CT measurement of coronary calcium mass: impact on global cardiac risk assessment

Coronary calcium mass percentiles can be derived from electron beam CT as well as from multidetector-row CT of all manufacturers. Coronary calcium mass may serve as a more individualized substitute for age for cardiac risk stratification. The aim was to investigate the potential impact of CT coronary calcium mass quantification on cardiac risk stratification using an adjusted Framingham score. Standardized coronary calcium mass was determined by multidetector-row CT in a total of 1,473 patients (1,038 male, 435 female). The impact on risk stratification of replacing the traditional Framingham age point score by a point score based on calcium mass relative to age was tested. Any coronary calcium found in males in the age group of 20–34 years and females in the age group of 20–59 years results in an increase of the Framingham score by 9 and 4–7 points, respectively. Only in males 65 years of age and older, none or minimal amounts of coronary calcium decrease the Framingham score by three points. The coronary calcium mass and age-related scoring system may have impact on the reassignment of patients with an intermediate Framingham risk to a lower or higher risk group.     

Prognostic value of cardiac risk factors and coronary artery calcium screening for all-cause mortality

PURPOSE: To develop risk-adjusted multivariable models that included risk factors and coronary calcium scores determined with electron-beam computed tomography (CT) in asymptomatic patients for the prediction of all-cause mortality. MATERIALS AND METHODS: We followed up a cohort of 10,377 asymptomatic individuals undergoing cardiac risk factor evaluation and coronary calcium screening with electron-beam CT. Multivariable Cox proportional hazards models were developed to predict all-cause mortality. Risk-adjusted models incorporated traditional risk factors for coronary disease and coronary calcium scores. RESULTS: Cardiac risk factors such as family history of coronary disease (69%), hypercholesterolemia (62%), hypertension (44%), smoking (40%), and diabetes (9%) were prevalent. The frequency of coronary calcium scores was 57%, 20%, 14%, 6%, and 3% for scores of 10 or less, 11-100, 101-400, 401-1,000, and greater than 1,000, respectively. During a mean follow-up of 5.0 years +/- 0.0086 (standard error of the mean), the death rate was 2.4%. In a risk-adjusted model (model chi2 = 388.2, P <.001), coronary calcium was an independent predictor of mortality (P <.001). Risk-adjusted relative risk values for coronary calcium were 1.64, 1.74, 2.54, and 4.03 for scores of 11-100, 101-400, 401-1,000, and greater than 1,000, respectively (P <.001 for all values), as compared with that for a score of 10 or less. Five-year risk-adjusted survival was 99.0% for a calcium score of 10 or less and 95.0% for a score of greater than 1,000 (P <.001). With a receiver operating characteristic curve, the concordance index increased from 0.72 for cardiac risk factors alone to 0.78 (P <.001) when the calcium score was added to a multivariable model for prediction of death. CONCLUSION: This large observational data series shows that coronary calcium provides independent incremental information in addition to traditional risk factors in the prediction of all-cause mortality.     

冠状动脉与颈动脉钙化的相关性分析及其危险因素

目的 评价冠状动脉钙化与颈动脉钙化的关系及其危险因素.方法 2周内先后完成冠状动脉和颈动脉CT平扫检查的162例患者,采用相同的重建条件,分别进行钙化积分的测量,用Spearman相关分析进行两者的比较.同时记录患者的性别、年龄、血压、总胆固醇、甘油三脂、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)、糖尿病、吸烟史、冠心病早发病史等,用Logistic回归分析冠状动脉及颈动脉钙化积分与多个临床危险因素之间的关系.结果 在162例患者中,冠状动脉钙化积分(CACS)与颈动脉钙化积分之间存在线性正相关关系,r值为0.690,P<0.01.CACS的危险因素包括年龄、糖尿病、总胆固醇、LDL,颈动脉钙化的危险因素为年龄和糖尿病.结论 冠状动脉钙化与颈动脉钙化呈线性正相关,但冠状动脉与颈动脉钙化的危险因素不完全相同.     

The relationship between coronary artery calcification detected by non-gated multi-detector CT in patients with suspected ischemic heart disease and myocardial ischemia detected by thallium exercise stress testing

OBJECTIVE: To examine whether we could predict myocardial ischemia when coronary artery calcification is detected by non-gated multidetector CT in patients with suspected ischemic heart disease. METHODS: Eighty-three patients suspected of having ischemic heart disease (55 men, 28 women; age range 36-83 years; mean age 68 years) underwent multidetector CT and T1-201 single photon emission computed tomography. Prediction of myocardial ischemia by coronary arterial calcification detected on CT was evaluated by comparing the coronary artery territories that showed calcification with the area of myocardial ischemia determined by SPECT. The sensitivity, specificity, positive predictive value, and negative predictive value of multidetector CT for predicting myocardial ischemia were calculated. Coronary angiography was also examined and compared with multidetector CT. Risk factors, including hypertension, smoking, hyperlipidemia, diabetes, and family history, were compared for evidence of coronary artery calcification detected by multidetector CT and myocardial ischemia detected by thallium nuclear scans. RESULTS: For analysis by patients, the sensitivity, specificity, positive predictive value, and negative predictive value of coronary artery calcification for myocardial ischemia detection were 65, 63, 56, and 71%, respectively. Similarly, for analysis by coronary arterial territories, those values were 56, 77, 41 and 86%, respectively. Coronary stenosis on CAG was also related to the ischemia determined by SPECT and calcification on multidetector CT. Ischemia was better influenced by risk factors than was coronary arterial calcification. CONCLUSIONS: For analysis by coronary arterial territories, the specificity and negative predictive value of coronary arterial calcification seen by multidetector CT are relatively high.     

The association between carotid calcium on dental panoramic radiographs and coronary calcium score on chest computerized tomography

Objectives:Coronary artery calcium measured by CT predicts future coronary events. Similarly, carotid artery calcium on dental panoramic radiographs has been associated with increased cardiovascular events. Pre-procedural assessment of candidates for valve replacement in our institution includes panoramic radiographs and chest tomography. We aimed to assess the association of carotid calcium on panoramic radiographs with coronary artery calcium on chest tomography.Methods:Paired pre-procedural panoramic radiographs and chest tomography scans were done in 177 consecutive patients between October 2016 and October 2017. Carotid calcium was quantified using NIH’s ImageJ. Coronary artery calcium was quantified by the Agatston score using Philips Intellispace portal, v. 8.0.1.20640.Results:Carotid calcium maximal intensity, area and perimeter were higher among patients with high coronary artery calcium. Non-zero carotid calcium was found in half of patients with high coronary artery calcium, doubling prevalence of low coronary artery calcium.Conclusion:Carotid calcium identified in panoramic radiographs was associated with high coronary artery calcium. Awareness of carotid calcium recognized by dental practitioners in low-cost, low radiation and commonly done panoramic radiographs may be useful to identify patients at risk of coronary disease with potential future cardiovascular events.     

Calcium begets calcium: progression of coronary artery calcification in asymptomatic subjects

PURPOSE: To test the hypothesis that the rate of coronary artery calcium progression is sex specific, namely, that it is greater in men than in women, and that it is age related, particularly in women. MATERIALS AND METHODS: This was a retrospective study of the progression of coronary artery calcium in 217 consecutive asymptomatic subjects who underwent at least two electron-beam computed tomographic studies of the heart. Calcium in the distribution of the epicardial arteries was quantified by using both the conventional coronary artery calcium score (CCS) and the calcium volume score (CVS). Linear regression models were used to judge the joint influence of various risk factors, including sex and age, on rates of coronary artery calcium progression. RESULTS: This study included 103 women and 114 men. The mean interval between the subjects' first and last studies was 25 months +/- 11 (SD). Regression analyses clearly demonstrated that the amount of coronary artery calcium present at the initial study was the most important determinant of calcium progression. This was true when coronary artery calcium was quantified by using the conventional CCS (P <.001) or CVS (P <.001). Neither sex nor age was a significant predictor of coronary artery calcium progression. Among traditional risk factors, only hypertension (P =.02) and diabetes (P =.01) were significant independent factors for calcium progression. CONCLUSION: In asymptomatic subjects, the initial CCS and CVS were the most important factors that affected rate of coronary artery calcium progression. Neither age nor sex was as important as these factors in determination of coronary artery calcium progression.     

Myocardial hypoenhancement in a case of acute coronary syndrome with normal coronary arteries: demonstration by 64-slice multidetector computed tomography

A 48-year-old man presented with severe chest pain that had started 2 h before and ST elevation on the electrocardiogram. Cardiac computed tomography (CT) was performed using a 64-slice multidetector scanner (MDCT) to assess coronary artery stenosis at 3 h after the onset. Coronary CT angiography showed no significant stenosis at the coronary arteries, but CT myocardial images at systole demonstrated predominantly subendocardial hypoenhancement in the anterior wall. Cardiac CT that combined coronary angiography and myocardial imaging demonstrated myocardial hypoenhancement in a case of acute coronary syndrome with normal coronary arteries, which may be related to microvascular dysfunction caused by vasospastic angina or microvascular angina.     

Coronary artery calcium measurement: agreement of multirow detector and electron beam CT

OBJECTIVE: The purpose of our study was to establish the most suitable algorithm to compare coronary artery calcium measurements performed with electron beam CT and multirow detector CT for the assessment of coronary artery disease. SUBJECTS AND METHODS: Coronary artery screening was performed in 100 patients with both electron beam and multirow detector CT. The images were transferred to a dedicated workstation for determination of the calcium score, volume, mass, density, and number of lesions. In addition to the traditional threshold of 130 H, the score of multirow detector CT studies was reevaluated at a threshold of 90 H. Fifty-nine of the patients underwent conventional coronary catheterization. Receiver operating characteristic curve analysis of the different scoring algorithms for detection of significant coronary artery stenosis was performed. RESULTS: The correlation between electron beam CT and multirow detector CT was high for every quantification algorithm. Determination of the score and the number of lesions with multirow detector CT revealed a systematic error of the measurement compared with electron beam CT. The areas under the curve in the receiver operating characteristic curve analyses for electron beam and multirow detector CT were similar for the score, volume, and mass, whereas they were lower for the density. No significant difference was found for the areas under the curve between scores using a 130-H and those using a 90-H threshold. CONCLUSION: Volume and mass indexes are superior to the traditional score, density, and number of lesions for comparing the results of electron beam and multirow detector CT and for determining significant coronary artery disease.     

MRI detects increased coronary wall thickness in asymptomatic individuals: the multi-ethnic study of atherosclerosis (MESA)

PURPOSE: To evaluate the use of coronary wall MRI as a measure of atherosclerotic disease burden in an asymptomatic population free of clinical cardiovascular disease. Coronary wall magnetic resonance imaging (MRI) is a noninvasive method for evaluation of arterial wall remodeling associated with atherosclerosis. MATERIALS AND METHODS: Asymptomatic participants of the Multi-Ethnic Study of Atherosclerosis (MESA) study were studied using black blood MRI. MRI-assessed coronary wall thickness was compared with computed tomography calcium score, carotid intimal-medial thickness, and risk factors for coronary artery disease. RESULTS: Eighty-eight arterial segments were evaluated in 38 MESA participants (mean age, 61.3+/-8.7 years). The maximum coronary wall thickness was greater for participants with two or more cardiovascular risk factors than for those with one or no risk factors (2.59+/-0.33 mm vs. 2.36+/-0.30 mm, respectively, P=0.05.) For participants with zero calcium score, the mean and maximum coronary wall thickness for subjects with two or more risk factors for coronary artery disease were greater than the wall thickness for subjects with one or no risk factors (mean thickness: 1.95+/-0.17 mm vs. 1.7+/-0.19 mm; maximum thickness: 2.67+/-0.24 mm vs. 2.32+/-0.27 mm, respectively, P<0.05). Subjects with increased carotid intimal-medial thickness also had increased coronary artery wall thickness (P<0.05). CONCLUSION: Coronary artery wall MRI detects increased coronary wall thickness in asymptomatic individuals with subclinical markers of atherosclerotic disease and in individuals with zero calcium score.     

16层螺旋CT扫描技术在冠状动脉钙化评分中的临床应用

目的:应用Toshiba Aquilion M16全身螺旋CT扫描机,对心脏冠状动脉粥样钙化进行前瞻性的扫描,旨在对冠状动脉的粥样钙化程度做出较准确的评分。方法:应用心电门控技术,使CT在心脏处于舒张期时相进行扫描,同时利用ECG技术获得重建图像的数据。使用Toshiba Aquilion M16全身CT扫描机制造商日本东芝提供的专用测量软件(Agatstonscore)进行钙化评分。结果:应用此方法对128例患者进行CT扫描,96例能显示满意的冠脉钙化影像,27例显示欠佳,5例显示不满意。结论:当患者心率介于60次/min和80次/min之间时,在心电门控控制下所获得的冠脉影像为最佳影像,并能做出准确的钙化评分。因此,无创特点使MSCT(multi-slice CT)在筛查冠状动脉钙化病变方面具备优势,可为临床诊断提供有力的证据。     

Using ECG-gated multidetector CT to evaluate global left ventricular myocardial function in patients with coronary artery disease

OBJECTIVE: Retrospectively ECG-gated three-dimensional volume data from multidetector CT (MDCT) coronary angiography enable image reconstruction of the cardiac cycle in the diastolic and systolic phases. The objective of our study was to investigate the feasibility of determining left ventricular function from MDCT coronary angiography data sets in 22 patients with coronary artery disease and to study the correlation of MDCT results with those of functional data from biplane cineventriculography. CONCLUSION: Multiplanar reformations from three-dimensional MDCT data allowed good delineation of endocardial and epicardial left ventricular contours. In patients evaluated for coronary artery disease, MDCT coronary angiography with retrospective ECG gating provides functional data in an acceptable correlation (r = 0.8; p < 0.05) to biplane cineventriculography.     

基于冠状动脉CT血管成像定量钙化负荷的可行性研究

目的 探讨冠状动脉CT血管成像（CCTA）一站式计算冠状动脉钙化积分（CCTA-CS）和体积积分（CCTA-VS）的可行性,并分析其与心电门控CT平扫测得标准积分（CACS、VS）的相关性。 方法 本研究回顾性连续纳入1 075例受试者,男447例,女628例,平均年龄（56.79±9.49）岁。全部受试者均行包括门控CT平扫和CCTA的常规冠状动脉CT检查,测量CACS、VS、CCTA-CS和CCTA-VS。选择CACS与CCTA-CS均不为0的影像数据进行分析。采用组内相关系数（ICC）评估2名观察者间及观察者内测量CCTA-CS和CCTA-VS的一致性。采用线性相关分析与Bland-Altman检验分析CCTA与门控CT平扫所测评分的相关性与一致性。根据CACS对受试者进行心血管病危险度分层,并采用Kruskal-Wallis H检验比较多组间的CCTA-CS与CCTA-VS。采用二元Logistic回归分析影响钙化积分的危险因素。采用独立样本t检验比较CCTA和常规冠状动脉CT检查的有效辐射剂量（ED）。 结果 CACS和CCTA-CS不为0的受试者共437例。2名观察者间和观察者内测量的CCTA-CS和CCTA-VS的一致性均较好（均ICC>0.960）。CCTA-CS与CACS、CCTA-VS与VS均呈较好的正相关（r²=0.98、0.96,均P<0.05）。Bland-Altman检验结果显示CCTA与门控CT平扫所测评分间的一致性较高。不同危险分层病人的CCTA-CS和CCTA-VS差异均有统计学意义（均P<0.05）。Logistic回归分析显示高血压、糖尿病、高脂血症、吸烟史、脑血管病均为CACS、CCTA-CS的危险因素。CCTA检查的ED低于常规冠状动脉CT检查,Flash扫描可减少21.2%,Sequence扫描可减少18.6%。 结论 CCTA一站式测量可以精确定量钙化,测得的CCTA-CS、CCTA-VS与标准积分有较好的相关性,且能有效降低辐射剂量。     

Causes of interscan variability of coronary artery calcium measurements at electron-beam CT

RATIONALE AND OBJECTIVES: The authors performed this study to investigate the causes of interscan variability of coronary artery calcium measurements at electron-beam computed tomography (CT). MATERIALS AND METHODS: Two sets of electron-beam CT scans were obtained in 298 consecutive patients who underwent electron-beam CT to screen for coronary artery calcium. Interscan variations of coronary artery calcium characteristics and the effects of heart rate, electrocardiographic (ECG) triggering method, image noise, and coronary motion on interscan variability were analyzed. RESULTS: The interscan mean variabilities were 21.6% (median, 11.7%) and 17.8% (median, 10.8%) with the Agatston and volumetric score, respectively (P < .01). Variability decreased with increasing calcification score (34.6% for a score of 11-50 and 9.4% for a score of 400-1,000, P < .0001). The absolute difference in Agatston score between scans was 44.1 +/- 95.6. The correlation coefficient between the first and second sets of scans was 0.99 (P < .0001). Lower interscan variability was found in younger patients (<60 years), patients with stable heart rates (heart rate changing less than 10 beats per minute during scanning), patients with no visible coronary motion, and those with an optimal ECG triggering method (P < .05 for all). Results of multivariate logistic analysis showed that changes in calcium volume, mean attenuation, and peak attenuation were significant predictors of interscan variability and caused the interscan variations of the coronary artery calcium measurements (r2 = 0.83, P < .0001). CONCLUSION: Coronary calcification at electron-beam CT varies from scan to scan. Volumetric scoring and optimal ECG triggering should be used to reduce interscan variability. Baseline calcium score and interscan variability must be considered in the evaluation of calcium progression.     

Coronary artery calcification scoring by prospectively triggered multidetector-row computed tomography: is it reproducible?

The objective of this study was to measure the interobserver and interscan variation of coronary artery calcium scores using multidetector-row computed tomography (MDCT). Seventy-five patients underwent 2 sequential MDCT scans for coronary artery calcification. Each patient's score was separately measured by 3-blinded radiologists. Scores were treated as discrete and continuous data, and independent statistical analysis was performed on all results. There was a high proportion of interscan and inter-reader concordance for the presence of coronary calcium (range, 0.893-0.973) and for its quantity (range, 0.936-0.988). Overall, prospectively triggered multidetector-row calcium scoring is reproducible though there is more variation in those patients with already high scores. There is no need to scan patients twice at the same sitting.     

Coronary artery calcium scoring using ECG-gated multidetector CT: effect of individually optimized image-reconstruction windows on image quality and measurement reproducibility

OBJECTIVE: We studied the effect of using individually optimized image-reconstruction windows on image quality and measurement reproducibility in coronary artery calcium scoring using ECG-gated multidetector CT (MDCT). SUBJECTS AND METHODS: In 50 patients, the coronary arteries were investigated twice with ECG-gated MDCT with 500-msec rotation time. Per scan, three sets of images were reconstructed, respectively, at an image-reconstruction window of 40%, 50%, and 60% of the R-R interval. Image quality was assessed, and the optimal image-reconstruction window per scan and per coronary territory was determined. The interscan variability of calcium mass measurements was calculated for different strategies (use of fixed image-reconstruction window [40%, 50%, or 60%] versus individually optimized image-reconstruction window). RESULTS: A significant improvement in image quality was obtained by selecting the best of three reconstructed data sets (mean image quality score, 4.4 vs 3.7; p < 0.001). Even with individually optimized image-reconstruction window values, we obtained high values for interscan variability (mean +/- SD, 27% +/- 22% vs 31% +/- 35% with a fixed image-reconstruction window). CONCLUSION: The use of individually optimized image-reconstruction windows leads to a significant improvement in image quality. However, interscan variability of calcium mass measurements remains high.     

Coronary CT angiography: How should physicians use it wisely and when do physicians request it appropriately?

Coronary CT angiography has been increasingly used in the diagnosis of coronary artery disease due to rapid technological developments, which are reflected in the improved spatial and temporal resolution of the images. High diagnostic accuracy has been achieved with 64- and more slice CT scanners and in selected patients, coronary CT angiography is regarded as a reliable alternative to invasive coronary angiography. Although the tremendous contributions of coronary CT angiography to cardiac imaging are acknowledged, appropriate use of cardiac CT as the first line technique by physicians has not been well established. Optimal selection of cardiac CT is essential to ensure acquisition of valuable diagnostic information and avoid unnecessary invasive procedures. This is of paramount importance since cardiac CT not only involves patient risk assessment, prediction of major cardiac events, but also impacts physician decision-making on patient management. Applications of CT in cardiac imaging include coronary artery calcium scoring for predicting the patient risk of developing major cardiac events, followed by coronary CT angiography which is commonly used to determine the diagnostic and prognostic accuracy in the coronary artery disease. This review presents an overview of the applications of CT in cardiac imaging in terms of coronary calcium scoring and coronary CT angiography. Judicious use of both cardiac CT tools will be discussed with regard to their value in different patient risk groups with the aim of identifying the appropriate criteria for choosing a cardiac CT modality. An effective diagnostic pathway is finally recommended to physicians for appropriate selection of cardiac CT in clinical practice.     

MSCT检查冠心病的应用及临床价值分析

目的探讨冠心病患者多层螺旋CT(MSCT)重建技术诊断效能及其危险因素分析。方法选取我院收治的102例疑似冠心病患者作为观察对象,均接受心电图(ECG)、MSCT重建技术检查。以冠状动脉造影检查(GAG)为金标准,统计MSCT重建技术及ECG冠心病及对不同冠状动脉狭窄程度诊断效能,logistic回归分析冠心病形成影响因素。结果1)102例疑似冠心病患者中,确诊78例冠心病,以此为根据分为冠心病组(n=78)和正常组(n=24);2)合并高血压、合并糖尿病、合并高脂血症、长期吸烟史、冠心病家族史、长期酗酒史是导致冠心病形成危险因素(P<0.05);3)以GAG检查结果为金标准。MSCT重建技术诊断准确度、敏感度、特异度高于ECG检查(P<0.05);4)MSCT重建技术对≥50%及≥75%冠状动脉狭窄诊断准确度、敏感度、特异度高于ECG检查(P<0.05)。结论MSCT重建技术可提高冠心病患者诊断价值,为临床选取合理诊治提供依据。     

Estimation of cardiac event risk by MDCT

Coronary calcifications are specific markers for coronary atherosclerosis. The amount of coronary calcium is related to the likelihood of vulnerable plaques. Vulnerable plaques may rupture and may result in sudden coronary thrombus formation, occlusion, ischemia and ventricular fibrillation and finally cardiac death. Therefore, it is reasonable to believe that the risk of cardiac events can be assessed by the quantification of the extent of coronary calcium. However, until now, the predictive value of coronary calcium and the advantage over conventional risk factors has not yet been proven by any prospective cohort study. In practice uncertainty exists in the group of patients with an intermediate risk for cardiac events. In this particular cohort it is likely that the assessment of coronary atherosclerosis may help in the decision to initiate or discard a specific therapy. For this purpose it has been suggested to replace the Framingham age score by a score corrected by the amount of coronary calcium. Follow-up investigations may be helpful in the short term to determine the efficiency of different therapeutical options. To determine a significant progression of the amount of coronary calcium, the absolute mass should be determined in a period of 1 year.     

Catheter-induced aortic dissection after invasive coronary angiography: evaluation with MDCT

OBJECTIVE: The purpose of this study was to describe the MDCT findings of retrograde aortic extension of catheter-induced coronary artery dissection and the use of MDCT in follow-up of this complication. CONCLUSION: Coronary artery dissection with aortic extension can be a fatal although infrequent complication. The coronary artery entry point is usually stented in the catheterization laboratory. Thereafter, CT is the imaging modality of choice for immediate confirmation of the presence of residual iatrogenic aortic dissection and evaluation of its extent and later noninvasive follow-up.     

Malignant right coronary artery anomaly simulated by motion artifacts on MDCT

OBJECTIVE: The aim of our study was to determine the prevalence of anomalous right coronary artery imitation due to motion artifacts in MDCT. Routine chest MDCT for reasons other than cardiac or vascular imaging is usually performed using breath-hold technique but without retrospective ECG gating and consequently yields pulsating motion artifacts. A possible artifact in front of the aortic root imitates an anomalous right coronary artery originating from the left posterior sinus. This course of the right coronary artery is considered a malignant variant and raises the question of far-reaching consequences such as a bypass operation. SUBJECTS AND METHODS: We performed a prospective study involving 355 patients undergoing routine chest CT examinations. To determine the prevalence of anomalous right coronary artery imitation caused by this motion artifact, all images were evaluated prospectively by an experienced radiologist. RESULTS: Twenty-one patients (5.9%) were suspected of having a malignant variant of the right coronary artery. However, in all patients prior chest CT or additional coronary MR angiography showed a normal origin of the right coronary artery. CONCLUSION: Routine chest MDCT without retrospective ECG gating may produce artifacts around the aorta simulating a malignant variant of the right coronary artery. Considering the low incidence of this malignant interarterial variant, the need for routine chest CT examinations combined with ECG gating and further workup can be disputed from an economic point of view. This artifact should be known to avoid unnecessary further examinations.