Multislice CT angiography in coronary artery disease: Technical developments, radiation dose and diagnostic value

Multislice computed tomography (CT) angiography has been increasingly used in the detection and diagnosis of coronary artery disease because of its rapid technical evolution from the early generation of 4-slice CT scanners to the latest models such as 64-slice, 256-slice and 320-slice CT scanners. Technical developments of multislice CT imaging enable improved diagnostic value in the detection of coronary artery disease, and this indicates that multislice CT can be used as a reliable less-invasive alternative to invasive coronary angiography in selected patients. In addition, multislice CT angiography has played a significant role in the prediction of disease progression and cardiac events. Despite promising results reported in the literature, multislice CT has the disadvantage of having a high radiation dose which could contribute to the radiation-induced malignancy. A variety of strategies have been currently undertaken to reduce the radiation dose associated with multislice CT coronary angiography while in the meantime acquiring diagnostic images. In this article, the author will review the technical developments, radiation dose associated with multislice CT coronary angiography, and strategies to reduce radiation dose. The diagnostic and prognostic value of multislice CT angiography in coronary artery disease is briefly discussed, and future directions of multislice CT angiography in the diagnosis of coronary artery disease will also be highlighted.     

Radiation dose measurements in coronary CT angiography

Coronary computed tomography (CT) angiography is associated with high radiation dose and this has raised serious concerns in the literature. Awareness of various parameters for dose estimates and measurements of coronary CT angiography plays an important role in increasing our understanding of the radiation exposure to patients, thus, contributing to the implementation of dose-saving strategies. This article provides an overview of the radiation dose quantity and its measurement during coronary CT angiography procedures.     

Prognostic value of coronary CT angiography

Coronary computed tomography angiography (CTA) is a highly accurate noninvasive test that is increasingly used in symptomatic patients primarily for the diagnosis of coronary artery disease (CAD). Beyond its proven accuracy, data have now clearly demonstrated the incremental prognostic information available from coronary CTA related to the presence, extent, and severity of obstructive and nonobstructive CAD across a variety of clinical settings and patient populations. Current evidence supports the use of coronary CTA not only for the diagnosis of CAD in appropriately selected symptomatic patients but also to further refine their cardiovascular risk assessment following testing.     

冠状动脉CTA双低技术的临床应用

目的探讨应用双低技术——低千伏(100 kV)技术联合低对比剂浓度在冠状动脉CT血管造影(CCTA)中的可行性。方法选取拟行冠状动脉CTA检查患者80例患者(体重指数≤26.0 kg/m2),随机分为A、B两组,A组(n=40)采用100kV,270 mg/ml威视派克对比剂及自适应迭代算法重建(ASiR),B组(n=40)采用120 kV,350 mg/ml欧乃派克对比剂及滤波反投影算法重建(FBP)。测量主动脉、皮下脂肪和竖脊肌的CT值和SD值,平均SD值计算为图像噪声。测量左冠状动脉前降支(LAD),左冠状动脉回旋支(LCX)和右冠状动脉(RCA)的CT值和SD值,并计算对比噪声比(CNR)。采用5分法对所有图像进行主观质量评分。记录CT剂量指数,并进行有效辐射剂量计算。结果A组患者平均碘用量比B组患者下降22.8%。两组患者LAD、LCX和RCA血管CT值、CNR值、图像噪声及图像质量主观评分,均无统计学差异(P均0.05)。A组患者的有效辐射剂量明显低于B组患者,差异有统计学意义(P0.05)。结论对于体重指数≤26的患者,低对比剂浓度和低千伏(100 kV)相对于常规扫面能够提供相似的图像质量,并减少对比剂的碘用量及有效辐射剂量。     

Subtraction coronary CT angiography for calcified lesions

One of the main problems in coronary angiography using 64-row computed tomography (CT) is that the presence of severe calcification interferes with the assessment of lesions, which reduces diagnostic accuracy and may even make assessment of some coronary artery segments impossible. With 320-row CT, it is possible to avoid this problem by performing subtraction coronary CT, which fully exploits the performance capabilities of the CT system. However, subtraction coronary CT has several limitations. When these limitations have been overcome, this technique is expected to become a useful method for assessing patients with severe calcification and evaluating coronary artery stents.     

Coronary CT angiography: Dose reduction strategies

With the introduction of 64- and post-64 slice computed tomography (CT) technology, coronary CT angiography has been increasingly used as a less invasive modality for the diagnosis of coronary artery disease. Despite its high diagnostic value and promising results compared to invasive coronary angiography, coronary CT angiography is associated with high radiation dose, leading to potential risk of radiation-induced cancer. A variety of dose-reduction strategies have been reported recently to reduce radiation dose with effective outcomes having been achieved. This article presents an overview of the various methods currently used for radiation dose reduction.     

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.     

64-multislice detector computed tomography coronary angiography as potential alternative to conventional coronary angiography: a systematic review and meta-analysis.

AIMS: To evaluate the diagnostic accuracy of 64-slice multi-detector computed tomography coronary angiography (64-SCTA) compared with the standard reference conventional coronary angiography (CCA). METHODS AND RESULTS: Based on a systematic search, 27 studies including 1740 patients were eligible for meta-analyses. Nineteen studies examined native coronary arteries (n = 1,251), four studies examined coronary artery by-pass grafts (CABG) (n = 271), and five studies examined coronary stents (n = 270). Overall 18 920 segments were assessable and 810 (4%) were unassessable. The prevalence of native coronary artery stenosis in per-segment (19 studies) and per-patients (13 studies) populations were 19 and 57.5% respectively. Accuracy tests with 95% confidence intervals comparing 64-SCTA vs. CCA showed that sensitivity, specificity, positive predictive and negative predictive values for native coronary arteries were 86(85-87), 96(95.5-96.5), 83, and 96.5% by per-segment analysis; 97.5(96-99), 91(87.5-94), 93, and 96.5% by per-patient analysis; 98.5(96-99.5), 96(93.5-97.5), 92 and 99% for CABGs; 80(70-88.5), 95(92-97), 80, and 95% for stent restenosis; and 87(86.5-88), 96(95.5-96.5), 83.5, and 97% by overall per-segment analysis. CONCLUSION: The high diagnostic accuracy of 64-SCTA validates this non-invasive technique as a potential alternative to CCA in carefully selected populations suspected for coronary stenosis.     

Coronary CT angiography:State of the art

Coronary computed tomography(CT)angiography has been recognized as the most rapidly developed imaging technique in the diagnosis of coronary artery disease due to the emergence and technological advances in multislice CT scanners.Coronary CT angiography has been confirmed to demonstrate high diagnostic and predictive value in coronary artery disease when compared to invasive coronary angiography.However,it suffers from high radiation dose which raises concerns in the medical field.Various dose-reduction strategies have been proposed with effective outcomes having been achieved to reduce radiation exposure to patients.This article provides an introduction and overview of the series of articles that will focus on each particular topic related to coronary CT angiography.     

Identifying and redefining stenosis by CT angiography

Coronary computed tomographic angiography (CCTA) has emerged as a novel noninvasive method for the evaluation of not only coronary artery stenosis but also arterial wall and plaque features. Recent developments in CCTA technology enable the simultaneous assessment of coronary stenosis, atherosclerotic plaque characteristics, physiologic significance of lesion-specific ischemia, and cardiac function. Through these studies, the prognostic significance of individual coronary lesions and ventricular function can be determined and used to direct therapy. Future studies are needed to establish the totality of coronary artery plaque measures that improve clinical utility.     

Use of coronary CT angiography in the diagnosis of patients with suspected coronary artery disease: findings and clinical indications

Objective To investigate the clinical applications of coronary CT angiography in patients with suspected coronary artery disease and identify factors that affect CT findings. Methods Medical records of patients suspected of coronary artery disease over a period of 12 months from a tertiary teaching hospital were retrospectively reviewed. Patient age, sex (male/female), duration of symptoms and abnormal rates of coronary CT angiography scans were analysed to investigate the relationship among these parameters. The patients by age were characterized into five groups: under 36 years, 36–45 years, 46–55 years, 56–65 years and more than 66 years, respectively; while the duration of symptoms was also classified into five groups: less than one week, one week to one month, one to three months, three to six months and more than six months. Results Of the 880 patient records reviewed, 800 met the above study criteria. Five hundred and forty nine patients demonstrated abnormal CT findings (68.6%). There was no significant difference in the percentage of abnormal CT findings based on patient sex and the duration of symptoms (P = 0.14). The abnormal rates of coronary CT angiography, however, increased significantly with increasing age (P < 0.001); with patients over 65 years of age 2.5 times more likely to have an abnormal CT scan relative to a patient under 45 years. A significant difference was found between abnormal coronary CT angiography and the duration of symptoms (P = 0.012). Conclusions Our results indicate coronary CT angiography findings are significantly related to the patient age group and duration of symptoms. Clinical referral for coronary CT angiography of patients with suspected coronary artery disease needs to be justified with regard to the judicious use of this imaging modality.     

64-slice CT for diagnosis of coronary artery disease: a systematic review

Purpose

The purpose of this systematic review was to assess the accuracy of 64-slice CT coronary angiography for the diagnosis of coronary artery disease.

Methods

We attempted to identify all published trials in all languages that used 64-slice CT to diagnose coronary artery disease. Results of 64-slice CT coronary angiography were compared with invasive coronary angiography or intravascular ultrasound.

Results

Sensitivity of 64-slice CT for significant (≥50%) stenosis, based on pooled data from all studies, was ≥90% in patient-based evaluations, named vessels, segments, and coronary artery bypass grafts, except the left circumflex (sensitivity 88%), distal segments (80%), and stents (88%). Specificity was 88% in patient-based evaluations, and ≥90% at individual sites. Positive predictive values for patient-based evaluations, left main coronary artery, and coronary artery bypass grafts ranged from 91% to 93%, but elsewhere ranged from 69% to 84%. Negative predictive values were 96% to 100%. Positive likelihood ratios for patient-based evaluations were 8.0 and, at specific sites, were ≥9.7. Negative likelihood ratios, except for distal segments, were <0.1.

Conclusion

Negative 64-slice CT reliably excluded significant coronary disease. However, the data suggest that stenoses shown on 64-slice CT require confirmation. Combining the results of 64-slice CT with a pre-CT clinical probability assessment would strengthen the diagnosis. Due to the risk of radiation-induced cancer, patients should be selected carefully for this test, and scan protocols should be optimized to minimize risk.     

Coronary computed tomography angiography in coronary artery disease

AIM: To investigate the research directions of coronary computed tomography (CT) angiography in the diagnosis of coronary artery disease (CAD) based on a systematic review of the literature.METHODS: A search of articles on coronary CT angiography in the diagnosis of CAD was performed during a 6-year-period between 2005 and 2010 from f ive main radiology journals namely, Radiology, American Journal of Roentgenology, European Radiology, European Journal of Radiology and British Journal of Radiology. Analysis of the references was focused on the research directions of coronary CT angiography with regard to the type of studies in terms of diagnostic value, application of dose-reduction strategies and resultant effective radiation doses with use of these techniques.RESULTS: One hundred and forty two studies were identified which met the selection criteria and were included in the analysis. 64-slice CT (single source anddual-source CT) dominated 78% of the coronary CT angiography studies. Prior to 2007, research was focused on the diagnostic value of coronary CT angiography, but since 2008 more attention has been paid to radiation dose reduction. Radiation dose was reported in 64 studies, representing 45% of total studies published in the f ive radiology journals. Various dose-saving strategies have been implemented and prospective electrocardiography-triggering and high pitch techniques were found to be the most effective approaches for radiation dose reduction, with the corresponding mean effective dose being 3.5 ± 1.9 mSv and 1.7 ± 0.6 mSv, respectively.CONCLUSION: This review shows that the current research in coronary CT angiography has shifted from the previous focus on diagnostic accuracy in CAD to more emphasis on radiation dose reduction.     

Feasibility of ultra low-dose coronary computed tomography angiography

There is an urgent need to develop new protocols to reduce radiation dose of coronary computed tomography angiography (CTA). The aim of this pilot study was to demonstrate the feasibility of an ultra-low dose CTA scanning.     

Adjunctive value of CT coronary angiography in the diagnostic work-up of patients with typical angina pectoris.

AIMS: To determine the adjunctive value of CT coronary angiography (CTCA) in the diagnostic work-up of patients with typical angina pectoris. METHODS AND RESULTS: CTCA was performed in 62 consecutive patients (45 male, mean age 58.8 +/- 7.7 years) with typical angina undergoing diagnostic work-up including exercise-ECG and conventional coronary angiography. Only patients with sinus heart rhythm and ability to breath hold for 20 s were included. Patients with initial heart rates >/=70 beats/min received beta-blockers. We determined the post-test likelihood ratios, to detect or exclude patients with significant (>/=50% lumen diameter reduction) stenoses, of exercise-ECG and CTCA separately, and of CT performed after exercise-ECG testing. The prevalence of patients with significant coronary artery disease (CAD) was 74%. Positive and negative likelihood ratios for exercise-ECG were 2.3 [95% confidence interval (CI): 1.0-5.3] and 0.3 (95% CI: 0.2-0.7) and for CTCA 7.5 (95% CI: 2.1-27.1) and 0.0 (95% CI: 0.0-8), respectively. CTCA increased the post-test probability of significant CAD after a negative exercise-ECG from 58 to 91%, and after a positive exercise-ECG from 89 to 99%, while CT correctly identified patients without CAD (probability 0%). CONCLUSION: Non-invasive CTCA is a potentially useful tool, in the diagnostic work-up of patients with typical angina pectoris, both to detect and to exclude significant CAD.     

Detection of coronary artery stenoses using multi-detector CT with 16x0.75 collimation and 375 ms rotation

Aims Insufficient spatial and temporal resolutions have limitedimage quality and accuracy of multi-detector CT (MDCT) for coronaryartery visualization and detection of stenoses. We assessedthe accuracy of a new 16-slice scanner with 370 ms rotationand 0.75 mm collimation for detection of coronary stenosesusing an analysis approach based on coronary artery segments. Methods and results Fifty consecutive patients scheduled fordiagnostic coronary angiography in stable clinical conditionand sinus rhythm were enrolled. All patients with a heart rate>60 b.p.m. received 100 mg atenolol p.o. and upto four doses of 5 mg metoprolol i.v. before the scan.MDCT was performed using 16x0.75 mm collimation, 120 kV,and ECG-gated tube current modulation. Ninety millilitres ofcontrast agent was injected intravenously. MDCT images werevisually analysed using the 16-segment coronary artery modelof the American Heart Association and compared with invasive,quantitative coronary angiography in a blinded fashion. A significantstenosis was assumed if the diameter reduction was 50%. Meanheart rate was 58 b.p.m. during MDCT. After exclusion oftwo patients with not fully evaluable data sets, MDCT correctlyidentified at least one coronary stenosis in all 25 patientswith significant coronary lesions in angiography and correctlydemonstrated the absence of stenoses in 19/23 patients (sensitivity100%, specificity 83%). Sensitivity and specificity for all50 patients were 93 and 83%, respectively. On a per-segmentbasis, nine coronary segments distal of total occlusions and128 coronary segments with a reference diameter <1.5 mmwere excluded from the analysis. Twenty-eight of the included663 segments (4%) were unevaluable due to calcification or motionartefact. In the remaining 635 segments, 50/53 stenoses weredetected by MDCT (sensitivity 94%, specificity 96%, negativepredictive value 99%, positive predictive value 69%). Conclusion Increasing temporal and spatial resolutions of MDCTlead to improved evaluation and diagnostic accuracy for detectionof coronary stenoses.     

Flash双源CT冠脉成像与心肌灌注显像对冠心病诊断价值的临床研究

目的探讨Flash双源CT冠状动脉成像（DS—CTA）与心肌灌注显像（DS—CTP）一站式检查对冠心病诊断的价值。方法对60例临床考虑冠心病的患者行双源CT检查,所有患者均接受冠状动脉造影检查。以冠状动脉造影为参考标准,根据冠脉造影结果分为狭窄〈50％和狭窄≥50％,计算对于狭窄≥50％者双源CT冠脉成像及联合心肌灌注显像对冠心病诊断的敏感性、特异性、阳性预测值、阴性预测值和准确性。结果60例患者行DSCT冠脉成像与心肌灌注显像,其中59例均显示良好符合诊断要求。以冠状动脉造影为参考标准：①对于血管狭窄≥50％的血管,Flash双源CT诊断敏感性、特异性、阳性预测值和阴性预测值分别为84．O％、92．7％、88．9％和89．1％;②DS—CTA联合DS—CTP诊断冠心病的敏感性、特异性、阳性预测值和阴性预测值分别为96．8％、90．7％％、88．5％和97．5％。结论DS—CTA联合DS—CTP对冠心病具有很高的诊断价值。双源CT这种融合解剖学及功能学成像的“一站式”检查方法在冠心病的诊断及预后方面有重要优势。     

Incidental coronary calcifications on routine chest CT: Clinical implications

Coronary artery calcification (CAC) is a marker of atherosclerosis and an independent risk factor for cardiac-related mortality, with much of the 50% decline in mortality over the past 30 years being attributed to early detection of coronary disease and intervention of modifiable risk factors. With over 10 million computed tomography (CT) examinations of the chest performed in the United States yearly, CAC can be identified in a very large number of patients. In this review, we discuss the clinical evidence underlying the relationship between radiologic identification of CAC, atherosclerosis, and cardiac outcomes and the implications of its assessment on standard chest CT. We conclude that reporting of incidental coronary calcification found on non-gated chest CT would have a great impact on both management and mortality and thus, in the appropriate setting, should be noted in the impression of the radiologic report when identified.     

Ultra-fast,low dose high-pitch (FLASH) versus prospectively-gated coronary computed tomography angiography: Comparison of image quality and patient radiation exposure

Background

Coronary computed tomography angiography (CCTA) is increasingly being used for the evaluation of coronary artery disease; however, radiation exposure remains a major limitation of its use.