| Objective:This paper was to discuss the application of isotonic low concentration of contrast medium(320 mgI/ml) and the low voltage(80 KV) in coronary CT examination, and thereby to optimize the inspection technology and reduce the radiation dose and the intake of iodine contrast agent. The specific targets:(1) Reasonable scanning schemes were presented by using lower tube voltage and lower iodine contrast agent in coronary CT examination in order to reduce the radiation dose and the intake of iodine contrast agent.(2) Gemstone CT iterative reconstruction algorithm was used to reconstruct the images of coronary artery in order to obtain better image quality and so can provide the basis for coronary heart disease diagnosis. Methods:(1) Collecting the data of patients, who carried on CCTA examination in our hospital for the first time, including their gender, age, height, weight, heart rate and BMI.(2) Patients were randomly divided into a treatment group(Group A) treated by using contrast agent Iodixanol(320mgI/ml), tube voltage 80 kv and ASIR iterative reconstruction technique and a control group(Group B) treated by using contrast agent Iopamidol(370mgI/ml), voltage 120 kv and FBP(filtered back-projection) algorithm.(3) The quality of all the images were evaluated and analyzed by means of the subjective and objective method and the radiation dose and the iodine content that the patients received were also assessed with quantitative index.The subjective diagnostic scores were given by two experienced senior radiologists who will analyze the coronary artery images and then grade them respectively. The 1-5-grade scoring system will be adopted: 5—distinction; 4—credit; 3—average; 2—considered as an image for clinical diagnosis; 1—cannot be used in diagnostic procedures.The objective assessment was based on the average value of enhanced CT(st) of ascending aortic root(AS), proximal segment of left anterior descending branch(LAD-p), proximal segment of left circumflex branch(LCX-p) and proximal segment of right coronary artery(RCA-p). The SD of AS lumen’s CT value was deeded as image noise. Measurement the CT value of adjacent tissue around vessels, the difference between the CT value of vascular lumen and CT value of tissue around vessels was deeded as enhanced contrast. The signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR) were calculated based on the previous data.The assessment of radiation dose the patients received was based on the volume CT dose index(CTDIvol) which was automatically generated by the CT scanner and the dose length product(DLP). The effective radiation dose(ED) and the intake of iodine contrast agent were calculated based on the previous data. Results:No significant difference was found between the patients of two groups, including their age, height, weight, BMI, heart rate, CTDIvol and DLP. The ED of the experimental group is 1.2mSv and the ED of the control group is 2.7mSv. This difference between the two groups was statistically significant. The enhanced CT value of AS, LAD-p, LCX-p and RCA-p was significantly little than that of the control group. The difference was statistically significant. Image noise, SNR、CNR between the two groups there were no significantly difference in the found. The subjective ratings of the two groups was no statistically significant. The intake of iodine contrast agent that the patients in experimental group received was 19.2g, 13.5% lower than the control group. Conclusion:In double low coronary artery imaging, gemstone CT and its ASIR technology can dramatically reduce the radiation dose that the patients received and the their total intake of iodine on the premise of relatively good image quality and no interference on medical diagnosis, thereby increasing the treatment safety. |
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