Application Of Prospective Ecg-gated High-pitch Spiral Dual-source CT Angiography In Follow-up Of Non-calcified Coronary Plaque After Medical Treatment

Chapter Ⅰ Feasibility of prospectively ECG-gated high-pitch spiral double acquisition in coronary dual-source CT angiographyObjective: To compare the image quality, radiation dose of prospectively ECG-gated high-pitch spiral double acquisition(Double Flash) and prospectively ECG-gated sequential acquisition in coronary dual-source CT angiography with a stable heart rate(HR) < 75 bpm, and to compare the diagnostic accuracy of of two scanning mode for coronary artery disease(diameter stenosis≥50%, coronary angiography(CAG) was taken as golden standard).Material and Methods: 53 patients with suspected coronary artery disease were enrolled as study group according to the inclusion criteria and exclusion criteria. All the patients who underwent prospectively ECG-gated CTCA in Double Flash mode were divided into two subgroups according to heart rate(HR), slow heart rate group with HR <65 bpm(29cases) and fast heart rate group with HR ranged 65 bpm to 75 bpm(24 cases). 40 patients underwent sequential acquisition in the same criteria were selected as control group. Both study and control groups received prospectively ECG-triggered high-pitch spiral calcium score scan(Fl_Ca Sc), with trigger phase at 60% R-R interval. The scanning range of CTCA was adjusted according to Fl_Ca Sc image. CTCA parameters: 0.28 s gantry rotation time, 2×64×0.6 mm detector collimation, a slice collimation 2×128×0.6 mm by z-flying focal spot technique, Body mass index(BMI)-adapted tube voltage(100 kv for BMI<25 kg/m2; 120 kv for BMI≥25 kg/m2), CARE Dose 4D Tube current regulation mode opened, referred tube current 420 m As/r. Scanning of study group was trigged at60% and 25% R-R interval for twice acquisition with pitch 3.4 and time interval for 3 seconds. Data acquisition phase for control group was set at 60%-70% R-R interval. After CT scan, all data with recontruction slice thickeness 0.6 mm,interval 0.5 mm,soft tissue algorithm and convolution function B26 f were transferred to Siemens Syngo and Syngo via Client workstations. 13 segments of coronary artery were analyzed by two experienced radiologists with blinding mathod, the image of the first scan, the second scan, and the combined analysis of both scan in study group, and auto-reconstructed image in control group were evaluated respectively. Blinded to the CAG results, another two experienced radiologists assessed the coronary artery stenosis using visual diameter method. Diagnosis of coronary artery disease was made based on the combined analysis of both scan for study group. Referred to the CAG results, the diagnostic accuracy for coronary artery disease of study and control group were compared. The effective radiation dose(ED) of two group were calculated and also compared.Results: There was no significant difference in clinical data between study group and control group(P> 0.05). The agreement for the image quality scoring of all coronary arterie segments between the two observers was excellent(k=0.83). Proportion of coronary segments with diagnosable image quality(IQ) had no significant difference(P>0.05)between two groups. Proportion of the excellent IQ of study group was lower than that of control group, with significant difference(P<0.05). There was no statistical difference for mean IQ between study group and control group(P>0.05). In study group,the mean IQ of the first scan and combined analysis showed no statistical significant in slow HR subgroup(P> 0.05), both the mean IQ of the first scan and the second scan were higher than that of the combined analysis in fast HR subgroup, with significant difference(P<0.05). The diagnostic accuracy was 97.91% in study group and 98.76% in control group, respectively, with no significant difference(P>0.05). The effective radiation dose of study group(2.08±0.39 m Sv) was lower than that of control group(3.67±1.11 m Sv) by43.32%, with significant difference(P<0.05).Conclusion: 1. Coronary dual-source CT angiography with prospectively ECG-gated high-pitch spiral double acquisition could be used for patients with stable HR<75 bpm,with a diagnosable image quality and high diagnostic accuracy for coronary artery disease at a lower radiation dose. 2. The second scan gives limited contribution in improving the image quality for slow HR patients, while the combined analysis can improve image quality for fast HR patients.ChapterⅡ: The value of prospective ECG-gated high-pitch spiral CT angiography in monitoring outcome of non-calcified coronary plaques after medical treatmentObjective: To evaluate the outcome and its influential factors of non-calcified coronary plaques after medical treatment by coronary dual-source CT angiography with prospectively ECG-gated high-pitch spiral single acquisition(HR < 65 bpm and fluctuation ranges<5 bpm) or double acquisition(65 bpm≤HR<75 bpm or 5 bpm≤fluctuation ranges<10 bpm).Material and Methods: As a prospective study, 151 local patients planning to undergo prospective ECG-gated high-pitch spiral CT angiography between March 2014 and July2014 were enrolled as base study population(HR<75 bpm with fluctuation ranges<10bpm before examination, sinus rhythm, controlled breath, no history of coronary artery bypass grafting or percutaneous coronary intervention), 144 of whom examined successfully without any complication, unsuccessful scan appeared in 5 cases, and adverse reaction of contrast medium happened in 2 cases. 31 cases with 36 non-calcified plaques were screened out form 144 patients and selected as the follow-up subjects according to the inclusion criteria and exclusion criteria. All of them received standardized medical treatment, mainly including oral Atorvastatin(20mg qn), Aspirin(100mg qn) and unified lifestyle guidance. A follow-up CTCA would be taken 12 months later according to follow-up files and cards, and DSCT prospective ECG-gated high-pitch spiral scanning mode would be used again for all the follow-up examination(single acquisition mode with triggered phase at 60% R-R interval was selected for patients with HR<65 bpm and fluctuation ranges<5 bpm, and double acquisition mode with triggered phase at 60% and 25% R-R interval was selected for patients with 65 bpm≤HR<75 bpm or 5 bpm≤fluctuation ranges<10 bpm). A routine prospective ECG-gated high-pitch spiral calcium score scanning(Fl_Ca Sc) was performed for every patient. Scanning parameters for calcium score scan and CTCA were set to be similar to the first chapter of this paper. Consistent imaging reconstruction techniques and measurement principles were used before and after treatment. All the data were measured and recorded in consultation by two experienced radiologists. Plaque volume, minimal CT value of plaque,lipid rich plaque or not, vascular remodeling index, ratio of diameter stenosis, and total calcium score were recorded as a mean value of at least 3 independent measurements.Results: Six cases of 31 patients were lost in follow-up, and 25 patients had complete follow-up data. The average effective radiation dose before and after scanning were 1.88± 0.14 m Sv and 1.83 ± 0.14 m Sv respectively, with no significant difference. 29 target plaques in 25 cases could be clearly shown in the follow-up CTCA images. After treatment, low-density lipoprotein cholesterol(LDL-C) level decreased by 35.38%,high-density lipoprotein cholesterol(HDL-C)level increased by 18.92%, plaque volume reduced by 25.40%, vascular remodeling index reduced by 13.01%, and total calcium score increased by 7.5% with significant difference(P<0.05). Plaque volume reduction rate were influenced by lipid rich plaque, vascular remodeling index, gender and LDL-C level shown from multiple linear regression analysis, and their standardized regression coefficients were 0.450、0.294、0.276、0.247(P<0.05), respectively. Additional multiple linear regression analysis demonstrated that descending degree of LDL-C level after medical treatment could affect plaques volume reduction rate, with standardized regression coefficients 0.554(P<0.05).Conclusion: 1. Standard medical treatment can reduce LDL-C levels in patients, with regression and composition changes of non-calcified coronary plaques. 2. Lipid-rich plaques, positive vascular remodeling, female and high LDL-C level before medical treatment could be refered to speculate a high plaques volume reduction rate. 3.Descending degree of LDL-C level after medical treatment also might be used to predict a high plaques volume reduction rate. 4. Non-calcified coronary artery plaques can be followed up by DSCT prospective ECG-gated high-pitch spiral mode CTCA at low radiation dose.