Detection of coronary artery stenoses by contrast-enhanced, retrospectively electrocardiographically-gated, multislice spiral computed tomography

MR and CT assessment for ischemic cardiac disease

Magnetic resonance imaging and/or contrast-enhanced multidetector computed tomography may be used separately or, often more effectively, in an integrated fashion, to address important issues in patients with coronary artery disease causing ischemic cardiac disease (ICD). These issues include complications of myocardial infarction, such as ventricular dysfunction, myocardial wall rupture, aneurysm formation, intracavitary thrombus, mitral insufficiency, and pericarditis, as well as aspects of planning and monitoring therapy for ICD, such as revascularization and ventricular aneurysm repair.

Evaluation of Plaque Texture by Means of Multislice Computed Tomography in Patients With Acute Coronary Syndrome and Stable Angina

BACKGROUND

In the present study, multislice spiral computed tomography (MSCT), which allows non-invasive assessment of coronary artery plaque, was used to compare the CT density of plaque between patients with acute coronary syndrome (acs) and those with stable angina (sa).

METHODS AND RESULTS

MSCT was performed in 20 patients with ACS (17 with acute myocardial infarction, 3 with unstable angina) and 22 patients with SA. The presence of the plaque was defined on the basis of multiplanar reformation and axial images. At least 4 regions of interest were then placed within the plaque and the minimum CT density was measured and expressed as Hounsfield units (HU). The number of plaques did not differ between the 2 groups, but the minimum CT density was significantly lower in patients with ACS (25+/-15 HU) than in those with SA (71+/-16 HU, range 46-101 HU, p<0.001). Similarly, the minimum plaque density was significantly lower in the culprit coronary segment (26+/-16 HU) than in the non-culprit segment (48+/-17 HU) in 15 ACS patients with multiple plaques.

CONCLUSION

MSCT can potentially differentiate vulnerable from stable plaque in patients with coronary artery disease, although long-term, prospective analysis is needed to establish the conclusion.

Multidetector row computed tomography for follow-up of patients with coronary artery aneurysms due to Kawasaki disease

Multidetector row computed tomography (MDCT) coronary angiography was performed using a 16-slice MDCT scanner in three children with coronary aneurysms due to Kawasaki disease. Patients were given a beta-blocker. Following contrast injection, all data were acquired during a 20-second breathhold. Results were compared with those of conventional coronary angiography performed previously. MDCT provided clear visualization of coronary artery aneurysms, with coronary calcifications but which had not yet progressed to stenotic lesions. Because MDCT allows noninvasive detection and exclusion of coronary obstructions, it may be able to replace repeat conventional angiography as a follow-up study for children with coronary artery disease.

Gauging Effective Spatial Resolution in Multirow Helical Cardiac Computed Tomography With a Dynamic Phantom

PURPOSE

To devise a numerical indicator of image quality for multirow helical cardiac computed tomography (CT) and its relation to temporal resolution.

MATERIALS AND METHODS

A pulsatile cardiac assist device was used to simulate cardiac wall motion by mechanically transmitting the device dynamics to a piece of tungsten wire. Wire motion induced by different device rates was captured with an 8-row subsecond helical CT scanner operating with various scanning parameters. Image artifacts were visually assessed and compared with the image point spread function (PSF) using the full width at half maximum (FWHM) area as a numerical estimate of spatial accuracy.

RESULTS

At rest, the FWHM area was determined as 1.3 mm2. At a device rate of 60 bpm, the FWHM area ranged from 1.51 mm2 to 21.62 mm2, depending on the time of image reconstruction. Mean reproducibility of the FWHM area measurements was determined as 0.05, whereas visual estimates of motion artifact were highly variable between different readers (kappa = 0.19). Visually determined image quality correlated closely with the FWHM area metric (Spearman's rank correlation, P = 0.0001, rho = 0.841). At a device rate of 100 bpm, the minimum FWHM area was 2.00 mm2 using a single-sector algorithm, 1.41 mm2 using a 2-segment algorithm, and 1.37 mm2 using a 4-segment algorithm.

CONCLUSIONS

Use of a pulsatile cardiac assist device could serve as an in vitro test bed for cardiac CT imaging methods. Area FWHM of the PSF correlates well with visually determined image quality of a dynamic phantom, but provides better reproducibility than visual analysis.

Imaging of coronary calcification by computed tomography

As an unequivocal biomarker for arteriosclerosis, the presence of coronary calcium serves as a qualitative reflection of the severity of coronary artery disease (CAD). Greater calcium burdens correlate with more advanced disease, a higher likelihood of coronary stenoses, and a higher risk for coronary heart disease (CHD). Empirically, the quantification of coronary calcium not only provides an accurate reflection of disease severity, but also has great potential as a screening tool for CHD. Computed tomography (CT) has been shown to be capable of providing accurate, noninvasive measurements of coronary calcification. Evidence shows that calcium measurements by CT correlate well with histological plaque analyses, and that calcium burdens accurately reflect disease severity and can be used to assess individual risk for CHD. The purpose of this review article is to examine the accumulated evidence that has attempted to validate CT as a diagnostic tool for CAD and as a screening exam for CHD.

Past, present, and future perspective of cardiac computed tomography

In the United States, more than 1 million diagnostic invasive coronary angiograms are performed annually, and in about 50% the investigation is followed by an interventional procedure. The remaining symptomatic patients after angiography are treated conservatively or by bypass graft surgery. In recent decades coronary angiography has advanced to a fast and safe investigation. Nevertheless, in particular, patients are well aware of the small but not negligible risk of complications and the discomfort of the invasive procedure. In addition to electrocardiogram (EKG) or ultrasound stress test and thallium scintigraphy, there is further need for another noninvasive method that displays the morphology of the coronary arteries in a way that would allow the triage of patients with suspicion of coronary artery disease (CAD) for a conservative, interventional, or surgical treatment.

Current concepts in multi-detector row CT evaluation of the coronary arteries: principles, techniques, and anatomy

Cardiac imaging is becoming a practical application of mechanical computed tomography (CT) with the availability of four, eight, and 16 detector row scanners. The role of imaging is progressing from simple determination of the presence of arterial calcifications on nonenhanced scans to demonstration of vascular stenoses on coronary CT angiograms. Optimization of the imaging technique and knowledge of coronary artery anatomy are both important for the development of CT of the heart. Technical factors such as a slow heart rate, a short scanning time, subcentimeter spatial resolution, high temporal resolution, and reconstruction of multiple image data sets at various intervals in the cardiac cycle result in optimal visualization of the coronary arteries. Axial, thin-slab maximum intensity projection, and volume-rendered images are used to display the normal anatomy and anomalies of the coronary arteries. The challenges of CT angiography of the coronary arteries have been partially met and will likely be overcome with continued evolution of the technology.

Coronary artery disease: new insights and their implications for radiology

Coronary artery disease (CAD) diminishes local, regional, or global blood supply to the heart and is most commonly caused by coronary atherosclerosis. New insights into the etiology of atherosclerosis suggest that CAD is an inflammatory disorder that responds well to modulation rather than an unchangeable chronic process. Since 75% of all acute coronary syndromes result from rupture of atherosclerotic plaques, factors causing rupture have a crucial role. Magnetic resonance imaging and CT have the potential to visualize the composition of coronary artery plaques and thus to identify plaques at risk. Considering the new insights into stunning and hibernation, myocardial late enhancement on MRI might provide pivotal information for therapeutic decision making among lysis therapy, catheter intervention, and bypass surgery. Exercise electrocardiography without or with right precordial leads, stress echocardiography, and stress scintigraphy are simple clinical procedures to identify CAD with high sensitivities of 67, 92, 76, and 88%, respectively. The MRI and CT have to be compared with these good results. Nevertheless, we are expecting that MRI and CT will replace the conventional diagnostic modalities, gain a central role in diagnosing patients with suspected CAD, and prove to be cost-effective in this regard.

Noninvasive evaluation of the prevalence of noncalcified atherosclerotic plaques by multi-slice detector computed tomography: results of a pilot study

BACKGROUND

Multi-slice detector computed tomography (MDCT) not only allows for the determination of coronary calcifications, but also for the noninvasive visualization of noncalcified plaques. Thus, coronary artery disease (CAD) can be detected at a fairly early stage. Since data on the prevalence of potentially rupture prone noncalcified coronary lesions are still missing, it was aim of the present investigation to study this in patients with a distinct cardiovascular risk profile, but without known CAD.

METHODS

68 patients with clinical suspicion of CAD and multiple cardiovascular risk factors were included in this prospective study. Calcium scoring, as well as the detection of noncalcified plaques were performed using a Somatom VZ scanner (Siemens, Forchheim, Germany).

RESULTS

Calcium scoring could be performed in all patients on native scans; 63/68 (96%) of contrast enhanced scans showed sufficient image quality to perform a screening for noncalcified plaques. The three scans without diagnostic image quality had been performed at heart rates of 95 +/- 18/min. Coronary calcifications were found in 36/65 (55%) patients (Agatston score: 247 +/- 358). Additional noncalcified plaques were detected in 16/36 (45%) of these patients; 29/65 (45%) patients had no coronary calcifications (Agatston score: 0), but noncalcified plaques could be detected in 3/29 (10%) of these patients.

CONCLUSIONS

The prevalence of noncalcified plaques was 29% in the whole study group, and even in 10% of patients without coronary calcifications. Further prospective large scale studies are required to confirm these data, and to evaluate the clinical implication of this finding.

Clinical utility of computed tomography and magnetic resonance techniques for noninvasive coronary angiography

OBJECTIVE

The purpose of this study was to provide a comprehensive review of the literature relating to electron beam angiography (EBA), magnetic resonance angiography, and spiral computed tomography, currently the three most promising noninvasive methods to visualize obstructions in the coronary tree.

BACKGROUND

Given the high costs and invasiveness of coronary angiography, there is increased interest in noninvasive coronary angiography, which has made great strides to become a clinically useful tool to augment conventional coronary angiography (CCA).

METHODS

MEDLINE searches were performed to include all articles related to noninvasive angiography utilizing either magnetic resonance imaging (MRI), multi-row detector spiral computed tomography (MDCT), and electron beam tomography (EBT). Weighted analysis was performed to define the published sensitivity and specificity for each technique.

RESULTS

Electron beam angiography (EBA) provides an overall sensitivity of 87% and specificity of 91% for the detection of obstructive coronary artery disease (CAD). Four-level MDCT data demonstrated an overall sensitivity of 59% and specificity of 89%, with higher accuracy in two recent studies of 16-level detector devices. Magnetic resonance angiography demonstrated sensitivity for detection of obstructive CAD of 77% and specificity of 71%.

CONCLUSIONS

Noninvasive coronary angiography is a rapidly developing technique and currently not an alternative to CCA in all cases. All three methods are currently used clinically in certain centers with appropriate expertise. Selective use should prove both cost-effective and provide a safer, less-invasive method for patients to determine the need for medical versus revascularization therapy.

Quantitative parameters of image quality in multidetector spiral computed tomographic coronary imaging with submillimeter collimation

Multidetector computed tomography (MDCT) permits visualization of the coronary arteries, but limited spatial and temporal resolution can lead to artifacts. We quantitatively evaluated the image quality that can be obtained with the latest generation of MDCT scanners with submillimeter collimation and increased gantry rotation speed. Thirty patients with angiographically proved absence of significant coronary artery stenoses (mean age 56 +/- 13 years, mean heart rate 62 +/- 13 beats/min) were studied by MDCT (12 x 0.75 mm collimation, 420-ms tube rotation, 210-ms temporal resolution, 500 mA, 120 kVp, retrospective electrocardiographic gating). In multiplanar reconstructions of the 4 major coronary arteries (left main, left anterior descending, left circumflex, and right coronary artery), the overall visualized vessel length and the length of segments without motion artifacts were measured. Vessel diameters at 8 predefined locations were measured in MDCT maximum intensity projections and in corresponding invasive angiograms. The mean lengths of visualized coronary arteries were left main 13 +/- 6 mm, left anterior descending 138 +/- 39 mm, left circumflex 84 +/- 34 mm, and right coronary artery 155 +/- 41 mm. On average, 93 +/- 13% of the total visualized vessel length was depicted without motion artifacts (left main 100 +/- 0%, left anterior descending 93 +/- 12%, left circumflex 91 +/- 17%, and right coronary artery 87 +/- 14%). The percentage of vessel length visualized free of motion artifacts was significantly higher in patients with a heart rate </=60 beats/min compared with patients with a heart rate >60 beats/min (96 +/- 8% vs 89 +/- 17%, p <0.05). Vessel diameters in MDCT correlated closely to quantitative coronary angiography (R(2) 0.83 to 0.87). In conclusion, MDCT with submillimeter collimation and improved temporal resolution permits reliable visualization of the vessel lumen and accurate measurements of vessel dimensions.

Evaluation of Patients after Coronary Artery Bypass Surgery: CT Angiographic Assessment of Grafts and Coronary Arteries

PURPOSE

To evaluate the accuracy of electrocardiography (ECG)-gated multi-detector row computed tomography (CT) in enabling the detection of obstruction of both bypass grafts and coronary arteries in symptomatic patients who have undergone coronary artery bypass grafting.

MATERIALS AND METHODS

ECG-gated contrast material-enhanced multi-detector row CT angiography was performed in 24 patients after bypass surgery. Two independent blinded observers evaluated all graft and coronary segments (> or =2.0-mm diameter) for occlusion and stenosis (50%-99% luminal reduction). Conventional angiography was regarded as the standard of reference. Descriptive parameters were calculated, and the results for arterial grafts, venous grafts, and coronary arteries, as well as for high and low heart rates, were compared by using a two-sided Fisher exact test.

RESULTS

The following results were obtained by observers 1 and 2, respectively: Of the 60 venous graft segments, 60 (100%) and 57 (95.0%) were assessable, with an overall detection of all 17 occlusions (both observers) and three (50.0%) and five (83.3%) of six stenoses. Of 26 arterial graft segments, 19 (73.1%) and 15 (57.7%) were assessable. In the assessable segments, four of four (100%) and two of three (66.7%) stenoses and occlusions were detected, while one and two obstructions were located in nonassessable segments. Of 211 coronary segments, 146 (69.2%) and 140 (66.4%) were assessable, and detection of 50%-100% obstruction yielded a sensitivity of 89.9% (71 of 79) and 79.4% (54 of 68) and a specificity of 74.6% (50 of 67) and 72.2% (52 of 72) for each observer. Unlike the assessment of venous and arterial grafts, assessment of the coronary arteries with multi-detector row CT was significantly better in patients with low heart rates (P <.01).

CONCLUSION

Multi-detector row CT allows noninvasive angiographic evaluation of both coronary arteries and bypass grafts in patients who have undergone bypass surgery. Multi-detector row CT is more effective in examining venous grafts compared with arterial grafts and diffusely diseased coronary arteries.

MS-CT Coronary Imaging

Magnetic resonance imaging and computed tomography (CT) have recently emerged as two techniques that can noninvasively visualize the coronary arteries. The latest generation 16-row detector multislice CT scanner is now considered the most reliable technique to visualize the coronaries. The sensitivity and specificity to detect a significant (>50% diameter stenosis) coronary stenosis is +/-94% and +/-90%, respectively. Further technical improvements are necessary to make CT a clinically reliable diagnostic tool.

ECG-gated multislice spiral computed tomography to clarify lesion severity in a case of left main stenosis. Multislice spiral computed tomography to clarify lesion severity

This case report describes the use of retrospectively ECG-gated multislice spiral computed tomography (MSCT) for evaluation of lesion severity in a patient with relevant left main stenosis by visual analysis of the coronary angiogram. For further diagnostic evaluation the patient underwent intravascular ultrasound (IVUS) imaging, which showed a maximal 30% area stenosis, and MSCT, which demonstrated a maximal 48% area stenosis. MSCT was useful in this case to defer cardiac surgery and might be used as a noninvasive alternative to IVUS imaging in case of doubtful lesion severity.

Clinical results of minimally invasive coronary angiography using computed tomography

Fast, high-resolution CT techniques, such as EBCT and MDCT permit imaging of the coronary arteries. Continuous improvements in the capabilities of both technologies for visualization of the coronary lumen and detection of coronary artery stenoses are being made. Image quality currently is not robust enough in all patients to consider non-invasive coronary angiography by EBCT and MDCT a routine clinical tool. In selected patients and carefully performed, however, they show promise as means to exclude the presence of coronary artery stenoses in a non-invasive fashion. This may become a beneficial and important application of these technologies. Other possible applications pertain to smaller patient subsets, such as patients with anomalous coronary arteries, fistulas or aneurysms. The development of techniques to visualize non-calcified plaque is interesting with respect to assessment of coronary risk, but this requires further investigation.

Assessment of coronary arterial stents by multislice-CT angiography

PURPOSE

To assess patency and lumen visibility of coronary artery stents by multislice-CT angiography (MSCTA) in comparison with conventional coronary angiography as the standard of reference.

MATERIAL AND METHODS

47 stents of 13 different types were evaluated in 29 patients. MSCTA was performed on a 4-slice scanner with a standard coronary protocol (detector collimation 4 x 1 mm; table feed 1.5 mm/rotation, 400 mAs, 120 kV). Image evaluation was performed by two readers who were blinded to the reports from the catheter angiography. MIP reconstructions were evaluated for image quality on a 4-point scale (1 = poor, 4 = excellent) and stent patency (contrast distal to the stent as an indirect patency sign). Axial images and multiplanar reformations through the stents were used for assessment of stent lumen visibility (measurement of the visible stent lumen diameter) and detection of relevant in-stent stenosis (> or =50%).

RESULTS

Image quality was fair to good on average (score 2.64 +/- 1.0) and depended on the heart rate (heart rate 45-60: average score 3.2, heart rate 61-70: average score 2.8, heart rate >71: average score 1.4). Thirty-seven stents were correctly classified as patent, 1 was correctly classified as occluded and 9 stents were not assessible due to insufficient image quality because of triggering artifacts. Parts of the stent lumen could be visualized in 30 cases. On average, 20-40% of the stent lumen diameter was visible. Twenty-five stents were correctly classified as having no stenosis, 1 was falsely classified as stenosed, 1 was correctly classified as occluded. In 20 stents lumen visibility was not sufficient for stenosis evaluation.

CONCLUSION

Although the stent lumen may be partly visualized in most stents, a reliable evaluation of in-stent stenoses does not seem practical by 4-slice MSCT. Nevertheless, for stent patency evaluation, MS-CTA might provide valuable clinical information. With submillimeter MSCT (e.g., 16-slice scanners) and more sophisticated reconstruction algorithms, further improvements may be expected.

Three dimensional volume quantification of aortic valve calcification using multislice computed tomography

OBJECTIVE

To assess a new multislice computed tomography (CT) technique for three dimensional quantification of aortic valve calcification volume (3D AVCV) and to study the relation between stenosis and calcification of the aortic valve.

METHODS

50 patients with echocardiographic calcification of the aortic valve underwent two separate ECG triggered multislice CT for quantification of 3D AVCV. The agreement between the two 3D AVCV scores was assessed and 3D AVCV was compared with echocardiographic markers of severity of aortic stenosis.

RESULTS

Overall the level of agreement between the two 3D AVCV scores was excellent (median interscan variability 7.9% (interquartile range 10.1); correlation coefficient, r = 0.99; repeatability coefficient 237.8 mm3 (limits of agreement -393 to 559 mm3)). However, the magnitude of the 3D AVCV did influence the interscan variability. The 3D AVCV correlated closely with the maximal predicted transvalvar gradient (r2 = 0.77) and aortic valve area (r2 = 0.73).

CONCLUSIONS

Multislice CT provides a technique for quantifying 3D AVCV that has good reproducibility. There is a close non-linear relation between echocardiographic parameters of severity of valve stenosis and 3D AVCV scores.

Morphologic assessment of patent ductus arteriosus in adults using retrospectively ECG-gated multidetector CT

OBJECTIVE

Noninvasive imaging of a persistently patent ductus arteriosus in adults remains a challenge. Bearing in mind the excellent spatial resolution provided by multidetector CT (MDCT), we postulated that MDCT might be used to evaluate this anatomic defect. We sought to show that MDCT can depict in detail patent ductus arteriosus in adults and allow determination of the size of the duct, degree of calcification, and morphologic classification.

CONCLUSION

MDCT represents a novel method of noninvasively assessing patent ductus arteriosus in adults that provides detailed anatomic information. Comparison with invasive angiographic findings is needed to validate the technique of sizing of ducts using MDCT.

Evaluation of left ventricular dysfunction using multiphasic reconstructions of coronary multi-slice computed tomography data in patients with chronic ischemic heart disease: validation against cine magnetic resonance imaging

PURPOSE

Multi-slice computed tomography (MSCT) is an emerging technique for the angiographic assessment of coronary artery disease (CAD). The purpose of this work was to determine if multiphasic reconstructions of the same data used for the assessment of CAD could also be used for global functional evaluation of the left ventricle (LV).

MATERIALS AND METHODS

Fifteen patients with chronic ischemic heart disease (CIHD) were imaged for CAD using a contrast-enhanced retrospective electrocardiographic-gated spiral technique on a MSCT scanner. The same data were reconstructed at both end-diastole and end-systole in order to measure left ventricular end-diastolic volume (LVEDV), end-systolic volume (LVESV), and ejection fraction (LVEF). The results were compared to values obtained using a cine true-fast imaging with steady-state precession technique on a magnetic resonance imaging (MRI) scanner. Interobserver variability in the measurement from MSCT images was also evaluated.

RESULTS

For LVEF, there was substantial agreement between MSCT and MRI (intraclass correlation coefficient of 0.825); the intermodality reproducibility for LVEF (5%) was within an acceptable clinical range. However, mean values of LVEDV and LVESV with MSCT compared to cine MRI (LVEDV: 262.0 +/- 85.6 ml and 297.2 +/- 98.8 ml, LVESV: 196.2 +/- 75.6 ml and 218.6 +/- 90.99 ml, respectively) were significantly less for both volumes (p < 0.015). Intermodality variabilities for these measurements were high (15 and 13% for LVEDV and LVESV, respectively). Readers' mean measurements of LVESV from MSCT images were significantly different (p = 0.003) resulting in differences in calculation of LVEF (p < 0.024). Still, interobserver variabilities for all values were acceptable (6, 8, and 5% for LVEDV, LVESV, and LVEF, respectively).

CONCLUSION

Although values for LVEDV and LVESV were less with MSCT than with MRI, LVEF values were in agreement. This suggests that combined imaging of CAD and the evaluation of global LV dysfunction due to CIHD is feasible with the same MSCT acquisition.

Non-invasive evaluation of coronary artery bypass grafts using multi-slice computed tomography: initial clinical experience

Recurrence of angina pectoris in patients with previous coronary artery bypass graft (CABG) surgery due to severe coronary artery disease (CAD) is a common problem. Non-invasive imaging of coronary artery bypass grafts by computed tomography was first described in the early 1980s. Meanwhile, multi-slice computed tomography (MSCT) is now available. This new technique allows detection of coronary lesions with good sensitivity and specificity due to continuous improvement and modification of this method. The aim of this study was to investigate whether stenosis or occlusion of CABG can be detected by MSCT. Ten consecutive male patients (mean age 61+/-9.1 years) with previous CABG surgery and 21 bypass grafts (14 venous grafts, seven arterial grafts) were included in this study. Conventional coronary angiography and MSCT angiography (MSCTA) were performed in all patients. MSCTA results were compared with coronary angiography in regard of visualization and lesion detection in CABG. The analysis of MSCTA was performed blinded to the angiographic results. It was found that 18 of 21 bypass grafts (86%) were analyzable by MSCTA: seven of 21 (33%) grafts showed a significant stenosis (>75%), while six of them were detected by MSCTA (sensitivity: 86%, positive predictive value: 0.75). Dissection of one arterial graft could not be evaluated by MSCTA. Twelve of 13 grafts without severe lesion showed no significant stenosis in MSCTA (negative predictive value: 0.86). All grafts without severe lesions by MSCT showed no significant lesion in X-ray angiography (specificity: 100%). MSCTA is a promising new method for the detection of lesions in coronary artery bypass grafts. However, these data based on a small number has to be reevaluated by larger studies.

Thoracic aorta at multi-detector row CT: motion artifact with various reconstruction windows

The authors assessed motion artifact of the thoracic aorta in 25 patients who underwent multi-detector row computed tomography (CT) with retrospective electrocardiographic (ECG) gating. CT reconstructions centered at four phases of diastole were compared for five different levels of the thoracic aorta. A significant positive correlation was observed between heart rate and motion artifact (r = 0.72, P <.001). The optimal reconstruction phase varied between patients, and this was directly related to heart rate. For patients with a heart rate of 70 beats per minute, the reconstruction phase centered at 75% of the R-R interval had the significantly least motion artifact (P =.004). Conversely, the optimal reconstruction phase for patients with heart rates above 70 beats per minute was centered at 50% of the R-R interval (P =.09).

Refined computed tomography of the thoracic aorta: the impact of electrocardiographic assistance

There have been a number of advances in helical computed tomography (CT) in recent years, which have had a beneficial impact on the quality of imaging of the thoracic aorta. These advances include sub-second gantry rotation, multislice acquisition, and the use of electrocardiographic (ECG) assistance. We examine these techniques with emphasis on the principles behind ECG assistance and its use to reduce aortic motion artefact. We highlight examples of ECG-assisted multislice CT in a spectrum of pathologies of the thoracic aorta.

Statin treatment and progression of atherosclerotic plaque burden

Atherosclerosis is a progressive systemic disorder that, in the initial stages, is often asymptomatic. The measurement of atherosclerotic burden using imaging techniques enables the clinical benefits of lipid-modifying therapies to be assessed in early atherosclerosis and facilitates more rapid evaluation of interventions in clinical trials compared with the measurement of clinical outcome. The effect of HMG-CoA reductase inhibitors, commonly referred to as 'statins', on disease progression has been assessed in a number of imaging studies both in patients with established coronary heart disease (CHD) and in those with subclinical atherosclerosis. Statins slow plaque progression and, in early atherosclerosis, they have been demonstrated to promote regression of atherosclerotic lesions. The benefits of statin therapy on soft atherosclerotic plaques that are still developing support the use of vascular measures to detect subclinical atherosclerosis, and the subsequent early intervention with statin therapy. Moreover, given that the effects of statins on atherosclerosis progression are evident even in normocholesterolaemic patients at increased risk of developing CHD, early intervention with statin therapy may be effective in preventing CHD, irrespective of lipid level.

Non-invasive intravenous coronary angiography using electron beam tomography and multislice computed tomography

BACKGROUND

Electron beam computed tomography (EBCT) and multislice computed tomography (MSCT) are both suitable for non-invasive identification of coronary stenoses.

OBJECTIVE

To compare intravenous coronary EBCT angiography (EBCTA) and MSCT angiography (MSCTA) with regard to image quality and diagnostic accuracy.

METHODS

EBCTA was done using an Imatron C-150 XP scanner in 101 patients following a standard protocol (slice thickness 3 mm, overlap 1 mm, acquisition time 100 ms, prospective ECG trigger). For MSCTA in a different set of 91 patients (using a Siemens Somatom Plus4VZ scanner), the whole volume of the heart was covered in a spiral technique by four simultaneous detector rows. Using retrospective ECG gating, the raw data were reconstructed in (mean (SD)) 215 (12) axial slices acquired in diastole (slice thickness 1.25 mm, overlap 0.5 mm, acquisition time 250 ms/slice).

RESULTS

With EBCTA, 76% of predetermined coronary segments in a nine segment model could be assessed with diagnostic image quality, and with MSCTA, 82%. A low contrast to noise ratio with EBCTA, and the presence of motion artefacts with MSCTA were the main reasons for inadequate image quality. Using conventional angiography as the gold standard, 77% of stenoses of > 50% could be identified correctly with EBCTA and 82% with MSCTA. Significant stenoses were correctly ruled out in 93% of segments with EBCTA, and in 96% of segments with MSCTA. The average contrast to noise ratio was higher with MSCTA than with EBCTA (9.4 v 6.5; p < 0.001).

CONCLUSIONS

EBCTA and MSCTA show similarly high levels of accuracy for determining and ruling out significant coronary artery stenoses. MSCTA is capable of providing good image quality in more coronary segments than EBCTA because of its better contrast to noise ratio and higher spatial resolution. Motion artefacts seen at heart rates of > 75 beats/min and a higher radiation exposure are the main limitations of MSCTA.

Multislice spiral computed tomography for the detection of coronary stent restenosis and patency

BACKGROUND

Multislice spiral computed tomography (MSCT) has evolved as a new promising method for non-invasive visualization of the coronary arteries and detection of native coronary artery stenosis. We determined the value of MSCT to non-invasively detect significant in-stent restenosis after coronary artery stenting.

METHODS

Twenty patients (age 56.3+/-8.6 years) were investigated by MSCT (4x1 mm cross-sections, 500 ms tube rotation, table feed 1.5 mm/rotation, intravenous contrast agent, retrospectively ECG-gated image reconstruction) at a mean interval of 9.6+/-4.2 months after coronary stent implantation. Results were compared with conventional quantitative coronary angiography (QCA). A total number of 32 stents were studied, four different stent types were evaluated.

RESULTS

QCA showed in-stent restenosis >50% diameter stenosis in five (16%) stents. Using MSCT it was impossible in all stents, irrespective of stent type or diameter, to directly visualize the stent lumen due to partial volume effects and beam hardening. MSCT allowed the visualization of the coronary vessel proximal and distal to the stent. This allowed confirmation of stent patency in 18/18 cases and correct identification of total stent occlusion in two patients.

CONCLUSIONS

MSCT allows no direct visualization of coronary in-stent restenosis, but it correctly differentiates between stent patency and stent occlusion. The reasons are mainly partial volume effects and beam hardening, which are induced by the stent material.

Value of 3D-volume rendering in the assessment of coronary arteries with retrospectively ECG-gated multislice spiral CT

PURPOSE

To assess the diagnostic value and measurement precision of 3D volume rendering technique (3D-VRT) from retrospectively ECG-gated multislice spiral CT (MSCT) data sets for imaging of the coronary arteries.

MATERIAL AND METHODS

In 35 patients, retrospectively ECG-gated MSCT of the heart using a four detector row MSCT scanner with a standardized examination protocol was performed as well as quantitative X-ray coronary angiography (QCA). The MSCT data was assessed on segmental basis using 3D-VRT exclusively. The coronary artery diameters were measured at the origin of each main coronary branch and 1 cm, 3 cm and 5 cm distally. The minimum, maximum and mean diameters were determined from MSCT angiography and compared to QCA.

RESULTS

A total of 353 of 525 (67.2%) coronary artery segments were assessable by MSCT angiography. The proximal segments were more often assessable when compared to the distal segments. Stenoses were detected with a sensitivity of 82.6% and a specificity of 92.8%. According to the Bland-Altman method the mean differences between QCA and MSCT ranged from -0.55 to 1.07 mm with limits of agreement from -2.2 mm to -2.7 mm.

CONCLUSION

When compared to QCA, the ability of 3D-VRT to quantitatively assess coronary artery diameters and coronary artery stenoses is insufficient for clinical purposes.

Comparative study with a moving heart phantom of the impact of temporal resolution on image quality with two multidetector electrocardiography-gated computed tomography units

OBJECTIVE

The objective of this study was to compare the temporal resolution-related image quality of electrocardiography-gated images acquired with two multidetector computed tomography (CT) units with a moving heart phantom, at similar fixed heart rates, using half-scan and multisector acquisition modes.

METHODS

An adjustable moving heart phantom (Limbsandthings, Horfield, Bristol, UK) was used. Specific heart rates (47, 55, 64, 66, 69, and 73 beats per minute [bpm]) were chosen. On a General Electric CT unit (LightSpeed Plus; General Electric Medical Systems, Milwaukee, WI), retrospective half-scan and multisector mode protocols were performed. On a Siemens CT unit (Somatom Volume Zoom; Siemens, Forchheim, Germany), a retrospective half-scan mode was performed at 47, 55, and 64 bpm, and a two-sector mode was performed at 66, 69, and 73 bpm. Reformatted maximum intensity projection images were qualitatively compared and related to their temporal resolution.

RESULTS

Half-scan mode protocols provided similar good results with both CT units up to 55 bpm. The two-sector mode improved image quality compared with the half-scan mode. High temporal resolution with the multisector mode provided the best results.

CONCLUSION

For coronary artery imaging, acquisition protocols that provide the highest temporal resolution are mandatory. The multisector mode is one technique that allows high temporal resolution but may be clinically inappropriate at heart rates below 65 bpm or when heart rate variation is observed during scan time.

Noninvasive assessment of coronary artery disease by multislice spiral computed tomography using a new retrospectively ECG-gated image reconstruction technique

The present study was designed to investigate the accuracy of multislice spiral computed tomography (MSCT) in detecting coronary artery disease, compared with coronary angiography (CAG), using a new retrospectively ECG-gated reconstruction method that reduced cardiac motion artifact. The study group comprised 54 consecutive patients undergoing MSCT and CAG. MSCT was performed using a SOMATOM Volume Zoom (4-detector-row, Siemens, Germany) with slice thickness 1.0 mm, pitch 1.5 (table feed: 1.5 mm per rotation) and gantry rotation time 500 ms. Metoprolol (20-60 mg) was administered orally prior to MSCT imaging. ECG-gated image reconstruction was performed with the reconstruction window (250 ms) positioned immediately before atrial contraction in order to reduce the cardiac motion artifact caused by the abrupt diastolic ventricular movement occurring during the rapid filling and atrial contraction periods. Following inspection of the volume rendering images, multiplanar reconstruction images and axial images of the left main coronary artery (LMCA), left anterior descending artery (LAD), left circumflex artery (LCx) and right coronary artery (RCA) were obtained and evaluated for luminal narrowing. The results were compared with those obtained by CAG. Of 216 coronary arteries, 206 (95.4%) were assessable; 10 arteries were excluded from the analysis because of severe calcification (n=4), stents (n=3) or insufficient contrast enhancement (n=3). The sensitivity to detect coronary stenoses >or=50% was 93.5% and the specificity to define luminal narrowing <50% was 97.2%. The positive predictive value and the negative predictive value were 93.5% and 97.2%, respectively. The sensitivity was still satisfactory (80.6%) even when non-assessable arteries were included in the analysis. The new retrospectively ECG-gated reconstruction method for MSCT has excellent diagnostic accuracy in detecting significant coronary artery stenoses.

Detection of coronary artery aneurysms, stenoses and occlusions by multislice spiral computed tomography in adolescents with kawasaki disease

In patients with Kawasaki disease (KD), serial evaluation of coronary artery aneurysms (CAAs) and luminal narrowing is essential for risk stratification and therapeutic management. Therefore, non-invasive assessment of the status of the coronary artery is of utmost importance in patient management. Multislice spiral computed tomography (MSCT) permits non-invasive visualization of the entire coronary artery system and was used in the evaluation of 4 patients with KD. CAAs and high-grade coronary artery stenoses were detected by MSCT and corroborated the findings of coronary angiograms performed within the previous 2 years. MSCT has the potential to be the standard diagnostic tool in adolescents with KD.

Multislice computed tomographic coronary angiography: experience in a UK centre

AIM

To evaluate the technique of coronary angiography with retrospectively electrocardiogram (ECG)-gated four-slice helical computed tomography (CT).

MATERIALS AND METHODS

Within 1 month of undergoing routine day-case diagnostic coronary angiography, 30 consecutive patients also underwent retrospectively ECG-gated multislice CT coronary angiography. This enabled direct comparison of seven segments of proximal and mid-coronary artery for each patient by two blinded assessors. Each segment of coronary artery from the multislice CT image was evaluated initially for "assessability" and those segments deemed assessable were subsequently investigated for the presence or absence of a significantly (n=70%) stenotic lesion.

RESULTS

Overall 68% of proximal and mid-coronary artery segments were assessable. The sensitivity and specificity of four-slice CT coronary angiography in assessable segments for detecting the presence or absence (n=70%) of stenoses were 72 and 86%, respectively. These results correspond to a positive predictive value of 53% and a 93% negative predictive value. If the 32% of non-assessable segments are added into the calculation then the sensitivity and specificity fall to 49 and 66%, respectively.

CONCLUSION

Although multislice CT coronary angiography is a promising technique, the overall assessability and diagnostic accuracy of four-slice CT acquisition is not sufficient to justify routine clinical use. Further, evaluation should investigate the benefit of the reduction in temporal and spatial resolution offered by 16 and 32 slice acquisition.

Multiplanar and three-dimensional imaging of the thorax

Although axial images are sufficient for diagnosis in most instances, knowledge of multiplanar imaging techniques is essential to apply them in appropriate circumstances. In particular, appropriately applied multiplanar imaging adds confidence to interpretations and assists surgeons and bronchoscopists in planning procedures. The need for multiplanar imaging must be assessed before performing any study so that the image acquisition parameters allow for suitable reformations.

Multidetector-row CT of the heart

Despite worldwide efforts aimed at primary and secondary prevention, heart disease is still the leading cause of death in the western world. There is great interest in developing tools for noninvasive assessment of the presence and degree of coronary artery disease. The advent of multidetector-row CT allows high-resolution volume coverage of the entire thorax and motion-free imaging of the heart and adjacent vessels within one breathhold. An exciting application with significant potential for cardiac risk stratification, which may overcome the obvious limitations of coronary calcium imaging in the future, is the use of the cross-sectional nature of contrast-enhanced multidetector-row CT coronary angiography for assessment of total coronary artery plaque burden.

Noninvasive visualization of atherosclerotic plaque with electron beam and multislice spiral computed tomography

As an alternative to intracoronary modalities, electron beam computed tomography (EBCT) and multislice spiral computed tomography (MSCT) are able to noninvasively image the coronary arteries. In addition to stenosis detection by imaging the vessel lumen, MSCT has the ability to visualize the coronary artery wall. By using computed tomography (CT), the various components of atherosclerotic plaque may be distinguished and characterized, which holds the promise of, eventually, identifying vulnerable plaque.

Angiographic assessment of coronary stenoses: a review of the techniques

This article reviews the fundamental techniques to quantify the physiological severity of (coronary) stenoses. Although a wide survey of different techniques and applications is provided, the focus of this review is on: 1) the assessment of the immediate effect of the stenoses on blood flow (i.e., the hemodynamic severity), and not on the assessment of the pathology of the vessel itself; 2) the flow reserve methods to defining the physiological severity of stenoses; and 3) the determination of blood flow and tissue perfusion by X-ray angiography (a short survey of other imaging modalities is provided as well). Although the practical implementation of the techniques is illustrated by applying them to coronary stenoses, most of the issues involved are of interest in other application areas (using other imaging modalities) as well. This review consists of four parts. The first part deals with the definition of stenoses severity; the second part with tracer kinetic theory necessary to determine flows by imaging; the third part focusses on (cardiac) imaging modalities, with an emphasis on X-ray angiography; and the last part illustrates the practical implementation of the techniques in cardiology.

Multislice computed tomography of the coronary arteries

Multislice spiral CT (MSCT) of the coronary arteries is developing rapidly as a noninvasive method for assessing coronary artery anatomy and for calculating various parameters of cardiac function. This article reviews the issues involved in MSCT coronary angiography and the methods used to overcome them. The current clinical applications for MSCT coronary angiography are summarized with reference to published clinical studies. The capabilities of CT are compared with those of MRI. Both modalities have a wide range of indications in the noninvasive diagnostic assessment of the heart and partly overlap in their clinical application.

[Influence of heart rate on image quality and detection of coronary stenoses with multislice spiral CT]

Multi-slice spiral CT (MSCT) permits the detection of coronary stenoses. We investigated the influence of the patient's heart rate (HR) during the scan on stenosis detection and the presence of motion artifacts. In 100 patients MSCT was performed and retrospectively ECG-gated cross-sectional images were reconstructed. 115 of 400 coronary arteries (29%) were unevaluable due to motion artifacts (84/115) or other reasons (31/115). In evaluable arteries, sensitivity was 91% (51/56 high grade stenoses detected), specificity was 89%. With increasing HR, the number of unevaluable arteries increased and overall sensitivity for stenosis detection decreased from 62% (HR < or = 70 bpm) to 33% (HR > 70 bpm). MSCT permits detection of coronary stenoses, but evaluability and accuracy decrease with increasing HR.

Coronary artery imaging with real-time navigator three-dimensional turbo-field-echo MR coronary angiography: initial experience

PURPOSE

To examine the value of a commercially available three-dimensional (3D) real-time navigator magnetic resonance (MR) coronary angiographic examination for detection of significant coronary artery stenoses, with conventional coronary angiography as the standard of reference.

MATERIALS AND METHODS

Twenty-one patients underwent 3D navigator MR coronary angiography immediately before catheterization. Two observers independently graded image quality on a scale from 1 (unreadable) to 5 (excellent), quantified coronary artery visualization, and evaluated the presence of significant (ie, >50% narrowing) stenoses. kappa statistics were used to assess interobserver agreement, and receiver operating characteristic (ROC) analysis was used to assess stenosis detection.

RESULTS

For two of 21 patients, MR coronary angiogram quality was insufficient for analysis (mean score < 2). For the remaining 19 patients, the mean image quality scores assigned by observers 1 and 2 were 3.3 +/- 1.0 (SD) and 3.2 +/- 0.9, respectively. A mean of 71% of all coronary artery segments were visible at MR coronary angiography, and there was 91% agreement between the observers (kappa = 0.78). Observers 1 and 2 detected significant stenoses (n = 29) at MR coronary angiography with sensitivities of 44.4% and 55.5%, respectively; specificities of 95.1% and 83.7%, respectively; and 80% agreement (kappa = 0.35). Areas under the ROC curve were 0.817 and 0.795 for observers 1 and 2, respectively.

CONCLUSION

Large portions of the coronary arteries can be visualized with MR coronary angiography. Imaging results are not consistently reliable, however. The examination is premature for routine clinical assessment of significant coronary artery stenosis owing to low sensitivity and large observer variability.

In vivo validation of cardiac spiral computed tomography using retrospective gating

BACKGROUND

Cardiac functional assessment represents the basis for diagnostics and cardiac operation planning. Spiral computed tomography (CT) combines the advantages of three-dimensional imaging and high temporal resolution when using gating techniques. However, in vivo validation data of this novel imaging technology are lacking. The purpose of this study was to validate in vivo the new imaging method using retrospective gating and to evaluate the clinical usefulness of the achieved temporal resolution.

METHODS

In domestic pigs (n = 10, weight 35 to 40 kg) a flowmeter was placed surgically on the ascending aorta. Flow velocity integrated over systole served as the gold standard for left ventricular (LV) stroke volume (LVSV-FM). CT signal, projection data, pacemaker signal, and flow velocity were recorded simultaneously at constant heart rate (pacemaker, 90 beats per minute). End-systolic and end-diastolic frames were calculated by retrospective gating. LV volumes were traced, the difference representing CT stroke volume (LVSV-CT). Image data were three-dimensionally reconstructed using ray-tracing.

RESULTS

Temporal resolution was 170 ms. Correlation of stroke volumes was high (r = 0.94, mean difference 1.75 mL). Intraobserver (0.49 mL for LVEDV, 0.31 for LVESV) and interobserver variability (p = 0.21 and p = 0.06, respectively) were low. Postprocessing resulted in four-dimensional beating-heart models useful for operation planning.

CONCLUSIONS

Spiral CT using retrospective gating was validated in vivo. Clinically acceptable temporal resolution and accuracy in determining cardiac stroke volumes were found. As a true volumetric imaging modality the method may now play an important role in computer-assisted diagnostics and surgery.

Comparison of image quality in contrast-enhanced coronary-artery visualization by electron beam tomography and retrospectively electrocardiogram-gated multislice spiral computed tomography

RATIONALE AND OBJECTIVES

To compare the image quality of electron beam tomography (EBT) and multislice spiral CT (MSCT) for coronary artery visualization.

MATERIALS AND METHODS

Two groups of 30 patients without coronary stenoses were studied by MSCT (4 x 1 mm collimation) or EBT (3 mm slice thickness). Contrast-to-noise ratio (CNR), overall length of the visualized arteries and vessel length free of motion artifacts were measured.

RESULTS

Length of visualized arteries was equal in MSCT and EBT. In EBT, longer segments were depicted free of motion artifacts (MSCT: 73%, EBT: 92% of visualized length, P< 0.001) and CNR was significantly higher than in MSCT (15.4 vs. 9.0; P< 0.001). In both modalities, vessel diameters correlated closely to quantitative coronary angiography.

CONCLUSIONS

EBT and MSCT permit reliable coronary artery visualization and measurement of vessel diameters. For the used scan protocol, MSCT images had a lower CNR and were more frequently affected by motion.

Noninvasive coronary artery imaging by multislice spiral computed tomography

Although the excellent spatial resolution of multislice spiral computed tomography (MSCT) enables the coronary arteries to be visualized, its limited temporal resolution results in poor image reproducibility because of cardiac motion artifact (CMA) and hence limits its widespread clinical use. A novel retrospectively ECG-gated reconstruction method has been developed to minimize CMA. In 88 consecutive patients, the scan data were reconstructed using 2 retrospectively ECG-gated reconstruction methods. Method 1: the end of the reconstruction window (250 ms) was positioned at the peak of the P wave on ECG, which corresponded to the end of the slow filling phase during diastole immediately before atrial contraction. Method 2 (conventional method): relative retrospective gating with 50% referred to the R-R interval was performed so that the beginning of the reconstruction window (250 ms) was positioned at the halfway point between the R-R intervals of the heart cycle. The quality of the coronary artery images was evaluated according to the presence or absence of CMA. The assessment was applied to the left main coronary artery (LMCA), the left anterior descending artery (LAD, segments #6, #7 and #8), the left circumflex artery (LCx, segments #11 and #13) and the right coronary artery (RCA, segments #1, #2 and #3). The first diagonal artery (#9-1), the obtuse marginal artery (#12-1), the posterior descending artery (#4-PD), the atrioventricular node branch (#4-AV) and the first right ventricular branch (RV) were also evaluated. Of the 88 patients, 85 were eligible for image evaluation. Method 1 allowed visualization of the major coronary arteries without CMA in the majority of patients. The LCA system (segments #5-7, #11 and #13) and the proximal portion of the RCA were visualized in more than 94% of patients. Artifact-free visualization of the distal portion of the LAD (segment #8) and RCA (#4PD and #4AV), and side branches (#9-1, #12-1 and RV) was also achieved in more than 80% of patients. On the other hand, CMA occurred frequently on images obtained by Method 2. The LCx and RCA systems were the most affected by CMA, revealing only 41% artifact-free visualization of the segment #13, 39% of #1, 15% of #2 and 32% of #3. Thus, Method 1, which avoids the ventricular motion occurring during the rapid filling and atrial contraction phases, gives superior image quality over the conventional ECG-gated reconstruction method.

Evaluation of left ventricular dysfunction using multiphasic reconstructions of coronary multi-slice computed tomography data in patients with chronic ischemic heart disease: validation against cine magnetic resonance imaging

PURPOSE

Multi-slice computed tomography (MSCT) is an emerging technique for the angiographic assessment of coronary artery disease (CAD). The purpose of this work was to determine if multiphasic reconstructions of the same data used for the assessment of CAD could also be used for global functional evaluation of the left ventricle (LV).

MATERIALS AND METHODS

Fifteen patients with chronic ischemic heart disease (CIHD) were imaged for CAD using a contrast-enhanced retrospective electrocardiographic-gated spiral technique on a MSCT scanner. The same data were reconstructed at both end-diastole and end-systole in order to measure left ventricular end-diastolic volume (LVEDV), end-systolic volume (LVESV), and ejection fraction (LVEF). The results were compared to values obtained using a cine true-fast imaging with steady-state precession technique on a magnetic resonance imaging (MRI) scanner. Interobserver variability in the measurement from MSCT images was also evaluated.

RESULTS

For LVEF, there was substantial agreement between MSCT and MRI (intraclass correlation coefficient of 0.825); the intermodality reproducibility for LVEF (5%) was within an acceptable clinical range. However, mean values of LVEDV and LVESV with MSCT compared to cine MRI (LVEDV: 262.0 +/- 85.6 ml and 297.2 +/- 98.8 ml, LVESV: 196.2 +/- 75.6 ml and 218.6 +/- 90.99 ml, respectively) were significantly less for both volumes (p < 0.015). Intermodality variabilities for these measurements were high (15 and 13% for LVEDV and LVESV, respectively). Readers' mean measurements of LVESV from MSCT images were significantly different (p = 0.003) resulting in differences in calculation of LVEF (p < 0.024). Still, interobserver variabilities for all values were acceptable (6, 8, and 5% for LVEDV, LVESV, and LVEF, respectively).

CONCLUSION

Although values for LVEDV and LVESV were less with MSCT than with MRI, LVEF values were in agreement. This suggests that combined imaging of CAD and the evaluation of global LV dysfunction due to CIHD is feasible with the same MSCT acquisition.

Noninvasive Detection of Coronary Artery Bypass Graft Patency by Intravenous Electron Beam Computed Tomographic Angiography

This study evaluates the usefullness of intravenous electron beam computed tomographic angiography (EBA) for the detection of coronary artery bypass graft patency in 43 patients (33 men and 10 women, mean age, 65 years) who had coronary artery bypass graft surgery. EBA was performed a few days before selective bypass graft angiography (SGA). Forty axial cross-sections of angiographic images of the heart were acquired consecutively by an electrocardiographic trigger signal at 40% of the RR interval, which corresponds to the end-systolic phase. EBA data were reconstructed as a three-dimensional shaded surface display of the heart and bypass grafts. Detectability of the patency of bypass gratis was evaluated, taking selective angiographic images of the bypass grafts as a gold standard. One hundred and nine grafts (96%) out of 114 grafts were subjected to evaluation: 37 grafts were left internal mammary artery grafts (LIMA), 7 were right internal mammary artery grafts (RIMA), 6 were gastroepiploic artery grafts (GEA), 7 were free gastroepiploic artery grafts with venous drainage (free-GEA), 7 were radial artery grafts (RAG), and 45 were saphenous vein gratis (SVG). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of EBA were 98%, 100%, 100%, 91%, and 98%, respectively. EBA sampled at the end-systolic period was determined to be useful for the detection of coronary artery bypass graft patency and occlusion.

Image quality in a standardized algorithm for minimally invasive coronary angiography with multislice spiral computed tomography

PURPOSE

To report our experience with a standardized approach to pharmacologic heart rate control and image postprocessing for computed tomographic coronary angiography (CTCA) with multislice computed tomography (MSCT).

METHOD

Two experienced observers used transaxial tomograms and maximum-intensity projections to classify coronary segments (12 per patient, 135 consecutive patients) for degree of stenosis. One factor affecting image quality was identified for each segment that could not be assessed.

RESULTS

Nine patients (7%) were excluded for technical reasons. Of 1,512 segments from 126 patients, 1,086 (72%) were assessable (8.6 per patient). Of 300 segments from 25 patients who also had selective coronary angiography, CTCA was able to assess 211 (70%) and detected significant disease in 27 (82% sensitivity, 96% specificity, 73% positive predictive value, and 97% negative predictive value). Vessel caliber, heart rate, and Agatston score were associated with inability to assess 426 coronary segments (28%).

CONCLUSION

Heart rate and Agatston score are important predictors of the ability to assess proximal and midcoronary segments by CTCA with MSCT.