***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: AIMS To prospect ively compare multislice computed tomography ( MSCT ) and exercise electrocardiography ( ex-ECG ) for diagnosis of coronary artery disease ( CAD ) with conventional coronary angiography as the reference st and ard . METHODS AND RESULTS A consecutive cohort of 80 patients with suspected CAD was examined with MSCT using 16 x 0.5 mm detector collimation , ex-ECG , and conventional coronary angiography according to st and ard protocol s. Results were compared using the paired McNemar 's test , the chi(2 ) test , and 95%CIs . Both the sensitivity and specificity of MSCT [ 91 % ( 40 of 44 patients , 95%CI 78 - 97 % ) and 83 % ( 30 of 36 patients , 95%CI 67 - 94 % ) ] were significantly higher ( P = 0.039 and P < 0.001 ) than those for ex-ECG [ 73 % ( 32 of 44 patients , 95%CI 57 - 85 % ) and 31 % ( 11 of 36 patients , 95%CI 16 - 48 % ) ] . The pairwise McNemar 's test showed significant differences between  MSCT and ex-ECG  in the overall diagnosis in patients with suspected CAD ( P = 0.036 ) . The rate of non-diagnostic examinations was not significantly ( P = 0.078 ) different between MSCT and ex-ECG [ 8 % ( 6 of 80 patients , 95%CI 3 - 16 % ) vs. 19 % ( 15 of 80 patients , 95%CI 11 - 29 % ) ] . CONCLUSION In this consecutive cohort of patients scheduled to undergo conventional coronary angiography , the performance of MSCT for diagnosis of CAD was superior to that of ex-ECG OBJECTIVES In this prospect i ve evaluation we investigated the accuracy of 64-slice computed tomography angiography ( CTA ) in an unselected but symptomatic patient population for detection of stenoses in bypass grafts when compared with invasive angiography . BACKGROUND The assessment of significant stenosis in bypass grafts is important for patients with recurrent angina symptoms after bypass surgery . METHODS High-resolution 64-slice computed tomography ( 0.6 mm collimation , 330 ms gantry rotation time ) and invasive angiography were performed in 138 consecutive patients with a total of 418 bypass grafts . Relevant stenosis was defined as diameter reduction > or = 50 % . During CTA , arrhythmias were present in 42 ( 30 % ) patients who were not excluded from the analysis . RESULTS The assessment of stenosis or occlusion of bypass grafts result ed in a sensitivity of 97 % , specificity of 97 % , and positive and negative predictive values of 93 % and of 99 % , respectively . The diagnostic accuracy for the detection of graft occlusion or stenosis did not differ between arterial and venous grafts . The evaluability of bypass grafts was significantly lower in patients with arrhythmias or with heart rates > or = 65 beats/min during scanning . However , in the assessment of evaluable bypass grafts , no significant differences were detected in the diagnostic accuracy in these subgroups . CONCLUSIONS This large prospect i ve study demonstrates that 64-slice CTA is a reliable method for the assessment of bypass graft patency and stenoses even in an unselected " real-world " patient population INTRODUCTION AND OBJECTIVES Although it has been demonstrated that the diagnostic accuracy of computed tomography in the non-invasive assessment of major epicardial coronary arteries is high , only a few studies have evaluated the technique 's reliability in assessing coronary artery bypass grafts . The aim of this study was to determine the diagnostic accuracy of multidetector computed tomography in the assessment of coronary grafts . PATIENTS AND METHOD We prospect ively evaluated 117 coronary grafts in 38 patients who had undergone coronary artery bypass graft surgery and who had a clinical indication for angiographic graft assessment . All patients were in sinus rhythm and had a heart rate below 75 bpm . A 16-detector scanner was used for non-invasive assessment of the coronary grafts at a slice thickness of 1.2 mm . The diagnostic accuracy of computed tomography in the non-invasive assessment of significant lesions ( i.e. , occluded lesions or those with a stenosis greater than 50 % ) in coronary artery bypass grafts was evaluated by comparison with the results of conventional angiography . RESULTS Of the 117 grafts evaluated , 99 ( 84.6 % ) were visualized by conventional angiography and 109 ( 93.2 % ) by computed tomography . Overall , 98 grafts were analyzed using both techniques . The sensitivity and specificity of  computed tomography in detecting significant lesions were : 92 % and 97.3 % , respectively , for all grafts ; 89.5 % and 97.6 % , respectively , for venous grafts ; and 100 % and 96.8 % , respectively , for arterial grafts . CONCLUSIONS The diagnostic accuracy of multidetector computed tomography in coronary artery bypass graft assessment was high PURPOSE multislice CT has been shown as a promising tool for coronary artery imaging . Our goal was to investigate the value of the new sixteen-slice , CT technology for non-invasive visualization of coronary arteries and assessment of coronary stenosis . MATERIAL S AND METHODS we assessed coronary artery visualization in 30 consecutive patients using  16-slice CT  and compared the findings with conventional coronary angiography . The whole heart was scanned using 0.75 millimeter slices after injection of contrast medium . Retrospective ECG-gated reconstructions were performed and images were analyzed using axial CT , maximum intensity projection and 3D images , blind to the conventional angiography findings . Seventeen main coronary segments of more than 1.5 mm were analyzed and stenosis was grade d on a four-point scale . RESULTS CT angiography attained diagnostic quality for the whole coronary artery tree in 90 % ( 27/30 ) of patients . Sixteen of 493 segments ( 4 % ) were not interpreted because of substantial motion artifacts ( n=12 ) or heavy calcifications or stenting ( n=4 ) . Thirty seven of the 43 cases of significant stenosis ( > 50 % ) identified on coronary angiograms were correctly identified with multislice CT . All 6 false negatives involved stenosis of the circumflex artery or branches . Five false positive stenoses were found in 432 non stenotic segments . The sensitivity was thus 86 % , specificity 99 % for stenosis of more than 50 % . CONCLUSION 16-slice CT provides an excellent visualization of the coronary tree in most patients , allowing accurate non-invasive detection of significant coronary stenosis . Stenoses of the left circumflex artery remain more difficult to detect PURPOSE To investigate the ability of 16-slice multidetector-row computed tomography ( MDCT ) to visualize coronary artery bypass graft ( CABG ) patency and to detect bypass stenoses . MATERIAL S AND METHODS Thirty-two patients with 94 grafts ( 20 mammary artery grafts , 74 venous grafts ) were investigated by 16-slice MDCT using a scan protocol with 12 x 0.75 mm slice collimation ( pitch 0.3 ) , 420 ms rotation time and simultaneous electrocardiogram (ECG)- registration . One hundred milliliters iodinated contrast agent were injected with a delay according to the individually determined contrast agent transit time . Patients with heart rates above 60 bpm received oral beta-blockade .  Cross-sectional images with a slice width of 1.0 mm ( 0.5 mm increment ) were reconstructed using an ECG-gated half-scan reconstruction or a multisegment reconstruction algorithm depending on the heart rate . Bypass grafts were evaluated concerning patency and presence of stenoses > or = 50 % diameter reduction on cross-sectional images , multiplanar reformations and maximum intensity projections by two independent observers . Results were compared to coronary bypass angiography . RESULTS Sixteen-slice MDCT results were compared to those of invasive coronary angiography concerning absence or presence of bypass graft occlusion or relevant stenosis > or = 50 % lumen reduction . Coronary CT angiography ( CTA ) permitted detection of bypass occlusion with 100 % sensitivity ( 28/28 ) and 98 % specificity ( 64/65 ) . Seventy-eight percent ( observer 1 ) and 84 % ( observer 2 ) of all patent grafts were found to be evaluable concerning presence or absence of stenosis . In 34 of 40 ( observer 1 ) and 38 of 43 ( observer 2 ) bypass grafts , high- grade stenoses were correctly ruled out ( specificity 85 % versus 88 % , sensitivity 80 % and 82 % ) . Yet , if all patients with either unevaluable grafts/graft anastomosis or relevant graft stenosis were excluded , only 8/32 patients ( 25 % ) had fully diagnostic " negative " graft-CTA . According to Kappa statistics , agreement between the observers was 1.0 and 0.93 concerning occlusion and relevant stenosis , respectively . CONCLUSION Sixteen-slice coronary CTA with sub-millimeter spatial resolution and premedication with oral beta-blockade permits non-invasive assessment of coronary artery bypass grafts with decreasing numbers of unevaluable graft segments . However , patient-based analysis reveals that only a relatively small number of patients ( " negative " and completely evaluable graft-CTA ) truly profits from noninvasive work-up and could be spared invasive angiography Background —Multislice spiral computed tomography ( MSCT ) is a promising technique for noninvasive coronary angiography , although clinical application has remained limited because of frequently incomplete interpretability , caused by motion artifacts and calcifications . Methods and Results —In 59 patients ( 53 male , aged 58±12 years ) with suspected obstructive coronary artery disease ,  ECG-gated MSCT angiography  was performed with a 16-slice MSCT scanner ( 0.42-s rotation time , 12 × 0.75-mm detector collimation ) . Thirty-four patients were given additional & bgr;-blockers  ( average heart rate : 56±6 min−1 ) . After contrast injection , all data were acquired during an approximately 20-s breath hold . The left main ( LM ) , left anterior descending ( LAD ) , left circumflex ( LCX ) , and right coronary artery ( RCA ) , including ≥2.0-mm side branches , were independently evaluated by two blinded observers and screened for ≥50 % stenoses . The consensus reading was compared with quantitative coronary angiography . MSCT was successful in 58 patients . Eighty-six of the 231 evaluated branches were significantly diseased . Without exclusion of branches , the sensitivity , specificity and positive and negative predictive value to identify ≥50 % obstructed branches was 95 % ( 82/86 ) , 86 % ( 125/145 ) , 80 % ( 82/102 ) , and 97 % ( 125/129 ) , respectively . The overall accuracy for the LM , LAD , RCA , and LCX was 100 % , 91 % , 86 % , and 81 % , respectively . No obstructed LM , LAD , or RCA branches remained undetected . Classification of patients as having no , single , or multivessel disease was accurate in 78 % ( 45/58 ) of patients and no patients with significant obstructions were incorrectly excluded . Conclusions —Improvements in MSCT technology , combined with heart rate control , allow reliable noninvasive detection of obstructive coronary artery disease OBJECTIVES We studied the diagnostic performance of 64-slice computed tomography coronary angiography ( CTCA ) to rule out or detect significant coronary stenosis in patients referred for valve surgery . BACKGROUND Invasive conventional coronary angiography ( CCA ) is recommended in most patients scheduled for valve surgery . METHODS During a 6-month period , 145 patients were prospect ively identified from a consecutive patient population scheduled for valve surgery . Thirty-five patients were excluded because of CTCA criteria : irregular heart rhythm ( n = 26 ) , impaired renal function ( n = 5 ) , and known contrast allergy ( n = 4 ) . General exclusion criteria were : hospitalization in community hospital ( n = 4 ) , no need for CCA ( n = 4 ) , previous coronary artery bypass surgery ( n = 1 ) , or percutaneous coronary intervention ( n = 4 ) . Of the remaining 97 patients , 27 denied written informed consent . Thus , the study population comprised 70 patients ( 49 male , 21 female ; mean age 63 + /- 11 years ) . RESULTS Prevalence of significant coronary artery disease , defined as having at least 1 > or = 50 % stenosis per patient , was 25.7 % . Beta-blockers were administered in 71 % , and 64 % received lorazepam . The mean heart rate dropped from 72.5 + /- 12.4 to 59.5 + /- 7.5 beats/min . The mean scan time was 
    Output:
    
MSCT is a promising technology for the assessment of coronary artery stenosis .