***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objectives : The aim of this prospect i ve study was to assess the accuracy of 64-multidetector-row computed tomography coronary angiography ( CTA ) in the diagnosis of coronary artery disease ( CAD ) . Patients and Methods : Ninety-two patients suspected of having CAD underwent  CTA using a 64-slice CT scanner before a scheduled , conventional coronary angiogram ( CCA ) . Blinded assessment of CTA to detect CAD was performed . The accuracy of CTA in detecting significant stenoses ( ≥50 % ) was compared to CCA . Data analysis was performed on 73 patients because the scans were nondiagnostic in 5 patients and 14 refused to undergo coronary angiography .  Results : The CTAs of 21 of these 73 patients were considered as normal ; 19 were confirmed on CCA . For the remaining 52 diagnosed as abnormal , 51 were confirmed on CCA . For patient-based analysis , CTA had a sensitivity of 95 % , a specificity of 96 % , a positive predictive value of 98 % and a negative predictive value of 90 % . For the whole vessel , the sensitivity of CTA was 60–100 % , for all vessels and the specificity was 82–100 % . Pooled sensitivity was 92 % and pooled specificity was 98 % . For the segments , the sensitivity  of CTA was 64 % or above for all vessels except for the distal left anterior descending artery ( 40 % ) , mid circumflex artery ( 50 % ) and posterior descending artery ( 60 % ) ; the pooled sensitivity was 79 % . The specificity for the segments was 82–100 % for all vessels and pooled specificity was 94 % . Conclusion : The sensitivity and specificity for patient-based analysis and for the main coronary vessels were high whereas for the segments , the sensitivity was moderately good , but the specificity was high , confirming that a negative CTA is useful to rule out significant CAD . A coordinated classification system between radiologists and cardiologists is required to eliminate errors in segment classification Background — Noninvasive coronary angiography with the use of multislice computed tomography ( CT ) scanners is feasible with high sensitivity and negative predictive value ; however , the radiation exposure associated with this technique is rather high . We evaluated coronary angiography using whole-heart 320-row CT , which avoids exposure-intensive overscanning and overranging . Methods and Results — A total of 30 consecutive patients with suspected coronary artery disease referred for clinical ly indicated conventional coronary angiography ( CCA )  were included in this prospect i ve intention-to-diagnose study . CT was performed with the use of up to 320 simultaneous detector rows before same-day CCA , which , together with quantitative analysis , served as the reference st and ard . The per-patient sensitivity and specificity for CT compared with CCA were 100 % ( 95 % confidence interval [ CI ] , 72 to 100 ) and 94 % ( 95 % CI , 73 to 100 ) , respectively . Per-vessel versus per-segment sensitivity and specificity were 89 % ( 95 % CI , 62 to 98 ) and 96 % ( 95 % CI , 90 to 99 ) versus 78 % ( 95 % CI , 56 to 91 ) and 98 % ( 95 % CI , 96 to 99 ) , respectively . Interobserver agreement between the 2 readers was significantly better for CCA ( 97 % of 121 coronary arteries ) than for CT ( 90 % ; P=0.04 ) . Percent diameter stenosis determined with the use of CT showed good correlation with CCA ( P<0.001 , R=0.81 ) without significant underestimation or overestimation ( −3.1±24.4 % ; P=0.08 ) . Intraindividual comparison of CT with CCA revealed a significantly smaller effective radiation dose ( median , 4.2 versus 8.5 mSv ; P<0.05 ) and amount of contrast agent required ( median , 80 versus 111 mL ; P<0.001 ) for 320-row CT . The majority of patients ( 87 % ) indicated that they would prefer CT over CCA for future diagnostic imaging ( P<0.001 ) . Conclusions — CT with the use of emerging technology has the potential to significantly reduce the radiation dose and amount of contrast agent required compared with CCA while maintaining high diagnostic accuracy Background —Both whole-heart magnetic resonance coronary angiography ( WH-MRCA ) and multidetector computed tomography ( MDCT ) have been proposed for the noninvasive identification of the coronary stenosis . The authors sought to directly compare the diagnostic accuracy of these noninvasive imaging techniques using the invasive quantitative coronary angiography as a reference st and ard . Methods and Results —Seventy-seven consecutive patients ( 56 men , 61±14 years ) prospect ively underwent  WH-MRCA and 40- or 64-slice MDCT before the quantitative coronary angiography .  Diagnostic accuracy of WH-MRCA and MDCT for the visual identification of > 50 % diameter stenosis in segments of > 1.5 mm size was compared using the quantitative coronary angiography as a reference . According to the quantitative coronary angiography , 49 of 992 coronary segments > 1.5 mm diameter had > 50 % diameter stenosis . MDCT had a higher success rate ( 100 % versus 88 % , P<0.001 ) and enabled identification of more segments ( 963 versus 726 , P<0.001 ) than did WH-MRCA . On a per-segment basis , WH-MRCA had similar sensitivity ( 47/49 or 96 % versus 48/49 or 98 % , P=0.9 ) but significantly lower specificity ( 644/943 or 68 % versus 863/943 or 92 % , P<0.001 ) and accuracy ( 691/992 or 70 % versus 911/992 or 92 % , P<0.001 ) for the detection of > 50 % diameter stenosis  than did MDCT . On a per-patient basis , the sensitivity was similar ( 17/17 or 100 % versus 16/17 or 94 % , P=0.9 ) , but specificity ( 43/60 or 72 % versus 53/60 or 88 % , P=0.024 ) and diagnostic accuracy ( 60/77 or 78 % , versus 69/77 or 90 % , P=0.044 ) of WH-MRCA for the detection of > 50 % diameter stenosis were significantly lower than of MDCT . Conclusions —Because of the higher success rate and higher number of interpretable segments , 40- or 64-slice MDCT performs better than WH-MRCA OBJECTIVES The aim of this study was to compare the diagnostic performance of multidetector computed tomography ( MDCT ) with prospect i ve electrocardiogram ( ECG ) triggering versus retrospective ECG triggering . BACKGROUND MDCT allows the noninvasive visualization of the coronary arteries . However , radiation exposure is a reason for concern . METHODS One hundred eighty consecutive patients scheduled for invasive coronary angiography were enrolled in this study . Twenty patients were excluded due to contraindications to sustain MDCT .  Of the 160 remaining patients , 80 were studied with MDCT with prospect i ve ECG triggering ( Group 1 ) and 80 with a retrospective ECG triggering ( Group 2 ) . The individual radiation dose exposure was estimated . RESULTS In nonstented segments , the evaluability of Groups 1 and 2 was 96 % versus 97 % , respectively ( p = 0.05 ) , the accuracy in segment-based model was 93 % versus 96 % , respectively ( p < 0.05 ) including diagnostic segments and 91 % versus 94 % , respectively ( p < 0.01 ) including all segments , whereas the accuracy in a patient-based model was 98 % in both groups . In stented segments the evaluability in Groups 1 and 2 was 92 % versus 94 % , respectively , and the accuracy was 93 % versus 92 % , respectively , including diagnostic stented segments and 90 % versus 89 % , respectively , including all stented segments . Group 1 presented lower radiation dose compared with Group 2 ( 5.7 + /- 1.5 mSv vs. 20.5 + /- 4.3 mSv , p < 0.01 ) . CONCLUSIONS Prospect i ve ECG-triggering computed tomography allows an accurate detection of coronary stenosis , despite a slight reduction of diagnostic performance , with a low radiation dose Objective : To investigate the performance of low-dose , dual- source computed tomography ( DSCT ) coronary angiography in the step- and -shoot ( SAS ) mode for the diagnosis of significant coronary artery stenoses in comparison with conventional coronary angiography ( CCA ) . Design , setting and patients : Prospect i ve , single-centre study conducted in a referral centre enrolling 120 patients ( 71 men , mean ( SD ) age 68 ( 9 ) years , mean ( SD ) body mass index 26.2 ( 3.2 ) kg/m2 ) . All study participants underwent DSCT in the SAS mode and CCA within 14 days . Twenty-seven patients were given intravenous β blockers for heart rate reduction before CT . Patients were excluded if a target heart rate ⩽70 bpm could not be achieved by β blockers or when the patients were in non-sinus rhythm . Two blinded readers independently evaluated coronary artery segments for assessability and for the presence of significant ( > 50 % ) stenoses . Sensitivity , specificity , negative ( NPV ) and positive predictive values ( PPV ) were determined , with CCA being the st and ard of reference . Radiation dose values were calculated . Results : DSCT coronary angiography in the SAS mode was successfully performed in all 120 patients . Mean ( SD ) heart rate during scanning was 59 ( 6 ) bpm ( range 44–69 ) . 1773/1803 coronary segments ( 98 % ) were depicted with a diagnostic image quality in 109/120 patients ( 91 % ) . The overall patient-based sensitivity , specificity , PPV and NPV for the diagnosis of significant stenoses were 100 % , 93 % , 94 % and 100 % , respectively . The mean ( SD ) effective dose of the CT protocol was 2.5 ( 0.8 ) mSv ( range 1.2–4.4 ) . Conclusions : DSCT coronary angiography in the SAS mode allows , in selected patients with a regular heart rate , the accurate diagnosis of significant coronary stenoses at a low radiation dose OBJECTIVE The purpose of this study was to prospect ively evaluate the effects of mean heart rate and heart rate variability on image quality at coronary 64-MDCT angiography of patients with atrial fibrillation and to determine the efficacy of coronary 64-MDCT angiography in the detection of significant ( > 50 % ) coronary artery stenosis in patients with atrial fibrillation . SUBJECTS AND METHODS Sixty patients ( 37 women , 23 men ; mean age , 58.7 years ) underwent both coronary 64-MDCT angiography and conventional coronary angiography .  Heart rate variability was calculated as the SD from the mean heart rate during scanning . Image quality ( good , moderate , or poor ) and the presence of significant ( > 50 % ) stenosis at coronary CT angiography were evaluated by two radiologists blinded to the results of conventional coronary angiography . The sensitivity , specificity , positive predictive value , and negative predictive value of coronary CT angiography were calculated with conventional angiography as the reference st and ard . Pearson 's correlation analysis and chi-square tests were performed to compare image quality with mean heart rate and heart rate variability in each patient . Differences in detection of coronary artery stenosis between coronary 64-MDCT angiography and conventional coronary angiography were evaluated with McNemar 's test , and agreement between techniques was calculated with kappa statistics . RESULTS The mean heart rate was 90 + /- 13.1 beats/min with variability of 19.35 + /- 6.95 beats/min . Of 803 segments evaluated , 26 ( 3 % ) were considered to have poor image quality . Highly significant correlation was found between mean heart rate and image quality for all segments in each patient ( r = 0.51 , p < 0.001 ) , for the right coronary artery ( r = 0.43 , p = 0.001 ) , and for the distal portion of the coronary arteries ( r = 0.50 , p < 0.001 ) . Heart rate variability also correlated in a highly significant way with image quality in all segments ( r = 0.57 , p < 0.001 ) , the right coronary artery ( r = 0.46 , p < 0.001 ) , and the middle ( r = 0.44 , p = 0.001 ) and distal ( r = 0.41 , p = 0.001 ) portions of the coronary arteries . The best diagnostic image quality was obtained in end systole ( 200 - 400 milliseconds ) . Image quality decreased significantly with a mean heart rate greater than 100 beats/min or with an SD of heart rate greater than 24 beats/min . The overall sensitivity , specificity , positive predictive value , and negative predictive value per segment level were 86.4 % , 
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Furthermore , pooled analysis revealed that each QUADAS item that is not fulfilled has the potential to change estimates of diagnostic accuracy .
Conclusions The method ological quality of studies investigating the diagnostic accuracy of non-invasive coronary CT is only moderate and was found to affect the sensitivity and specificity .
Weak method ological quality will affect the sensitivity and specificity .
• No improvement in method ological quality was observed over time . •