Introduction: Higher body mass index (BMI) is associated with increased cardiac risk factors, but... more Introduction: Higher body mass index (BMI) is associated with increased cardiac risk factors, but its relationship with incident coronary artery disease (CAD) and adverse events is not clear. Metho...
ABSTRACT The status of automated nap-of-the-earth (NOE) flight guidance is discussed by examining... more ABSTRACT The status of automated nap-of-the-earth (NOE) flight guidance is discussed by examining two current research efforts that approach the problem of performing obstacle avoidance along a pre-planned course from different perspectives. The first, a real-time guidance system developed by Systems Technology Inc., focuses on the issue of pilot acceptable maneuvers, under the assumption of an ideal, but nonrealizable, obstacle detection system. The second, a system created at NASA Ames, concentrates on the utilization of realistic on-board sensor data for obstacle detection and avoidance-maneuver decisions. This paper examines the strengths and weaknesses of these two approaches, and how they might complement each other. The goal is an automatic NOE system that is both acceptable to pilots and capable of making intelligent use of realistic sensor information and path-selection logic.
2006 IEEE/WIC/ACM International Conference on Web Intelligence (WI 2006 Main Conference Proceedings)(WI'06), 2006
... Furthermore, virus infection, phishing fraud, and pornographic messages are often harmful to ... more ... Furthermore, virus infection, phishing fraud, and pornographic messages are often harmful to users. ... [2] http://www.mail-abuse.org, accessed ... MSR-TR 2000-23, Microsoft Research (2000) [11] H. Drucker, D. Wu, and VN Vapnik, Support Vector Machines for Spam Categorization ...
2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, 2008
Abstract In Web forum analysis, both the discussion topics and author interests are greatly conce... more Abstract In Web forum analysis, both the discussion topics and author interests are greatly concerned. We introduce a linked topic and interest model based on latent Dirichlet allocation (LDA) to explore discussion topics and author interests. Rather than having two ...
ABSTRACT In this article, we investigate supply chain-related drivers that contribute to organiza... more ABSTRACT In this article, we investigate supply chain-related drivers that contribute to organizational flexibility (i.e., the ability of top management to be responsive to a firm's internal and external needs). Organizational flexibility occurs when a firm outsources manufacturing and operates with a more flexible structure. Drawing upon the supply network perspective, this study develops hypotheses relating attributes of the supplier, customer and focal industries to the use of a flexible organizational strategy. Using an industry-level data set to test the hypotheses, we show that heterogeneity of supply sources and scale economies (in the focal and downstream industries) are positively associated with a greater degree of organizational flexibility, in terms of contract manufacturing in the focal industry. However, industry concentration levels in the focal and downstream industries are negatively associated with organizational flexibility.
Proceedings of the 1999 ACM SIGMOD international conference on Management of data - SIGMOD '99, 1999
The Cornell Jaguar Project is exploring a variety of issues related to mobility and query process... more The Cornell Jaguar Project is exploring a variety of issues related to mobility and query processing. One broad theme is to break down the traditional client and server boundaries, leading to ubiquitous query processing. Another theme is to extend database and query processing techniques to small-scale and mobile devices. The project builds on and extends the Cornell PREDATOR database engine.
... Page 3. 822 V. Cheng, C.-s. Yeung, and C.-h. Li 2.1 Similarity Measure for Threads Using Text... more ... Page 3. 822 V. Cheng, C.-s. Yeung, and C.-h. Li 2.1 Similarity Measure for Threads Using Text ... It is because a thread in a forum usually condense a group of posters sharing similar interest. Imagine a thread discussing audio cables in a Hi-Fi forum. ...
2007 IEEE/AIAA 26th Digital Avionics Systems Conference, 2007
In support of the NASA-Ames implementation of the NGATS(Next Generation Air Transportation System... more In support of the NASA-Ames implementation of the NGATS(Next Generation Air Transportation System) ATM (Air Traffic Management) Airportal Program, a real-time simulation study investigated the changes in roles and responsibilities for tower controllers brought about by the introduction of new technology to achieve precision taxiing. The prototype tool that the controller interacted with was GoSAFE (Ground Operation, Situation Awareness and Efficiency Flow), which is part of a future surface concept. This future surface concept envisages that future surface operations will involve taxi clearances containing precisely timed taxi routes. The study was done in two parts: (1) the first phase was used to identify new areas of responsibilities for the tower controllers, and (2) the second phase was used to test those responsibilities. Four retired controllers participated in a Human-in-the-Loop study and the test bed used was DFW airport (East side only). The controllers interacted with the tool under two conditions-one using datalink and another using voice to issue and deliver clearances to the pilots. Phase-1 data analysis results showed a significant difference in the average workload reported at different controller positions, with the local east (LE1) controller being particularly busy. Phase-2 data analysis results indicated a more balanced redistribution of workload and communications among the controller positions. Comparison of the two phases has been described in the results section, which includes an analysis of the dependent measures of workload, situation awareness, and nature of communications.
Deÿning a good distance (dissimilarity) measure between patterns is of crucial importance in many... more Deÿning a good distance (dissimilarity) measure between patterns is of crucial importance in many classiÿcation and clustering algorithms. While a lot of work has been performed on continuous attributes, nominal attributes are more di cult to handle. A popular approach is to use the value di erence metric (VDM) to deÿne a real-valued distance measure on nominal values. However, VDM treats the attributes separately and ignores any possible interactions among attributes. In this paper, we propose the use of adaptive dissimilarity matrices for measuring the dissimilarities between nominal values. These matrices are learned via optimizing an error function on the training samples. Experimental results show that this approach leads to better classiÿcation performance. Moreover, it also allows easier interpretation of (dis)similarity between di erent nominal values.
This article is an interdisciplinary study of Chinese Communist Party (CCP) military decision mak... more This article is an interdisciplinary study of Chinese Communist Party (CCP) military decision making at the outset of the civil war. The historical phenomenon of the Communists’ invocation of “Madrid” is studied in the context of the Chinese civil war in Manchuria, particularly the battle of Sipingjie. The strategic culture of the Communist leaders is discussed thematically in terms of their desire for a decisive battle, their expectation of a short war, and their propensity for preemptive strikes. Analyzing newly released primary documents, the author argues that norms, beliefs, and material conditions work in tandem in the making of strategy in a way that the realist premise fails to explain. He concludes that the interaction of normative and material factors, symbolized by the Madrid concept, heightened the CCP policy makers’ acceptance of risk in 1946, which foreshadowed the open general war in China over the following three years.
Journal of the American College of Cardiology, 2010
Background: How stenosis severity on coronary CT angiography (CCTA) relates to myocardial ischemi... more Background: How stenosis severity on coronary CT angiography (CCTA) relates to myocardial ischemia is not well defined. We examined the relationship between stenosis severity measured by CCTA and the presence of stress-induced ischemia on single photon emission computed tomographic myocardial perfusion imaging (SPECT-MPI). Methods and Results: We studied 292 patients (age 26-91 years, median 62; 73% male) with no prior history of CAD who underwent CCTA and SPECT-MPI within 6 months of each other for suspected ischemic heart disease. ECG-gated CCTA was performed using dual-source CT. Maximal stenosis severity, graded as ≥50%, ≥70%, and ≥90% diameter reduction, was consensually determined by two blinded expert readers. Perfusion defect on SPECT-MPI was measured by computer-assisted expert visual interpretation, using the standard 17 myocardial segment, 5 point-scoring model (≥5% perfusion defect during stress = abnormal). Stenosis severity on CCTA was compared to SPECT-MPI perfusion abnormalities. By SPECT-MPI, 46/292 (16%) patients and 59/875 (7%) vascular territories demonstrated stress perfusion defect. Defining CAD with increasing degrees of stenosis severity on CCTA resulted in a progressive increase in positive predictive value (PPV): 43%, 57%, and 67% (p=0.03) on a per-patient basis, and 38%, 49%, and 60% (p=0.01) on a per-vessel basis. Negative predictive value (NPV) remained relatively unchanged: 97%, 95% and 91% for per-patient analysis, and 99%, 98%, and 97% for per-vessel analysis (p=NS for both). In a multivariate analysis that included luminal stenosis of 50%-89% and ≥90%, multivessel disease with stenosis ≥50%, plaque composition and presence of 2 or more serial stenoses ≥50% in a coronary artery, the strongest predictors of ischemia were stenosis of 50-89% (odds ratio 7.5, p=0.004), stenosis ≥90% (odds ratio 48.1, p=0.001), and serial stenoses ≥50% (odds ratio 4.4, p= 0.004). Conclusions: Prediction of ischemia by CCTA significantly improves as stenosis severity increases. Adopting a diameter stenosis cutoff of ≥70% instead of ≥50% increases PPV while preserving NPV. Serial stenoses of ≥50% in a vessel contribute incremental value in predicting ischemia.
Journal of the American College of Cardiology, 2011
Background: Epicardial fat volume (EFV) is emerging as an important parameter that may mediate th... more Background: Epicardial fat volume (EFV) is emerging as an important parameter that may mediate the development of coronary artery calcium (CAC) via the activation of local inflammatory cytokines. There is little data on whether EFV also affects the development of adjacent aortic valve calcification (AVC) and ascending aorta calcification (AAoC). Methods: We evaluated 203 patients (89 men, median age 61 years) who underwent a non-contrast ECG-gated cardiac CT scan. CAC, AVC and AAoC were calculated using semi-automated commercially available software (ScImage Inc., Los Altos, CA, USA). Using validated software developed at our center, the 3-dimensional pericardial contour from the pulmonary artery bifurcation to the posterior descending artery was created. Inside this contour, EFV was quantified by determining the volume occupied by voxels with attenuation values between-30 to-190 Hounsfield units. The relationship of EFV to the presence of CAC, AVC and AAoC was assessed using binary logistic regression for non-parametric data and the Spearman test for correlation for absolute values. Results: CAC was found in 169 patients (83.3%), AVC in 31 patients (15%), and AAoC in 48 patients (23.6%). Compared to patients without CAC, EFV was significantly higher in patients with CAC [80 cm3 (range 27-226) vs. 65 cm3 (range 28-116), p=0.002]. No significant difference in EFV was found when patients were categorized by presence of AVC [72 cm3 with AVC (range 35-276) vs. 77 cm3 without (range 27-232), p=0.9] or AAoC [73 cm3 with AAoC (range 27-232) vs. 70 cm3 without (range 28-218), p=0.7]. Absolute EFV was weakly correlated to CAC value (r=0.2, p=0.009) and not to AVC (r=-0.02, p=0.7) or AAoC (r=0.1, p=0.6). On multivariable binary logistic regression adjusting for age, body mass index, dyslipidemia, diabetes and hypertension, only EFV (OR 2.3, 95% CI 1.0-5.4) and age (OR 3.0, 95% CI 1.9-5.2) remained predictive of the presence of CAC. There were no predictors of AVC or AAoC. Conclusions: EFV is related to the presence of coronary artery calcification but not to aortic valve or ascending aortic calcification. These findings support a local paracrine effect of epicardial fat in mediating coronary atherosclerosis.
Journal of the American College of Cardiology, 2012
Background: Prior studies have evaluated the prognostic utility of left ventricular systolic dysf... more Background: Prior studies have evaluated the prognostic utility of left ventricular systolic dysfunction (LVSD) by cardiac CT angiography (CCTA), but have been limited to measures of normal versus abnormal function. Whether the degree of LVSD improves risk stratification and discrimination for mortality prediction has not been examined. Methods: From 27125 subjects in the CONFIRM registry, we identified subjects without prior known coronary artery disease (CAD) who underwent CCTA with quantitative LVSD assessment. LVSD was categorized by ejection fraction (EF) as normal (> 55%), mildly abnormal (45% < EF < 55%), moderately abnormal (35% < EF < 45%) and severely abnormal (< 35%). CAD extent and severity was categorized as none (0%), non-obstructive (50%) 1-, 2-and 3-vessel disease. EF and CAD were examined in relation to risk prediction and discrimination for future mortality employing Cox proportional hazards models and area under the receiver operating characteristics curve (AUC), respectively. Results: In a follow-up of 2.2 +/-0.9 years, 7907 patients (58.4 +/-13.0 years, 54.4% male) were studied with 6283 (79.5%), 1080 (13.7%), 316 (4.0%) and 228 (2.9%) patients having normal, mildly abnormal, moderately abnormal, and severely abnormal EF, respectively. Worsening EF was associated with older age, male gender, hypertension, diabetes, smoking, increased CAD extent and severity and higher mortality (p<0.01 for all). In multivariable analyses, worsening EF was independently associated with mortality for moderately (hazards ratio 3.13, 95% confidence interval 2.00-4.91, p<0.001) and severely (hazards ratio 5.23, 95% confidence interval 3.44-7.94, p<0.001) abnormal EF, but not for mildly abnormal EF (hazards ratio 1.40, 95% confidence interval 0.94-2.09, p=0.10). LVSD demonstrated improved discrimination (AUC 0.8123) for identification of individuals at risk of death, when compared to CAD extent and severity alone (0.7866) or CAD risk factors alone (0.7768) [p<0.001]. Conclusions: Incremental to clinical variables and CAD extent and severity, the degree of LVSD by CCTA offers improved risk prediction and discrimination for future mortality.
Journal of the American College of Cardiology, 2012
Background: Although family history (FH) of premature coronary artery disease (CAD) has been show... more Background: Although family history (FH) of premature coronary artery disease (CAD) has been shown to imply worsened prognosis, the prevalence, severity and prognosis of coronary atherosclerosis in young patients with FH of CAD has been inadequately studied to date. Methods: From 27125 consecutive patients undergoing coronary computed tomography angiography, 6308 young patients-defined as male <55 and female <65 years of age-without known CAD in the CONFIRM registry were identified. Obstructive CAD was defined as >50% luminal stenosis in a coronary artery >2mm diameter. Risk-adjusted logistic regression and Cox proportional hazards models were employed to compare patients with and without FH of CAD for risk of subsequent myocardial infarction (MI)(n = 42). Results: As compared to individuals without FH of CAD (FH-)(n = 4327), those with FH of CAD (FH+)(n = 1981) were younger (49+8 vs. 50+9 years, P < 0.001) with higher prevalence of dyslipidemia (55% vs. 51%, P = 0.007) and smoking (22% vs. 15%, P < 0.001). Compared to FH-patients, FH+ patients exhibited higher frequency of any coronary atherosclerosis (40% vs. 30%, P < 0.001) and obstructive CAD (11% vs. 7%, P < 0.001), with multivariable odds of FH+ increasing the likelihood of obstructive CAD (odds ratio = 1.71, 95% confidence interval (CI) = 1.42-2.07, P < 0.001). At a follow-up of 2.3+1.2 years, FH+ was the strongest risk-adjusted clinical predictor of incident MI (hazard ratio = 2.60, 95%CI = 1.41-4.79, P = 0.002). Conclusion: Young patients with FH of CAD possess higher prevalence of coronary atherosclerosis, obstructive CAD and incident MI. Compared to other clinical variables, FH in young patients is the strongest clinical predictor of future unheralded MI.
Journal of the American College of Cardiology, 2012
Background: The effect of hypertension (HTN) on the prevalence, severity, and risk of coronary ar... more Background: The effect of hypertension (HTN) on the prevalence, severity, and risk of coronary artery disease (CAD) by coronary computed tomographic angiography (CCTA) is not established in large studies. Methods: From the multinational CONFIRM registry of individuals undergoing CCTA, we examined 15,091 individuals without known CAD and available follow-up for adverse events [death or non-fatal myocardial infarction (MI)]. We compared CAD findings and adverse events between individuals with (n=7251) and without (n=7840) HTN. Results: Mean age was 56.8 ±11.8 years; 55.1% were male. There were 390 events (175 deaths, 215 MI); mean follow-up was 2.3 ±1.2 years. Individuals with vs. without HTN had increased prevalence of any CAD (60.6% vs. 47.6%, p<0.001) and obstructive (≥50% stenosis) CAD (23.1% vs. 14.2%, p<0.001). After adjusting for risk factors, HTN was associated with an increased presence of any CAD [odds ratio (OR) 1.24, 95% confidence interval (CI) 1.15-1.34, p<0.001] and obstructive CAD (OR 1.39, 95% CI 1.27-1.52, p<0.001). Both HTN and obstructive CAD were associated with increased events (Figure 1). Obstructive CAD was independently associated with risk of adverse events in hypertensives [hazards ratio (HR) 3.58, 95% CI 2.76-4.65, p<0.001]. Conclusion: Individuals with HTN have an increased prevalence and severity of CAD by CCTA, and these findings are associated with an increased risk of adverse events. Figure 1. Adverse Events in Patients Stratified by HTN and Obstructive CAD.
Background. We aimed to determine in phantom and cardiac clinical studies the impact of a new hig... more Background. We aimed to determine in phantom and cardiac clinical studies the impact of a new high-resolution PET image reconstruction. Methods. A phantom with cardiac insert filled with 18 F, 14 18 F-FDG viability studies and 15 82 Rb perfusion studies were acquired on a Siemens Biograph-64 (4-ring). The data were reconstructed with 2D-and 3D-attenuation weighted ordered subsets expectation maximization (AWOSEM), and high-definition reconstruction (HDÁPET). We calculated wall/cavity contrast, contrast-to-noise ratio (CNR), wall thickness, motion/thickening and ejection fraction. Results. In the phantom study, we found an increase in defect size (up to 26%), contrast (up to 48%) and CNR (1.9) with HDÁPET as compared to standard techniques. The contrast increased on HDÁPET images compared to 2D-and 3D-AWOSEM for viability (14.0% ± 4.8%) and perfusion studies (7.3% ± 4.3%) (P < .05). Average CNR increased with HDÁPET by 79.4% ± 17.1% and 68.8% ± 3.0% in viability and perfusion studies respectively (all P < .05). Average wall thickness with HDÁPET decreased in the phantom study by 1.3 ± 0.3 mm and the viability studies by 1.9 ± 0.7 mm but not in the perfusion studies. The functional measurements were not significantly different for any techniques. Conclusions. We demonstrated both in phantom and patient cardiac studies that HDÁPET improves image contrast, defect definition, and CNR.
Introduction: Higher body mass index (BMI) is associated with increased cardiac risk factors, but... more Introduction: Higher body mass index (BMI) is associated with increased cardiac risk factors, but its relationship with incident coronary artery disease (CAD) and adverse events is not clear. Metho...
ABSTRACT The status of automated nap-of-the-earth (NOE) flight guidance is discussed by examining... more ABSTRACT The status of automated nap-of-the-earth (NOE) flight guidance is discussed by examining two current research efforts that approach the problem of performing obstacle avoidance along a pre-planned course from different perspectives. The first, a real-time guidance system developed by Systems Technology Inc., focuses on the issue of pilot acceptable maneuvers, under the assumption of an ideal, but nonrealizable, obstacle detection system. The second, a system created at NASA Ames, concentrates on the utilization of realistic on-board sensor data for obstacle detection and avoidance-maneuver decisions. This paper examines the strengths and weaknesses of these two approaches, and how they might complement each other. The goal is an automatic NOE system that is both acceptable to pilots and capable of making intelligent use of realistic sensor information and path-selection logic.
2006 IEEE/WIC/ACM International Conference on Web Intelligence (WI 2006 Main Conference Proceedings)(WI'06), 2006
... Furthermore, virus infection, phishing fraud, and pornographic messages are often harmful to ... more ... Furthermore, virus infection, phishing fraud, and pornographic messages are often harmful to users. ... [2] http://www.mail-abuse.org, accessed ... MSR-TR 2000-23, Microsoft Research (2000) [11] H. Drucker, D. Wu, and VN Vapnik, Support Vector Machines for Spam Categorization ...
2008 IEEE/WIC/ACM International Conference on Web Intelligence and Intelligent Agent Technology, 2008
Abstract In Web forum analysis, both the discussion topics and author interests are greatly conce... more Abstract In Web forum analysis, both the discussion topics and author interests are greatly concerned. We introduce a linked topic and interest model based on latent Dirichlet allocation (LDA) to explore discussion topics and author interests. Rather than having two ...
ABSTRACT In this article, we investigate supply chain-related drivers that contribute to organiza... more ABSTRACT In this article, we investigate supply chain-related drivers that contribute to organizational flexibility (i.e., the ability of top management to be responsive to a firm&amp;#39;s internal and external needs). Organizational flexibility occurs when a firm outsources manufacturing and operates with a more flexible structure. Drawing upon the supply network perspective, this study develops hypotheses relating attributes of the supplier, customer and focal industries to the use of a flexible organizational strategy. Using an industry-level data set to test the hypotheses, we show that heterogeneity of supply sources and scale economies (in the focal and downstream industries) are positively associated with a greater degree of organizational flexibility, in terms of contract manufacturing in the focal industry. However, industry concentration levels in the focal and downstream industries are negatively associated with organizational flexibility.
Proceedings of the 1999 ACM SIGMOD international conference on Management of data - SIGMOD '99, 1999
The Cornell Jaguar Project is exploring a variety of issues related to mobility and query process... more The Cornell Jaguar Project is exploring a variety of issues related to mobility and query processing. One broad theme is to break down the traditional client and server boundaries, leading to ubiquitous query processing. Another theme is to extend database and query processing techniques to small-scale and mobile devices. The project builds on and extends the Cornell PREDATOR database engine.
... Page 3. 822 V. Cheng, C.-s. Yeung, and C.-h. Li 2.1 Similarity Measure for Threads Using Text... more ... Page 3. 822 V. Cheng, C.-s. Yeung, and C.-h. Li 2.1 Similarity Measure for Threads Using Text ... It is because a thread in a forum usually condense a group of posters sharing similar interest. Imagine a thread discussing audio cables in a Hi-Fi forum. ...
2007 IEEE/AIAA 26th Digital Avionics Systems Conference, 2007
In support of the NASA-Ames implementation of the NGATS(Next Generation Air Transportation System... more In support of the NASA-Ames implementation of the NGATS(Next Generation Air Transportation System) ATM (Air Traffic Management) Airportal Program, a real-time simulation study investigated the changes in roles and responsibilities for tower controllers brought about by the introduction of new technology to achieve precision taxiing. The prototype tool that the controller interacted with was GoSAFE (Ground Operation, Situation Awareness and Efficiency Flow), which is part of a future surface concept. This future surface concept envisages that future surface operations will involve taxi clearances containing precisely timed taxi routes. The study was done in two parts: (1) the first phase was used to identify new areas of responsibilities for the tower controllers, and (2) the second phase was used to test those responsibilities. Four retired controllers participated in a Human-in-the-Loop study and the test bed used was DFW airport (East side only). The controllers interacted with the tool under two conditions-one using datalink and another using voice to issue and deliver clearances to the pilots. Phase-1 data analysis results showed a significant difference in the average workload reported at different controller positions, with the local east (LE1) controller being particularly busy. Phase-2 data analysis results indicated a more balanced redistribution of workload and communications among the controller positions. Comparison of the two phases has been described in the results section, which includes an analysis of the dependent measures of workload, situation awareness, and nature of communications.
Deÿning a good distance (dissimilarity) measure between patterns is of crucial importance in many... more Deÿning a good distance (dissimilarity) measure between patterns is of crucial importance in many classiÿcation and clustering algorithms. While a lot of work has been performed on continuous attributes, nominal attributes are more di cult to handle. A popular approach is to use the value di erence metric (VDM) to deÿne a real-valued distance measure on nominal values. However, VDM treats the attributes separately and ignores any possible interactions among attributes. In this paper, we propose the use of adaptive dissimilarity matrices for measuring the dissimilarities between nominal values. These matrices are learned via optimizing an error function on the training samples. Experimental results show that this approach leads to better classiÿcation performance. Moreover, it also allows easier interpretation of (dis)similarity between di erent nominal values.
This article is an interdisciplinary study of Chinese Communist Party (CCP) military decision mak... more This article is an interdisciplinary study of Chinese Communist Party (CCP) military decision making at the outset of the civil war. The historical phenomenon of the Communists’ invocation of “Madrid” is studied in the context of the Chinese civil war in Manchuria, particularly the battle of Sipingjie. The strategic culture of the Communist leaders is discussed thematically in terms of their desire for a decisive battle, their expectation of a short war, and their propensity for preemptive strikes. Analyzing newly released primary documents, the author argues that norms, beliefs, and material conditions work in tandem in the making of strategy in a way that the realist premise fails to explain. He concludes that the interaction of normative and material factors, symbolized by the Madrid concept, heightened the CCP policy makers’ acceptance of risk in 1946, which foreshadowed the open general war in China over the following three years.
Journal of the American College of Cardiology, 2010
Background: How stenosis severity on coronary CT angiography (CCTA) relates to myocardial ischemi... more Background: How stenosis severity on coronary CT angiography (CCTA) relates to myocardial ischemia is not well defined. We examined the relationship between stenosis severity measured by CCTA and the presence of stress-induced ischemia on single photon emission computed tomographic myocardial perfusion imaging (SPECT-MPI). Methods and Results: We studied 292 patients (age 26-91 years, median 62; 73% male) with no prior history of CAD who underwent CCTA and SPECT-MPI within 6 months of each other for suspected ischemic heart disease. ECG-gated CCTA was performed using dual-source CT. Maximal stenosis severity, graded as ≥50%, ≥70%, and ≥90% diameter reduction, was consensually determined by two blinded expert readers. Perfusion defect on SPECT-MPI was measured by computer-assisted expert visual interpretation, using the standard 17 myocardial segment, 5 point-scoring model (≥5% perfusion defect during stress = abnormal). Stenosis severity on CCTA was compared to SPECT-MPI perfusion abnormalities. By SPECT-MPI, 46/292 (16%) patients and 59/875 (7%) vascular territories demonstrated stress perfusion defect. Defining CAD with increasing degrees of stenosis severity on CCTA resulted in a progressive increase in positive predictive value (PPV): 43%, 57%, and 67% (p=0.03) on a per-patient basis, and 38%, 49%, and 60% (p=0.01) on a per-vessel basis. Negative predictive value (NPV) remained relatively unchanged: 97%, 95% and 91% for per-patient analysis, and 99%, 98%, and 97% for per-vessel analysis (p=NS for both). In a multivariate analysis that included luminal stenosis of 50%-89% and ≥90%, multivessel disease with stenosis ≥50%, plaque composition and presence of 2 or more serial stenoses ≥50% in a coronary artery, the strongest predictors of ischemia were stenosis of 50-89% (odds ratio 7.5, p=0.004), stenosis ≥90% (odds ratio 48.1, p=0.001), and serial stenoses ≥50% (odds ratio 4.4, p= 0.004). Conclusions: Prediction of ischemia by CCTA significantly improves as stenosis severity increases. Adopting a diameter stenosis cutoff of ≥70% instead of ≥50% increases PPV while preserving NPV. Serial stenoses of ≥50% in a vessel contribute incremental value in predicting ischemia.
Journal of the American College of Cardiology, 2011
Background: Epicardial fat volume (EFV) is emerging as an important parameter that may mediate th... more Background: Epicardial fat volume (EFV) is emerging as an important parameter that may mediate the development of coronary artery calcium (CAC) via the activation of local inflammatory cytokines. There is little data on whether EFV also affects the development of adjacent aortic valve calcification (AVC) and ascending aorta calcification (AAoC). Methods: We evaluated 203 patients (89 men, median age 61 years) who underwent a non-contrast ECG-gated cardiac CT scan. CAC, AVC and AAoC were calculated using semi-automated commercially available software (ScImage Inc., Los Altos, CA, USA). Using validated software developed at our center, the 3-dimensional pericardial contour from the pulmonary artery bifurcation to the posterior descending artery was created. Inside this contour, EFV was quantified by determining the volume occupied by voxels with attenuation values between-30 to-190 Hounsfield units. The relationship of EFV to the presence of CAC, AVC and AAoC was assessed using binary logistic regression for non-parametric data and the Spearman test for correlation for absolute values. Results: CAC was found in 169 patients (83.3%), AVC in 31 patients (15%), and AAoC in 48 patients (23.6%). Compared to patients without CAC, EFV was significantly higher in patients with CAC [80 cm3 (range 27-226) vs. 65 cm3 (range 28-116), p=0.002]. No significant difference in EFV was found when patients were categorized by presence of AVC [72 cm3 with AVC (range 35-276) vs. 77 cm3 without (range 27-232), p=0.9] or AAoC [73 cm3 with AAoC (range 27-232) vs. 70 cm3 without (range 28-218), p=0.7]. Absolute EFV was weakly correlated to CAC value (r=0.2, p=0.009) and not to AVC (r=-0.02, p=0.7) or AAoC (r=0.1, p=0.6). On multivariable binary logistic regression adjusting for age, body mass index, dyslipidemia, diabetes and hypertension, only EFV (OR 2.3, 95% CI 1.0-5.4) and age (OR 3.0, 95% CI 1.9-5.2) remained predictive of the presence of CAC. There were no predictors of AVC or AAoC. Conclusions: EFV is related to the presence of coronary artery calcification but not to aortic valve or ascending aortic calcification. These findings support a local paracrine effect of epicardial fat in mediating coronary atherosclerosis.
Journal of the American College of Cardiology, 2012
Background: Prior studies have evaluated the prognostic utility of left ventricular systolic dysf... more Background: Prior studies have evaluated the prognostic utility of left ventricular systolic dysfunction (LVSD) by cardiac CT angiography (CCTA), but have been limited to measures of normal versus abnormal function. Whether the degree of LVSD improves risk stratification and discrimination for mortality prediction has not been examined. Methods: From 27125 subjects in the CONFIRM registry, we identified subjects without prior known coronary artery disease (CAD) who underwent CCTA with quantitative LVSD assessment. LVSD was categorized by ejection fraction (EF) as normal (> 55%), mildly abnormal (45% < EF < 55%), moderately abnormal (35% < EF < 45%) and severely abnormal (< 35%). CAD extent and severity was categorized as none (0%), non-obstructive (50%) 1-, 2-and 3-vessel disease. EF and CAD were examined in relation to risk prediction and discrimination for future mortality employing Cox proportional hazards models and area under the receiver operating characteristics curve (AUC), respectively. Results: In a follow-up of 2.2 +/-0.9 years, 7907 patients (58.4 +/-13.0 years, 54.4% male) were studied with 6283 (79.5%), 1080 (13.7%), 316 (4.0%) and 228 (2.9%) patients having normal, mildly abnormal, moderately abnormal, and severely abnormal EF, respectively. Worsening EF was associated with older age, male gender, hypertension, diabetes, smoking, increased CAD extent and severity and higher mortality (p<0.01 for all). In multivariable analyses, worsening EF was independently associated with mortality for moderately (hazards ratio 3.13, 95% confidence interval 2.00-4.91, p<0.001) and severely (hazards ratio 5.23, 95% confidence interval 3.44-7.94, p<0.001) abnormal EF, but not for mildly abnormal EF (hazards ratio 1.40, 95% confidence interval 0.94-2.09, p=0.10). LVSD demonstrated improved discrimination (AUC 0.8123) for identification of individuals at risk of death, when compared to CAD extent and severity alone (0.7866) or CAD risk factors alone (0.7768) [p<0.001]. Conclusions: Incremental to clinical variables and CAD extent and severity, the degree of LVSD by CCTA offers improved risk prediction and discrimination for future mortality.
Journal of the American College of Cardiology, 2012
Background: Although family history (FH) of premature coronary artery disease (CAD) has been show... more Background: Although family history (FH) of premature coronary artery disease (CAD) has been shown to imply worsened prognosis, the prevalence, severity and prognosis of coronary atherosclerosis in young patients with FH of CAD has been inadequately studied to date. Methods: From 27125 consecutive patients undergoing coronary computed tomography angiography, 6308 young patients-defined as male <55 and female <65 years of age-without known CAD in the CONFIRM registry were identified. Obstructive CAD was defined as >50% luminal stenosis in a coronary artery >2mm diameter. Risk-adjusted logistic regression and Cox proportional hazards models were employed to compare patients with and without FH of CAD for risk of subsequent myocardial infarction (MI)(n = 42). Results: As compared to individuals without FH of CAD (FH-)(n = 4327), those with FH of CAD (FH+)(n = 1981) were younger (49+8 vs. 50+9 years, P < 0.001) with higher prevalence of dyslipidemia (55% vs. 51%, P = 0.007) and smoking (22% vs. 15%, P < 0.001). Compared to FH-patients, FH+ patients exhibited higher frequency of any coronary atherosclerosis (40% vs. 30%, P < 0.001) and obstructive CAD (11% vs. 7%, P < 0.001), with multivariable odds of FH+ increasing the likelihood of obstructive CAD (odds ratio = 1.71, 95% confidence interval (CI) = 1.42-2.07, P < 0.001). At a follow-up of 2.3+1.2 years, FH+ was the strongest risk-adjusted clinical predictor of incident MI (hazard ratio = 2.60, 95%CI = 1.41-4.79, P = 0.002). Conclusion: Young patients with FH of CAD possess higher prevalence of coronary atherosclerosis, obstructive CAD and incident MI. Compared to other clinical variables, FH in young patients is the strongest clinical predictor of future unheralded MI.
Journal of the American College of Cardiology, 2012
Background: The effect of hypertension (HTN) on the prevalence, severity, and risk of coronary ar... more Background: The effect of hypertension (HTN) on the prevalence, severity, and risk of coronary artery disease (CAD) by coronary computed tomographic angiography (CCTA) is not established in large studies. Methods: From the multinational CONFIRM registry of individuals undergoing CCTA, we examined 15,091 individuals without known CAD and available follow-up for adverse events [death or non-fatal myocardial infarction (MI)]. We compared CAD findings and adverse events between individuals with (n=7251) and without (n=7840) HTN. Results: Mean age was 56.8 ±11.8 years; 55.1% were male. There were 390 events (175 deaths, 215 MI); mean follow-up was 2.3 ±1.2 years. Individuals with vs. without HTN had increased prevalence of any CAD (60.6% vs. 47.6%, p<0.001) and obstructive (≥50% stenosis) CAD (23.1% vs. 14.2%, p<0.001). After adjusting for risk factors, HTN was associated with an increased presence of any CAD [odds ratio (OR) 1.24, 95% confidence interval (CI) 1.15-1.34, p<0.001] and obstructive CAD (OR 1.39, 95% CI 1.27-1.52, p<0.001). Both HTN and obstructive CAD were associated with increased events (Figure 1). Obstructive CAD was independently associated with risk of adverse events in hypertensives [hazards ratio (HR) 3.58, 95% CI 2.76-4.65, p<0.001]. Conclusion: Individuals with HTN have an increased prevalence and severity of CAD by CCTA, and these findings are associated with an increased risk of adverse events. Figure 1. Adverse Events in Patients Stratified by HTN and Obstructive CAD.
Background. We aimed to determine in phantom and cardiac clinical studies the impact of a new hig... more Background. We aimed to determine in phantom and cardiac clinical studies the impact of a new high-resolution PET image reconstruction. Methods. A phantom with cardiac insert filled with 18 F, 14 18 F-FDG viability studies and 15 82 Rb perfusion studies were acquired on a Siemens Biograph-64 (4-ring). The data were reconstructed with 2D-and 3D-attenuation weighted ordered subsets expectation maximization (AWOSEM), and high-definition reconstruction (HDÁPET). We calculated wall/cavity contrast, contrast-to-noise ratio (CNR), wall thickness, motion/thickening and ejection fraction. Results. In the phantom study, we found an increase in defect size (up to 26%), contrast (up to 48%) and CNR (1.9) with HDÁPET as compared to standard techniques. The contrast increased on HDÁPET images compared to 2D-and 3D-AWOSEM for viability (14.0% ± 4.8%) and perfusion studies (7.3% ± 4.3%) (P < .05). Average CNR increased with HDÁPET by 79.4% ± 17.1% and 68.8% ± 3.0% in viability and perfusion studies respectively (all P < .05). Average wall thickness with HDÁPET decreased in the phantom study by 1.3 ± 0.3 mm and the viability studies by 1.9 ± 0.7 mm but not in the perfusion studies. The functional measurements were not significantly different for any techniques. Conclusions. We demonstrated both in phantom and patient cardiac studies that HDÁPET improves image contrast, defect definition, and CNR.
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