CT of coronary artery disease

Effectiveness of dual-source CT coronary angiography for the evaluation of coronary artery disease in patients with atrial fibrillation: initial experience

PURPOSE

To prospectively evaluate the sensitivity and specificity of dual-source CT for significant coronary stenosis (>50% narrowing) in patients with atrial fibrillation (AF), by using conventional coronary angiography as the reference standard.

MATERIALS AND METHODS

Institutional Review Board approval and informed consent were obtained. Fifteen consecutive patients (nine men, six women; mean age, 58.47 years) were examined. Image quality (good, moderate, or poor) and significant stenosis (>50%) were evaluated by two radiologists blinded to the conventional coronary angiography results. Sensitivity, specificity, positive predictive value (PPV), and negative predictive values (NPV) were calculated. McNemar test was used to search for any significant difference between dual-source CT and conventional coronary angiography in helping detect coronary stenosis. kappa statistics were calculated for intermodality and interobserver agreement.

RESULTS

Sixteen segments by reader 1 and 13 segments by reader 2 were considered as poor image quality and rejected for further analysis. All segments with good image quality were correctly diagnosed. The respective overall sensitivity, specificity, PPV, and NPV values were 87%, 98%, 77%, and 99% for reader 1 and 80%, 99%, 80%, and 99% for reader 2. No significant difference between dual-source CT and conventional coronary angiography was found in helping detect significant stenosis. kappa statistics demonstrated good intermodality and excellent interobserver agreement.

CONCLUSION

Dual-source CT technology provides a temporal resolution that allows CT coronary angiography at higher heart rates and even with AF.

Three-dimensional isotropic wavelets for post-acquisitional extraction of latent images of atherosclerotic plaque components from micro-computed tomography of human coronary arteries

RATIONALE AND OBJECTIVES

The capability of wavelet transforms to separate signals into frequency bands is the basis for its use in image compression and storage, data management and transmission, and, recently, extraction of latent images of tissue components from noisy medical images. Analysis of temporal variations of radiofrequency backscatter of intravascular ultrasound with one-dimensional wavelets can detect lipid-laden plaque in coronary arteries with a sensitivity and specificity of >80%. In this study we evaluate the capability of a novel, 3-dimensional isotropic wavelet analysis to perform high resolution, non-directionally biased, statistically reliable, non-invasive discrimination between components of human coronary atherosclerotic plaques in micro-CT.

MATERIALS AND METHODS

Coronary artery segments (5-15 mm) were excised at necropsy from 18 individuals with advanced coronary atherosclerosis. Specimens were imaged using a GE Locus SP ex vivo micro-CT scanner and processed for histological correlation (833 sections). The isotropic wavelet constructs were applied to the entire volume of CT data of each arterial segment to distinguish tissue textures of varying scales and intensities. Voxels were classified and plaque characterization achieved by comparing the relative magnitudes of these wavelet constituents to that of several reference plaque tissue components.

RESULTS

Processing of micro-CT images via these isotropic wavelet algorithms permitted 3-D, color-coded, high resolution, digital discrimination between lumen, calcific deposits, lipid-rich deposits, and fibromuscular tissue providing detail not possible with conventional thresholding based on Hounsfield intensity units. Using the isotropic wavelets (with histology as the gold standard), lipid-rich pools approaching the size of the filter for the isotropic wavelet algorithm (0.25 mm [250 microns] in length) were identified with 81% sensitivity and 86% specificity. Calcific deposits, fibromuscular tissue, and lumen equal to or larger than the wavelet filter size were detected without error (100% sensitivity and specificity).

CONCLUSION

Isotropic wavelet analysis permits high resolution, multi-dimensional identification of coronary atherosclerotic plaque components in micro-CT with sensitivity and specificity similar to that achieved with data obtained invasively (from IVUS in vivo) using one-dimensional wavelets. Further studies are necessary to test the applicability of this technology to clinical, multi-detector scanners.

Cardiac CT of the transplanted heart: indications, technique, appearance, and complications

Effective antirejection therapy and infection control have significantly improved the long-term survival of heart transplant recipients, but coronary allograft vasculopathy remains an important limiting factor. Most heart transplant recipients undergo annual coronary angiography for the detection of allograft vasculopathy, which is often clinically silent. Angiography allows detection of vasculopathy only indirectly, with depiction of the lumen, and does not depict the wall thickening and intimal hyperplasia that typify this disease; the procedure also is invasive and is associated with a 1%-2% risk of complication. In contrast, electrocardiographically gated multidetector computed tomography (CT) can provide a comprehensive and noninvasive evaluation of the transplanted heart in a single study. Cardiac CT enables evaluation of the coronary artery lumen and wall and thus may be used for screening, diagnosis, grading, and follow-up of coronary allograft vasculopathy. It also may be used to detect other posttransplantation complications, such as malignancy and infection, and to assess cardiac and vascular anastomoses and cardiac function. However, special strategies may be needed to reduce the transplant heart rate so as to obtain images of diagnostic quality.

Prognostic value of multidetector coronary computed tomographic angiography for prediction of all-cause mortality

OBJECTIVES

The purpose of this study was to examine the association of all-cause death with the coronary computed tomographic angiography (CCTA)-defined extent and severity of coronary artery disease (CAD).

BACKGROUND

The prognostic value of identifying CAD by CCTA remains undefined.

METHODS

We examined a single-center consecutive cohort of 1,127 patients > or =45 years old with chest symptoms. Stenosis by CCTA was scored as minimal (<30%), mild (30% to 49%), moderate (50% to 69%), or severe (> or =70%) for each coronary artery. Plaque was assessed in 3 ways: 1) moderate or obstructive plaque; 2) CCTA score modified from Duke coronary artery score; and 3) simple clinical scores grading plaque extent and distribution. A 15.3 +/- 3.9-month follow-up of all-cause death was assessed using Cox proportional hazards models adjusted for pretest CAD likelihood and risk factors. Deaths were verified by the Social Security Death Index.

RESULTS

The CCTA predictors of death included proximal left anterior descending artery stenosis and number of vessels with > or =50% and > or =70% stenosis (all p < 0.0001). A modified Duke CAD index, an angiographic score integrating proximal CAD, plaque extent, and left main (LM) disease, improved risk stratification (p < 0.0001). Patients with <50% stenosis had the highest survival at 99.7%. Survival worsened with higher-risk Duke scores, ranging from 96% survival for 1 stenosis > or =70% or 2 stenoses > or =50% (p = 0.013) to 85% survival for > or =50% LM artery stenosis (p < 0.0001). Clinical scores measuring plaque burden and distribution predicted 5% to 6% higher absolute death rate (6.6% vs. 1.6% and 8.4% vs. 2.5%; p = 0.05 for both).

CONCLUSIONS

In patients with chest pain, CCTA identifies increased risk for all-cause death. Importantly, a negative CCTA portends an extremely low risk for death.

ACR clinical statement on noninvasive cardiac imaging

Coronary artery disease and other acquired and congenital cardiac diseases are major medical and socio-economic problems. Historically, imaging has had a critical role in the diagnosis and evaluation of acquired and congenital cardiac disease. Advances in computed tomography (CT), with multidetector CT and electron beam CT technology, and magnetic resonance (MR) imaging, now make it possible to noninvasively image the coronary arteries, cardiac chambers, valves, myocardium, and pericardium and assess cardiac function, and CT and MR imaging are becoming increasingly important in the evaluation of cardiac disease. Radiologists, because of their extensive experience in CT and MR imaging, have an important role in imaging cardiac patients using these modalities. This clinical statement of the ACR discusses various technical and patient safety issues related to cardiac CT and MR imaging, and it suggests appropriate qualifications for radiologists until such time as ACR practice guidelines for the performance of cardiac CT and cardiac MR imaging are written and approved through the usual ACR process. It stresses that the interpreting physician is responsible for examining not only the cardiac structures of interest but also all the visualized noncardiac structures and must report any clinically relevant abnormalities of these adjacent structures.

ACR practice guideline for the performance and interpretation of cardiac computed tomography (CT)

Cardiac computed tomography (CT) is an evolving modality that includes a variety of examinations to assess the anatomy and pathology of the cardiac chambers, valves, myocardium, coronary arteries and veins, pericardium, aortic root, and central great vessels. The development of multidetector CT scanners with increasing numbers of detector rows, narrow section thicknesses, increasing scanner speeds, the ability for electrocardiographic gating, and radiation dose modulation allows the performance of CT coronary arteriography. Computed tomography coronary arteriography enables the assessment of multiple types of cardiac pathology, including intraluminal coronary arterial plaque formation, coronary artery stenosis, congenital anomalies, coronary artery aneurysms, sequelae of cardiac ischemia, and the assessment of prior vascular interventions, while providing information about cardiac and valvular function. Noncardiac structures included in cardiac CT examinations must also be evaluated. This guideline attempts to maximize the probability of detecting cardiac abnormalities with cardiac CT. American College of Radiology requirements for physicians and personnel performing examinations are also addressed and will become applicable by July 1, 2008.

Coronary CT Angiography

Owing to ongoing technical refinements and intense scientific and clinical evaluations, computed tomography (CT) of the heart has left the research realm and matured into a clinical application that is about to fulfill its promise to replace invasive cardiac catheterization in selected patient populations. CT coronary angiography is technically more challenging than other CT applications owing to the nature of its target, the continuously moving heart. Rapid technical developments in this field require constant adaptation of acquisition protocols. These challenges, however, are in no way insurmountable for users with knowledge of the general CT technique. The intent of this communication is to provide those interested in and involved with coronary CT angiography with a step-by-step "manual" describing the authors' approach to performing coronary CT angiography. Included are considerations regarding appropriate patient selection, patient medication, radiation protection, contrast enhancement, acquisition and reconstruction parameters, image display and analysis techniques, and the radiology report. The recommendations are based on the authors' experience, which spans the evolution of multi-detector row CT for cardiac applications, from its beginning to the advent of the most current generations of 64-section and dual-source CT technologies, which they believe herald the entrance of this examination into routine clinical practice.

A comparative study of thoracic radiation doses from 64-slice cardiac CT

The goal of this study was to measure radiation doses for 64-slice cardiac CT angiography studies and to study the dose-savings features of these CT scanners. This was done using various phantoms. These radiation doses were compared with those from typical helical body CT scans, fluoroscopy cardiac catheterization studies and mammography examinations. Radiation measurements were made with a CT ionization detector and a solid state dosimeter. A GE 64-slice Lightspeed VCT and a Siemens Somatom Sensation 64 CT were used to scan a standard 32 cm acrylic phantom and an anthropomorphic phantom. Data were collected in axial and various gated cardiac helical modes. Organ doses and the effective doses were calculated from the measurements. In gated CT cardiac mode with the 32 cm acrylic phantom, the measured radiation doses per study were generally three to seven times greater than those from typical body helical CT examinations; the range depended upon selectable scan parameters. With the anatomical phantom, the surface doses in the anteroposterior (AP) plane were typically 20-60% higher than those measured using the 32 cm phantom. The lateral surface doses were -4% to +15%. These results can be attributed to the shorter AP dimension and the air in the lungs. The CT skin entrance radiation doses were 80-90% less than diagnostic cardiac catheterization studies, and organ doses were similar. Because 64-slice cardiac gated CT uses pitches equal to 0.20-0.27 and high mAs values, the patient radiation doses are appreciably higher than in routine body CT examinations. The female breast, which could receive a radiation dose 10-30 times that received from mammography screening, is an organ of particular concern.

Midterm follow-up of patients receiving radial artery as coronary artery bypass grafts using 16-detector-row CT coronary angiography

PURPOSE

The study was undertaken to evaluate the 3-year outcome of patients undergoing coronary artery bypass grafting (CABG) involving the use of the radial artery (RA) in comparison with the left internal mammary artery (LIMA) and saphenous vein (SV) grafts by using 16-slice multidetector computed tomography (MDCT).

MATERIALS AND METHODS

Fifty-one patients underwent electrocardiogram (ECG)-gated 16-MDCT 32+/-4 months after surgery. A total of 50 LIMA grafts, 55 SV grafts and 51 RA grafts were studied. Approximately 68.6% or RAs were free, 21.5% sequential and 9.8% composite. Grade 0 was defined as complete patency, grade 1 as focal stenosis (>70%) and grade 2 as graft occlusion. The Fisher exact test was used to analyse variables (p<0.05 significant). Concordance between readers for the detection of patency was calculated by the kappa-value.

RESULTS

LIMA had the best patency rate (94.0%), followed by SV (83.6%) and RA (74.5%). Regarding RA, the patency rate by territory was 79.4% in the left circumflex coronary artery (LCX), 72.7% in the left anterior descending (LAD) and 50% in the right coronary artery (RCA); the occlusion rate was 20.0% among free grafts, 18.2% among sequential grafts and 20.0% among composite grafts. The kappa-value was 0.86.

CONCLUSIONS

Sixteen-slice MDCT scanners enable accurate analysis of CABG status and are a useful noninvasive diagnostic tool for midterm clinical follow-up of patients who have undergone CABG involving the use of RA.

Detection of significant coronary artery stenosis with 64-section MDCT angiography

PURPOSE

To prospectively evaluate the diagnostic performance of 64-section multidetector computed tomography (MDCT) to detect significant coronary artery stenosis using conventional coronary angiography (CCA) as the reference standard.

MATERIALS AND METHODS

Institutional Review Board approval and informed consent were obtained. In this prospective study, 80 patients (61 male, 19 female, mean age 56) were examined. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated. McNemar test was used to search for the significant difference between 64-section MDCT angiography and CCA to detect stenosis. Also, kappa index (kappa) for the agreement between MDCT angiography and CCA was calculated.

RESULTS

The sensitivity, specificity, positive (PPV) and negative predictive values (NPV) for detecting significant stenosis were 96%, 98%, 91%, 99%, respectively. The sensitivity, specificity, PPV and NPV for classification of patients with or without CAD were 100% for all. McNemar test demonstrated no significant difference between 64-section MDCT angiography and CCA. Also, kappa index (kappa) indicated excellent agreement.

CONCLUSION

Sixty-four section MDCT angiography is an effective diagnostic tool for the detection of significant coronary artery stenosis. Especially, the potential to differentiate patients with and without CAD may provide MDCT an important role in the prevention of unnecessary invasive diagnostic procedures.

Optimization of contrast material administration for electrocardiogram-gated computed tomographic angiography of the chest

OBJECTIVE

Electrocardiogram-gated computed tomographic angiography is increasingly used in the differential diagnosis of acute chest pain. We studied the optimal timing of contrast material injection using a test bolus and a bolus-tracking technique.

MATERIALS AND METHODS

Thirty patients were prospectively included in the study. Volume and flow of high concentration contrast material were adapted to body weight. The scan delay was determined using either a test bolus or a bolus-tracking technique. Attenuation profiles of the different vascular districts were measured to evaluate the timing techniques.

RESULTS

In all the patients except for one, an adequate and homogeneous contrast enhancement of more than 200 Hounsfield units (HU) was achieved (285 +/- 45 HU) in the different vascular districts. The pulmonary transit time in the test bolus group was 7 seconds (range, 4-11 seconds). Differences and variability of pulmonary and aortic enhancement were small in both groups (13 +/- 48 HU vs -9 +/- 21 HU), with differences of less than 70 HU over the craniocaudal range and very small intraindividual differences between pulmonary attenuation and systemic attenuation.

CONCLUSIONS

Contrast administration regimens for electrocardiogramgated computed tomographic angiography of the chest can be optimized using the bolus-tracking method in the ascending aorta, with a short delay after trigger. Body weight adaptation of volume and injection rate of the contrast material results in a reliable simultaneous opacification of the pulmonary and systemic vasculature.

Does two-segment image reconstruction at 64-section CT coronary angiography improve image quality and diagnostic accuracy?

PURPOSE

To prospectively evaluate the effect of single- versus two-segment image reconstruction on image quality and diagnostic accuracy at 64-section multidetector computed tomographic (CT) coronary angiography by using conventional coronary angiography as the reference standard.

MATERIALS AND METHODS

The study design was approved by a human research committee; patients gave informed consent. The study was HIPAA compliant. Forty consecutive patients (22 men, 18 women; mean age, 61 years +/- 8 [standard deviation]) underwent both 64-section multidetector CT coronary angiography and conventional angiography. All data sets were reconstructed by using single- and two-segment image reconstruction algorithms, with resulting temporal resolution of 82.5-165 msec. Two experienced observers independently evaluated image quality and signs of coronary artery disease. A five-level grading scheme was used to grade stenosis (0%, <50%, <70%, <99%, 100%) and image quality (1[unacceptable] to 5[excellent]). Interobserver correlation, Spearman correlation coefficients, and diagnostic accuracy were calculated.

RESULTS

Six hundred coronary artery segments were visible on conventional angiograms, of which 560 (93.3%) were seen by using single-segment and 561 (93.5%) were seen by using two-segment image reconstruction (P=.35). Mean quality scores were not significantly different (P=.22) for single- (3.1 +/- 0.9) and two-segment (3.2 +/- 0.8) reconstruction. Significantly (P=.03) better image quality was observed for two-segment reconstruction only at heart rates of 80-82 beats per minute, at which temporal resolution was approximately 83 msec. For grading coronary artery stenosis, correlation was 0.64 for single- and 0.66 for two-segment reconstruction (P=.43). Significant stenosis (>50%) was detected on a per-segment basis with 77.1% sensitivity and 98.6% specificity by using single-segment and with 79.2% sensitivity and 99.1% specificity by using two-segment image reconstruction.

CONCLUSION

At heart rates of more than 65 beats per minute, use of two-segment reconstruction improves image quality at multidetector CT coronary angiography but does not significantly affect overall diagnostic accuracy compared with single-segment reconstruction.

Aortic root catheter-directed coronary CT angiography in swine: coronary enhancement with minimum volume of iodinated contrast material

OBJECTIVE

The purpose of this study was to evaluate the minimum amount of contrast material for coronary imaging with aortic root catheter-directed enhancement and 64-MDCT angiography (MDCTA).

MATERIALS AND METHODS

A 64-MDCT scanner was used after animal institutional review board approval to study four swine (40-60 kg). Heart rate reduction to 65 beats per minute was achieved with atenolol by mouth and i.v. Cardizem. Common femoral artery access was obtained with a 5-French micropuncture kit and sonographic guidance. A diffusiontip (640 side holes), 5-French pigtail catheter was positioned in the aortic root on the CT table with a retrofitted C-arm fluoroscopy unit and connected to an arterial power injector. Aortic root MDCTA (retrospective ECG gating; collimation, 0.6 mm; tube rotation time, 0.33 second; scanning time, 10-12 seconds; tube voltage, 120 kVp; effective mAs, 850 mAs; pitch, 0.2; field of view, 109-123 mm; slice thickness and increment, 0.6 and 0.3 mm) was begun 1 second after the injection of 100 mL of various Visipaque (iodixanol) concentrations (10%, 20%, 30%, 40%) at 10 mL/s. Coronary mean and peak densities, 3D maximum intensity projections, and 4D projections were obtained.

RESULTS

The mean pooled coronary attenuation values (H +/- SD) for the right (RCA), left anterior descending (LAD), and left circumflex (LCx) coronary arteries at various concentrations (10%, 20%, 30%, 40%) were as follows: 10% (RCA [232.6 +/- 64.0], LAD [180.4 +/- 45.1], and LCx [176.6 +/- 56.2]); 20% (RCA [383.0 +/- 98.7], LAD [324.3 +/- 60.1], and LCx [331.8 +/- 105.5]); 30% (RCA [441.8 +/- 137.6], LAD [401.3 +/- 125.8], and LCx [418.5 +/- 173.0]); and 40% (RCA [717.3 +/- 377.7], LAD [573.3 +/- 233.3], and LCx [584.8 +/- 189.0]). Coronary imaging with aortic root MDCTA was feasible at all concentrations, and the attenuation values were statistically significantly greater than 250 H at 20%, 30%, and 40% (p < 0.05). The attenuation values with aortic root MDCTA using one fifth of the volume of contrast material are comparable to those currently achieved both clinically and experimentally with peripheral i.v. MDCTA.

CONCLUSION

Aortic root MDCTA can depict the coronary arteries with as little as 20 mL of contrast material. This may provide an alternative means of coronary evaluation in patients with renal insufficiency.

Dual-source-CT in der Diagnostik des Thoraxschmerzes

BACKGROUND

With the depiction of pulmonary arteries, coronary arteries, and the aorta, CT angiography of the chest offers a comprehensive diagnostic work-up of unclear chest pain. The aim of this study was to assess the diagnostic accuracy of dual-source CT in this patient group.

MATERIALS AND METHODS

A total of 47 patients suffering from unclear chest pain were examined with a Siemens Somatom Definition. Volume and flow of contrast media (Ultravist, Schering) were adapted to the body weight. The examinations were evaluated with regard to image quality and contrast opacification and to the diagnostic accuracy with reference to the final clinical diagnosis.

RESULTS

Adequate contrast opacification was achieved in all examinations. The depiction of the coronary arteries was diagnostic in all cases. The cause of chest pain could be identified in 41 cases. Among the diagnoses were coronary and myocardial pathologies, valvular disease, aortic aneurysms and dissections, pulmonary embolism, and pneumonic consolidation.

CONCLUSION

DSCT angiography of the chest offers a very good image quality even at high heart rates so that a high diagnostic accuracy is achieved in patients with acute chest pain.

Identification of Tricuspid Valve Vegetation by Computed Tomography Scan

We report a patient with disseminated sepsis in whom a large vegetation involving the tricuspid valve was seen on a routine nongated computed tomography (CT) study emphasizing the potential role of CT scan in endocarditis.

Volumetric quantification of atherosclerotic plaque in CT considering partial volume effect

Coronary artery calcification (CAC) is quantified based on a computed tomography (CT) scan image. A calcified region is identified. Modified expectation maximization (MEM) of a statistical model for the calcified and background material is used to estimate the partial calcium content of the voxels. The algorithm limits the region over which MEM is performed. By using MEM, the statistical properties of the model are iteratively updated based on the calculated resultant calcium distribution from the previous iteration. The estimated statistical properties are used to generate a map of the partial calcium content in the calcified region. The volume of calcium in the calcified region is determined based on the map. The experimental results on a cardiac phantom, scanned 90 times using 15 different protocols, demonstrate that the proposed method is less sensitive to partial volume effect and noise, with average error of 9.5% (standard deviation (SD) of 5-7mm(3)) compared with 67% (SD of 3-20mm(3)) for conventional techniques. The high reproducibility of the proposed method for 35 patients, scanned twice using the same protocol at a minimum interval of 10 min, shows that the method provides 2-3 times lower interscan variation than conventional techniques.

Patient acceptance of noninvasive and invasive coronary angiography

BACKGROUND

Noninvasive angiography using multislice computed tomography (MSCT) is superior to magnetic resonance imaging (MRI) for detection of coronary stenoses. We compared patient acceptance of these two noninvasive diagnostic tests and invasive conventional coronary angiography (Angio).

METHODS AND FINDINGS

A total of 111 consecutive patients with suspected coronary artery disease underwent MSCT, MRI, and Angio. Subsequently, patient acceptance of the three tests was evaluated with questionnaires in all patients. The main acceptance variables were preparation and information prior to the test, degree of concern, comfort, degree of helplessness, pain (on visual analog scales), willingness to undergo the test again, and overall satisfaction. Preparation for each test was not rated significantly differently, whereas patients were significantly more concerned about Angio than the two noninvasive tests (p<0.001). No pain during MSCT, MRI, and Angio as assessed on visual analog scales (0 to 100) was reported by 99, 93, and 31 patients, respectively. Among the 82 patients who felt pain during at least one procedure, both CT (0.9+/-4.5) and MRI (5.2+/-16.6) were significantly less painful than Angio (24.6+/-23.4, both p<0.001). MSCT was considered significantly more comfortable (1.49+/-0.64) than MRI (1.75+/-0.81, p<0.001). In both the no-revascularization (55 patients) and the revascularization group (56 patients), the majority of the patients (73 and 71%) would prefer MSCT to MRI and Angio for future imaging of the coronary arteries. None of the patients indicated to be unwilling to undergo MSCT again. The major advantages patients attributed to MSCT were its fast, uncomplicated, noninvasive, and painless nature.

CONCLUSIONS

Noninvasive coronary angiography with MSCT is considered more comfortable than MRI and both MSCT and MRI are less painful than Angio. Patient preference for MSCT might tip the scales in favor of this test provided that the diagnostic accuracy of MSCT can be shown to be high enough for clinical application.

Coronary stent patency and in-stent restenosis: determination with 64-section multidetector CT coronary angiography--initial experience

PURPOSE

To prospectively assess the diagnostic performance of 64-section multidetector computed tomography (CT) for the evaluation of coronary stent stenosis and occlusion by using conventional coronary angiography as the reference standard.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Thirty patients (27 men, three women; mean age, 58.2 years; range, 42-67 years) with 39 coronary stents were examined with 64-section multidetector CT. Scanning was retrospectively electrocardiographically gated, and an automatic bolus-tracking method was used. For image reconstruction, an edge-enhancing kernel (B46f) was chosen. Evaluations were performed by two radiologists who were blinded to the results of conventional coronary angiography performed within 2-3 days after CT. Sensitivity, specificity, and positive and negative predictive values were calculated.

RESULTS

At conventional angiography, nine of the 39 stents were shown to be totally occluded. All of the occluded stents were correctly diagnosed with CT angiography. Nineteen of 20 patent stents were correctly demonstrated with CT angiography. Ten stents had in-stent restenosis; eight were correctly diagnosed with CT. The sensitivity, specificity, and positive and negative predictive values of 64-section multidetector CT were 89% (17 of 19), 95% (19 of 20), 94% (17 of 18), and 90% (19 of 21), respectively, for in-stent restenosis and occlusion. With the McNemar test, no significant difference was found between 64-section multidetector CT and conventional coronary angiography for the detection of coronary in-stent restenosis and occlusion.

CONCLUSION

Sixty-four-section multidetector CT coronary angiography is a promising method for the noninvasive diagnosis of in-stent restenosis and occlusion.

Coronary CTA

Computed tomography (CT) of the heart, because of ongoing technical refinement and intense scientific and clinical evaluation, has left the research realm and has matured into a clinical application that is about to fulfill its promise to replace invasive cardiac catheterization in some patient populations. By nature of its target, the continuously moving heart, CT coronary angiography is technically more challenging than other CT applications. Also, rapid technical development requires constant adaptation of acquisition protocols. Those challenges, however, are in no way insurmountable for users with knowledge of general CT technique. The intent of this communication is to provide for those interested in and involved with coronary CT angiography a step-by-step manual, introducing our approach to performing coronary CT angiography. Included are considerations regarding appropriate patient selection, patient medication, radiation protection, contrast enhancement, acquisition and reconstruction parameters, image display and analysis techniques and also the radiology report. Our recommendations are based on our experience which spans the evolution of multidetector-row CT for cardiac applications from its beginnings to the most current iterations of advanced acquisition modalities, which we believe herald the entrance of this test into routine clinical practice.

CT of Coronary Artery Disease

The clinical relevance of coronary artery disease has considerably driven the recent development of radiologic tools for noninvasive cardiac imaging. Modern multidetector row computed tomographic (MDCT) systems combine high temporal and spatial resolution, electrocardiographic synchronization, and ease of use. In cardiac imaging, MDCT has not only replaced electron-beam CT, but also challenges competing methods such as magnetic resonance imaging, echocardiography, or even coronary catheterization. Noncontrast material-enhanced assessment of atherosclerotic plaques (CT calcium scoring) seems useful for the cardiac risk stratification in asymptomatic patients and monitoring of medical (statin) therapy. Contrast material-enhanced CT coronary angiography has become established as a valuable method for several clinical indications such as evaluation of coronary artery anomalies, bypass patency, or preoperative planning. Particularly, the high negative predictive value of a normal CT coronary angiogram allows reliable exclusion of coronary artery stenosis. Plaque characterization is another promising area of research in MDCT cardiac imaging. However, with current technology a reliable distinction between atheroma and fibroatheroma is impaired by restrictions in spatial resolution. Recent studies indicate that CT angiography may also be suited for other clinical applications such as triage of patients with acute coronary syndrome and inconclusive clinical presentation, patients with symptomatic chest pain, and intermediate risk profile or cardiac risk stratification in asymptomatic patients.

Prediction of aortic peak enhancement in monophasic contrast injection protocols at multidetector CT: phantom and patient studies

PURPOSE

The aim of this study was to investigate whether it is possible to predict aortic peak enhancement (APE) from the contrast dose and injection rate.

MATERIALS AND METHODS

We first undertook an experimental study using a flow phantom that simulates the human circulation. We delivered 90-150 ml of iomeprol-350 at various injection rates and measured the APE values of the simulated aorta. In our clinical study we randomized 20 patients into four groups. In groups A, B, and C the iodine dose per kilogram of body weight (BW) ranged from 450 to 600 mg, and the injection duration was fixed at 30 s; group D received 450 mg/kg over 25 s. We then measured APE in all patients at the whole aorta, averaged the three highest values, and took the result as APE.

RESULTS

In the phantom study, the decision coefficient for the best-fit equation obtained by multiple regression analysis of the relation between the iodine dose and injection rate and the simulated APE was high (0.93). In the patient study, the predicted APE values almost corresponded with the averaged APE values when we applied the fitness equation.

CONCLUSION

Using our fitness equation, APE on contrast-enhanced computed tomography can be predicted from the iodine dose and the contrast injection rate per patient weight.

Applications of multislice computed tomography in coronary artery disease

Multislice computed tomography (MSCT) provides high accuracy for noninvasive assessment of coronary artery disease (CAD). The introduction of the latest computed tomography (CT) technology allows comprehensive evaluation of various aspects of CAD, including the coronary calcium score, coronary artery stenoses, bypass patency, and myocardial function. Other applications, such as plaque characterization, first-pass perfusion imaging, and viability imaging using delayed contrast enhancement, are still under development and may demonstrate clinical utility in the future. Further improvements in CT hardware and imaging protocols are expected that may result in improved coronary artery imaging, new applications, and a significant reduction of radiation dose.

Comparative Use of Radionuclide Stress Testing, Coronary Artery Calcium Scanning, and Noninvasive Coronary Angiography for Diagnostic and Prognostic Cardiac Assessment

Noninvasive cardiac imaging has undergone a recent resurgence with the development of new approaches for imaging coronary atherosclerosis. Non-contrast computed tomography (CT) for imaging the extent of coronary artery calcification (CAC) and contrast CT for noninvasive coronary angiography (CTA) are developments with a growing evidence base regarding risk assessment and the diagnosis of obstructive coronary disease. This review discusses the role of CAC for risk assessment of asymptomatic individuals and for the use of coronary CTA in symptomatic patients. By comparison, gated myocardial perfusion scintigraphy (MPS) is a well-established noninvasive imaging modality that is a core element in evaluation of patients with stable chest pain syndromes. Stress MPS is the most commonly used stress imaging technique for patients with suspected or known coronary disease. In contrast to the nascent evidence noted with coronary CTA, MPS has a robust evidence base, including the support of numerous clinical guidelines. We highlight the current evidence supporting the diagnostic accuracy and risk stratification data for MPS for symptomatic patients with known or suspected coronary artery disease. It is likely that assessing the extent of atherosclerosis using CAC or coronary CTA will become an increasing part of mainstream cardiovascular imaging practices. In some patients, further ischemia testing with MPS will be required. Similarly, in some patients referred for MPS, anatomic definition of atherosclerosis using CAC by CT may be appropriate. Thus, this review also provides a synopsis of the available literature on imaging that integrates both CT and MPS in combined strategies for the assessment of atherosclerotic and obstructive coronary disease burden. We also propose possible risk-based strategies through which imaging might be used to identifying candidates for more intensive prevention and risk factor modification strategies as well as those who would benefit from referral to coronary angiography and revascularization.

Evaluation of three-dimensional navigator-gated whole heart MR coronary angiography: The importance of systolic imaging in subjects with high heart rates

PURPOSE

To evaluate the influence of heart rate (HR) on magnetic resonance coronary angiography (MRCA) image quality in diastolic and systolic phases.

MATERIALS AND METHODS

Twenty-seven healthy volunteers (9 men; 33+/-9 years, HR 53-110 bpm), were evaluated with the electrocardiography and three-dimensional navigator-gating MRCA in a 1.5-T MR scanner (Avanto, Siemens) in diastolic and systolic phases (steady-state free precession; TR/TE/flip angle=3.2 ms/1.6 ms/90 degrees). The timing of scanning was individually adapted to the cardiac rest periods obtained in the prescanning, by visually identifying when the movement of right coronary artery was minimized during diastole and systole. Images of two phases were side-by-side compared on a four-point scale (from 1=poor to 4=excellent visibility; score of 3 or 4 as diagnostic).

RESULTS

Of 13 subjects with HR < or =65 bpm (low HR group, mean 59.8+/-4.9 bpm, range 53-65), the image quality scores were significantly better than that with higher heart rates (73.9+/-9.0 bpm, range 68-110) in diastolic MRCA. The image quality was significantly improved during systole in high HR group. Overall, 91.3% of low HR group had MRCA image of diagnostic quality acquired at diastole, while 88.3% of high HR group had diagnostic images at systole by segmental analysis (p=NS).

CONCLUSIONS

MRCA at systole offered superior quality in patients with high heart rates.

ECG-Gated 64-MDCT Angiography in the Differential Diagnosis of Acute Chest Pain

OBJECTIVE

The most important differential diagnoses of acute chest pain include myocardial infarction, aortic dissection, and pulmonary embolism. The purpose of this study was to evaluate the diagnostic value of an ECG-gated 64-MDCT angiography protocol for simultaneous assessment of the pulmonary arteries, coronary arteries, and aorta within a single breath-hold.

SUBJECTS AND METHODS

In 55 patients with acute chest pain, ECG-gated CT angiography was performed with a CT system in which 64 slices per gantry rotation were acquired. Density measurement and visual assessment of motion artifacts were performed to evaluate image quality. CT findings were correlated with results of laboratory tests and clinical follow-up. For 20 patients, two independent blinded reviewers compared findings on CT angiography with those on X-ray coronary angiography.

RESULTS

Adequate contrast enhancement of the pulmonary vessels, coronary arteries, and aorta was achieved in all cases. Regarding image quality of the coronary arteries, there was minor blurring in seven patients, and in one examination the images did not provide enough information for diagnosis. The average image quality rating was 1.2 on a scale in which 1 indicated no artifacts; 2, minor motion artifacts; and 3, image insufficient for diagnosis. The cause of chest pain was correctly identified with MDCT in 37 patients. The diagnoses included pulmonary embolism (n = 10), coronary stenosis (n = 9), and aortic dissection (n = 1). In four patients, additional diagnoses were found with other examinations.

CONCLUSION

With current techniques, ECG-gated CT angiography of the entire chest has very good image quality. The protocol proved helpful in the differential diagnosis of acute chest pain.

Coronary artery calcifications: a critical assessment of imaging techniques

The presence of coronary artery calcifications is a distinct marker of atherosclerosis and the severity of calcifications is claimed to reflect a patient's individual plaque burden. Calcium deposits can be detected non-invasively by cardiac computed tomography (CT). This enables detection of coronary artery disease in a subclinical stage, description of the extent of the disease and risk estimation of future cardiovascular events. However, calcium quantification may also be used to monitor atherosclerotic disease, for example in the context of an intensified medical treatment. For years, electron-beam CT has been considered the gold-standard for calcium scoring. However, multi-slice spiral CT has recently captured the market and seems to achieve better measuring results with regard to the accuracy and reproducibility of calcium scores because of its superior image quality. For an optimal comparability of different CT techniques the calcium load should now be reported as absolute calcium mass rather than the traditional scoring methods.

Pulmonary Artery CTA

The latest with the introduction of multidetector row computed tomography (MDCT), CT has been firmly established as the modality of choice for imaging the pulmonary arteries, particularly as the de facto first line test for imaging patients with suspected acute pulmonary embolism (PE). Before the introduction of MDCT, remaining concerns regarding CTs accuracy for diagnosis of isolated peripheral emboli had prevented the unanimous acceptance of this test as the reference standard for imaging PE. After a decade of uncertainty, there is now conclusive evidence that CT, if positive, provides reliable confirmation of the presence of PE and, more importantly, if negative effectively rules out clinically significant PE. Current endeavors to streamline and facilitate workflow for CT diagnosis of PE will further improve the acceptance, utility, and importance of this test. Examples include improvements in workflow, CT derivation of right ventricular function parameters for triage and prognostication of patients with acute PE and the comprehensive assessment of patients with acute chest pain for PE, coronary disease, aortic disease, and pulmonary disease by means of a single, contrast enhanced, ECG-synchronized CT scan. Although the diagnosis or exclusion of acute PE is the most common and important application of CT pulmonary angiography, the ease of scan acquisition and the high spatial resolution of modern CT techniques make this test ideally suited for the greatest majority of congenital and acquired, acute and chronic disorders of the pulmonary arteries.

Evaluation of in-stent restenosis in proximal coronary arteries with multidetector computed tomography (MDCT)

The purpose of this study was to assess the ability of 16-slice computed tomography (CT) to detect in-stent restenosis of proximal coronary arteries. From November 2002 to April 2004, 134 consecutive patients with proximal stents (3.25 +/- 0.47 mm) were prospectively studied. Multidetector CT (MDCT) was performed 24 h (baseline) and 6 months after angioplasty and analysed by two radiologists blinded to the results of the coronary angiography. Sensitivity, specificity, positive and negative predictive values for in-stent restenosis were compared with conventional quantitative coronary angiography (QCA). Stenosis with a diameter >or=50% was considered diagnostic of in-stent restenosis. The CT analysis was performed in 131 and 114 patients at baseline and 6 months, respectively. The in-stent lumen was evaluable in 111 (121 stents) and 99 patients (108 stents) at baseline and 6 months, respectively. The prevalence of in-stent restenosis was 22.5%. Restenoses were correctly identified in 91.7 and 87.5% by the two radiologists. The sensitivity, specificity, positive and negative predictive values for the assessment of significant in-stent restenosis were 92, 67, 43, 97% and 87, 66, 41, 95% for the radiologists, respectively. MDCT is a potential non-invasive technique for the screening of in-stent restenosis of proximal coronary arteries that needs further improvements.

Quantitative assessment of the atherosclerotic burden of the aorta by combined FDG-PET and CT image analysis: a new concept

INTRODUCTION

Our objective was to develop a technique for quantifying the extent of atherosclerosis in the aorta by combining standard uptake values (SUVs) in the aortic wall with volumetric data provided by computed tomography (CT).

METHODS

Eighteen patients who had both 18-fluorodeoxyglucose (FDG)-positron emission tomography (PET) and contrast-enhanced CT of the chest and abdomen were selected. All had homogeneous diffuse FDG wall uptake in four segments of the aorta. We divided the patients into three groups according to their age and measured FDG uptake in all four segments of the aorta by calculating the mean SUV for each segment. On each axial CT image, region-of-interest tracings along the inner and outer wall contours of the aorta were generated. The inner surface area was subtracted from the outer surface area. The net area values for each segment were subsequently multiplied by slice thickness to calculate arterial wall volume. By multiplying SUV with wall volume, we were able to calculate the atherosclerotic burden (AB) for each segment of the aorta. We compared the aortic wall volumes, SUVs and AB values in each arterial segment for each age group.

RESULTS

In each aortic wall segment, AB values, SUVs and wall volumes increased with age (P<.05).

CONCLUSION

AB can be used as an indicator of the extent of the atherosclerotic process in the aorta through the use of both metabolic and morphologic data provided by FDG-PET and CT, respectively. This may allow for the optimal screening, diagnosis and management of patients with this common and potentially lethal disorder.

Cardiac issues in the young athlete

Young athletes are disproportionately plagued with congenital cardiac disease. Many of these diseases predispose to sudden cardiac death (SCD), a dramatic and tragic outcome for any young athlete. In many cases, conditions that predispose to SCD do not cause symptoms or show signs on examination, making diagnosis of cardiac disease and prevention of SCD difficult. Clinicians should be familiar with common causes of SCD and their symptoms, perform careful evaluations, refer athletes in whom there are concerns, and make sure any concerning findings receive thorough evaluation. Clinicians should also be familiar with and follow recent guidelines on return to play. Unfortunately, most preparticipation examinations are inadequate, due in part to use of inadequate forms. Better forms are available and should replace inadequate ones.

Comprehensive evaluation of atrial septal defects in individuals undergoing percutaneous repair by 64-detector row computed tomography

Transcatheter atrial septal defect closure is becoming more commonplace as it has been demonstrated to be safe, efficacious and associated with low morbidity. Pre-procedural assessment of individuals has primarily relied upon transesophageal echocardiography. We present four individuals who underwent both transesophageal echocardiography as well as cardiac multidetector computed tomography. In all four cases, multidetector computed tomography added incremental information above the transesophageal echocardiogram. Multidetector computed tomography may play an essential role in individuals with atrial septal defects undergoing percutaneous transcatheter closure.

Coronary Artery Calcium Scoring With Multislice Computed Tomography

OBJECTIVES

We sought to compare an 80-kVp coronary calcium scoring protocol with the standard protocol of 120 kVp in terms of accuracy and reproducibility and to assess its dose reduction potential.

MATERIALS AND METHOD

An anthropomorphic heart phantom with calcium cylinders was scanned with different tube currents at 80 kVp and 120 kVp using a 16-slice multislice CT (MSCT) scanner. An adapted threshold for 80 kVp was calculated. Accuracy and reproducibility for calcium mass, volume, and Agatston score were analyzed using F-tests. The radiation doses needed to produce artifact-free images were determined.

RESULTS

Accuracy (measurement errors: mass 120 kVp +4.6%, mass 80 kVp -6.9%, volume 120 kVp +78.8%, volume 80 kVp +58.2%) and reproducibility (F-tests: mass: P = 0.4998, volume: P = 0.9168, Agatston: P = 0.5422) were comparable at both tube voltages. Avoiding the appearance of artificial lesions, a CTDI(w,eff) of 10.7 mGy was needed at 120 kVp versus 4.6 mGy at 80 kVp (dose reduction of 57%).

CONCLUSIONS

Using an 80-kVp protocol in coronary calcium scoring, a relevant dose reduction is possible without compromising reproducibility and accuracy.

How predictive is breast arterial calcification of cardiovascular disease and risk factors when found at screening mammography?

OBJECTIVE

The purpose of this study was to examine the relationship between breast arterial calcification (BAC), commonly found on mammography, and cardiovascular disease and its risk factors.

SUBJECTS AND METHODS

The study population, nested within the European Prospective Investigation of Cancer-Norfolk (EPIC-Norfolk) cohort study, consisted of 1,590 women older than 55 years, not taking hormone replacement therapy, and with available screening mammograms. Mammograms were coded by three radiologists for presence or absence of BAC. History of coronary heart disease (CHD), stroke, and diabetes and risk factors for cardiovascular disease (including smoking status, body mass index [BMI], blood pressure, diabetes, and glycosylated hemoglobin [HbA1c]) were independently measured from health examinations in the EPIC study.

RESULTS

The prevalence of BAC was 16.0%. Women with BAC were significantly older than those without it. BAC was associated with prevalent CHD, but not stroke. The odds ratio of having CHD was 2.54 (95% confidence interval, 1.03-6.30). The sensitivity and specificity were 32.4% and 85.5%, respectively. Except for smoking, which showed an inverse association, there was no consistent significant association of BAC with cardiovascular disease risk factors including BMI, diabetes, HbA1c, or lipids.

CONCLUSION

BAC found on mammograms was associated with prevalent CHD after adjustment for age, but with low sensitivity. BAC may provide additional information toward identifying cardiovascular disease risk among otherwise healthy women.

Assessment of left ventricular wall motion using 16-channel multislice computed tomography: comparison with left ventriculography

PURPOSE

Using the raw data from coronary computed tomography (CT) angiography, multislice CT (MSCT) can be used to evaluate cardiac function. However, the accuracy of left ventricular (LV) wall motion assessment by MSCT has not been thoroughly investigated. We investigated whether 16-channel MSCT could accurately assess LV wall motion by comparing its results with those of conventional biplane left ventriculography (LVG).

MATERIALS AND METHODS

The study included 20 patients with various kinds of heart disease. All patients underwent both contrast-enhanced MSCT and biplane LVG. Using a retrospective electrocardiography-gating technique, 10 phases over one cardiac cycle were extracted. The left ventricle was divided into seven segments according to the American Heart Association classification. Wall motion was scored as follows: 1, normal; 2, mild to moderate hypokinesis; 3, severe hypokinesis; 4, akinesis; 5, dyskinesis; and 6, aneurysm. The scores obtained by MSCT were compared with those obtained by LVG. The wall motion scores were analyzed using the chi-squared independence test (6 x 6 contingency table).

RESULTS

Wall motion could be assessed in all segments of the 20 patients using interactive multiplanar animation. Among a total of 140 segments in 20 patients, scores in 118 were concordant between MSCT and LVG (118/140, 84.3%).

CONCLUSION

The 16-MSCT can accurately assess LV wall motion.

Aortic valve bypass for aortic stenosis: imaging appearances on multidetector CT

OBJECT

Aortic valve bypass is a technique used in high-risk patients with critical aortic stenosis that consists of placement of a conduit from the left ventricular apex to descending aorta. We describe the imaging appearances of this apicoaortic conduit on multidetector CT (MDCT).

METHODS

Each patient underwent retrospective ECG-gated MDCT using a 16-detector-row scanner several days after placement of an apicoaortic conduit. All images were assessed by two radiologists who reviewed the appearance of the apicoaortic conduit and any post-operative complications. Follow-up studies were available for several patients.

RESULTS

Twelve patients (9 men, 3 women, mean age - 78 years) underwent evaluation and the conduit was visible in each. The valve within the conduit was visible in ten (91%) of the 11 patients who received intravenous contrast material. Common findings were periconduit outpouching and hypoperfusion involving the left ventricle. Complications included pericardial hemorrhage, hemothorax and ventricular pseudoaneurysm. Mild to moderate increase in wall thinning was identified in the three patients who underwent follow-up imaging.

CONCLUSION

Aortic valve bypass with an apicoaortic conduit appears to be a feasible alternative to aortic valve replacement in high-risk patients. MDCT is an excellent method to assess the imaging features of such conduits.

Beta-blockers for cardiac CT: a primer for the radiologist

OBJECTIVE

The objective of this article is to describe a protocol for the administration of beta-blockers for cardiac CT. A low and regular heart rate is necessary for optimal visualization of the coronary arteries on CT and can be achieved by the administration of medications.

CONCLUSION

Beta-blockers can be safely given, orally or IV, to most patients to lower the heart rate for cardiac CT. A protocol can be implemented and patients can be screened for certain contraindications to allow successful administration of these medications by radiologists.

Coronary CT angiography and MR angiography of Kawasaki disease

Although the incidence of coronary artery aneurysms has diminished in patients with Kawasaki disease, coronary artery involvement is still regarded as a major complication of the disease, significantly affecting morbidity and mortality. Recent technical advances in coronary CT angiography (CTA) and MR angiography (MRA) have led to the possibility of using these two imaging methods as minimally invasive alternatives to the more invasive diagnostic catheter angiography in evaluating coronary artery abnormalities, such as aneurysm, stenosis, and occlusion. In this article, we describe imaging techniques and findings of coronary CTA and MRA in Kawasaki disease.

Establishing a cardiac imaging rotation in radiology residency

RATIONALE AND OBJECTIVE

The advent of new technologies for cardiac imaging such as magnetic resonance imaging (MRI) and cardiac computed tomography (CT) have added new tools in the armamentarium of noninvasive methods for predicting cardiac disease. However, training in cardiac anatomy and physiology is critical if radiology is to meet the demands of this service.

MATERIALS AND METHODS

We designed a core rotation in cardiac imaging at the Beth Israel Deaconess Medical Center, Harvard Medical School, to train residents in noninvasive cardiac imaging methods, such as cardiac echocardiography, nuclear cardiac imaging, cardiac MRI, and with special emphasis on cardiac CT.

RESULTS

This 1-month block includes cardiac imaging conferences and a lecture series, hands-on training in the use of imaging software, introduction to cardiac catheterization, and clinical cardiology. Residents are provided with a set of research and review articles along with textbooks on coronary imaging to serve as references for this rotation.

CONCLUSION

We believe that this educational exercise will establish a core of young, knowledgeable, and capable physicians who will be able to meet the clinical demand for noninvasive cardiac imaging and maintain a major role in this emerging specialty.

Variability of Repeated Coronary Artery Calcium Measurements on Low-Dose ECG-Gated 16-MDCT

OBJECTIVE

High reproducibility on coronary artery calcium (CAC) scoring is a key requirement in monitoring the progression of coronary atherosclerosis. Retrospective ECG-gated helical CT has been shown to be superior to prospective gating helical CT in the reproducibility of CAC measurements. However, it brings with it a high level of radiation exposure. The purpose of this study was to compare low- and standard-dose protocols in the variability of CAC scores and in image quality, thereby assessing the feasibility of low-dose retrospective ECG-gated helical CT in CAC measurements.

SUBJECTS AND METHODS

Eighty-six patients with CAC were scanned using a tube current setting of 100 mA once and then a tube current setting equivalent to the patient's body weight twice. CAC scores (Agatston and volume) and interscan variability were evaluated. The mean and SD of the CT attenuation values in regions of interest in the aorta were measured, and the value (mean + 2 x SD) was obtained.

RESULTS

A high correlation of log(10) (Agatston score + 1) was observed between sequential helical CT scans (r = 0.998). The variability in CAC measurements ranged from 11% to 12% for both the Agatston and volume scores. With the tube current equivalent to body weight, the value (mean + 2 x SD) did not exceed a CT attenuation value of 130 H.

CONCLUSION

Low-dose retrospective ECG-gated helical CT-yielding low variability and achieving the level of image quality needed to measure CAC-can be used to monitor patients with coronary atherosclerosis.

Accuracy of 64-row multidetector computed tomography in detecting coronary artery disease in 134 symptomatic patients: influence of calcification

BACKGROUND

The new 64-row multidetector computed tomography (CT)-assisted angiography can now detect coronary artery disease with shorter breath-hold time and at faster heart rates for symptomatic patients. We aim to determine if the 64-row scanner can also overcome limitations due to mild to moderate calcification.

METHODS

Scheduled for conventional coronary angiography, 134 symptomatic patients underwent multidetector CT-assisted angiography within 3 months. Patients were divided into those with low or high calcium score (median score 142) by modified Agatston formula: group A calcium score <142 Agatston score (68 patients, mean age 53 years, heart rate 62 beat/min) and group B calcium score > or = 142 Agatston score (66 patients, mean age 57 years, heart rate 62 beat/min). Eleven major coronary segments were evaluated.

RESULTS

In group A, 93.6% of segments were evaluable with 97.3% correlation. Segment-by-segment analyses for sensitivity, specificity, and positive and negative predictive values were 85.4%, 98.1%, 76.7%, and 99.2%, respectively. For group B, 86.9% of segments were evaluable with 90.5% correlation. Sensitivity, specificity, and positive and negative predictive values were 79.9%, 92.8%, 78.8%, and 93.5%, respectively.

CONCLUSIONS

The 64-slice multidetector CT coronary angiography can reliably detect the presence of significant coronary stenosis in symptomatic patients with mild calcification, but remains limited by moderate to heavy calcification.

Association of coronary artery calcified plaque with clinical coronary heart disease in the National Heart, Lung, and Blood Institute's Family Heart Study

The presence of calcified coronary artery plaque has shown variable association with clinical coronary heart disease (CHD), particularly after adjustment for other risk factors. From 2002 to 2004, as part of the National Heart, Lung, and Blood Institute's Family Heart Study, coronary artery calcium (CAC) scans by 4-slice multidetector computed tomography were performed in 3,359 subjects, including 389 with clinically diagnosed CHD. Among these was a cohort of 2,254 patients who had been asymptomatic at an initial examination 7 to 9 years previously (1994 to 1996), with 111 who had developed newly diagnosed, nonfatal CHD since the initial examination. In cross-sectional analyses, we examined associations between CAC and CHD in the entire group and in the subgroup seen at the initial examination. In the 2 sets of analyses, odds ratios for CHD ranged from approximately 4 in those with CAC scores of 100 to 199 (p <0.01) to >20 in those with CAC scores >/=1,000 (p <0.0001) compared with those with no measurable CAC. This steep gradient of risk persisted after adjustment for risk factors. A quantitative CHD family history score was significantly associated with CHD even after adjusting for all standard risk factors and including CAC in the model. In conclusion, CAC was strongly associated with CHD even after adjustment for standard risk factors and family history contributed independently to CHD risk.

MDCT Angiography of Acute Chest Pain: Evaluation of ECG-Gated and Nongated Techniques

OBJECTIVE

The objective of our study was to compare MDCT angiography protocols used in patients with acute chest pain caused by vascular, nonvascular, and cardiac abnormalities.

SUBJECTS AND METHODS

In four groups of 20 patients with chest pain each, four MDCT protocols were used based on monitoring vascular attenuation: pulmonary embolism (150 H at pulmonary artery), aortic dissection (200 H at aortic arch), chest pain (200 H at pulmonary artery), and chest pain with ECG gating (150 H at pulmonary artery). Vascular enhancement was assessed by attenuation measurements taken from locations in the pulmonary artery (n = 3) and thoracic aorta (n = 4). The appearance of the coronary artery in regard to opacification and motion was assessed on a scale of 1 to 5 (best).

RESULTS

The mean pulmonary artery and aorta attenuation (372 H and 352 H, respectively) was significantly higher (p < 0.005, Student's t test) and the number of vessel attenuation points measuring less than 200 H (1/140) was significantly smaller (p < 0.001, chi-square test) in the chest pain compared with the dissection (318 H, 310 H; 16/140), gated chest pain (304 H, 286 H; 17/14), and pulmonary embolism (302 H, 220 H; 28/140) groups. The median coronary artery visualization score was 4; the proximal regions received a significantly (p < 0.005, Mann-Whitney test) higher grade compared with the middle and distal regions (medians, 5, 4, and 2, respectively). Artifacts were noted on the gated scans.

CONCLUSION

The chest pain protocol can be used to assess both the pulmonary arteries and the thoracic aorta, whereas the ECG-gating protocol appears to be a promising adjunct for a comprehensive single chest pain protocol.

Multidetector-row computed tomography in the planning of abdominal perforator flaps

An accurate preoperative evaluation of the vascular anatomy of the abdominal wall is extremely valuable in improving the surgical strategy in abdominal perforator flaps. The multidetector-row computer tomography offers thin slice coverage of extended volumes with an extremely high spatial resolution. From October 2003 to December 2004, 66 female patients had breast reconstruction surgery in our department using the deep inferior epigastric artery perforator flap. Our multidetector-row computer tomography studies were performed using a 16-detector-row computer tomography scanner. The image assessment was carried out using the following protocol: we first identified the best three perforators from each side of the abdomen. Then we conducted a three-dimensional reconstruction of the abdomen by identifying exactly where the three best perforators emerged from the rectus abdominis fascia. We then transferred the data obtained from the image to the patient using a coordinate system. In addition, we also placed the dominant perforators in the patient by using a conventional hand-held Doppler. During the operation we compared intra-operative findings, Doppler results and computer tomography outcomes. Neither false positive nor false negative results were found in the computer tomography outcome. Multidetector-row computer tomography provides us with an easy method of interpreting the virtual anatomic dissection in three dimensions. It has high sensitivity and specificity and provides a good quality evaluation of the perforator vessels. This information allows reduction of operating time and safer performance of surgery. The multidetector-row computer tomography is a highly effective tool in the preoperative study of abdominal perforator flaps.

The clinical value of a negative multi-detector computed tomographic angiography in patients suspected of coronary artery disease: A meta-analysis

The aim of this meta-analysis was to calculate the sensitivity of contrast-enhanced multi-detector computed tomography (MDCT) compared with coronary angiography (CAG) in incident patients suspected of coronary artery disease (CAD). We searched PubMed, Embase, bibliographies of original papers and reviews to identify original papers including > or =20 patients. Two independent reviewers selected papers and judged eligible papers on quality. Heterogeneity was assessed and homogeneous subgroups were pooled. Of the 15 included studies, ten provided moderately homogeneous patient-based analyses with absolute diagnostic numbers (n = 630 patients). Pooled sensitivity was 89% (95% confidence interval: 85-92%). Scanners with 16 detectors (n = 4) had higher sensitivities (pooled sensitivity: 91%) than four-detector scanners (n = 6; pooling not possible due to heterogeneity). Seven studies reported sensitivity for a proximal stenosis, but different definitions were used making pooling impossible; sensitivities ranged from 75 to 100%. The sensitivity of four- and 16-detector MDCT is not sufficient to rule out any stenosis in patients suspected of CAD. No conclusions can be drawn with respect to the sensitivity for clinically relevant or proximal stenoses.