 70%-80% of the RR-interval. The technique that automatic tube current modulation is used to automatically adjust the tube current according to the size and attenuation characteristics of the body part being scanned. The image quality was divided into four levels. Three groups coronary CT image value, signal-to-noise ratio and patients accepted effective radiation measurement were recorded. Using SPSS 19.0 software on date obtained were statistically analyzed by one-way ANOVA, the variance analysis between the three groups of coronary angiography and its branches of blood vessel within the CT value,descending aortic image noise, the signal-to-noise ratio(SNR) and radiation dose, if the difference was statistically significant differences between the pairwise comparison were evaluated by LSD. X 2 test to compare among the three groups of coronary angiography image quality grading show the number of segments.Results: CT values in vessels difference between groups was statistically significant(P<0.05),the difference was not statistically significant(P> 0.05) between group A and B,there was significant difference between the group A and C(P<0.05), there was significant difference between the group B and C(P<0.05). Ascending aortic image noise followed(25.01±3.32)HU,(25.98±4.33)HU,(25.11±3.59)HU, no significant differences between groups(P> 0.05). The signal-to-noise ratio(SNR) followed 22.28±5.22, 20.42 ± 4.05, 16.98 ± 3.29, difference between groups was statistically significant(P<0.05), the difference was not statistically significant(P> 0.05) between group A and B, there was significant difference between the group A and C(P<0.05),there was significant difference between the group B and C(P<0.05). A total of 1217 segments of coronary artery diameter≥1.5 mm in three groups of patients, 389 segments of group A, 215 excellent, accounting for 55.27% of group A; good 169, accounting for43.44% of group A, medium 4, accounted for 1.01% of group A; difference of one segment, accounting for 0.26% of group A; image quality for a good total of 384 segments, accounting for 98.71% of group A. Group B, 411 coronary artery segments,score of 231 was excellent, accounting for 56.2% of group B; good 174, accounting for42.23% of group B; medium of paragraph 5, accounting for 1.22% of group B; difference of one segment, accounting for 0.24% of group B and a total of 405 segments, excellent or good image quality, accounting for 98.54% of group B. Group C, 417 coronary artery segments, the score was excellent in 220, accounting for 52.76% of group C; good 192,accounting for 46.04% of group C; Paragraph 3 medium, accounting for 0.72% of group C; difference between two segments accounted 0.47% of group C and a total of 412 segments, excellent or good image quality, accounting for 98.80% of group C. There was no significant difference of Percentage of excellent or good imaging quality among the three groups(x2=0.112, P=0.945). The average effective dose was(2.34±0.48) m Sv in group A,the average effective dose was(2.82±0.65) m Sv in group B, the average effective dose was(2.83 ± 0.65) m Sv in group C. Three groups of difference was statistically significant(P<0.05) there was significant difference between the group A and B(P<0.05), there was significant difference between the group A and C(P<0.05), the difference was not statistically significant(P> 0.05) between group B and C, and the average effective dose of group A was decreased by17.02% compared with that of group B, and decreased by17.31% compared with that of group C.Conclusions: For overweight patients(30kg/m2 ≥ BMI ≥ 25.0kg/m2), 640-slice volume CT with 100 k V tube voltage and 51 ml contrast medium can preserving good diagnostic image quality.
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