Coronary CT angiography with single-source and dual-source CT: Comparison of image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated protocols

Background

This study is conducted to investigate and compare image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated coronary CT angiography (CCTA) with the use of single-source CT (SSCT) and dual-source CT (DSCT).

Methods

A total of 209 patients who underwent CCTA with suspected coronary artery disease scanned with SSCT (n = 95) and DSCT (n = 114) scanners using prospective ECG-triggered and retrospective ECG-gated protocols were recruited from two institutions. The image was assessed by two experienced observers, while quantitative assessment was performed by measuring the image noise, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Effective dose was calculated using the latest published conversion coefficient factor.

Results

A total of 2087 out of 2880 coronary artery segments were assessable, with 98.0% classified as of sufficient and 2.0% as of insufficient image quality for clinical diagnosis. There was no significant difference in overall image quality between prospective ECG-triggered and retrospective gated protocols, whether it was performed with DSCT or SSCT scanners. Prospective ECG-triggered protocol was compared in terms of radiation dose calculation between DSCT (6.5 ± 2.9 mSv) and SSCT (6.2 ± 1.0 mSv) scanners and no significant difference was noted (p = 0.99). However, the effective dose was significantly lower with DSCT (18.2 ± 8.3 mSv) than with SSCT (28.3 ± 7.0 mSv) in the retrospective gated protocol.

Conclusions

Prospective ECG-triggered CCTA reduces radiation dose significantly compared to retrospective ECG-gated CCTA, while maintaining good image quality.     

64层CT冠状动脉成像的前瞻性与回顾性心电门控比较

目的 比较前瞻性心电门控和回顾性心电门控64层CT冠状动脉成像的辐射剂量和成像质量,探讨低剂量前瞻性心电门控CT冠状动脉成像的可行性.方法 两组心率≤65次/min各100例患者分别进行前瞻性和回顾性心电门控扫描,并采用多平面重组(MPR)、最大密度投影(MIP)、曲面重组(CPR)及容积再现(VR)多种重组技术显示冠状动脉,图像质量根据运动伪影影响分为优、良、差,使用剂量长度计算各自的有效辐射剂量,并进行统计学分析.结果 前瞻性组平均辐射剂量为(2.81±0.48)mSv明显低于回顾性组的(10.16±1.09)mSv(P＜0.01);前瞻性组诊断性冠状动脉节段和非诊断性冠状动脉节段为95.2%(1165/1224)和4.8%(59/1224),与回顾性组的94.1%(1186/1261)和5.9%(75/1261)比较,差异无统计学意义.结论 对于心率稳定在65次/min以下的患者,前瞻性心电门控64层CT冠状动脉成像,能以较低的辐射剂量达到回顾性心电门控诊断质量的影像,是切实町行的方法.     

前瞻性心电触发轴位扫描技术在64层螺旋CT中的应用

目的探讨在64层螺旋CT冠状动脉成像中采用前瞻性心电触发轴位扫描技术的图像质量和辐射剂量。方法选择采用前瞻性心电触发轴位扫描技术进行64层螺旋CT冠状动脉成像的患者160例作为前瞻组。将相同扫描参数输入回顾性心电门控螺旋扫描程序,获得扫描剂量数据作为回顾组。由2名放射科医师分别进行图像重建和图像质量评价。冠状动脉图像质量分级采用4级评分法。结果 2名放射科医师在图像重建和图像质量评价方面均有良好的一致性。160例患者除8例图像有严重血管错层伪影、2例冠状动脉严重钙化,共显示1449个冠状动脉节段。1～3分以上的1431个节段(98.76%)具有较好的图像质量,可以满足临床诊断要求。前瞻组与回顾组的平均有效剂量差异有统计学意义[(3.17±1.17)mSv vs (22.09±6.72)mSv,P0.01]。结论在64层螺旋CT冠状动脉成像中采用前瞻性心电触发轴位扫描技术可在保证图像质量的同时显著降低辐射剂量。     

Flash双源CT大螺距冠状动脉成像与冠状动脉造影对比的临床研究

目的评价Flash双源CT大螺距前瞻性心电门控扫描模式（flashspril）诊断冠状动脉狭窄的准确性。方法30例患者行Flash双源CT冠状动脉成像（CTCA）后进行冠状动脉造影术（CCA）检查。以冠状动脉造影术结果作为金标准,统计Flash双源CTCA显示冠脉病变的敏感性、特异性、阳性预测值和阴性预测值,统计冠状动脉各段图像质量评分及有效射线剂量。结果①准确性评价：基于节段水平分析,敏感性93．2％,特异性96．8％,阳性预测值86．0％,阴性预测值98．5％。基于血管水平分析,敏感性97．9％,特异性83．8％,阳性预测值88．7％,阴性预测值96．8％。基于患者水平分析,敏感性、特异性、阳性预测值、阴性预测值均为100％。CTCA显示冠状动脉狭窄结果与CCA高度一致。②图像质量：右冠状动脉不可诊断血管节段占右冠状动脉的3．4％,左冠状动脉主干、前降支不可诊断血管节段为0,回旋支不可诊断血管节段低于1．0％。③射线剂量：平均有效射线剂量（1．72±0．10）mSv。结论Flash双源CTflashspril模式CTCA评价冠状动脉狭窄的准确性高,图像质量好,运动伪影小,有效射线剂量低。     

Comparison of intravascular ultrasound, quantitative coronary angiography, and dual-source 64-slice computed tomography in the preprocedural assessment of significant saphenous vein graft lesions

The correlation between cardiac computed tomographic (CT) and intravascular ultrasound (IVUS) assessment of saphenous vein graft (SVG) lesions has not been studied. The aim of this study was to evaluate the accuracy of dual-source computed tomography in quantitative assessment of significant SVG lesions scheduled for percutaneous coronary intervention (PCI). Preintervention dual-source CT (DSCT) scans were performed in consecutive patients before PCI of the SVG lesion. All subjects underwent IVUS examination of the target lesion before stent implantation. Lesion characteristics were described using dual-source computed tomography, quantitative coronary angiography, IVUS, and visual estimation. Luminal areas and diameters, lesion lengths, and DSCT suggested stent dimensions were compared. Twenty-two SVG lesions were assessed in 22 patients. Minimal lumen area measured by IVUS was larger than by dual-source computed tomography (3.5 ± 1.2 vs 3.0 ± 1.2 mm(2), p = 0.04), although there was close correlation between measurements (R = 0.7, p = 0.007). Proximal and distal reference lumen diameters by IVUS and dual-source computed tomography were similar (3.3 ± 0.4 vs 3.4 ± 0.6 mm, p = 0.5, and 3.4 ± 0.6 vs 3.5 ± 0.6 mm, p = 0.4, respectively) and were well correlated (R = 0.85, p <0.0001, and R = 0.81, p <0.0001, respectively). Lesion length by IVUS averaged 18.3 ± 6.1 versus 17.6 ± 5.3 mm by dual-source computed tomography (p = 0.1). There was good correlation between mean reference lumen diameter by dual-source computed tomography and diameter of the implanted stent (R = 0.84, p = 0.0009) and a very good correlation between stent length and lesion length as assessed by dual-source computed tomography (R = 0.9, p <0.0001). In conclusion, DSCT measurements in SVGs correlate with IVUS so that DSCT scan data before PCI of an SVG lesion may be helpful in stent size selection.     

Double Flash扫描方式在冠状动脉计算机断层扫描中的应用

目的 探讨双源计算机断层扫描（computerized tomography,CT）大螺距前瞻性心电触发采集模式（Flash模式）在冠状动脉CT中的应用价值.方法 随访中国人民解放军总医院行冠状动脉CT检查的患者120例,其中采用Double Flash扫描方式组60例（A组）,常规螺旋扫描方式组60例（B组）.入选患者在CT检查过程中心率均＜70次/min,窦性心律且节律整齐,且体质量＜100 kg.采用4分法对图像质量进行评价（1分为图像质量极好,2分为图像质量好,3分为图像质量一般,4分为图像质量差）,并记录两组患者整个扫描过程中的总有效剂量值及总剂量长度乘积.结果 两组间图像质量评分比较,差异无统计学意义（P＞0.05）.A组整个扫描过程中的总有效剂量值明显低于B组,差异有统计学意义[（2.6±0.8） mSv vs.（8.6±1.3） mSv,P＜0.05];总剂量长度乘积也明显低于B组,差异有统计学意义[（145.8±13.5） mGy·cm vs.（621.4±129.8）mGy.cm,P＜0.05].结论 双源CT大螺距前瞻性心电触发采集模式应用于心率＜70次/min的患者时与常规螺旋扫描模式比较,在保证图像质量的同时,还可显著降低辐射剂量.     

Radiation dose and diagnostic accuracy of multidetector computed tomography for the detection of significant coronary artery stenoses: A meta-analysis

We conducted a meta-analysis evaluating the critical ratio between effective radiation dose (ED), feasibility (Fe) and diagnostic accuracy (Ac) of multidetector computed tomography (MDCT) for the detection of significant coronary artery disease. By using our predetermined criteria, we selected human studies published in English in which the ED and raw data of Ac vs. invasive coronary angiography in a segment based model were specified. Data from 31 studies including 3661 patients (mean age 61.9±4.5years, heart rate 62.5±6.7bpm) and 50,236 coronary artery segments were analysed and are reported. Overall, Fe, sensitivity, specificity, negative predictive value, positive predictive value, Ac and ED were 95%, 90%, 96%, 99%, 69%, 95% and 10.4±5.4mSv, respectively. Multivariate analysis showed that prospective ECG-gating (-8.8mSv CI95% -13.4 to -4.3mSv, p=0.001), dual-source (-3.7mSv CI95% -7.9 to 0mSv, p=0.05) and BMI-adapted scanning protocols (-4.5mSv CI95% -8.7 to -2.7mSv, p=0.03) were independent predictors of ED reduction. In patients with low heart rate, the best compromise between ED, Fe and Ac (2.5mSv, 97% and 98%, respectively) was obtained combining prospective ECG-gating and BMI-adapted scanning protocols, while in patients with high heart rate the strategy associated with the best results (10mSv, 98% and 97%, respectively) was the use of dual-source MDCT with retrospective ECG gating and modulation dose. In conclusion, careful selection of CT scanning protocols according to the patient's characteristics is critical for keeping the radiation exposure "as low as reasonably achievable" (ALARA) without impairing Fe and Ac.     

第二代双源CT Flash Spiral模式高心率冠状动脉成像的图像质量及准确性评价

目的评价第二代双源CT大螺距前瞻性螺旋扫描（Flash Spiral）高心率冠脉成像的图像质量、准确性及有效射线剂量。方法前瞻性入选心率〉65次／min的连续性患者268例,随机分为两组。A组134例,采用Flash Spiral模式扫描,采集图像时间为RR间期20％-30％;B组134例,采用回顾性心电门控扫描模式（Spiral）扫描。30d内A组有47例行冠状动脉造影术（CCA）检查（A1组）,B组中有45例行CCA检查（B1组）。比较两组患者一般情况、图像质量评分、图像噪声、对比信噪比（CNR）和有效射线剂量。以CCA结果为金标准,分别计算A1、B1两组FlashDSCT显示冠脉病变的敏感性、特异性、准确率、阳性预测值和阴性预测值。结果①两组患者一般情况比较差异无统计学意义。②两组不可诊断节段基于血管节段评价分别为1．52％和1．74％,基于患者评价分别为7．5％和6．7％,差异均无统计学意义（P=0．345,P=0．812）。两组图像质量评分均数分别为1．064±0．306和1．084±0．327,差异无统计学意义（P=0．063）。A组平均图像噪声19±27（21．4±4．5）HU,CNR6．4-25．3（12．1±4．2）：B组分别为19±28（20．9±4.3）HU和7．1-28．2（13．8±5．1）,两组比较差异无统计学意义。③心率变异性：A组图像质量评分3分的病例平均心率变异性明显小于B组。④与CCA比较,两组患者评价冠状动脉狭窄的敏感性、特异性差异均无统计学意义。⑤射线剂量：A组平均有效射线剂量显著低于B组[（1．04±0．16）mSv比（7．05±1．05）mSv,P=0．001]。结论高心率患者（心率〉65次／min）采用Flash双源CT大螺距前瞻性心电门控螺旋扫描在RR间期20％±30％成像,图像质量、准确性与回顾性心电门控扫描接近,而有效射线剂量显著减低。心率变异性对高心率患者FlashSpiral模式扫描图像质量的影响较大。     

心电门控320排容积CT在急性胸痛中应用价值的前瞻性研究

目的:探讨前瞻性心电门控320排容积CT对急性胸痛成像的可行性及诊断价值。方法:对连续61例急性胸痛患者不控制心率条件下行前瞻性心电门控wide-volume模式并强制在一个心动周期扫描,曝光时间窗根据心率不同预设在40%~50%R-R间期(心率≥70次/min)或70%~80%R-R间期(心率70次/min)。2个volume涵盖自胸廓入口至心膈面,对比剂采用三相注射法以便同时显示主动脉、冠状动脉、肺动脉三大血管床。评价三大血管床的图像质量及对胸痛病因的诊断能力。记录患者的有效辐射剂量、对比剂用量。结果:61例患者的三大血管床(主动脉、冠状动脉及肺动脉)均得到明显均匀强化。主动脉和肺动脉均获得良好的可诊断图像(可诊断率达100%,61/61)。2例患者因屏气不良冠状动脉图像无法评价,在其余59例患者的625个冠状动脉节段中,图像质量为1级的占94.2%(589/625),2级图像质量占3.2%(20/625),总的可评价率达97.4%。观察者之间总的一致性较好(k=0.83,95%CI:0.60~1.00)。平均有效辐射剂量为(5.44±1.15)mSv,对比剂总量平均为(75.7±4.35)mL。本扫描计划对胸痛病因阳性诊断率为82%(50/61),CTA诊断为阴性的18%(11/61)的患者中随诊一月内无不良并发症出现。结论:320排容积CT的前瞻心电门控wide-volume扫描模式在不控制心率情况下可低辐射剂量及低对比剂用量地对急性胸痛患者进行评价。     

迭代重建技术在前门控结合体质量调节管电压管电流心脏CT成像的研究——降低辐射剂量及控制图像质量简

目的 探讨迭代重建技术（iDose4）在前瞻性心电门控结合体质量调节管电压管电流心脏螺旋计算机断层扫描（computerized tomography,CT）成像中降低辐射剂量及控制图像质量的应用价值.方法 选取实验猪10只,每只猪均进行以体质量调节管电压管电流为基础的常规剂量（A组）及在此基础上降低管电流[分别降低30％（B组）、50％（C组）、70％（D组）]的256层前瞻性心电门控心脏CT扫描,所有数据均分别采用滤波反投影（filtered back projection,FBP）和iDose4重建,计算猪接受的辐射剂量,测量升主动脉根部及左心室腔噪声、信噪比（SNR）、对比噪声比（CNR）,分别对总体图像质量和冠状动脉图像质量进行评分（5分法评分）,3分及以上为图像质量可满足诊断,并对两种重建方法处理后所得结果进行比较.结果 A、B、C、D组的有效辐射剂量（ED）分别为（3.13±0.63） mSv、（2.26±0.51） mSv、（1.61±0.36） mSv、（1.01±0.23）mSv.随着X线剂量降低,图像噪声增加,信噪比、对比噪声比降低,图像质量下降.各组内比较,iDose4重建的图像噪声均较FBP重建者明显降低,而信噪比及对比噪声明显提高,差异均有统计学意义（P均=0.000）.A、B、C、D各组内经FBP/iDose4重建后总体图像质量评分分别为（3.80±0.42）分/（4.60±0.52）分、（3.60±0.52）分/（4.40±0.52）分、（3.00±0.67）分/（3.80±0.42）分、（2.00±0.67）分/（3.40±0.52）分,各组内比较差异均有统计学意义（P＜0.05）.用FBP重建,A、B、C、D组近、远端冠状动脉的可诊断率分别为100％、95％、70％、20％和92％、72％、36％、0;经iDose4重建后,A、B、C组近、远端冠状动脉的可诊断率均大于经FBP重建后A组的可诊断率或与其相当（P＞0.05）,而D组的可诊断率明显低于FBP重建后A组的可诊断率,差异有统计学意义（P＜0.05）.结论 在前门控结合体质量调节管电压管电流心脏CT成像中,应用iDose4较FBP可显著降低图像噪声,提高信噪比及对比噪声比,提高图像质量;用iDose4重建可以在现有辐射剂量基础上降低50％的剂量进行扫描而图像质量保持不变.     

Feasibility of low-dose coronary CT angiography: first experience with prospective ECG-gating.

AIMS: To determine the feasibility of prospective electrocardiogram (ECG)-gating to achieve low-dose computed tomography coronary angiography (CTCA). METHODS AND RESULTS: Forty-one consecutive patients with suspected (n = 35) or known coronary artery disease (n = 6) underwent 64-slice CTCA using prospective ECG-gating. Individual radiation dose exposure was estimated from the dose-length product. Two independent readers semi-quantitatively assessed the overall image quality on a five-point scale and measured vessel attenuation in each coronary segment. One patient was excluded for atrial fibrillation. Mean effective radiation dose was 2.1 +/- 0.6 mSv (range, 1.1-3.0 mSv). Image quality was inversely related to heart rate (HR) (57.3 +/- 6.2, range 39-66 b.p.m.; r = 0.58, P < 0.001), vessel attenuation (346 +/- 104, range 110-780 HU; r = 0.56, P < 0.001), and body mass index (26.1 +/- 4.0, range 19.1-36.3 kg/m(2); r = 0.45, P < 0.001), but not to HR variability (1.5 +/- 1.0, range 0.2-5.1 b.p.m.; r = 0.28, P = 0.069). Non-diagnostic CTCA image quality was found in 5.0% of coronary segments. However, below a HR of 63 b.p.m. (n = 28), as determined by receiver operator characteristic curve, only 1.1% of coronary segments were non-diagnostic compared with 14.8% with HR of >63 b.p.m. (P < 0.001). CONCLUSION: This first experience documents the feasibility of prospective ECG-gating for CTCA with diagnostic image quality at a low radiation dose (1.1-3.0 mSv), favouring HR <63 b.p.m.     

窄窗扫描技术在高心率患者320排CT冠状动脉成像中的应用研究

目的：探讨高心律患者320排CT冠状动脉成像使用前瞻性心电门控窄窗扫描技术对图像质量和辐射剂量的影响。方法80例心率在80~100次/min的患者随机分成观察组和对照组。观察组按R- R间期30％～50％进行前瞻性窄窗扫描3个心动周期,对照组按R- R间期30％～80％进行常规扫描3个心动周期,冠状动脉节段图像质量采用4级评分法评分,辐射剂量值由设备自动计算。结果可评价血管段和优良率两组间差异无统计学意义（P＞0.05）。冠状动脉总节段、右冠状动脉（RCA）、左冠状动脉主干（LM）、左前降支（LAD）和旋支（LCX）的质量评分两组间差异无统计学意义（P＞0.05）。观察组的RCA和LCX与心律波动呈中等程度负相关（r =0.41、0.47）。观察组和对照组平均辐射剂量分别为（7.63±3.29）和（12.85±2.71）mSv,差异有统计学意义（t=1.384,P＜0.05）。结论窄窗扫描技术可应用在心律波动不大的高心率患者,能明显降低辐射剂量而不影响图像质量。     

Influence of heart rate on the diagnostic accuracy of dual-source computed tomography coronary angiography.

OBJECTIVES: We evaluated the influence of heart rate on image quality and diagnostic accuracy of dual-source computed tomography (DSCT) coronary angiography. BACKGROUND: Multidetector computed tomography (MDCT) coronary angiography has demonstrated an inverse relationship between heart rate and image quality. Dual-source CT provides a higher temporal resolution. METHODS: One hundred patients were studied by DSCT (DEFINITION, Siemens Medical Solutions, Forchheim, Germany). A contrast-enhanced volume dataset was acquired (two tubes, 120 kV, 400 mAs/rot, collimation 64 x 0.6 mm). Datasets were evaluated concerning the presence of significant coronary stenoses and validated against invasive coronary angiography. RESULTS: In 44 patients with a heart rate > or =65 beats/min, 566 of 616 coronary segments were evaluable (92%), whereas in 56 patients with a heart rate <65 beats/min, 777 of 778 coronary segments were evaluable (100%, p < 0.001). On a per-patient basis, 93% of patients (> or =65 beats/min) and 100% of patients (<65 beats/min) were considered evaluable. By classifying unevaluable segments as positive for stenosis, per-patient sensitivity was 95% (19 of 20) for heart rates > or =65 beats/min and 100% (22 of 22) for heart rates <65 beats/min. Specificity was 87% (21 of 24) versus 76% (26 of 34), and overall diagnostic accuracy was 91% (40 of 44) versus 86% (48 of 56). None of these differences were statistically significant. Similarly, no difference in diagnostic accuracy was found in per-vessel and -segment analyses. CONCLUSIONS: In 100 patients studied without beta-blocker pre-medication, DSCT demonstrated slightly lower per-segment evaluability for high heart rates but no decrease in diagnostic accuracy for the detection of coronary artery stenoses.     

双源CT对冠状动脉支架靶血管再狭窄的诊断价值

目的:探讨双源CT（DSCT）对冠状动脉支架置入靶血管再狭窄的诊断价值。方法:对我院69例冠状动脉支架置入患者（共111枚支架）进行DSCT,评价支架图像质量得分与靶血管级别的相关性;并对部分患者同期进行冠状动脉造影（CAG）检查,对比分析DSCT对冠状动脉支架置入靶血管病变的真实性。结果:DSCT支架图像质量得分与靶血管级别正相关;DSCT对支架靶血管再狭窄诊断的灵敏度82%、特异度98%、和准确度95%;DSCT与CAG对不同直径支架的靶血管再狭窄检出率差异无统计学意义,但DSCT对直径≥3.0 mm支架靶血管再狭窄检出的特异度和准确度明显高于直径＜3.0 mm支架靶血管的相应指标（均P＜0.05）,而灵敏度的差异未达到显著水平。结论:DSCT可清晰的显示冠状动脉支架靶血管的病变情况,能较准确地评价冠状动脉支架靶血管再狭窄的发生,具有临床应用价值。     

Effect of a standardized quality-improvement protocol on radiation dose in coronary computed tomographic angiography

Coronary computed tomographic angiography (CCTA) is associated with ionizing radiation, prompting concerns of future cancer risk. Recent studies have reported reduced radiation doses and similar image quality by the selective use of dose reduction techniques, although the clinical penetration of these methods has been limited. In a quality improvement initiative, a comprehensive, standardized radiation dose reduction protocol was implemented, and its effect on radiation dose and image quality was assessed. A total of 449 patients who underwent 64-detector CCTA at 3 centers were prospectively evaluated, and patients were compared before (n = 247) and after (n = 202) the implementation of a standardized body mass index-based and heart rate-based protocol that simultaneously incorporated multiple dose reduction strategies. Median radiation dose decreased from 2.6 mSv (interquartile range 2.0 to 4.2) to 1.3 mSv (interquartile range 0.8 to 1.9) after the implementation of the standardized protocol (p < 0.001). On multivariate analysis, reduction in overall radiation dose was observed by numerous dose reduction techniques, with varying efficacy of dose lowering: prospective (vs retrospective) electrocardiographic gating (-82%), reduced tube voltage (-41% for 100 vs 120 kV), lower tube current (-25% per -100 mA), and reduced overall scan length (-6% per -1 cm) (p < 0.001 for each). No differences were observed between patients before and after the initiation of the protocol for study interpretability (96% vs 96%, p = 0.66). There was an increase in signal-to-noise ratio after implementing the standardized protocol (11 ± 3 vs 12 ± 4, p < 0.01). In conclusion, a quality improvement protocol for CCTA incorporating multiple dose reduction techniques permits significant radiation dose reduction and may improve the safety profile of CCTA.     

低剂量、大螺距双源CT前瞻性心电门控冠状动脉成像在心房颤动患者中的初步应用

目的评价第二代双源CT大螺距前瞻性心电门控扫描模式（fllash spiral）在房颤患者中应用的可行性。方法从我院接受大螺距双源CT冠状动脉成像检查的1077例患者中,选择房颤患者10例,分别采用HP前瞻性心电门控扫描（flash spiral模式）和回顾性心电门控模式扫描（spiral模式）。Flash spiral模式采集图像时间选择为RR间期的20％-30％成像。结果10例患者均采用flash模式扫描,其中7例患者图像质量好（评分1分）,3例患者有轻度伪影,但可评价血管（评分2分）。SpirM扫描中,4例病例右冠状动脉伪影重,为非诊断血管病例,1例回旋支重度伪影。Flash模式扫描有效射线剂量为O．680-1．887mSv,8例患者低于1mSv。Spiral扫描有效射线剂量为14．920-21．306mSv。结论①房颤患者采用大螺距flash spiral模式单个心动周期成像可获得良好的效果,且图像质量优于回顾性心电门控模式。②由于RR间期不规则,房颤患者flash spirM扫描时必须在下一个R波前完成扫描,需提前采集数据时间（RR间期的20％-30％采集为最佳）。③房颤患者flash spiral扫描有效射线剂量低于1mSv。     

起搏器置入患者的640层CT冠状动脉成像初步研究

目的 探讨心脏起搏器置入患者应用640层动态容积CT行冠状动脉(冠脉)成像的可行性和图像质量.方法 16例体内置入心脏起搏器的连续病例应用640层容积CT行前瞻性心电门控冠脉成像.由两位有经验的放射诊断医师双盲评价冠脉15个节段的图像质量以及起搏器电极的金属伪影对冠脉节段的影响,同时记录扫描过程中的心电资料,进行统计分析.结果 起搏器置入患者640层CT冠脉造影图像质量优良率达到99.07%,1级占到83.64%,低心率组与高心率组、正常起搏心律组与心律失常组的冠脉图像质量评分以及起搏器电极的金属伪影对冠脉节段的影响差异均无统计学意义,P＞0.05.起搏器电极的金属伪影可降低右冠脉近段(S1)、中段(S2)、远段(S3)及后降支(S4)、左前降支远段(S8)的图像质量,其中以右冠脉近段(S1)、中段(S2)多见.调整重建期相后,冠脉节段的图像质量明显改善,重建期相调整前后的差异有统计学意义(x2=151.818,P＜0.01).结论 心脏起搏器置入患者行前瞻性心电门控640层容积CT冠脉成像能提供优秀的图像质量,起搏器电极金属伪影可降低部分冠脉节段的图像质量,改变重建期相能显著改善伪影.

Abstract：

Objective To investigate the feasibility and image quality of coronary artery angiography with 640-slice CT system in the pacemaker patients. Methods ECG-triggered 640-slice CT coronary angiography was performed in 16 pacemaker patients. Image quality of the fifteen coronary segments and metal-related artifact originating from pacemaker were assessed by two experienced radiologists in consensus.Image quality was assessed using a 4-point grading scale. ECG trigger information was recorded. Results The rate of available diagnostic images was 99. 07% ( Grade 1 in 83.64%, Grade 2 in 15.42%, Grade 3 in 0. 47% and Grade 4 in 0. 47% of patients, respectively). Image quality and the effect of streak artifact were similar between the high heart rate group and low heart rate group ( P ＞ 0. 05 ) and between normal pacing group and arrhythmia group ( P ＞ 0. 05 ). In coronary MSCT angiography, streak artifact of the pacemaker can render segments of the coronary artery uninterpretable, especially on S1, S2, S3, S4 and S8 segments of the coronary artery. Small shifts in the reconstruction window resulted in significance reduction of streak artifact ( x2 = 151. 818, P ＜ 0. 01 ). Conclusions 640-slice gated CT coronary angiography could provide excellent image quality for patients with pacemaker. The streak artifact induced by pacemaker on some segments of the coronary artery could be improved by small shifts in the reconstruction window.     

双源CT 100kV管电压在冠脉成像中的应用价值

目的:探讨双源CT应用100 k V管电压扫描方案在冠状动脉成像中的应用价值。方法:将70例临床怀疑或确诊为冠心病患者,随机分为管电压100 k V组(低剂量组,35例)与120 k V组(常规组,35例)。其他条件一致,分别对两组图像质量和辐射剂量进行评价。入组条件:体质量指数(BMI)为20~24,窦性心率。结果:两组冠脉成像图像质量无显著差别,而100 k V辐射剂量较120 k V组显著降低(P<0.01)。结论:应用双源CT做冠脉CT血管造影,给予100 k V管电压能够在保证图像质量,满足诊断要求同时降低辐射剂量。     

Diagnostic accuracy of dual-source multi-slice CT-coronary angiography in patients with an intermediate pretest likelihood for coronary artery disease.

AIMS: The aim of the present study was to assess the clinical performance of a dual X-ray source multi-slice CT (MSCT) with high temporal resolution to assess the coronary status in patients with an intermediate pretest likelihood for significant coronary artery disease (CAD) without using negative chronotropic pretreatment. METHODS AND RESULTS: Dual-source CT (DSCT) angiography (Siemens Definition) was performed in 90 patients with an intermediate likelihood for CAD who were referred for invasive coronary angiography. DSCT generated data sets with diagnostic image quality in 88 of the overall 90 patients. In six of seven patients with atrial fibrillation and in 46 of 48 patients with heart rates (HR)>65 b.p.m. image quality was diagnostic. In 20 of 21 patients with at least one stenosis>50% (sensitivity 95%) were correctly identified by DSCT-angiography. In 60 of 67 patients, a lesion>50% was correctly excluded (specificity 90%; positive predictive value 74%). The accuracy to detect patients with coronary stenoses>50% (sensitivity 92 vs. 100%; specificity 88 vs. 91%) was not significantly different among patients with HR>65 b.p.m. (n=46) and <65 b.p.m. The concordance of DSCT-derived stenosis quantification showed good correlation (r=0.76; P<0.001) to quantitative coronary angiography with a slight trend to overestimate the stenosis degree. CONCLUSION: DSCT is a non-invasive tool that allows to accurately rule out coronary stenoses in patients with an intermediate pretest likelihood for CAD, independent of the HR.     

心房颤动对双源CT冠状动脉血管成像的影响

目的探讨心房颤动（房颤）平均心室率、心率波动和心率变异性对冠状动脉CT血管成像（CTA）图像质量的影响。方法87例房颤患者和107例心律正常者进行了双源CT冠状动脉血管成像。平均心室率、心率波动和心率变异性与图像质量之间的关系采用相关分析和线性回归分析判断,各分段图像质量之间的差别采用卡方检验和非参数检验。结果房颤组共1218段血管纳入分析,达到诊断标准的血管共1038段（85．2％）。房颤组的平均心室率为（90．1±22．0）次／min,心率波动为（55．8±34．3）次／min,心率变异性为0．55±0．29,均高于对照组（P〈0．01）。部分动脉图像质量与平均心率无关（P〉0．05）。除左主干外,心率波动与其他分段图像质量呈负相关（P〈0．01）。心率变异性与所有分段图像质量呈负相关（0．01〈P〈0．05和P〈0．01）。左主干和回旋支近段高质量图像百分率较高,而后降支和钝缘支图像质量较差。结论双源CT能对大多数房颤患者冠状动脉进行评价,其获得的各近段动脉图像质量高于远段动脉。心率波动对房颤冠状动脉CTA图像质量起主导影响作用。