Dose performance and image quality: dual source CT versus single source CT in cardiac CT angiography

Objective

To evaluate dose performance and image quality of 64-slice dual source CT (DSCT) in comparison to 64-slice single source CT (SSCT) in cardiac CT angiography (CTA).

Methods

100 patients examined by DSCT and 60 patients scanned by SSCT were included in this study. Objective indices such as image noise, contrast-to-noise ratio and signal-to-noise ratio were analyzed. Subjective image quality was assessed by two cardiovascular radiologists in consensus using a four-point scale (1 = excellent to 4 = not acceptable). Estimation of effective dose was performed on the basis of dose length product (DLP).

Results

At low heart rates (<70 bpm), image quality of SSCT was equivalent to that of DSCT (P > 0.05), but, at high heart rates (>70 bpm), DSCT provided robust image quality (P < 0.05). The average effective dose of SSCT was 9.3 ± 0.9 mSv at low heart rates (<70 bpm) while, the average estimated effective doses of DSCT were 9.1 ± 1.3 mSv, 8.3 ± 1.1 mSv, 7.9 ± 1.1 mSv, 6.9 ± 0.7 mSv, and 5.9 ± 1.3 mSv, corresponding to heart rates of 50-59 bpm, 60-69 bpm, 70-79 bpm, 80-89 bpm, and 90-100 bpm.

Conclusion

For cardiac CTA, both DSCT and SSCT can get good image quality at low heart rates (<70 bpm) with a similar radiation dose, but, at high heart rates (>70 bpm), DSCT is able to provide robust diagnostic image quality at doses far below that of SSCT.     

双源CT诊断冠脉狭窄的价值—与冠状动脉造影对照分析

目的:探讨双源CT冠脉成像评价冠脉中度及中度以上狭窄的准确性及可行性。方法:入选60例临床高度怀疑或已确诊冠脉疾病的患者,行双源CT扫描,扫描过程中患者心率平稳,未出现心率不齐及心律失常。患者于1周内行经皮选择性冠状动脉造影,并以冠状动脉造影作为标准,从冠脉节段及冠脉分支角度分别评价双源CT诊断冠脉中度及中度以上狭窄的准确性、敏感性、特异性、阳性预测率及阴性预测率。结果:以冠脉节段为基础分析,双源CT诊断冠脉明显狭窄的敏感性、特异性、阳性预测率、阴性预测率、准确性分别为81.14%、97.57%、85.34%、96.74%、95.13%;以冠脉分支为基础分析,双源CT诊断冠脉明显狭窄的敏感性、特异性、阳性预测率、阴性预测率、准确性分别为84.21%、93.79%、89.88%、90.06%、90.0%。双源CT与选择性冠脉造影对发现冠脉狭窄节段及检查冠脉分支病变的能力进行卡方检验,χ2分别0.625、1.041;P0.05,双源CT与选择性冠脉造影比较在发现冠脉明显狭窄差异上无统计学意义。结论:双源CT在诊断冠脉明显狭窄时有很高的准确性,可作为无创性评价冠脉狭窄及疾病的手段。     

Technical principles of dual source CT

During the past years, multi-detector row CT (MDCT) has evolved into clinical practice with a rapid increase of the number of detector slices. Today's 64 slice CT systems allow whole-body examinations with sub-millimeter resolution in short scan times. As an alternative to adding even more detector slices, we describe the system concept and design of a CT scanner with two X-ray tubes and two detectors (mounted on a CT gantry with a mechanical offset of 90 degrees) that has the potential to overcome limitations of conventional MDCT systems, such as temporal resolution for cardiac imaging. A dual source CT (DSCT) scanner provides temporal resolution equivalent to a quarter of the gantry rotation time, independent of the patient's heart rate (83 ms at 0.33 s rotation time). In addition to the benefits for cardiac scanning, it allows to go beyond conventional CT imaging by obtaining dual energy information if the two tubes are operated at different voltages. Furthermore, we discuss how both acquisition systems can be used to add the power reserve of two X-ray tubes for long scan ranges and obese patients. Finally, future advances of DSCT are highlighted.     

双源CT在心律失常患者冠状动脉成像中的应用

目的:探讨双源CT在心律失常患者的冠状动脉成像扫描技术及图像后处理中的应用。方法:452例怀疑冠心病的患者行双源CT冠状动脉成像,心律失常患者70例,其中增强扫描过程中平均心率>100次/min的患者共56例,房性早搏(atrial premature beat)6例,室性早搏(ventricular oremature beat)5例,房颤(atrial fibrillation)3例。双源CT自动重建最佳收缩期(best diast)、最佳舒张期(best syst)图像,若图像欠佳者编辑心电图,然后重建图像,把增强扫描图像行多平面重组(MPR)、最大密度投影(MIP)、容积再现技术(VRT)重建、曲面(CPR)重建。将图像质量分为3级,以美国心脏协会(Americanheart association,AHA)推荐的解剖分段方法为标准评价冠状动脉各个节段的图像质量。结果:70例心律失常患者经过心电图编辑后冠状动脉重建的最佳时相均为收缩期。共评价561个节段冠状动脉,其中图像质量1级者占87.9%(493/561),图像质量2级者占7.5%(42/561),图像质量3级者占4.6%(26/561)。结论:双源CT用于心律失常患者的冠状动脉成像可获得满意的冠状动脉各节段图像。     

不同心率下双源CT冠状动脉成像最佳相位窗的研究

目的探讨双源CT冠状动脉成像在不同心率下最佳相位窗的选择。方法对100例临床怀疑冠心病或冠状动脉病变患者进行双源CT冠状动脉回顾性心电门控成像扫描,扫描后数据分别按R-R间期10%、20%、30%、40%、50%、60%、70%、80%、90%的相位进行后处理重组,图像行MPR、MIP、容积再现技术（VRT）重组,利用Inspace软件及Circulation软件分析,将图像质量分为4级,按冠状动脉分段标准评价各个节段的图像质量。扫描时记录心率,100例患者心率小于等于60次/min为1组,心率大于60次/min而小于等于80次/min为2组,心率大于80/min而小于等于100次/min为3组,心率大于100次/min为4组。分析观察不同心率组的各时相冠状动脉评分趋势。结果 1、2组70%相位图像质量最好,3、4组40%相位图像质量较好。冠状动脉的图像质量评分与心率有一定的相关性。结论心率越慢图像质量越好,心率越快图像质量越差。最佳时相的选择可以提高诊断冠心病的准确率。     

双源CT双能量自动减影去骨技术在颈动脉造影中的临床应用

目的 评价双源CT双能量自动减影去骨去钙化技术在颈动脉造影中的临床应用价值.方法 回顾性分析自2012年11月～2014年2月在本院就诊应用双源CT双能量颈动脉血管成像检查的患者126例,分析全部患者颈动脉双源CT双能量自动去骨去钙化技术对颈动脉的显示,并评价图像质量.其中阳性结果患者中有27例患者接受了头颈部血管造影(DSA)检查,并以DSA图像为金标准对照,评价双源CT双能量自动减影去骨去钙化技术诊断颈动脉狭窄与DSA对照的统计学意义.结果 126例患者颈动脉双能量自动去骨后,对颈总动脉(CCA)血管满意显示率为71.0％,颈内动脉颅外段(ICA-E)血管显示满意率为96.0％,颈内动脉颅内段(ICA-I)血管满意显示率为74.2％,ICA-E血管满意显示率最高,与CCA及ICA-I相比有统计学意义(P＜0.05),全部血管总满意显示率为80.4％.27例阳性患者颈动脉双能量自动去骨后与DSA对照,狭窄吻合率一致性很高(P＞0.05),尤其重度及闭塞吻合率达到95％以上.结论 双源CT双能量自动去骨去钙化技术在颈动脉成像中的应用是一种快速、有效、无创的检查新手段,获得的图像质量好,尤其在ICA-E段血管的显示几乎可以替代DSA检查.     

双源CT血管造影评价冠状动脉狭窄的临床价值

目的:评价双源CT定量诊断冠状动脉狭窄的准确性及临床价值。方法:对30例临床拟诊冠心病患者分别进行双源CT和传统冠状动脉造影检查,并将双源CT判定冠状动脉狭窄程度与冠脉造影结果进行对比分析。结果:30例共计450冠脉节段,双源CT均获得满意的评价图像(3例进行心电编辑)。双源CT判定轻度狭窄38个节段,中度狭窄23个节段,重度狭窄36个节段;与冠状动脉造影结果对比,双源CT诊断冠脉狭窄的敏感性、特异性和准确性分别为94.12%、95.34%和95.11%。结论:与冠状动脉造影对比,双源CT在定量诊断冠脉狭窄方面具有较高的敏感性和特异性,可为临床诊断冠心病提供一项准确可靠的无创手段。     

心电编辑对提高双源CT冠脉图像质量的初步研究

目的:探讨心电编辑在改善双源CT冠脉图像质量中的作用。方法:以冠脉分支为单位,回顾性分析60例心率变异过大或心律失常患者双源CT冠脉成像编辑前后的图像质量,总结不同类型的心电编辑方法。结果:60例心率变异过大或心律失常患者,心率范围为55～269次/min,平均心率(92.8±31.9)次/min,冠脉图像编辑前后的图像质量总评分分别为2.26±1.03、3.5±0.61(t=-17.85,P=0.001);表明编辑前后图像质量的评分有统计学意义,编辑后图像质量明显改善。结论:心电编辑技术可以明显改善心率变异过大或心律失常患者双源CT冠脉成像的图像质量。     

Reproducibility of coronary calcium quantification in repeat examinations with retrospectively ECG-gated multisection spiral CT

High reproducibility is a key requirement for coronary calcium scoring in follow-up examinations. We investigated the inter-examination reproducibility of calcium scoring with retrospectively ECG-gated multisection spiral CT (MSCT). Fifty patients were examined twice with MSCT. Slices were reconstructed with retrospective ECG gating in the diastolic phase with 3-mm slice width and up to 125-ms temporal resolution. We calculated the Agatston score, calcium volume with and without isotropic interpolation, and calcium mass, and derived the mean and median variability. We investigated the change of variability with use of 3-mm non-overlapping and overlapping increments (2, 1.5, 1 mm). Use of overlapping increment results in considerably reduced interscan variability. We observed a minimum mean variability of 12% and a minimum median variability of 9% for the Agatston score. For volume and mass quantification we obtained a minimum mean variability of 7.5% and a minimum median variability of 5%. Multisection spiral CT enables coronary calcium quantification with high reproducibility in follow-up examinations mainly founded on image data with reduced partial-volume errors due to overlapping increment.     

二代双源CT对冠状动脉支架的显示及辐射剂量的研究

目的 对比分析二代双源CT前瞻性心电触发高螺距螺旋扫描模式(Flash模式)和回顾性心电门控螺旋扫描模式(常规模式)下冠状动脉支架的显示质量和辐射剂量.方法 常规模式和Flash模式下共计120例患者的155个冠状动脉植入支架纳入本研究,平均年龄(64.9±10.6)岁,所有患者的心率均控制在≤65次/min,且心律规则.所有患者分成两组,分别接受Flash模式和常规模式的冠状动脉成像.冠状动脉原始图像均进行Kernel B26和Kernel B46的数据重建,并由两位医师对支架的显示质量进行独立的4级评分.两种模式下的冠状动脉显示质量利用卡方检验进行统计分析,而不同冠状动脉扫描模式下的容积CT剂量指数值(CTDIvol)和剂量长度乘积值(DLP),利用t检验进行辐射剂量的对比研究.结果 2位医师对所有冠状动脉支架显示质量的评分具有较好的一致性(Kappa=0.764,P＜0.001),Flash模式和常规模式的平均评分分别为:1.61±0.77和1.65±0.82.两种冠状动脉扫描模式的图像质量差异无统计学意义(x2=0.865,P=0.834).Flash模式的CTDIvol(3.24±1.21)明显低于常规模式(31.26±10.79),差异有统计学意义(t=19.83,P<0.001);Flash模式的DLP(54.61±19.88)同样低于常规模式(468.30±174.88),差异有统计学意义(t=18.06,P＜0.001).结论 控制患者心率≤65次/min且心律规则,Flash模式在降低辐射剂量的前提下可获得与常规模式相同质量的冠状动脉支架图像.

Abstract：

Objective To compare a prospective ECG-gated high-pitch spiral technique (Flash) and conventional retrospective ECG-gated spiral technique for the image quality of coronary artery stent and radiation dose with a dual source CT.Methods One hundred and fifty five coronary stents in one hundred and twenty patients (mean age 64.9 ± 10.6 years,heart rates≤65 bpm) were examined using a dual source CT.All patients were divided in two groups,receiving either Flash or conventional coronary artery CT angiography separately.After images of coronary artery were reconstructed using both the smooth (B26) and sharp (B46) kernel,the coronary stent image quality and stent lumen were scored by two observers individually using four point scale (1 = excellent,4 = unvaluable) .The effective radiation dose of volume CT dose index (CTDIvol,mGy) and dose length product (DLP,mGy x cm) were also calculated for each patient.x2-test analysis of image quality and t-test analysis of radiation dose were used respectively for statistical difference between two groups.Results Interobserver agreement for stent image quality was good (Kappa =0.764,P＜0.001).The mean scores were 1.61 ±0.77 and 1.65 ±0.82 in Flash group and conventional group respectively.There was no significant difference in image quality between the two groups (x2 = 0.865,P = 0.834).The effective radiation dose in Flash group was significantly lower than that in conventional group.The mean values of CTDIvol were 3.24 ± 1.21 in Flash group and 31.26 ± 10.79 in conventional group (t = 19.83,P < 0.001) ,and the mean values of DLP in Flash group and conventional group were 54.61 ±19.88 and 468.30 ± 174.88,respectively (t = 18.06,P < 0.001).Conclusions Compared with the conventiaonal coronary artery CT angiography,the Flash coronary artery CT angiography technique has a similar coronary stent image quality,but at a lower radiation dose in patients with heart rates lower than 65 beats per minute.     

Coronary plaque imaging by coronary computed tomography angiography

Coronary computed tomography angiography (CTA) has become the useful noninvasive imaging modality alternative to the invasive coronary angiography for detecting coronary artery stenoses in patients with suspected coronary artery disease (CAD). With the development of technical aspects of coronary CTA, clinical practice and research are increasingly shifting toward defining the clinical implication of plaque morphology and patients outcomes by coronary CTA. In this review we discuss the coronary plaque morphology estimated by CTA beyond coronary angiography including the comparison to the currently available other imaging modalities used to examine morphological characteristics of the atherosclerotic plaque. Furthermore, this review underlies the value of a combined assessment of coronary anatomy and myocardial perfusion in patients with CAD, and adds to an increasing body of evidence suggesting an added diagnostic value when combining both modalities. We hope that an integrated, multi-modality imaging approach will become the gold standard for noninvasive evaluation of coronary plaque morphology and outcome data in clinical practice.     

The utilization of dual source CT in imaging of polytrauma

Despite the growing role of imaging, trauma remains the leading cause of death in people below the age of 45 years in the western industrialized countries. Trauma has been touted as the largest epidemic in the 20th century. The advent of MDCT has been the greatest advance in trauma care in the last 25 years. However, there are still challenges in CT imaging of the polytrauma individual including time restraints, diagnostic errors, radiation dose effects and bridging the gap between anatomy and physiology. This article will analyze these challenges and provide possible solutions offered by the unique design of the dual source CT scanner.     

The accuracy of coronary CT angiography in patients with coronary calcium score above 1000 Agatston Units: Comparison with quantitative coronary angiography

BackgroundHigh amounts of coronary artery calcium (CAC) pose challenges in interpretation of coronary CT angiography (CCTA). The accuracy of stenosis assessment by CCTA in patients with very extensive CAC is uncertain.MethodsRetrospective study was performed including patients who underwent clinically directed CCTA with CAC score >1000 and invasive coronary angiography within 90 days. Segmental stenosis on CCTA was graded by visual inspection with two-observer consensus using categories of 0%, 1–24%, 25–49%, 50–69%, 70–99%, 100% stenosis, or uninterpretable. Blinded quantitative coronary angiography (QCA) was performed on all segments with stenosis ≥25% by CCTA. The primary outcome was vessel-based agreement between CCTA and QCA, using significant stenosis defined by diameter stenosis ≥70%. Secondary analyses on a per-patient basis and inclusive of uninterpretable segments were performed.Results726 segments with stenosis ≥25% in 346 vessels within 119 patients were analyzed. Median coronary calcium score was 1616 (1221–2118). CCTA identification of QCA-based stenosis resulted in a per-vessel sensitivity of 79%, specificity of 75%, positive predictive value (PPV) of 45%, negative predictive value (NPV) of 93%, and accuracy 76% (68 false positive and 15 false negative). Per-patient analysis had sensitivity 94%, specificity 55%, PPV 63%, NPV 92%, and accuracy 72% (30 false-positive and 3 false-negative). Inclusion of uninterpretable segments had variable effect on sensitivity and specificity, depending on whether they are considered as significant or non-significant stenosis.ConclusionsIn patients with very extensive CAC (>1000 Agatston units), CCTA retained a negative predictive value ​> ​90% to identify lack of significant stenosis on a per-vessel and per-patient level, but frequently overestimated stenosis.     

Coronary manifestations of Kawasaki Disease in computed tomography coronary angiography

Coronary arteritis in Kawasaki disease can lead to serious complications such myocardial infarction and sudden death. The identification of coronary manifestations with a method that is minimally invasive and of low radiation exposure is therefore important in paediatric patients with Kawasaki disease. Coronary CT angiography can be an attractive alternative to invasive coronary angiography. This paper describes imaging techniques for coronary CT angiography in pediatric patients and demonstrates the spectrum of cardiovascular manifestations in patients with Kawasaki disease.     

Coronary 64-slice CT angiography predicts outcome in patients with known or suspected coronary artery disease

The aim of this study was to assess the prognostic value of 64-slice CT angiography (CTA) in patients with known or suspected coronary artery disease (CAD). Sixty-four-slice coronary CTA was performed in 220 patients [mean age 63 ± 11 years, 77 (35%) female] with known or suspected CAD. CTA images were analyzed with regard to the presence and number of coronary lesions. Patients were followed-up for the occurrence of the following clinical endpoints: death, nonfatal myocardial infarction, unstable angina, and coronary revascularization. During a mean follow-up of 14 ± 4 months, 59 patients (27%) reached at least one of the predefined clinical endpoints. Patients with abnormal coronary arteries on CTA (i.e., presence of coronary plaques) had a 1st-year event rate of 34%, whereas in patients with normal coronary arteries no events occurred (event rate, 0%, p < 0.001). Similarly, obstructive lesions (≥50% luminal narrowing) on CTA were associated with a high first-year event rate (59%) compared to patients without stenoses (3%, p < 0.001). The presence of obstructive lesions was a significant independent predictor of an adverse cardiac outcome. Sixty-four-slice CTA predicts cardiac events in patients with known or suspected CAD. Conversely, patients with normal coronary arteries on CTA have an excellent mid-term prognosis.     

Evaluation of computed tomography coronary angiography in patients with a high heart rate using 16-slice spiral computed tomography with 0.37-s gantry rotation time

The aim of our study is to evaluate computed tomography (CT) coronary angiography in patients with a high heart rate using 16-slice spiral CT with 0.37-s gantry rotation time. We compare the image quality of patients whose heart rates were over 70 beats per minute (bpm) with that of patients whose heart rates were 70 bpm or less. Sixty patients with various heart rates underwent retrospectively ECG-gated multislice spiral CT (MSCT) coronary angiography. Two experienced observers who were blind to the heart rates of the patients evaluated all the MSCT coronary angiographic images and calculated the assessable segments. A total of 620 out of 891 (69.6%) segments were satisfactorily visualized. On average, 10.3 coronary artery segments per patient could be evaluated. In 36 patients whose heart rates were below 70 bpm [mean 62.2 bpm±5.32 (standard deviation, SD)], the number of assessable segments was 10.72±2.02 (SD). In the other 24 patients whose heart rates were above 70 bpm [mean 78.6 bpm±8.24 (SD)], the corresponding number was 9.75±1.74 (SD). No statistically significant difference was found in these two subgroups t test, P>0.05. The new generation of 16-slice spiral CT with 0.37-s rotation time can satisfactorily evaluate the coronary arteries of patients with high heart rates (above 70 bpm, up to 102 bpm).     

Quantification of coronary stenosis by dual source computed tomography in patients: a comparative study with intravascular ultrasound and invasive angiography

Objective

To determine the accuracy of dual-source CT (DSCT) to quantify coronary stenosis compared to intravascular ultrasound (IVUS) and quantitative coronary angiography (QCA).

Methods

21 patients (23 vessels) were examined with DSCT, IVUS and invasive coronary angiography. Coronary minimal luminal diameter (MLD) and area (MLA) were measured in cross-sectional multi-planar reformatted images perpendicular to the vessel long-axis. The vessel cross-sectional area stenosis (MLA/CSA ratio) was calculated. DSCT results were compared with IVUS and QCA.

Results

A good correlation between DSCT and IVUS was noted for diameter and area stenosis (r = 0.69 and r = 0.73), with an overestimation of MLD stenosis by DSCT (+9.1%) and an underestimation of MLA stenosis (−5.8%). For MLD and MLA, high correlation coefficients (r = 0.78 and r = 0.90, respectively) were found between DSCT and IVUS; and the bias was almost zero (−0.41 mm and +0.1 mm², respectively).The correlation between DSCT and QCA was moderate (r = 0.60) for MLD stenosis with minor overestimation by DSCT (+4.0%) and moderate (r = 0.59) for MLD (bias, +0.01 mm).The cross-sectional area stenosis showed a moderate correlation (r = 0.59) between DSCT and IVUS (+0.00).

Conclusions

DSCT allows accurate quantification of coronary stenosis as compared to IVUS. An excellent correlation was found for the MLA between DSCT and IVUS.