冠状动脉CT血管成像剂量降低技术的应用现状和进展

冠状动脉CT血管成像(CCTA)的辐射剂量在“后64层CT”时代仍得到广泛关注,各种剂量降低技术得到进一步发展,使得高端机型CCTA的辐射剂量显著降低.熟练掌握并综合应用不同的剂量降低技术,有效地降低管球曝光强度、缩短曝光时间和减少曝光范围,能够实现病人接受辐射剂量的最小化.就有关CCTA剂量降低技术及新进展予以综述.     

第3代双源CT低剂量Turbo Flash成像图像质量与诊断效能的临床研究

目的探讨第3代双源CT大螺距前瞻性心电门控扫描模式(Turbo Flash)冠状动脉CT成像(CCTA)评价冠状动脉狭窄的准确性、图像质量及有效辐射剂量。方法前瞻性收集2016年4月至2017年4月接受第3代双源CCTA检查的患者1003例,其中有70例患者在CCTA检查后30 d内行冠状动脉造影(CAG)。对冠状动脉各节段图像质量进行评分,计算有效辐射剂量。以CAG结果为“金标准”,计算CCTA显示冠状动脉病变的灵敏度、特异度、阳性预测值和阴性预测值;CCTA与CAG评价冠状动脉狭窄分级的一致性采用Kappa值并进行U检验。结果(1) 图像质量:右冠状动脉不可诊断血管节段为0,左冠状动脉主干及前降支不可诊断血管节段为0,左冠状动脉回旋支不可诊断血管节段为0.04% (3/835)。(2)准确性评价:基于节段水平分析,Force CT诊断冠状动脉狭窄的灵敏度为97.0% (289/298)、特异度为98.3% (706/718)、阳性预测值为96.0% (289/301)、阴性预测值为98.7% (706/715);基于血管分析,灵敏度为97.5% (159/163)、特异度为85.1% (40/47)、阳性预测值为95.8% (159/166)、阴性预测值为90.9% (40/44);基于患者分析,灵敏度、特异度、阳性预测值、阴性预测值均为100%。CCTA与CAG显示的冠状动脉狭窄部位高度一致(U=2.4,P=0.008)。(3)辐射剂量:有效辐射剂量为(1.17±0.29)mSv。结论第3代双源CT Turbo Flash模式可以在自然呼吸、无心率干预下进行冠状动脉成像,扫描成功率高,图像质量佳,评价冠状动脉狭窄的准确性高,有效辐射剂量低。     

低剂量冠状动脉CTA支架成像研究

【摘要】冠状动脉CT血管成像(CCTA)作为一种检测支架内再狭窄、支架断裂或支架内血栓形成等并发症的方法,其相对可靠和无创,在经皮冠状动脉介入治疗（PCI）术后随访中起到重要作用。如何使PCI术后患者在CCTA检查时既能保证图像质量、达到诊断要求,又能降低辐射剂量,仍是现在关注的热点之一。本文就近年来低剂量CCTA支架成像的研究进展作一综述。     

冠状动脉CT血管成像双低扫描技术应用进展

随着CT技术的不断进展,冠状动脉CT成像（CCTA）作为一种快速、准确的检查方法已经被临床认可,同时其辐射作用和对比剂不良反应也引起大家的关注。当前,不少降低辐射剂量和对比剂碘用量的新技术应用于临床,本文旨在结合近年国内外文献,就CCTA的双低扫描技术及进展做一综述。     

CCTA技术对冠状动脉狭窄及其钙化斑块的评估

冠状动脉CT血管成像（CCTA）是一种可无创检测冠状动脉粥样硬化性疾病的成像手段,已成为临床筛查及诊断冠心病的首要检查方法。但对于钙化严重的冠状动脉节段,CCTA的特异性及阳性预测值偏低,可导致病人过度治疗,因此限制了CCTA的临床应用。综述钙化斑块伪影对CCTA的影响,并就CCTA对冠状动脉狭窄准确评估的相关技术进展进行分析,以利于临床诊断中提高CCTA对冠状动脉狭窄率的评估。     

前瞻性心电门控联合70kV大螺距CT冠状动脉成像在临床应用中的影像质量、辐射剂量和诊断准确性:与有创性冠状动脉血管造影对比

正摘要目的以有创性冠状动脉造影(ICA)为标准,探索前瞻性心电门控联合70 k V大螺距冠状动脉CTA(CCTA)检查的影像质量、辐射剂量以及诊断准确性。方法 43例病人接受前瞻性心电门控联合CCTA检查,对比剂剂量为30 m L(11 g碘对比剂),管电压为70 k V,并接受ICA检查。对每例CCTA检查均行主观及客观的影像质量评价。评估CCTA狭窄程度≥50%的诊断性能。根据心率(HR)、体质量指数     

直接屏气方式在降低320排冠状动脉CT血管成像辐射剂量的应用研究

目的 探讨直接屏气方式在降低冠状动脉CT血管成像(CCTA)辐射剂量的可行性.方法 选取40例(心率<75次/min)临床拟诊冠心病行CCTA检查者.冠状动脉钙化积分(CS)采用吸气后屏气方式扫描,标记为A组;CCTA采用平静呼吸下直接屏气方式扫描,标记为B组.对比研究2组受检者平静呼吸时心率(基础心率)、扫描期间屏气...     

冠状动脉CTA管腔内衰减梯度的应用进展

冠状动脉CTA(coronary CTA, CCTA)已成为冠状动脉疾病无创筛查的首选检查方法。然而CCTA只能提供冠状动脉解剖学信息,无法提供血流动力学的改变。随着CCTA新技术的发展,CCTA管腔内衰减梯度(transluminal attenuation gradient, TAG)可以提供更多的功能学信息。本文对TAG在冠状动脉疾病中的应用进行综述。     

迭代重建技术的进展及其在冠状动脉CT血管成像中的应用

随着CT影像技术的不断发展及计算机性能的不断提高,传统CT影像重建算法——滤波反投影技术（FBP）受到明显制约,而迭代重建技术（IR）得以迅速发展并成功应用于临床。冠状动脉CT血管成像（CCTA）是CT影像检查的重要组成,IR技术在降低CCTA辐射剂量、减轻钙化斑块和冠状动脉支架伪影、提高粥样斑块显示等方面具有重要的临床价值,就IR技术的进展及其在CCTA中的应用予以综述。     

第三代双源CT能够准确诊断所有尺寸支架的冠状动脉再狭窄,且辐射剂量低并保持影像质量

目的探讨小剂量支架成像对第三代双源CT大口径(≥3 mm)和小口径(3 mm)支架的诊断价值。方法前瞻性纳入疑似患有支架内再狭窄(ISR)的病人。对1个月内的冠状动脉CT血管成像(CCTA)和有创性冠状动脉造影(ICA)进行相关性分析。双重ISR被定义为直径狭窄≥50%的支架内新生内膜增生。同时还评估了CCTA的辐射剂量和影像质量。结果最终纳入的69例病人共140个支架。所有病人行常规CCTA的平均总辐射剂量为(1.3±0.72)mSv,而高螺距为(0.95±0.17)mSv。基于病人、病变和支架的分析中CCTA支架成像的总体诊断准确度分别为95.7%、94.1%和94.3%。此外,小口径支架组(直径3 mm)CCTA的诊断准确度略低于大口径支架组(直径≥3 mm)(88.5%∶98.7%,P=0.01)。结论第三代双源CT能够准确诊断大小口径支架的冠状动脉ISR,还可在保持影像质量的情况下实现低辐射剂量。     

Trends in radiation protection in CT: Present and future status

With the introduction of modern multislice scanner generations, computed tomography (CT) has emerged as a useful tool for evaluation of the coronary arteries. A common application of coronary CT angiography (CCTA) is the examination of patients with intermediate pretest probability for obstructive coronary artery disease. Despite the widespread use of cardiac CT examinations in clinical practice, concern remains about the exposure to ionizing radiation and its potential hazards. Therefore, radiation dose and strategies for dose reduction have become an important focus of interest. Several smaller analyses have shown an effective radiation dose between 6.4 and 27.8 mSv for spiral CCTA image acquisition. The international Prospective Multicenter Study On RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy I (PROTECTION I) study, the largest observational study on radiation dose estimates of cardiac CT so far, determined radiation dose estimates of CCTA, as well as the effect of different strategies to reduce dose in clinical practice. The median dose-length-product of 1965 CCTA examinations was 885 mGy × cm, which corresponds to a median estimated effective radiation dose of 12 mSv. However, a large variation in dose between study sites was observed, indicating a large potential to reduce dose for individual sites. Several dose-saving scanning techniques and algorithms have been developed. This article discusses these strategies as well as their effect on radiation dose and image quality. Because the contrast-enhanced CT angiography is the largest part of the total study dose, the following described strategies focus on radiation dose reduction for CCTA image acquisition.     

Impact of new technologies on dose reduction in CT

The introduction of slip ring technology enables helical CT scanning in the late 1980's and has rejuvenated CT's role in diagnostic imaging. Helical CT scanning has made possible whole body scanning in a single breath hold and computed tomography angiography (CTA) which has replaced invasive catheter based angiography in many cases because of its easy of operation and lesser risk to patients. However, a series of recent articles and accidents have heightened the concern of radiation risk from CT scanning. Undoubtedly, the radiation dose from CT studies, in particular, CCTA studies, are among the highest dose studies in diagnostic imaging. Nevertheless, CT has remained the workhorse of diagnostic imaging in emergent and non-emergent situations because of their ubiquitous presence in medical facilities from large academic to small regional hospitals and their round the clock accessibility due to their ease of use for both staff and patients as compared to MR scanners. The legitimate concern of radiation dose has sparked discussions on the risk vs benefit of CT scanning. It is recognized that newer CT applications, like CCTA and perfusion, will be severely curtailed unless radiation dose is reduced. This paper discusses the various hardware and software techniques developed to reduce radiation dose to patients in CT scanning. The current average effective dose of a CT study is ∼10 mSv, with the implementation of dose reduction techniques discussed herein; it is realistic to expect that the average effective dose may be decreased by 2-3 fold.     

Future of cardiac computed tomography

Coronary computed tomography angiography (CCTA) has become an integral tool in the noninvasive diagnostic workup of patients with suspected coronary artery disease in both elective and emergency settings. Today, it represents a mature technique providing accurate, non-invasive morphological assessment of the coronary arteries and atherosclerotic plaque burden. Iterative reconstruction algorithms, low kV imaging, and single-heart beat acquisitions hold promise to further reduce dose requirements and improve the safety and robustness of the technique in several circumstances including imaging of heavily calcified vessels, patients with morbid obesity or irregular heart rates, and assessment in the emergency setting. However, it has become clear over recent years that cardiac radiologists need to take further steps towards the development and integration of functional imaging with morphological CCTA assessment to truly provide a comprehensive evaluation of the heart. Computed tomography myocardial perfusion imaging, including both dynamic and static dual-energy approaches, has demonstrated the ability to directly assess and quantify myocardial ischemia with simultaneous CCTA acquisition with a reasonable contrast medium volume and radiation dose delivered to the patient. In order to promote CCTA in the clinical and research environments, radiologists should prepare to embrace the change from morphological to functional imaging, furnishing all the necessary resources and information to referring clinicians.     

Effect of low tube kV on radiation dose and image quality in retrospective ECG-gated coronary CT angiography

IntroductionCoronary computed tomography angiography (CCTA) has emerged as a useful diagnostic imaging modality in the assessment of coronary artery disease. However, the potential risks due to exposure to ionizing radiation associated with CCTA have raised concerns.ObjectivesCCTA can be done with low dose technique to reduce radiation exposure, without compromise of image quality or diagnostic capabilities.Material and methodsForty patients referred for CCTA were examined with low kV (100 kV for patients ?85–61 kg and 80 kV for patients ?60 kg). The dose length product (DLP) were compared with other group (40 patients) with comparable body weight, scan length and acquisition parameters. The second group was selected from PACS database, for which CCTA was done with standard 120 kV.ResultsThere was considerable reduction of radiation dose about 40% with 100 kV and 60% with 80 kV compared to standard 120 kV CCTA protocols with preserved image quality.ConclusionThe use of lower tube voltage leads to significant reduction in radiation exposure in CCTA. Image quality in non-obese patients is not negatively influenced.     

Prospectively ECG-triggered sequential dual-source coronary CT angiography in patients with atrial fibrillation: comparison with retrospectively ECG-gated helical CT

Objective

To investigate the feasibility of applying prospectively ECG-triggered sequential coronary CT angiography (CCTA) to patients with atrial fibrillation (AF) and evaluate the image quality and radiation dose compared with a retrospectively ECG-gated helical protocol.

Methods

100 patients with persistent AF were enrolled. Fifty patients were randomly assigned to a prospective protocol and the other patients to a retrospective protocol using a second-generation dual-source CT (DS-CT). Image quality was evaluated using a four-point grading scale (1 = excellent, 2 = good, 3 = moderate, 4 = poor) by two reviewers on a per-segment basis. The coronary artery segments were considered non-diagnostic with a quality score of 4. The radiation dose was evaluated.

Results

Diagnostic segment rate in the prospective group was 99.4 % (642/646 segments), while that in the retrospective group was 96.5 % (604/626 segments) (P?<?0.001). Effective dose was 4.29?±?1.86 and 11.95?±?5.34 mSv for each of the two protocols (P?<?0.001), which was a 64 % reduction in the radiation dose for prospective sequential imaging compared with retrospective helical imaging.

Conclusion

In AF patients, prospectively ECG-triggered sequential CCTA is feasible using second-generation DS-CT and can decrease >60 % radiation exposure compared with retrospectively ECG-gated helical imaging while improving diagnostic image quality.

Key Points

? Coronary computed tomographic angiography (CCTA) can be difficult in patients with arrhythmias. ? Prospectively ECG-triggered sequential CCTA is feasible in patients with atrial fibrillation. ? Prospective sequential imaging can improve quality compared with retrospective analysis. ? Prospective sequential imaging decreases radiation exposure by 64 % compared with retrospective mode.     

Cardiac imaging to detect coronary artery disease in athletes aged 35 years and older. A scoping review

Sudden cardiac death (SCD ) is a devastating event in athletes. Screening efforts that were first directed at athletes younger than 35 years are now focusing on the rapidly growing group of older sportspersons. Athletes aged ≥35 years have a 10‐fold increased risk of exercise‐related cardiac arrest, mostly due to coronary artery disease (CAD ). Although cardiac imaging is pivotal in identifying CAD , the role of imaging modalities in screening asymptomatic older sportspersons remains unclear. We performed a scoping review to identify the role of cardiac imaging to detect CAD in older sportspersons and to identify gaps in the existing literature. We searched MEDLINE , EMBASE and the Cochrane library for studies reporting data on cardiac imaging of CAD in sportspersons ≥35 years. The systematic search yielded 1737 articles, and 14 were included in this scoping review. Imaging modalities included two echocardiography, one unenhanced computed tomography (CT ) for coronary artery calcium scoring (CACS ), three CACS and contrast‐enhanced CT angiography (CCTA ), two CACS and cardiac magnetic resonance (CMR ), one CCTA with CMR and echocardiography, two CCTA , two CMR , and one myocardial perfusion imaging article. The low number of relevant articles and the selection bias introduced by studying specific groups, like veteran marathon runners, indicate the need for future research. Cardiac CT (CACS and CCTA ) probably has the highest potential for pre‐participation screening, with high diagnostic value to detect CAD and low radiation dose. However, currently there is insufficient evidence for incorporating routine cardiac imaging in the pre‐participation screening of asymptomatic sportspersons over 35 years.     

第二代双源CT前门控冠状动脉成像与冠状动脉造影比较的初步研究

目的:探讨第二代双源CT前门控冠状动脉成像(CTCA)对冠状动脉狭窄病变的诊断价值。方法:连续44例同期行第二代双源CT前门控CTCA(其中前门控序列扫描35例,前门控大螺距螺旋扫描9例)及选择性冠状动脉造影(SCA)检查的患者,按冠脉病变狭窄程度分为:无狭窄;轻度狭窄(狭窄≤50%);中度狭窄(狭窄50%～75%);重度狭窄(狭窄≥75%);闭塞(狭窄100%),将中度及中度以上狭窄定义为有意义狭窄。以SCA为金标准,分析第二代双源CT前门控CTCA诊断冠状动脉狭窄的敏感性、特异性、阳性和阴性预测值及准确度,同时计算第二代双源CT前门控CTCA的辐射剂量。结果:44例患者冠脉直径2mm以上的节段共570个,其中12段图像质量较差,无法评估,可评估节段占97.89%。第二代双源CT前门控CTCA按冠脉节段计算,诊断冠状动脉狭窄的敏感度、特异度、阳性和阴性预测值、准确度分别为90.18%、93.05%、76.52%、97.42%、92.47%,诊断冠状动脉有意义狭窄的敏感度、特异度、阳性和阴性预测值、准确度分别为90.14%、95.69%、75.29%、98.52%、94.98%。第二代双源CT前门控CTCA与SCA比较对冠状动脉狭窄评价的差异无统计学意义(χ2=2.10,P>0.05),对冠状动脉有意义狭窄评价的差异无统计学意义(χ2=1.46,P>0.05)。第二代双源CT前门控CT-CA的平均辐射剂量为(3.36±1.59)mSv,其中前门控序列扫描的平均辐射剂量为(3.99±1.18)mSv,前门控大螺距螺旋扫描的平均辐射剂量为(1.11±0.44)mSv。结论:第二代双源CT前门控成像对诊断冠状动脉狭窄的准确度稍低于SCA,但其阴性预测值较高,同时其辐射剂量较低,可作为临床冠心病筛查的无创性检查手段。     

回顾性心电门控CT在儿童川崎病冠状动脉损伤评估中的应用

目的探讨回顾性心电门控冠状动脉CT血管造影(CCTA)评估川崎病(KD)患儿冠状动脉病变的可行性及成像技术,并与经胸超声心动图(TTE)对比研究。方法回顾性分析2014年1月—2018年7月经临床确诊的32例KD患儿资料[男19例,女13例,年龄2个月～10岁,平均(3.89±3.19)岁],所有患儿均行回顾性心电门控CT及TTE检查,由2名影像科医师独立对CT成像质量、重组时相,冠状动脉病变的数目、位置、大小及危险性分级进行测量和观察,并与TTE结果对比研究;计算所有患儿接受的有效辐射剂量。对两种方法测得的数据进行配对t检验及χ~2检验,一致性分析采用Kappa检验。结果CCTA可评价冠状动脉节段比为93.8%(120/128),共观察到46个冠状动脉瘤、33支瘤样扩张及1支动脉壁钙化,其中7个动脉瘤、5支瘤样扩张及1支动脉壁钙化TTE检查时未发现。两种方法对左右冠状动脉主干直径的测量值及对各节段冠状动脉损伤检出的阳性率的差异均无统计学意义(P0.05)。冠状动脉最优化重组相位位于45%及75%～85%两个相位间。2名放射科医师对所有CCTA影像质量主观评分一致性好(κ=0.87),对KD危险度分级完全一致。32例患儿的有效辐射剂量为(3.22±1.57)mSv。结论回顾性心电门控CCTA检查可以在降低辐射剂量的基础上取得良好的成像效果,能够精确地观察冠状动脉的全程各段及病变程度,对儿童KD的评价及其危险分级具有重要的临床价值。     

Coronary CT angiography with iterative reconstruction in early triage of patients with acute chest pain

Background

Patients who present to the emergency department (ED) complaining of acute chest pain are of clinical concern because a small percentage will have acute coronary syndrome (ACS). The American College of Cardiology (ACC) and the American Heart Association (AHA) recommend hospitalization for patients with a low-to-intermediate risk of ACS who have initial negative ECG and enzyme test results. A negative coronary CT angiography (CCTA) during the triage has a very high negative predictive value for ruling out ACS decreasing the length of hospital stay. Recent techniques e.g. ASiR in CCTA should be used to decrease the radiation dose as low as possible.

Objective

The aim of this study is to evaluate the role of low radiation dose CCTA with ASiR in triage of low-risk patients with acute chest pain in emergency department. A negative CCTA early in the workup may enable a shorter length of stay.

Subjects and methods

We studied 54 selected patients (55.6% men; mean age 48 ± 6 years) with chest pain who were awaiting hospital admission to rule out ACS despite the absence of diagnostic ECG changes and normal cardiac enzymes on ED presentation. Patients underwent CCTA before hospital admission. Afterward, patients received standard clinical care (SCC). ER physicians involved in the patient’s care were blinded to the results of CCTA. An expert panel established the presence or absence of ACS based on AHA guidelines. The CCTA images were evaluated for the presence of significant coronary artery stenosis (diameter reduction >50%) and were used to make a triage decision.

Results

Four patients (7.4%) with chest pain had at least one significant coronary stenosis on CCTA (sensitivity 100%, specificity 96%, accuracy 96.3%, positive predictive value (PPV) 66.7% and negative predictive value (NPV) 100%). Significant coronary stenosis was excluded in 48 of the 54 patients by CCTA (88.9%), potentially saving about 71.6% of unnecessary hospital admission hours.

Conclusion

CCTA based detection of significant coronary stenosis has potential role to decrease the length of hospital stay , without reducing appropriate patient care, in low risk patients with acute chest pain. CCTA should be done with lowest radiation possible using recent techniques.