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- How do you deal with dense calcification on Cardiac CTA?
- Iterative reconstruction
- Soft CT algorithms
- Widened display window (1500/200 HU) - “ We showed for the first time that in calcified segments, widening display window width significantly improved CTA quantification of stenosis compared to invasive coronary angiography.”
Optimizing Image Contrast Display Improves Quantitative Stenosis Measurement in Heavily Calcified Coronary Arterial Segments on Coronary CT Angiography
Shmilovich H et al.
Acad Radiol 2014;21:797-804 - “ In heavily calcified coronary artery segments, widening display window width significantly improved CTA quantification of coronary artery stenosis. Simply increasing window width to 1500 HU was as effective as adjusting window width to the attenuation intensity of individual calcified plaques.”
Optimizing Image Contrast Display Improves Quantitative Stenosis Measurement in Heavily Calcified Coronary Arterial Segments on Coronary CT Angiography
Shmilovich H et al.
Acad Radiol 2014;21:797-804 - “ Iterative model reconstruction (IMR) reduces intravascular noise on cCTA by 86-88% compared to Filtered back projection (FBP), and improves image quality at radiation exposure levels 80% below our standard technique.”
Evaluation of Coronary Artery Image Quality with Knowledge-based Iterative Model Reconstruction
Halpern EJ et al.
Acad Radiol 2014; 21:805-811 - “ Iterative model reconstruction (IMR) provides a substantial reduction in intravascular noise on cCTA by 86-88% compared to FBP performed with same acquisition parameters, allowing better definition of smaller coronary arteries, better discrimination of coronary calcification, better definition of noncalcified plaque, and improved overall diagnostic confidence in the presence or absence of coronary stenosis.”
Evaluation of Coronary Artery Image Quality with Knowledge-based Iterative Model Reconstruction
Halpern EJ et al.
Acad Radiol 2014; 21:805-811
- “ Heart rate frequency and absence of motion artifacts on preceding high-pitch CAC are significant independent predictors of image quality of high pitch coronary CTA.”
Predictors of Image Quality in High Pitch Coronary CT Angiography
Stolzmann P et al.
AJR 2011; 197:851-858 - “ At a HR frequency of - 63 bpm, 91% of high pitch coronary CTA will be of diagnostic image quality. If preceding high-pitch CAC shows no motion artifacts, high-pitch coronary will allow the diagnostic visualization of 96% of the studies regardless of HR frequency or variability.”
Predictors of Image Quality in High Pitch Coronary CT Angiography
Stolzmann P et al.
AJR 2011; 197:851-858 - OBJECTIVE: To evaluate the impact of a multimodality appropriate use criteria decision support tool (AUC-DST) on rates of appropriate testing and clinical decision-making
CONCLUSIONS: A point-of-order AUC-DST enabled rapid determination of test appropriateness for CAD evaluation and was associated with increased and decreased testing for appropriate and inappropriate indications, respectively. These changes in test ordering were associated with greater intended changes in post-test medical therapy.
Impact of an Automated Multimodality Point-of-Order Decision Support Tool on Rates of Appropriate Testing and Clinical Decision Making for Individuals with Suspected Coronary Artery Disease: A Prospective Multicenter Study
Lin FY et al
J Am Coll Cardiol 2013 May 22 pii: S0735-1097(13)01984-0. doi: 10.1016/j.jacc.2013.04.059. [Epub ahead of print] - “100 physicians used the AUC-DST for 472 patients (55.6 ± 9.6 years, 61% male, 52% prior known CAD) over 8 months for MPS (72%), STE (24%) and CCTA (5%). The AUC-DST required an average of 137 ± 360 seconds to determine appropriateness category that, by American College of Cardiology AUC were considered appropriate in 241 (51%), uncertain in 96 (20%), inappropriate in 85 (18%) and not addressed in 50 (11%). For tests ordered in the first 2 months compared to the last 2 months, appropriate tests increased from 49% to 61% (p=0.02), while inappropriate tests decreased from 22% to 6% (p<0.001). During this period, intended changes in medical therapy increased from 11% to 32% (p = 0.001).”
Impact of an Automated Multimodality Point-of-Order Decision Support Tool on Rates of Appropriate Testing and Clinical Decision Making for Individuals with Suspected Coronary Artery Disease: A Prospective Multicenter Study
Lin FY et al
J Am Coll Cardiol 2013 May 22 pii: S0735-1097(13)01984-0. doi: 10.1016/j.jacc.2013.04.059. [Epub ahead of print] - “The American College of Cardiology Appropriate Use Criteria (AUC) were developed to guide use of myocardial perfusion single-photon emission computed tomography (MPS), stress echocardiography, and cardiac computed tomographic angiography (CCTA). To date, cardiologist application of AUC from a patient-based multiprocedure perspective has not been evaluated. A Web-based survey of 15 clinical vignettes spanning a wide spectrum of indications for MPS, STE, and CCTA in coronary artery disease was administered to cardiologists who rated the ordered test as appropriate, inappropriate, or uncertain by AUC application and suggested a preferred alternative imaging procedure, if any. In total 129 cardiologists responded to the survey (mean age 49.5 years, board certification for MPS 65%, echocardiography 39%, CCTA 32%).”
Cardiologist concordance with the American College of Cardiology appropriate use criteria for cardiac testing in patients with coronary artery disease
Lin FY
Am J Cardiol 2012 Aug1;110(3):337-44 - “ Cardiologists agreed with published AUC ratings 65% of the time, with differences in all categories (appropriate, 50% vs 53%; inappropriate, 42% vs 20%; uncertain, 9% vs 27%, p <0.0001 for all comparisons). Physician age, practice type, or board certification in MPS or echocardiography had no effect on concordance with AUC ratings, with slightly higher agreement for those board certified in CCTA (68% vs 64%, p = 0.04). Cardiologist procedure preference was positively associated with active clinical interpretation of MPS and CCTA (p = 0.03 for the 2 comparisons) but not for ownership of the respective imaging equipment. In conclusion, cardiologist agreement with published AUC ratings is generally high, although physicians classify more uncertain indications as inappropriate. Active clinical interpretation of a procedure contributes most to increased procedure preference.”
Cardiologist concordance with the American College of Cardiology appropriate use criteria for cardiac testing in patients with coronary artery disease
Lin FY
Am J Cardiol 2012 Aug1;110(3):337-44
"Among 6920 patients, 1642 (23.7%) had one or more extracardiac findings for a total of 1,901 findings in the broad viewing scheme. Of the 6.920 patients, 16.2% had a finding necessitating therapy, workup or followup."
Extracardiac Findings on Coronary CT Angiograms: Limited Versus Complete Image Review
Johnson KM et al.
AJR 2010; 195:143-148"Almost one fourth of all patients who underwent diagnostic coronary CT angiography in this study had extracardiac findings. Several serious diagnoses were missed with the limited viewing approach, but use of the broad viewing approach led to more workup and follow-up imaging."
Extracardiac Findings on Coronary CT Angiograms: Limited Versus Complete Image Review
Johnson KM et al.
AJR 2010; 195:143-148- Large field of view vs Small field of view
- Large field of view was 35-40 cm and review was of soft tissue and lung windows
- Small field of view was 25 cm to include the heart and was reviewed at soft tissue windows only "Increasing body mass index ad the presence of breathing artifact were associated with poorer image quality whereas sex, CAC score, and heart rate variability were not. Compared with examinations of white patients, studies of black patient had significantly poorer image quality."
Patient Characteristics as Predictors of Image Quality and Diagnostic Accuracy of MDCT Compared with Conventional Coronary Angiography for Detecting Coronary Artery Stenoses:CORE-64 Multicenter International Trial
Dewey M et al
AJR 2010; 194:93-102- Modulation Selection for Cardiac CTA
- Heart rate under 60 BPM use 60-70% of RR interval
- Heart rate of 60-70 BPM use 50-80% of RR interval
- Heart rate greater than 70 BPM use 30-80% of RR interval "Effective dose from coronary CT angiography by using volume scanning with an optimized exposure time of 5.8 mSv at 120 kVp and 4.4 mSv at 100 kVp, using International Commission on Radiological Protection (ICRP) publication 103 tissue-weighting factors."
Radiation Dose from Single-Heartbeat Coronary CT Angiography Performed with 320-Detector Row Volume Scanner
Einstein AJ et al.
Radiology 2010;254:698-706"Volume scanning markedly decreases coronary CT angiography radiation doses compared with those at helical scanning. When conversion coefficients are used to estimate effective dose from DLP, they should be appropriate for the scanner and scan mode used and reflect current tissue weighting factors."
Radiation Dose from Single-Heartbeat Coronary CT Angiography Performed with 320-Detector Row Volume Scanner
Einstein AJ et al.
Radiology 2010;254:698-706"These features allow the reader to visualize a longer segment of a vessels course and tend to reduce percieved image noise. However, there is a loss of lesion information within the slab volume, as the MIP does not provide in-depth information or attenuation detail within the slice. Consequently MIP should not be the sole technique used for interpretation."
SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography
Raff GL et al.
J Cardiovasc Comput Tomogr 2009 March-April; 3(2):122-136"MIP is similar to MPR that orthogonal or oblique planes can be reviewed interactively. They differ in that generally, MIP is created by thicker sections, chosen to incorporate a volume that includes the entire vessel lumen and wall diameter (commonly 5 mm as an initial thickness for coronary interpretation) and that each pixel is represented by the maximum pixel value within the slab volume."
SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography
Raff GL et al.
J Cardiovasc Comput Tomogr 2009 March-April; 3(2):122-136"In summary, the committee believes it is critical to generate comprehensive reports for cardiac CT. The report should always contain adequate information to support clinical necessity of the procedure, sufficient technical details to allow reproduction of the study, and sufficient description of the clinical scan findings to allow clear understanding of the implications of the report."
SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography
Raff GL et al.
J Cardiovasc Comput Tomogr 2009 March-April; 3(2):122-136- Cardio Obese DSCT Mode
- 120 kV for each tube
- 425 mAs/rotation
- Full current between 40% and 70% of the R-R interval
- Gantry rotation of 0.33 sec and pitch of 0.2-0.43 "CCTA with DSCT using a modified scan protocol and adjustable temporal reconstructions provide diagnostic image quality in >90% of morbidly obese patients."
Improved noninvasive coronary angiography in morbidly obese patients with dual-source computed tomography
Chinnaiyan KM et al
J Cardiovasc Comout Tomogr (2009) 3, 35-42- CCTA Scanning Techniques
- Retrospective gating
- Retrospective gating with ECG modulation
- Prospective gating "When compared with the 2006 Appropriateness Criteria, opinion regarding clinical use of CCT has experienced a significant shift toward appropriateness across most indications, similarly judged among international cardiology and radiology experts in the field."
International,multidisciplinary update of the 2006 Appropriateness Criteria for Cardiac Computed Tomography
Carbonaro S et al.
J Cardiovasc Comput Tomogr (2009) 3, 224-232"Until more conclusive data are available, the decision to proceed with coronary CTA in the presence of a high coronary calcium score should be left to the discretion of the referring and attending physician."
SCCT Guidelines for Performance of Coronary Computed Tomographic Angiography: A Report of the Society of Cardiovascular Computed Tomography Guidelines Committee
Abbara S et al.
J Cardiovas Comput Tomgr (2009) 3, 190-204- CCTA requires vessel opacification of over 250 HU
- Injection rates should be 4-7 cc/se
- Contrast warming critical to reduce viscosity
- Higher concentrations of contrast should be used
- Test bolus vs bolus tracking is a site choice
- Nitroglycerin: Contraindications
- Recent use of ED medication
- Hypovolemia
- Raised intracranial pressure
- Cardiac tamponade
- Constrictive pericarditis
- Severe aortic stenosis
- Severe systolic hypotension
- CCTA: Pretest Instructions
- No food for 3 hours prior to the study
- Drink lots of fluids pre-study
- No caffeine products for 12 hours before the study
- Take all regular medications the day of the study
- If patients on Metformin discontinue use for 48 hours after the CT "Therefore, this publication aims to establish a consensus of the minimally required standards for appropriate coronary CT angiography acquisition and data processing and to provide recommendations for methods to optimize scan results, maximize image quality, and avoid unnecessarily high radiation exposure."
SCCT Guidelines for Performance of Coronary Computed Tomographic Angiography: A Report of the Society of Cardiovascular Computed Tomography Guidelines Committee
Abbara S et al.
J Cardiovas Comput Tomgr (2009) 3, 190-204"Literature and survey results suggest a consensus for the use of IV contrast volumes <100 mL, infusion rate of 5 mL/s and a saline chaser. A range of concentrations can be used to attain target coronary artery attenuation values."
IV Contrast Infusion for Coronary Artery CT Angiography: Literature Review and Results of a Nationwide Survey
Johnson PT, Pannu HK, Fishman EK
AJR 2009; 192:130"The superb resolution and the isotrophic image data acquisition of ECG-gated coronary CT Angiography (CTA) enable evaluation of the coronary arteries and cardiac anatomy in any selected plane ."
Anatomy and Terminology for the Interpretation and Reporting of Cardiac MDCT:Part 2, CT Angiography, Cardiac Function Assessment, and Noncoronary and Extracardiac Findings
Sundaram B, Kazerooni EA et al
AJR 2009;192:574-583"Structured cardiac CT reporting is important to effectively communicate with referring clinicians. Knowledge of cardiac CT technique, cardiac anatomy, and standard anatomic and physiologic terminology can assist the reader in creating a consistent and comprehensive cardiac CT report."
Anatomy and Terminology for the Interpretation and Reporting of Cardiac MDCT:Part 1, Structured Report, Coronary Calcium Screening, and Coronary Artery Anatomy
Sundaram B, Kazerooni EA et al
AJR 2009;192:574-583"Evaluation of proximal segments showed the best outcome for the left main segment (sensitivity of 100% and specificity of 99.1%) and the worst outcome for middle segment of the right coronary artery (sensitivity of 81.3% and specificity of 95.1%) ."
Meta-Analysis of 40 and 64-MDCT Angiography for Assessing Coronary Artery StenosisMeijer AB et al.AJR 2008; 191:1667-1675"Forty and 64-MDCT provide good to excellent performance in detecting or ruling out significant coronary artery stenosis, with better results for proximal than for distal coronary artery segments."
Meta-Analysis of 40 and 64-MDCT Angiography for Assessing Coronary Artery StenosisMeijer AB et al.AJR 2008; 191:1667-1675- Selection of Optimal Phase of RR Interval for Data Analysis
- predefined phase (75% of RR interval)
- manual selection by user (technologist usually)
- automated selection by the scanner software
"The automated phase selection method accurately detects the optimal diagnostic phase for CT coronary artery evaluation and has the potential to reduce operator time needed for image reconstruction."
Automated Cardiac Phase Selection with 64-MDCT Coronary AngiographyJoemai RMS et al.AJR 2008; 191:1690-1697- "To achieve a consistent contrast enhancement in cardiac CT Angiography (CTA), contrast medium dose should be adjusted with the body weight or the BSA (which accounts for both the body weight and height factors) to provide adjustment of iodine dose over a wide range of body scans."
Contrast Enhancement in Cardiovascular MDCT: Effect of Body Weight, height, Body Surface Area, Body Mass Index, and Obesity
Bae KT et al.
AJR 2008; 190:777-784
- "Using dual-source CT, the overall optimal reconstruction window is at 75% of the R-R interval in patients with low or intermediate heart rates. In patients with heart rates > 80 bpm, systolic reconstruction often yield superior image quality compared with diastolic reconstruction."
Optimal Systolic and Diastolic Reconstruction Windows for Coronary CT Angiography Using Dual Source CT
Seifarth H et al
AJR 2007; 189:1317-1323
- Bolus tracking for Cardiac CTA on 64 MDCT
- Use a threshold of 100 HU on the ascending aorta
- Whe reached wait 5 secons and then scan
- Bolus tracking for Cardiac CTA on 64 MDCT
"Sensitivity and specificity of CTCA are not influenced by the prevalence of CAD, whereas the negative predictive value is lower and the positive predictive value tends to be higher in patients with a high prevalence of CAD."
Comparison of Diagnostic Accuracy of 64-Slice Computed Tomography Coronary Angiography in patients with Low, Intermediate and High Cardiovascular Disease
Husman L et al.
Acad Radiol 2008; 15:452-461
- "The coronary artery calcium (CAC) score above which it is recommended that coronary computerized tomographic angiography (CTA) not be performed has been steadily increasing. Currently, calcium scores > 1000 are thought to prohibit CTA accurate interpretation. However, a reasoned approach suggests that there is no absolute upper limit that applies to all patients and imaging centers." How much calcium is too much calcium for coronary computerized tomographic angiography?
Hecht HS, Bhatti T
J Cardiovasc Comput Tomogr (2008) 2, 183-187
- "A CAC score of >1000 or a pattern of isolated large, dense calcifications with CAC < 1000 should alert personnel to potential interpretation problems and should not be followed by CTA if the interpreting physician does not have extensive experience in dealing with these issues.
How much calcium is too much calcium for coronary computerized tomographic angiography?
Hecht HS, Bhatti T
J Cardiovasc Comput Tomogr (2008) 2, 183-187
- Should the entire CT scan in a Cardiac CTA be reviewed in full field reconstruction?
- "Viewing of cardiac CT scans obtained only at a limited field of view can result in missing more than 67% of nodules greater than 1 cm. and more than 80% of nodules smaller than 1 cm.
Pulmonary Nodules Detected at Cardiac CT: Comparison of Images in Limited and Full Fields of View
Northam M et al.
AJR 2008; 191;878-881
- "The issue of incidental findings in medical imaging will always be with us. Budoff et al. reminded us of the cost of pursuing unrequested information. Northam et al. found potential benefit. We may debate whether to perform an imaging examination. Once an examination is performed, the noblest approach is to view and evaluate all available data, to apply appropriate judgment, and to proceed in the best interest of the patient and society."
- "The issue of incidental findings in medical imaging will always be with us. Budoff et al. reminded us of the cost of pursuing unrequested information. Northam et al. found potential benefit. We may debate whether to perform an imaging examination. Once an examination is performed, the noblest approach is to view and evaluate all available data, to apply appropriate judgment, and to proceed in the best interest of the patient and society."
Incidental Findings on Cardiac CT
Colletti PM
AJR 2008; 191:882-884
- "Once an examination is performed, the noblest approach is to view and evaluate all available data, to apply appropriate judgment, and to proceed in the best interest of the patient and society."
Incidental Findings on Cardiac CT
Colletti PM
AJR 2008; 191:882-884
- "In summary, while thick MIP images are visually appealing and can be used for rapid interpretation algorithms in the emergency setting, they must be used prudently. When the MIP thickness is increased, multiple structures are projected onto the same plane. Distinguishing details between these structures can be lost when the thickness is too large, and , thus, the user must have full understanding of the anatomic detail before MIP images can be safely rendered."
Utilization of thick (>3mm) maximum intensity projection images in coronary CTA interpretation
Rybicki FJ et al.
Emerg Radiol (2006) 13:157-159
- "In summary, while thick MIP images are visually appealing and can be used for rapid interpretation algorithms in the emergency setting, they must be used prudently."
Utilization of thick (>3mm) maximum intensity projection images in coronary CTA interpretation
Rybicki FJ et al.
Emerg Radiol (2006) 13:157-159
- "When the MIP thickness is increased, multiple structures are projected onto the same plane. Distinguishing details between these structures can be lost when the thickness is too large, and , thus, the user must have full understanding of the anatomic detail before MIP images can be safely rendered."
Utilization of thick (>3mm) maximum intensity projection images in coronary CTA interpretation
Rybicki FJ et al.
Emerg Radiol (2006) 13:157-159
- "Breath-holding during cardiac CT scan acquisition significantly lowers the mean heart rate by approximately 4 bpm, but heart rate variability is the same or less compared with normal breathing."
Analysis of Heart Rate and Heart Rate Variation During Cardiac CT Examinations
Zhang J et al.
Acad Radiol 2008;15:40-48
- "The main artifacts that hamper MDCT coronary angiography image interpretation are motion artifacts that cause blurring and incorrect diagnosis due to coronary artery calcifications."
Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJM et al.
AJR 2007; 189:581-591
- Artifacts in Cardiac CTA
- Blooming artifacts
- Blurring artifacts
- Streak artifacts
- Subtle discontinuities and missing data
- Stairstep artifacts
- Windmill artifacts
- Poor contrast in lumen of coronary artery
- Incomplete coverage
- Artifacts in Cardiac CTA
"Artifacts may be grouped in technical (physics based, scanner based, and reconstruction based), operator and patient related causes."
Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJM et al.
AJR 2007; 189:581-591
- Artifacts in Cardiac CTA
"In MDCT coronary angiography, the use of nitroglycerin has been found to increase proximal coronary artery diameters by 12-21%. However, the added value on diagnostic accuracy is not clear yet.."
Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJM et al.
AJR 2007; 189:581-591
- CT Noise (quantum mottle) is improved by (its reduced)
- Increasing kVp, mA, or scanning time
- Increasing voxel size
- Increasing reconstructed field of view
- Increasing slice thickness
- Image stacking
- Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJM et al.
AJR 2007; 189:581-591
- "Despite the fact that coronary artery MDCT is a new procedure, the concensus for many key parameters suggest that the basics of the study are becoming well defined."
64-MDCT Angiography of the Coronary Arteries: Nationwide Survey of Patient Preparation Practice
Johnson PT, Eng J, Pannu HK, Fishman EK
AJR 2008; 190:743-747
- "Despite the fact that coronary artery MDCT is a new procedure, the concensus for many key parameters suggest that the basics of the study are becoming well defined.These findings should facilitate implementation by new sites beginning this practice because they can build on the experience of others."
64-MDCT Angiography of the Coronary Arteries: Nationwide Survey of Patient Preparation Practice
Johnson PT, Eng J, Pannu HK, Fishman EK
AJR 2008; 190:743-747
- "An injection rate of 4-5 ml/sec as a saline solution chase is optimal for achieving maximum attenuation values of the aorta or coronary arteries by using 64-section CT with 60 mL contrast material."
Saline Flush Effect for Enhancement of Aorta and Coronary Arteries at Multidetector CT Coronary Angiography
Kim DJ et al
Radiology 2008; 246:110-115
- "The degree of contrast enhancement was affected by the injection rate of saline solution, and the attenuation values were higher as the injection rate increased up to 4-5 ml/sec. The values plateaued at rates over 5 ml/sec in the aorta and over 4 ml/sec in the coronary arteries."
Saline Flush Effect for Enhancement of Aorta and Coronary Arteries at Multidetector CT Coronary Angiography
Kim DJ et al
Radiology 2008; 246:110-115
- "In MDCT coronary angiography, image artifacts are the major cause of false-positive and false-negative interpretations regarding the presence of coronary artery stenoses. Hence, it is important that observors reporting these investigations are aware of the potential presence of image artifacts and that these artifacts are recognized."
Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJ et al
AJR 2007; 189:581-591
- "In MDCT coronary angiography, image artifacts are the major cause of false-positive and false-negative interpretations regarding the presence of coronary artery stenoses."
Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJ et al
AJR 2007; 189:581-591
- "Preliminary studies are showing that enlarging the field for CTA scans to look for incidental findings will suffer the same fate as body scanning and chest x-rays, as another form of screening that cannot be medicolegally justified because of severely high false positive rates and no improvement in outcomes. Until data are available to the opposite, we should use our good judgment and restraint and not perform large-field reconstructions for the explicit purpose of screening."
- "Preliminary studies are showing that enlarging the field for CTA scans to look for incidental findings will suffer the same fate as body scanning and chest x-rays, as another form of screening that cannot be medicolegally justified because of severely high false positive rates and no improvement in outcomes."
Incidental Findings on Cardiac Computed Tomography. Should We Look?
Budoff MJ, Gopal A
J Cardiovascular Comput Tomogr (2007) 1: 97-105
- "Until data are available to the opposite, we should use our good judgment and restraint and not perform large-field reconstructions for the explicit purpose of screening."
Incidental Findings on Cardiac Computed Tomography. Should We Look?
Budoff MJ, Gopal A
J Cardiovascular Comput Tomogr (2007) 1: 97-105
- "With the newer generations of multidetector CT scanners, the diagnostic performance for the assessment of coronary artery disease has significantly improved, and the proportion of nonassessable segments has decreased."
Diagnostic Performance of Multidetector CT Angiography for Assessment of Coronary Artery Disease: Meta-analysis
Vanhoenacker PK et al
Radiology 2007; 244:419-428