Meta-analysis of 40- and 64-MDCT angiography for assessing coronary artery stenosis

An exemplary reanalysis of coronary computed tomography angiography diagnostic meta-analyses shows insufficient data sharing and incorrect sensitivity and specificity estimates

OBJECTIVES

To systematically evaluate the reproducibility of primary data and, the reproducibility and correctness of pooled sensitivity and specificity estimates reported in a sample of diagnostic meta-analyses.

STUDY DESIGN AND SETTING

We conducted an exemplary systematic review of diagnostic meta-analyses comparing coronary computed tomography angiography to invasive coronary angiography in patients with suspected coronary artery disease. The objectives were to assess 1) the reproducibility of contingency tables, 2) the reproducibility of pooled sensitivity and specificity, and 3) differences to reported results when applying a recommended bivariate binomial model for pooling sensitivity and specificity. Therefore, we reproduced the contingency tables and recalculated sensitivity and specificity by utilizing both the pooling method of each meta-analysis and a bivariate binomial model. We used linear trends to assess the improvement of these objectives over time.

RESULTS

We identified 38 diagnostic meta-analyses, each including on average 19 primary studies (range: 3 to 89 studies; total: 715-including duplicates) with an average of approximately 1800 patients per meta-analysis (range: 118 to 7516 patients). For 31 meta-analyses (82%, 95% CI: 65%, 91%), the contingency tables were reproducible; however, only 15 published them. Using the pooling method of each meta-analysis, we obtained comparable recalculated sensitivities/specificities for 28 meta-analyses (74% [57%, 86%]). Only 11 meta-analyses pooled sensitivity/specificity using a bivariate binomial model (29% [16%, 46%]). When all meta-analyses were pooled with this model, published sensitivities/specificities were confirmed for 19 of 38 meta-analyses (50% [34%, 66%]). There was only marginal improvement in data availability and application of recommended pooling methods over time.

CONCLUSION

Data sharing should become standard practice along with the use of appropriate pooling methods. Journal publication requirements may play a key role in enhancing the quality of scientific reporting and methodological standards which may lead to more reliable and consistent outcomes. The ability to reproduce sensitivity and specificity estimates in diagnostic imaging meta-analyses is dependent on the availability of contingency tables and the explicit reporting of pooling methods and software used.

Diagnostic accuracy of low and high tube voltage coronary CT angiography using an X-ray tube potential-tailored contrast medium injection protocol

OBJECTIVES

To compare the diagnostic accuracy between low-kilovolt peak (kVp) (≤ 100) and high-kVp (> 100) third-generation dual-source coronary CT angiography (CCTA) using a kVp-tailored contrast media injection protocol.

METHODS

One hundred twenty patients (mean age = 62.6 years, BMI = 29.0 kg/m²) who underwent catheter angiography and CCTA with automated kVp selection were separated into two cohorts (each n = 60, mean kVp = 84 and 117). Contrast media dose was tailored to the kVp level: 70 = 40 ml, 80 = 50 ml, 90 = 60 ml, 100 = 70 ml, 110 = 80 ml, and 120 = 90 ml. Contrast-to-noise ratio (CNR) was measured. Two observers evaluated image quality and the presence of significant coronary stenosis (> 50% luminal narrowing).

RESULTS

Diagnostic accuracy (sensitivity/specificity) with ≤ 100 vs. > 100 kVp CCTA was comparable: per patient = 93.9/92.6% vs. 90.9/92.6%, per vessel = 91.5/97.8% vs. 94.0/96.8%, and per segment = 90.0/96.7% vs. 90.7/95.2% (all P > 0.64). CNR was similar (P > 0.18) in the low-kVp vs. high-kVp group (12.0 vs. 11.1), as ws subjective image quality (P = 0.38). Contrast media requirements were reduced by 38.1% in the low- vs. high-kVp cohort (53.6 vs. 86.6 ml, P < 0.001) and radiation dose by 59.6% (4.3 vs. 10.6 mSv, P < 0.001).

CONCLUSIONS

Automated tube voltage selection with a tailored contrast media injection protocol allows CCTA to be performed at ≤ 100 kVp with substantial dose reductions and equivalent diagnostic accuracy for coronary stenosis detection compared to acquisitions at > 100 kVp.

KEY POINTS

• Low-kVp coronary CT angiography (CCTA) enables reduced contrast and radiation dose. • Diagnostic accuracy is comparable between ≤ 100 and > 100 kVp CCTA. • Image quality is similar for low- and high-kVp CCTA. • Low-kVp image acquisition is facilitated by automated tube voltage selection. • Tailoring contrast injection protocols to the automatically selected kVp-level is feasible.

Coronary Computed Tomography Angiography in Combination with Coronary Artery Calcium Scoring for the Preoperative Cardiac Evaluation of Liver Transplant Recipients

Liver transplantation is the best treatment option for early-stage hepatocellular carcinoma, liver cirrhosis, fulminant liver failure, and end-stage liver diseases. Even though advances in surgical techniques and perioperative care have improved postoperative outcomes, perioperative cardiovascular complications are a leading cause of postoperative morbidity and mortality following liver transplantation. Ischemic coronary artery disease (CAD) and cardiomyopathy are the most common cardiovascular diseases and could be negative predictors of postoperative outcomes in liver transplant recipients. Therefore, comprehensive cardiovascular evaluations are required to assess perioperative risks and prevent concomitant cardiovascular complications that would preclude good outcomes in liver transplant recipients. The two major types of cardiac computed tomography are the coronary artery calcium score (CACS) and coronary computed tomography angiography (CCTA). CCTA in combination with the CACS is a validated noninvasive alternative to coronary angiography for diagnosing and grading the severity of CAD. A CACS > 400 is associated with significant CAD and a known important predictor of posttransplant cardiovascular complications in liver transplant recipients. In this review article, we discuss the usefulness, advantages, and disadvantages of CCTA combined with CACS as a noninvasive diagnostic tool for preoperative cardiac evaluation and for maximizing the perioperative outcomes of liver transplant recipients.

Relation Between Erectile Dysfunction and Silent Myocardial Ischemia in Diabetic Patients: A Multidetector Computed Tomographic Coronary Angiographic Study

INTRODUCTION

Erectile dysfunction (ED) can precede coronary artery disease. In addition, silent myocardial ischemia (SMI) is more common in diabetic patients and is a strong predictor of cardiac events and death.

AIM

To evaluate the presence of SMI in patients with diabetes and ED using multidetector computed tomographic coronary angiography (MDCT-CA).

METHODS

This study evaluated patients with diabetes and ED without any history of cardiac symptoms or signs. Erectile function was evaluated with the Sexual Health Inventory for Men score, erection hardness score (EHS), and maximal penile circumferential change by an erectometer. MDCT-CA was used for the detection of coronary artery stenosis.

MAIN OUTCOME MEASURES

Sexual Health Inventory for Men score, EHS, maximal penile circumferential change, and coronary artery stenosis by MDCT-CA.

RESULTS

Of 20 patients (mean age = 61.45 ± 10.7 years), MDCT-CA showed coronary artery stenosis in 13 (65%) in the form of one-vessel disease (n = 6, 30%), two-vessel disease (n = 2, 10%), and three-vessel disease (n = 5, 25%). Fifty percent of patients showed at least 50% vessel lumen obstruction of the left anterior descending coronary artery, which was the most commonly affected vessel (55%). Fifteen percent (3 of 20) of patients had greater than 90% stenosis, and two of them underwent an immediate coronary angioplasty with stenting to prevent myocardial infarction. Maximum coronary artery stenosis was positively correlated with age (P = 0.016, r = 0.529) and negatively correlated with EHS (P = .046, r = -0.449). Multivariate regression analysis using age and EHS showed that age was the only independent predictor of SMI (P = .04).

CONCLUSION

MDCT-CA can be a useful tool to identify SMI in diabetic patients with ED, especially in those of advanced age and/or with severe ED.

Improved image quality at 256-slice coronary CT angiography in patients with a high heart rate and coronary artery disease: comparison with 64-slice CT imaging

BACKGROUND

The 256-slice computed tomography (CT) scanners with wider detector coverage and faster gantry rotation speed are now available. The performance of scanners that feature a rotation speed of 270 ms at coronary CT angiography (CCTA) has not been evaluated in patients with a higher heart rate.

PURPOSE

To evaluate the image quality of 256-slice CT with faster gantry rotation speed in patients undergoing CCTA.

MATERIAL AND METHODS

We enrolled 886 patients; 357(40.3%) underwent study on a 64-slice CT at a rotation speed of 420 ms, the other 529 (59.7%) were examined using a 256-slice CT scanner at 270 ms. Two observers judged the image quality of 2658 imaged coronary arteries on a 4-point scale.

RESULTS

The mean image quality score was significantly higher for the 256 - than the 64-slice CT scans (3.94 ± 0.28 vs. 3.73 ± 0.61; P < 0.01). There was no significant difference in the image quality scores between 64 - and 256-slice scans in patients whose heart rate (HR) was <60 bpm. However, in patients whose HR exceeded 60 bpm these scores were significantly higher for 256-slice CT images (P < 0.01).

CONCLUSION

CCTA performed on the 256-slice CT scanner yielded significantly better image quality in patients with an HR exceeding 60 bpm.

Comparison between MDCT and Grayscale IVUS in a Quantitative Analysis of Coronary Lumen in Segments with or without Atherosclerotic Plaques

Background

The diagnostic accuracy of 64-slice MDCT in comparison with IVUS has been poorly described and is mainly restricted to reports analyzing segments with documented atherosclerotic plaques.

Objectives

We compared 64-slice multidetector computed tomography (MDCT) with gray scale intravascular ultrasound (IVUS) for the evaluation of coronary lumen dimensions in the context of a comprehensive analysis, including segments with absent or mild disease.

Methods

The 64-slice MDCT was performed within 72 h before the IVUS imaging, which was obtained for at least one coronary, regardless of the presence of luminal stenosis at angiography. A total of 21 patients were included, with 70 imaged vessels (total length 114.6 ± 38.3 mm per patient). A coronary plaque was diagnosed in segments with plaque burden > 40%.

Results

At patient, vessel, and segment levels, average lumen area, minimal lumen area, and minimal lumen diameter were highly correlated between IVUS and 64-slice MDCT (p < 0.01). However, 64-slice MDCT tended to underestimate the lumen size with a relatively wide dispersion of the differences. The comparison between 64-slice MDCT and IVUS lumen measurements was not substantially affected by the presence or absence of an underlying plaque. In addition, 64-slice MDCT showed good global accuracy for the detection of IVUS parameters associated with flow-limiting lesions.

Conclusions

In a comprehensive, multi-territory, and whole-artery analysis, the assessment of coronary lumen by 64-slice MDCT compared with coronary IVUS showed a good overall diagnostic ability, regardless of the presence or absence of underlying atherosclerotic plaques.

Is quality and completeness of reporting of systematic reviews and meta-analyses published in high impact radiology journals associated with citation rates?

Purpose

The purpose of this study is to determine whether study quality and completeness of reporting of systematic reviews (SR) and meta-analyses (MA) published in high impact factor (IF) radiology journals is associated with citation rates.

Methods

All SR and MA published in English between Jan 2007–Dec 2011, in radiology journals with an IF >2.75, were identified on Ovid MEDLINE. The Assessing the Methodologic Quality of Systematic Reviews (AMSTAR) checklist for study quality, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist for study completeness, was applied to each SR & MA. Each SR & MA was then searched in Google Scholar to yield a citation rate. Spearman correlation coefficients were used to assess the relationship between AMSTAR and PRISMA results with citation rate. Multivariate analyses were performed to account for the effect of journal IF and journal 5-year IF on correlation with citation rate. Values were reported as medians with interquartile range (IQR) provided.

Results

129 studies from 11 journals were included (50 SR and 79 MA). Median AMSTAR result was 8.0/11 (IQR: 5–9) and median PRISMA result was 23.0/27 (IQR: 21–25). The median citation rate for SR & MA was 0.73 citations/month post-publication (IQR: 0.40–1.17). There was a positive correlation between both AMSTAR and PRISMA results and SR & MA citation rate; ρ=0.323 (P=0.0002) and ρ=0.327 (P=0.0002) respectively. Positive correlation persisted for AMSTAR and PRISMA results after journal IF was partialed out; ρ=0.243 (P=0.006) and ρ=0.256 (P=0.004), and after journal 5-year IF was partialed out; ρ=0.235 (P=0.008) and ρ=0.243 (P=0.006) respectively.

Conclusion

There is a positive correlation between the quality and the completeness of a reported SR or MA with citation rate which persists when adjusted for journal IF and journal 5-year IF.

Automatic detection and quantification of the Agatston coronary artery calcium score on contrast computed tomography angiography

Potentially, Agatston coronary artery calcium (CAC) score could be calculated on contrast computed tomography coronary angiography (CTA). This will make a separate non-contrast CT scan superfluous. This study aims to assess the performance of a novel fully automatic algorithm to detect and quantify the Agatston CAC score in contrast CTA images. From a clinical registry, 20 patients were randomly selected for each CAC category (i.e. 0, 1-99, 100-399, 400-999, ≥1,000). The Agatston CAC score on non-contrast CT was calculated manually, while the novel algorithm was used to automatically detect and quantify Agatston CAC score in contrast CTA images. The resulting Agatston CAC scores were validated against the non-contrast images. A total of 100 patients (60 ± 11 years, 63 men) were included. The median CAC score on non-contrast CT was 145 (IQR 5-760), whereas the contrast CTA CAC score was 170 (IQR 23-594) (P = 0.004). The automatically computed CAC score showed a high correlation (R = 0.949; P < 0.001) and intra-class correlation (R = 0.863; P < 0.001) with non-contrast CT CAC score. Moreover, agreement within CAC categories was good (κ 0.588). Fully automatic detection of Agatston CAC score on contrast CTA is feasible and showed high correlation with non-contrast CT CAC score. This could imply a radiation dose reduction and time saving by omitting the non-contrast scan.

Comparison of stent length reported by the stent's manufacturer to that determined by quantitative coronary angiography at the time of implantation versus that determined by coronary computed tomographic angiography at a later time

The aim of this study was to assess whether coronary computed tomographic angiography (CCTA) would allow accurate length measurements that may help select optimal stent length. In 19 patients who underwent stent implantation and CCTA, the lengths of 30 implanted stents were assessed independently using quantitative coronary angiography (QCA) at the time of implantation and CCTA during follow-up. Measurements on CCTA and QCA were compared with the actual lengths of the implanted stents. The mean actual stent length was 17.3 ± 6.3 mm; the mean length of the stents measured using CCTA was 17.25 ± 5.54 mm, and the mean length of the stents measured using QCA was 15.92 ± 5.86 mm. There was a stronger positive correlation between measurements on CCTA versus actual stent lengths (R = 0.99, p = 0.0001) than between measurements on QCA versus actual stent lengths (R = 0.82, p = 0.0001) (p <0.0001 for the difference between correlation coefficients). In conclusion, the length measurements obtained with CCTA correlate better with an anatomic gold standard (actual stent lengths) than those obtained using QCA.

Imaging strategies for acute chest pain in the emergency department

OBJECTIVE

Echocardiography, radionuclide myocardial perfusion imaging (MPI), and coronary CT angiography (CTA) are the three main imaging techniques used in the emergency department for the diagnosis of acute coronary syndrome (ACS). The purpose of this article is to quantitatively examine existing evidence about the diagnostic performance of these imaging tests in this setting.

CONCLUSION

Our systematic search of the medical literature showed no significant difference between the modalities for the detection of ACS in the emergency department. There was a slight, positive trend favoring coronary CTA. Given the absence of large differences in diagnostic performance, practical aspects such as local practice, expertise, medical facilities, and individual patient characteristics may be more important.

Head-to-head comparison of prospectively triggered vs retrospectively gated coronary computed tomography angiography: Meta-analysis of diagnostic accuracy, image quality, and radiation dose

BACKGROUND

In coronary computed tomography (CT) angiography (CTA) prospective electrocardiography triggering requires less radiation dose than retrospective electrocardiography gating but provides less cardiac phases for interpretation. This meta-analysis presents a concise and comprehensive head-to-head comparison of image quality, diagnostic accuracy, and radiation dose of prospectively triggered coronary CTA vs retrospectively gated CTA in patients with suspected or known coronary artery disease (CAD).

METHODS

In patients with CAD and without tachyarrhythmia, eligible studies (selected from 4 databases) compared prospectively triggered vs retrospectively gated CTA (performed with ≥64-slice CT or dual-source CT) in 2 groups having approximately similar patient characteristics, scored CTA image quality, and/or assessed how accurately CTA diagnoses ≥50% coronary stenoses compared with catheter angiography and reported the radiation dose. The data were meta-analyzed by random-effects models, with CIs provided in the text.

RESULTS

Among 3,330 patients from 20 included studies, 91.3% of CTAs (segments: 97.8%) had diagnostic quality with prospective triggering and 93.3% of CTAs (segments: 98.4%) with retrospective gating (P > .05). Among 664 patients from 5 studies, the pooled sensitivity/specificity of diagnostic CTAs was 98.7%/91.3% (segment level: 91.3%/97.7%) with prospective triggering and 96.9%/95.8% (segment level: 93.1%/97.6%) with retrospective gating (P > .05). The pooled effective dose was 3.5 mSv with prospective triggering and thus, by a factor of 3.5, lower than the pooled effective dose of retrospective gating, which was 12.3 mSv (P < .01).

CONCLUSIONS

In patients with CAD and without tachyarrhythmia, prospectively triggered coronary CTA provides image quality and diagnostic accuracy comparable with retrospectively gated CTA, but at a much lower radiation dose.

Effect of dose reduction on image quality and diagnostic performance in coronary computed tomography angiography

To evaluate the effect of radiation dose reduction on image quality and diagnostic accuracy of coronary computed tomography (CT) angiography. Coronary CT angiography studies of 40 patients with (n = 20) and without (n = 20) significant (≥50 %) stenosis were included (26 male, 14 female, 57 ± 11 years). In addition to the original clinical reconstruction (100 % dose), simulated images were created that correspond to 50, 25 and 12.5 % of the original dose. Image quality and diagnostic performance in identifying significant stenosis were determined. Receiver–operator-characteristics analysis was used to assess diagnostic accuracy at different dose levels. The identification of patients with significant stenosis decreased consistently at doses of 50, 25 and 12.5 of the regular clinical acquisition (100 %). The effect was relatively weak at 50 % dose, and was strong at dose levels of 25 and 12.5 %. At lower doses a steady increase was observed for false negative findings. The number of coronary artery segments that were rated as diagnostic decreased gradually with dose, this was most prominent for smaller segments. The area-under-the-curve (AUC) was 0.90 (p = 0.4) at 50 % dose; accuracy decreased significantly with 25 % (AUC 0.70) and 12.5 % dose (AUC 0.60) (p < 0.0001), with underestimation of patients having significant stenosis. The clinical acquisition protocol for evaluation of coronary artery stenosis with CT angiography represents a good balance between image quality and patient dose. A potential for a modest (<50 %) reduction of tube current might exist. However, more substantial reduction of tube current will reduce diagnostic performance of coronary CT angiography substantially.

Stent sizing by coronary computed tomographic angiography: comparison with conventional coronary angiography in an experienced setting

OBJECTIVES

The goal was to compare stent sizing by coronary computed tomographic angiography (CCTA) with that deployed in an experienced setting based upon conventional coronary angiography (CA).

BACKGROUND

Stent sizing is currently performed by visual estimation, with infrequent guidance by intravascular ultrasound. CCTA permits quantitative determination of stent length (Stent L) and diameter (Stent D).

METHODS

Projected L (CTA-Stent L) and D (CTA-Stent D) were determined from CCTA obtained in 248 patients with 352 lesions undergoing percutaneous coronary intervention within 4 months of the CCTA, and were compared to the Stent-L and Stent-D of the actually deployed stents. The effects of lesion modification and calcified plaque were also evaluated.

RESULTS

There were significant correlations between CTA-Stent L and Stent L (r = 0.656, P < 0.0001) and between CTA-Stent D and Stent D (r = 0.40, P < 0.001). Median predicted CTA-Stent L was slightly longer (20 mm vs. 18 mm, P < 0.0001) and predicted CTA-Stent D was slightly smaller (3.0 mm vs. 3.2 mm, P < 0.0001) than Stent-L and Stent-D, respectively. The differences were unchanged in stents with lesion modification by pre-dilation or intracoronary nitroglycerin. CTA Stent-L and CTA Stent-D increased significantly with increasing calcium (P < 0.0001 and P = 0.019, respectively).

CONCLUSIONS

(1) There are significant correlations between CCTA and CA based stent sizing in an experienced setting. (2) CCTA projects slightly longer and slightly smaller diameter stents than those deployed during PCI irrespective of lesion modification; the small differences are unlikely to have clinical significance. (3) CCTA may offer a noninvasive alternative to intravascular ultrasound for stent planning.

Assessment of Agatston coronary artery calcium score using contrast-enhanced CT coronary angiography

OBJECTIVE

The purpose of this article is to evaluate to what extent Agatston scores may be derived from CT coronary angiography (CTA) examinations, compared with traditional unenhanced CT calcium scores.

MATERIALS AND METHODS

Fifty patients with a CT calcium score-Agatston score of zero and 50 patients with a CT calcium score-Agatston score of 1 or greater whose CT calcium scores had been calculated and who had undergone CTA using volumetric 320-MDCT were included. Agatston scores were obtained at 3.0-mm slices for CT calcium score and CTA. Method agreement, interobserver agreement, and diagnostic performance of CTA for detecting coronary calcium were evaluated.

RESULTS

Of 50 patients with a positive CT calcium score-Agatston score, coronary artery calcium was detected with CTA in 43 patients by observer 1 (mean CTA score, 102 ± 202; mean CT calcium score, 254 ± 501) and in 46 patients by observer 2 (mean CTA score, 94 ± 147; mean CT calcium score, 272 ± 531). Of the 50 patients with a CT calcium score-Agatston score of zero, 49 (98%, observer 1) and 50 (100%, observer 2) had a zero score with CTA as well. An intraclass correlation of 0.78 and 0.62 was found between CT calcium score and CTA (p < 0.01), whereas higher Agatston scores were underestimated with CTA. For observer 1, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for detection of coronary calcium with CTA were 86%, 98%, 98%, 88%, and 92%, respectively, and the corresponding values for observer 2 were 92%, 100%, 100%, 93%, and 96%, respectively. Interobserver agreement was 0.996 for CT calcium score and 0.93 for CTA.

CONCLUSION

Coronary artery calcium can be detected on CTA images with high accuracy. The Agatston calcium score derived from CTA images shows good correlation with unenhanced CT calcium score and is highly reproducible. However, higher Agatston scores are systematically underestimated when derived from CTA images.

Cost-effectiveness of coronary CT angiography in evaluation of patients without symptoms who have positive stress test results

OBJECTIVE

Patients without symptoms who have positive stress test results are often referred for diagnostic catheter angiography in an evaluation for coronary artery disease (CAD). The purpose of this study was to use decision tree analysis to determine the cost-effectiveness and radiation dose that would result from performing coronary CT angiography (CTA) before catheterization.

MATERIALS AND METHODS

A decision tree was constructed to compare the false-negative rates, false-positive rates, costs, and radiation exposure of direct referral of patients for cardiac catheterization with the values associated with performing coronary CTA before catheterization. We assumed that patients referred for coronary CTA proceed to catheterization only when significant disease is identified. Costs for coronary CTA and diagnostic catheterization were obtained from the 2009 physician Medicare fee schedule. Sensitivity, specificity, and radiation dose were obtained by literature review.

RESULTS

Cost reduction with coronary CTA depends on the prevalence of coronary artery disease, but overall costs are reduced as long as the prevalence is less than 85%. At a 50% prevalence of coronary artery disease, performing coronary CTA before cardiac catheterization results in an average cost saving of $789 per patient with a false-negative rate of 2.5% and average additional radiation exposure of 1-2 mSv.

CONCLUSION

Performing coronary CTA before cardiac catheterization is a cost-effective strategy in the care of patients without symptoms who have positive stress test results when the probability that the patient has significant coronary artery disease is less than 50%. The false-negative rate with this strategy compares favorably with the false-negative rate of stress testing. The use of coronary CTA in this role can avoid many unnecessary cardiac catheterization procedures.

Decision analytic model for evaluation of suspected coronary disease with stress testing and coronary CT angiography

RATIONALE AND OBJECTIVES

The aim of this study was to apply a decision analytic model for the evaluation of coronary artery disease (CAD) to define the optimal utilization of coronary computed tomographic angiography (cCTA) and stress testing.

MATERIALS AND METHODS

The model tested in this study assumes that CAD is evaluated with a stress test and/or cCTA and that a patient with positive evaluation results undergoes cardiac catheterization. On the basis of values of sensitivity, specificity, and radiation dose from the published literature and test costs from the Medicare fee schedule, a decision tree model was constructed as a function of disease prevalence.

RESULTS

The false-negative rate is lowest when cCTA is used as an isolated test. The false-positive rate is minimized when cCTA is used in combination with stress echocardiography. Effective radiation is minimized by use of stress electrocardiography or stress echocardiography alone or prior to cCTA. When the pretest probability of CAD is low, a strategy that uses stress echocardiography followed by cCTA minimizes the false-positive rate and effective radiation exposure, with relatively low imaging costs and with a false-negative rate only slightly higher than a strategy including stress myocardial scintigraphy. As the pretest probability of CAD increases above 20%, the false-negative rate of stress echocardiography followed by cCTA increases by >5% relative to cCTA alone.

CONCLUSION

Effective radiation dose and imaging costs for the workup of CAD may be minimized by an appropriate combination of stress testing and cCTA. A strategy that uses stress echocardiography followed by cCTA is most appropriate for the evaluation of low-risk patients with CAD with a pretest probability < 20%, while cCTA alone may be more appropriate in intermediate-risk patients.

Computed tomography of the coronary arteries in diagnosis

IMPORTANCE OF THE FIELD

Cardiac computed tomography (CT) has recently emerged as a non-invasive alternative to catheter angiography for the assessment of coronary artery disease. Rapid technological advances have rendered coronary CT angiography to a robust, accurate and fast imaging modality to assess coronary artery disease in selected patients. The list of further indications in which cardiac CT is an appropriate test remains a topic of discussion.

AREAS COVERED IN THIS REVIEW

This review discusses the main literature available on the use of cardiac CT in the indications considered appropriate in the 2006 Appropriateness Criteria by the American College of Radiology with special emphasis on the temporal trends in the utilization of cardiac CT in clinical practice and in the opinion of the experts, and provides an outlook on how cardiac CT might evolve in the future.

WHAT THE READER WILL GAIN

The reader will gain insight into the strengths and shortcomings of CT of the coronary arteries in coronary artery diagnosis and will learn why cardiac CT is appropriate in some indications but not in others.

TAKE HOME MESSAGE

Recent research in cardiac CT has substantially improved the evaluation of the coronary arteries with CT, and the list of indications cardiac CT is appropriate for might expand further in the coming years.

Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome

Triple-rule-out (TRO) computed tomographic (CT) angiography can provide a cost-effective evaluation of the coronary arteries, aorta, pulmonary arteries, and adjacent intrathoracic structures for the patient with acute chest pain. TRO CT is most appropriate for the patient who is judged to be at low to intermediate risk for acute coronary syndrome (ACS) and whose symptoms may also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. Although a regular cardiac rhythm remains an important factor in coronary CT image quality, newer CT scanners with 64 or more detector rows afford rapid electrocardiographically (ECG) gated imaging to provide high-quality TRO CT studies in patients with a heart rate of up to 80 beats per minute. Injection of iodinated contrast material (< or = 100 mL) is tailored to provide simultaneous high levels of arterial enhancement in the coronary arteries and aorta (> 300 HU) and in the pulmonary arteries (> 200 HU). To limit radiation exposure, the TRO CT examination does not include the entire chest but is constrained to incorporate the aortic arch down through the heart. Scanning parameters, including prospective ECG tube current modulation and prospective ECG gating with the "step-and-shoot" technique, are tailored to reduce radiation exposure (optimally, 5-9 mSv). When performed with appropriate attention to timing and technique, TRO CT provides coronary image quality equal to that of dedicated coronary CT angiography and pulmonary arterial images that are free of motion artifact related to cardiac pulsation. In an appropriately selected emergency department patient population, TRO CT can safely eliminate the need for further diagnostic testing in over 75% of patients.

Comparison of image quality and arterial enhancement with a dedicated coronary CTA protocol versus a triple rule-out coronary CTA protocol

RATIONALE AND OBJECTIVES

To compare the image quality of dedicated coronary computed tomography angiography (cCTA) to that of triple rule-out (TRO) CTA designed to evaluate the coronary arteries, thoracic aorta, and pulmonary arteries.

MATERIALS AND METHODS

Consecutive cCTA examinations performed by a single radiologist over 1 year were reviewed. Biphasic injection protocols were employed: 70 mL of optiray-350 followed by 40 mL of saline injected at 5.5 mL/second for dedicated cCTA; 70 mL of optiray-350 followed by 25 mL of the contrast diluted with 25 mL of saline injected at 5.0 mL/second for TRO-CTA. Two independent cardiovascular radiologists reviewed the coronary vessels in each case and rated diagnostic image quality on a 5 point scale (1, suboptimal; 3, adequate; 5, excellent). Vascular enhancement was measured in the coronary arteries, aorta, and pulmonary arteries.

RESULTS

There was excellent interobserver agreement between the cardiovascular radiologists (kappa = 0.91). Coronary image quality score were similar among 260 dedicated cCTA studies and 168 TRO-CTA studies (mean: 3.8-3.9. P > .18). At least one coronary segment demonstrated suboptimal image quality in 8% of examinations, including 18 dedicated cCTA studies and 16 TRO studies (P = .94). Enhancement was greater in the distal thoracic aorta of TRO patients (336 vs. 311 Hounsfield units; P = .01); no other significant differences in enhancement were identified in the aorta and coronary arteries of dedicated cCTA and TRO studies. Vascular enhancement was adequate for diagnostic evaluation of the pulmonary arteries in all TRO studies.

CONCLUSIONS

A TRO-CTA protocol using 95 mL of contrast can provide comparable coronary image quality and coronary vascular enhancement as compared to dedicated cCTA with 70 mL of contrast.