| Background:Coronary atherosclerotic heart disease(coronary heart disease)is one of the major diseases that seriously endanger human health.It has become one of the most common lethal causes at home and abroad,bringing heavy burden to current economic development.Currently,there are many methods for the diagnosis of coronary heart disease,among which the examination process of multi-slice spiral CT coronary CTA imaging is convenient,rapid,accurate and reliable,and has become one of the important imaging methods for the screening,diagnosis,curative effect evaluation and prognosis monitoring of coronary heart disease.Due to the advantages of CTA examination,this examination is widely used in clinical practice at home and abroad.Coronary artery CTA examinations should strictly comply with the radiation industry recognized "as low as possible,rational use of radiation dose"(ALARA)protection law.Therefore,how to reduce radiation dose based on good image diagnosis quality is a hot topic recently.There are three scanning methods for coronary CTA image data collection:retrospective helical scanning,prospective large-pitch helical scanning and prospective sequence scanning.Different scanning methods are applicable to different populations,image quality and radiation dose.For lower does not affect the premise of image diagnosis,in addition to change the way of image data acquisition scan,scholars both at home and abroad mainly using lower tube voltage,reduce the tube current and ae method to reduce coronary CTA with radiation dose of CT examination,but the double orientation as scanning in coronary CTA and its radiation dose correlation studies are rare.Foreign scholars have found that using the automatic exposure technology,using mutually perpendicular positioning images can effectively reduce the radiation dose of chest and abdomen CT.Objective:The purpose of this research,one of the aims to use the second generation dual-source CT,explore the perspective sequence scanning and big pitch spiral scan coronary CTA examination in patients with low heart rate,the image quality and radiation dose and dosage of contrast agent,contrast analysis,explore the big pitch spiral scanning applicable people and its influence on image quality and radiation dose.Second purpose of this study is to use the second generation dual-source CT,adopt double position(AP and lat)combined the technology of CARE Dose 4D and Care kV separately coronary artery prospective sequence scan or big pitch spiral scanning,combined with conventional single positioning as(AP)?the technology of CARE Dose 4D and Care kV,to explore its clinical application in lower CTA check the radiation Dose.Materials and methods:Study 1:One hundred and twenty cases of patients undergoing coronary artery CTA examination from January to June 2016 were collected,whose heart rate were ? 70 beats/min,and whose heart rate variation rate were<10 beats/min.The heart rhythm was stable without obvious arrhythmia.Exclusion criteria included:arrhythmia,renal failure,unstable clinical symptoms,contraindication of the ?-receptor blocker and inability to hold one's breath.A total of 160 patients were divided into group A and group B by the random number table method,with 80 patients in each group.Group A was the high-pitch helical scanning group,and group B was the sequence scanning group.The scan range was lcm below the tracheal carina to the cardiac diaphragm.Group A was triggered by perspective ECG triggered and began to scan and collect data at a 60%R-R interval of one cardiac cycle.Group B was the perspective ECG triggered sequence scan,and the scanning phase was 70%R-R interphase,and the data collection was completed after 3-4 cardiac cycles.Automatic flying spot technology and CARE kV technology are applied in scanning.Study 2:Four hundred and twelve cases of patients undergoing coronary CTA examination were collected from July 2016 to December 2017.According to the heart rate;the patients were divided into two groups.Group A was A flash scan(the heart rate was stable,and the heart rate was? 70 beats/min,and the heart rate variation rate was<10 beats/min).A prospective sequence scan was performed in group B(with a heart rate of>70 beats/min and a heart rate variability of>10 beats/min).The scanning method and scope are the same as that of study 1.The coronary artery imaging enhanced scan was performed via the right elbow vein with a double-tube high-pressure syringe for injection of Orapak,followed by an injection at the same rate for an additional 40mL of normal saline.The trigger threshold is 120HU using to trigger the scan.The scanned data was analyzed by the image reprocessing station(Syngo.Via,Siemens Forchheim,Germany).The American heart association AHA standard was used to divide the coronary artery into 16 segments or 4 segments for analysis.CT values of aortic root(AA),left coronary trunk(LM)proximal segment,right coronary artery(RCA)proximal segment,left anterior descending branch(LAD)proximal segment and mediastinal fat were measured respectively,and image noise,signal-to-noise ratio and contrast noise ratio were calculated.Dose length product(DLP)and CT volumetric dose index(CTDIvol)were calculated automatically by CT,and effective dose(ED)was calculated by multiplying DLP by a specific conversion coefficient k,with the conversion coefficient k value of 0.014 mSv · mGy-1 · cm-1).Results:Study 1:There were statistically significant differences between the two groups in image quality score,radiation dose,image noise,contrastagent dosage and contrast noise ratio(P<0.05).The mean heart rate,variability rate and other scanning parameters between the two groups were not statistically significant.In terms of segmental and vascular levels,the difference between the two groups in average subjective evaluation of image quality was statistically significant(P<0.05),while the individual level was not statistically significant.The image quality of group A was significantly better than that of group B.The subjective scores of the two evaluators were relatively consistent(Kappa = 0.530).There was no statistically significant difference between the two groups in diagnosis of segmental level,vascular and patient level.A total of 35 patients(413 segments)in group A and 36 patients(425 segments)in group B received conventional coronary angiography within 4 weeks after high pitch helical scan and sequential scan.The diagnostic accuracy of the two groups was 97.8%(404/413)and 97.9%(416/425),respectively,and the difference was not statistically significant.Between group A and B,in the ascending aorta(AA),right coronary artery(RCA),the left coronary artery(LM),left anterior descending branch(LAD)and left circumflex(LCX)image quality objective measurement parameter value,the image signal intensity,image noise,contrast to noise ratio,are statistically significant image signal-to-noise ratio between the two groups no significant statistical difference.Study 2:There was no significant difference in age,height,weight,BMI or heart width between group A and group B(P>0.05).In groups A and B,the root of ascending aorta(AA),right coronary artery(RCA)and left main coronary artery(LM)were the regions of interest and CT values were measured.The differences of image quality score,signal intensity,image noise,SNR,CNR and number of tube voltage selection between subgroups A and B were statistically significant(P<0.05).The difference of subjective image quality assessment between group A and group B was statistically significant,and the image quality of group A was superior to that of group B.The subjective scores of the two groups were consistent(Kappa =0.565).There was no statistically significant difference in image quality between the AP topogram scanning group(A1+B1 group)and the AP and Lateral topograms scanning group(A2+B2 group).There were statistically significant differences in signal intensity,image noise,and number of tube voltage selection between the A1 group and B1 group,but no statistically significant differences in image SNR and CNR.There was no statistically significant difference in the number of selected signal intensity,image noise,SNR,CNR and tube voltage between the two groups(all P values were>0.05).There were differences in the selection of signal intensity,image noise,SNR,CNR and tube voltage between the AP topogram scanning group(A1+B1 group)and AP and Lateral topograms scanning group(A2+B2 group),and the differences were statistically significant(P<0.05).At the vascular level,there was no statistically significant difference in the angiographic diagnostic rate between the subgroups A and B,Al and B1,A2 and B2,the single-site scanning group(A1+B1 group)and the dual-site scanning group(A2+B2 group).The average dose length product(DLP)and effective dose(ED)of the large-pitch helical scan group(group A)were 26.13%and 26.0%lower than that of the prospective sequence scan(group B),and the difference between them was statistically significant.There were statistically significant differences in DLP and ED between subgroups A and B,with 27.5%and 23.0%decreases in the dual-location phase group,respectively.Analysis of the number of different tube voltage selection cases among the four groups showed no statistical significance between the A2 and B2 groups,while there were statistically significant differences between the remaining A1 and A2 groups,B1 and B2 groups,A1 and B1 groups,A1+B1 and A2+B2 groups(P<0.05).Conclusion:For patients with low heart rate and relatively stable heart rate,the use of large-pitch helical scan mode in the middle period of cardiac diastole to carry out prospective adaptive sequence scanning of coronary artery CTA imaging can significantly reduce the radiation dose and contrast agent dosage of patients,without causing a decrease in image quality.The use of anteroposterior and lateral imaging scanning combined with CARE KV and CARE Dose 4D technology can reduce radiation dose while ensuring image quality,and the clinical operation is simple and feasible,which can be used in routine operation of coronary CTA examination,and can be expanded to other examination sites such as the chest and abdomen.The second-generation dual-source CT computer post-processing technology(SAFI RE reconstruction,CARE KV,CARE Dose 4D)can reduce image noise,significantly improve image quality,and indirectly reduce tube voltage and radiation Dose,which can be widely used in clinical practice. |
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