Application Of ECG Editing And Low-dose Techniques In Dual-source CT Coronary Angiography

[Objective]1. Explore various types of arrhythmias in the dual-source CT coronary image quality of the role of imaging. Analysis arrhythmias image quality control by ECG editing software.2. Comparison prospective and retrospective ECG-gated of dual-source CT coronary CTA image quality and radiation dose. Analysis the meaning of prospective ECG-gated scanning mode in the CT coronary angiography.[Meterials and Methods]1,The choice of subjectsPart I:51 cases arrhythmia patients among the patients of our hospital undergoing coronary CTA between June 2009 and February 2010, all the patients in the scan data were used for cardiac arrhythmia and ECG editing software to process and compare the treatment before and after image quality, editing features of the revised assessment of ECG arrhythmias different image value.51 patients, age 36 to 79 years old, with a median age of about 56 years old, of which 19 cases of atrial fibrillation, atrial premature beats in 6 cases, a single premature ventricular beats in 16 cases,5 cases of frequent premature ventricular contractions,2 rooms ventricular conduction block in 1 case, frequent ventricular premature 2 cases of atrial fibrillation, ventricular premature arrhythmia in 2 cases. Part II:78 patients underwent coronary CTA of our hospital in June 2009～February 2010, aged 25 and 65 years, median age 42 years, heart rate were 48～78 times/min between the coronary CTA, divided into two groups were prospectively and retrospectively ECG-gated coronary CTA, forward-looking group of 39 cases,39 cases review group. Case screening criteria:allergy to the iodine contrast agent, renal insufficiency, cardiac arrhythmia, heart rate large than 80 times/min, respiratory control was bad (coughing)2,Equipment and scanning methodsPart I:Siemens dual-source CT (Siemens Somatom Definition). Patient supine, connect the heart electrodes, first of all, scan for calcium score analysis, the parameters of scanning:120kV, 100mAs, collimator width 64×0.6mm, tube rotation time of 0.33s/week. Coronary artery imaging scan parameters:120kV,380mAs, pitch select 0.2, collimation width 64×0.6mm. Median cubital vein in patients with indwelling catheter, using binoculars high pressure syringe bolus injection of contrast agent was Iopromide (370 mgl/ml), the flow rate of 5.0～6.5ml/s, the total dose of contrast agent is about 60-80ml, inject NS 25ml, the flow rate of 5.0ml/s. Scan range:Carina 1cm to the heart diaphragm, using contrast agent tracer, tracer surface set at a little higher starting point of the aortic root coronary artery, trigger threshold was 90HU.Part II:Siemens dual-source CT (Siemens Somatom Definition). Patients divided into A, B groups, A:The forward group, scan parameters:120kV,371mAs, slice thickness 0.75mm, collimator width 64×0.6mm; B:The review group, scan parameters:120kV, 420mAs, collimator width 64×0.6mm, reconstruction thickness is 0.75mm, two groups were the same scan range, Median cubital vein in patients with indwelling catheter, using binoculars high pressure syringe bolus injection of contrast agent was Iopromide (370 mgl/ml), the flow rate of 5.0～6.5ml/s, the total dose of contrast agent is about 60-80ml, inject physiologic saline 20ml, the flow rate of 5.0ml/s. Scan range:coryna lcm to the heart diaphragm, using contrast agents tracer, tracer surface set at a little higher starting point of the aortic root coronary artery, trigger threshold was 90HU. 3,Image Processing and AnalysisPartⅠ:Dual source CT automatically after the reconstruction of the best images systole and diastole. Will not edit the original images in 3D post-processing workstation and Circulation functions within each window of blood vessels VR,MIP,CPR and other three-dimensional heart and coronary artery imaging, and image quality score before editing. ECG editing, first of all, need to rebuild the preview window using temporal phase of the best, and then conducted under real-time ECG-editing. Selection of optimum methods are:1. Relative phase method (0%～99% 20 image reconstruction intervals 5% interval in the RR); 2. Absolute time method (after 0 msec from R wave began to 10 msec time interval reconstruction of the RR interval have multiple images). ECG editing methods are:1.shift R-peak (Rwave offset); 2.disable Sync (with the exception synchronization waste); 3.delete Sync (excluding abnormal synchronization); 4.insert Sync (insert synchronization). Adopt different for different ECG arrhythmias editing method, and after ECG editing image image quality score.According to the American Heart Association, coronary artery improved segmentation method, image quality with 0～3 score:3:Vascular outline a clear, good continuity, no step artifacts; 2 score:a clear outline of blood vessels, poor continuity, a small amount of artifacts; 1 score:Vascular outline clear, poor continuity, a number of ladder-like artifacts, but does not affect the diagnosis; 0 score:vascular blurring, poor continuity, more artifacts, affect the diagnosis.2 points or more images is well,0:not diagnosis.PartⅡ:Prospective gating and retrospective gating incoming scanned original image post-processing workstations, and Circulation in the 3D function of the window after the vessels were on each VR, MIP, CPR and other heart and coronary arteries of three-dimensional imaging, and after reconstruction image quality score, Grading Ibid Also record prospective gating and retrospectively gated scan dose in patients with parameters:CT dose index volume (volume CT dose index, CTDIvol), dose length product (dose-length product, DLP) and effective dose (ED). ED=DLP×K, the effective dose (ED) is equal to the normalized DLP times the effective dose coefficient of the chest (k=0.014mSv/mGycm).4,Statistical analysisPartⅠ:Statistical analysis use SPSS version 13.0 statistical software, Statistically paired sign rank test Wilcoxon Signed Ranks Test to analysis cardiac arrhythmias in patients before and after editing the image quality score, Test levelα=0.05, P<0.05 considered significant difference.PartⅡ:Statistical analysis use SPSS version 13.0 statistical software, two different clinical samples with two independent samples t-test. Prospective gating and retrospective gating group Groups CT volume dose index (CTDIvol), dose length product (DLP) and effective dose (ED) with a mean of two independent samples t test. Test levelα=0.05, P<0.05 that the difference was statistically significant.[Results]PartⅠ:The study of 51 cases in 19 patients with atrial fibrillation, ECG editing images before coronary score is divided into 13 cases of 0 and 1 is divided into five cases,2 points,1 case of ECG R wave editing mainly partial shift will move the best collection signal phase zone, ECG editing the image score of 3 points in 17 cases,2 cases of 2 minutes, after which 2 cases, poor editing because too fast for the heart rate at 100 times/min; atrial premature beats in 6 cases,16 cases of single premature ventricular contractions, cardiac image editing score of 0 before the coronary artery is divided into 18 cases of right coronary section are staggered to form a ladder of artifacts, a share of 4 cases, edited by ECG abnormal pulse disable waste collection with the signal, edited 19 cases were able to achieve three points, only 3 cases of 2 points; frequent premature ventricular beats in 6 cases ECG Pre-editing were 0 edited by ECG joint insert mode disable the abnormal beating of disuse and insert a better signal acquisition phase of the acquisition signal, the second single joint legal or triple law can disable abnormal beating of the collection interval signal, ECG edited 2 cases were excellent, good in 3 cases,1 case,1 min at the same time due to respiratory failure in patients with good; 2 atrioventricular block in 1 case, using shift +disable+insert combined with ECG 0 points before editing, editing of ECG after 2 minutes; frequent ventricular premature 2 cases of atrial fibrillation, ventricular premature+arrhythmia in 2 cases, ECG editing using shift+disable, ECG Pre-editing to 0 points, the heart 2 minutes after editing power. Edit the image quality of ECG and ECG before editing the image quality by paired signed rank test (Wilcoxon Signed Ranks Test) after, Z=6.422, P=0.000, the difference was significant, ECG editing to improve image quality than the pre-editing, cardiac arrhythmia editing technology to improve image quality in patients with coronary artery plays a significant role.PartⅡ:Prospective gate group 2 patients heart rate fluctuations affect the artifacts lead to poor image observation, and the remaining 46 patients showed a total of 578 segments,43 segments as small vessels are not included in statistical analysis, the remaining 578 segments can meet the clinical diagnosis requirements; review group 2 patients with poor breathing, three cases of severe coronary artery calcification in effect result in poor image observation, and the remaining 43 patients with 523 segments can meet the clinical diagnostic requirements. Image quality evaluation of the two groups with no significant difference,t=0.843, P=0.090> 0.05. Prospect Group effective radiation dose (4.41±0.476) mSv, the effective radiation dose was recalled group (17.66±3.30) mSv, with t=23.655, P=0.000, significant difference; forward-looking group CTDIvol was (23.57±0.072) mGy, review group CTDIvol was (79.44±14.75) mGy, to t=24.813, P=0.000, significant difference; forward-looking group of DLP was (315.36±33.977) mGy.cm, DLP review group was (1261.46±235.68) mGy.cm,t=24.813, P=0.000, the difference was statistically significant.[Conclusions]PartⅠ:ECG editing function allows the use of more and more patients with mild arrhythmia can be used noninvasive coronary artery; Occasional PVCs, atrial premature, atrial fibrillation, sinoatrial block, ECG editing techniques to improve the quality of the image can play a significant role; Frequent PVCs, complex arrhythmia, due to the image signal Lack of serious cardiac image editing is more difficult to perfect, but improvements can still play a role..PartⅡ:For the patients with cardiac rhythm neat, forward-looking ECG-gated scanning and retrospective ECG-gated scanning was no significant difference in image quality, but the former significantly reduced the effective radiation dose. Therefore, compared with retrospective gating reduces the forward-looking gated coronary CTA, the radiation dose.