New technical developments in multislice CT, part 2: sub-millimeter 16-slice scanning and increased gantry rotation speed for cardiac imaging

Investigating the Influence of High-Speed Gantry Rotation in Cardiac CT on Motion Artifacts in Aortic Stenosis Patients Not Premedicated with β-Blockers: The FAST-CCT Randomized Trial Protocol

BACKGROUND

Coronary CT angiography (CCTA) is increasingly used as a non-invasive tool to assess coronary artery disease (CAD). However, CCTA is subject to motion artifacts, potentially limiting its clinical utility. Despite faster (0.35 and 0.28 s/rot) gantry rotation times, low (60-65 bpm) heartbeat is recommended, and the use of β-blockers is often needed. Technological advancements have resulted in the development of faster rotation speeds (0.23 s/rot). However, their added value in patients not premedicated with β-blockers remains unclear. This prospective single-center, two-arm, randomized, controlled trial aims to assess the influence of fast rotation on coronary motion artifacts, diagnostic accuracy of CCTA for CAD, and patient safety.

METHODS

We will randomize a total of 142 patients aged ≥ 50 scheduled for an aortic stenosis work-up to receive CCTA with either a fast (0.23) or standard (0.28 s/rot) gantry speed.

PRIMARY OUTCOME

rate of CCTAs with coronary motion artifacts hindering interpretation.

SECONDARY OUTCOMES

assessable coronary segments rate, diagnostic accuracy against invasive coronary angiography (ICA), motion artifact magnitude per segment, contrast-to-noise ratio (CNR), and patient ionizing radiation dose. The local ethics committee has approved the protocol. Potential significance: FAST-CCT may improve motion artifact reduction and diagnosis quality, thus eliminating the need for rate control and β-blocker administration.

CLINICALTRIALS

gov identifier: NCT05709652.

Evaluation of a new imaging tool for use with major trauma cases in the emergency department

BACKGROUND

The aim of this study was to evaluate potential benefits of a new diagnostic software prototype (Trauma Viewer, TV) automatically reformatting computed tomography (CT) data on diagnostic speed and quality, compared to CT-image data evaluation using a conventional CT console.

METHODS

Multiple trauma CT data sets were analysed by one expert radiology and one expert traumatology fellow independently twice, once using the TV and once using the secondary conventional CT console placed in the CT control room. Actual analysis time and precision of diagnoses assessment were evaluated. The TV and CT-console results were compared respectively, but also a comparison to the initial multiple trauma CT reports assessed by emergency radiology fellows considered as the gold standard was performed. Finally, design and function of the Trauma Viewer were evaluated in a descriptive manner.

RESULTS

CT data sets of 30 multiple trauma patients were enrolled. Mean time needed for analysis of one CT dataset was 2.43 min using the CT console and 3.58 min using the TV respectively. Thus, secondary conventional CT console analysis was on average 1.15 min shorter compared to the TV analysis. Both readers missed a total of 11 diagnoses using the secondary conventional CT console compared to 12 missed diagnoses using the TV. However, none of these overlooked diagnoses resulted in an Abbreviated Injury Scale (AIS) > 2 corresponding to life threatening injuries.

CONCLUSIONS

Even though it took the two expert fellows a little longer to analyse the CT scans on the prototype TV compared to the CT console, which can be explained by the new user interface of the TV, our preliminary results demonstrate that, after further development, the TV might serve as a new diagnostic feature in the trauma room management. Its high potential to improve time and quality of CT-based diagnoses might help in fast decision making regarding treatment of severely injured patients.

Recent technologic advances in multi-detector row cardiac CT

Recent technical advances in multi-detector row CT have resulted in lower radiation dose, improved temporal and spatial resolution, decreased scan time, and improved tissue differentiation. Lower radiation doses have resulted from the use of pre-patient z collimators, the availability of thin-slice axial data acquisition, the increased efficiency of ECG-based tube current modulation, and the implementation of iterative reconstruction algorithms. Faster gantry rotation and the simultaneous use of two x-ray sources have led to improvements in temporal resolution, and gains in spatial resolution have been achieved through application of the flying x-ray focal-spot technique in the z-direction. Shorter scan times have resulted from the design of detector arrays with increasing numbers of detector rows and through the simultaneous use of two x-ray sources to allow higher helical pitch. Some improvement in tissue differentiation has been achieved with dual energy CT. This article discusses these recent technical advances in detail.

Coronary CT angiography with dual source computed tomography in 170 patients

INTRODUCTION

In preliminary studies DSCT provides robust image quality over a wide range of heart rates and excludes CAD with high accuracy. The aim of the present study was to evaluate the reproducibility of these results in a large, unselected and consecutive group of patients scheduled for invasive coronary angiography (ICA).

MATERIAL AND METHODS

170 patients (124 men, 46 women; mean age: 64+/-9 years) with known CAD (101 patients) or suspected CAD (69 patients) scheduled for ICA were examined by coronary CTA prior to ICA. All coronary segments were assessed for image quality (1: excellent; 5: non-diagnostic). The presence of significant vessel stenosis (>50%) was calculated using ICA as standard of reference.

RESULTS

A total of 680 vessels were analyzed. Despite of 45 arrythmic patients all analyzed coronary segments were diagnostically evaluable. Mean Agatston score equivalent was 686 (range 0-4950). ICA revealed 364 lesions with > or =50% diameter stenosis. DSCT correctly identified 336 of these lesions. 115 lesions with a diameter stenosis < or =50% were overestimated by DSCT and thus considered as false-positive findings. On a per-segment basis, sensitivity was 92%, specificity 93%, positive predictive value (PPV) was 75% and negative predictive value (NPV) 98%. On a per-vessel basis DSCT revealed a sensitivity of 93%, a specificity of 88%, a PPV of 78% and a NPV of 97%. On a per-patient basis sensitivity was 94%, specificity 79%, PPV 88% and NPV 90%.

CONCLUSIONS

Initial results of preliminary studies showing robust image quality and high accuracy in DSCT cardiac imaging could be approved with the present study enclosing a large consecutive population. However severe coronary calcifications and irregular heart rate still remain limiting factors for coronary CTA. Despite improved image quality and high accuracy of coronary DSCT angiography, proof of indication is necessary, due to still remaining limiting factors.

Imaging of the heart with computed tomography

Imaging of the heart with computed tomography (CT) was already introduced in the 1980Is and has meanwhile entered clinical routine as a consequence of the rapid evolution of CT technology during the last decade. In this review article, we give an overview on the technology and clinical performance of different CT-scanner generations used for cardiac imaging, such as Electron Beam CT (EBCT), single-slice CT und multi-detector row CT (MDCT) with 4, 16 and 64 simultaneously acquired slices. We identify the limitations of current CT-scanners, indicate potential of improvement and discuss alternative system concepts such as CT with area detectors and dual source CT (DSCT).

Quantitative 4-dimensional volumetric analysis of left ventricle in ischemic heart disease by 64-slice computed tomography: a comparative study with invasive left ventriculogram

OBJECTIVE

To elucidate the usefulness of CT in evaluating left ventricular (LV) volumes and ejection fraction (EF) in ischemic heart disease (IHD), we compared 64-slice CT with conventional left ventriculography (CLVG).

MATERIALS AND METHODS

71 subjects with suspected or confirmed IHD underwent ECG-gated enhanced CT before or after cardiac catheterization. End-diastolic volume (EDV) and end-systolic volume (ESV) of LV were selected in 20 phases of R-R interval of ECG, and data sets were reconstructed to determine EDV, ESV, SV, and EF of LV using a multislice area summation method; in CLVG these parameters were calculated from the right anterior oblique 30-degree projection.

RESULTS

Correlation coefficients between CT and CLVG for EDV, ESV, SV, and EF were 0.759, 0.895, 0.550, and 0.836, respectively (P<0.01). In 35 subjects without apical asynergy of LV wall motion, correlation coefficients between CT and CLVG were 0.77, 0.91, 0.63, and 0.87 respectively (P<0.01); in 36 subjects, with apical asynergy, the correlation coefficients were 0.751, 0.875, 0.503, and 0.738, respectively (P<0.01). The limits of agreement of all parameters were wider in the subjects with apical asynergy of LV wall motion than the subjects without.

CONCLUSION

There was good correlation between EDV, ESV, SV, and EF estimated by CT and those by CLVG, but CT tended to overestimate EDV and ESV and underestimate EF. In subjects with apical asynergy of LV wall motion, estimates of EF were less correlated between CT and CLVG and the limits of agreement of all parameters were wider than in those without. These discrepancies may come from the capability of CT to estimate LV wall asynergy 3-dimensionally and more accurately.

[Clinical value of dual source computerized tomography in primary diagnosis of coronary heart disease]

Dual-source-CT-technology (DSCT) improves temporal resolution of cardiac computed tomography to 83 ms per heart-phase. In this study, the clinical performance of this new method is evaluated.

MATERIALS AND METHODS

In fifty patients (33 male, 17 female; age 50 +/- 13 years) with suspected coronary heart disease, CT angiography (slice thickness 0.75 mm, contrast-agent 60-80 ml iomeprol) was performed with a Somatom Definition scanner. Based on the coronary 15-segment-model of the AHA, scores for image quality and lumen reduction were established to enable the observer, to give recommendations for further therapy.

RESULTS

Out of 750 possible AHA-segments, 655 were depicted (87.3%). 591 segments (90.2%) were assessed without any limitation of quality, 49 (7.5%) segments showed moderate, and 15 (2.3%) segments severe limitation in image quality. 508 (77.6%) segments were without pathological findings, 92 (14.0%) segments had minimal atherosclerotic lesions, 42 (6.4%) segments suffered from stenoses with lumen reduction less than 70%, and 13 (2.0%) showed significant stenoses of more than 70%. In 31 patients (62%), coronary heart disease was ruled out by CT angiography without any need for further non-invasive or invasive diagnostics. 8 patients (16%) underwent stress-testing for ischemia. In 11 (22%) patients coronary angiography was recommended, and DSCT findings were confirmed in 10 cases. Only one LCx stenosis was overestimated in DSCT.

CONCLUSION

Contrast-enhanced DSCT is a powerful tool in diagnosis of coronary heart disease. 98% of coronary segments could be assessed in diagnostic quality, and at least 90% of haemodynamically significant coronary stenoses were detected.

Diagnostic Performance of 64-Slice Computed Tomography in Evaluation of Coronary Artery Bypass Grafts

OBJECTIVE

The purpose of this study was to compare the diagnostic accuracy of 64-slice CT with that of invasive angiography in the detection of greater than 50% graft stenosis within 2 weeks of coronary artery bypass grafting and to investigate the clinical value of 64-slice CT.

SUBJECTS AND METHODS

Forty-one patients (70 grafts, 46 arterial and 24 venous) underwent 64-slice CT a mean of 2.6 years after minimally invasive or conventional coronary artery bypass surgery.

RESULTS

All 70 grafts were assessable, and none of the grafts was excluded from analysis. For the detection of 50-90% graft stenosis, the sensitivity of CT was 75%, the specificity was 95%, the positive predictive value was 67%, and the negative predictive value was 97% (true disease prevalence, 8/70 grafts; 11%). Greater than 50% graft stenosis and occlusion pooled together (prevalence, 14/70; 20%) were detected with a sensitivity of 85%, specificity of 95%, positive predictive value of 80%, and negative predictive value of 96%. Vein graft disease was found in eight (42%) of 19 patent vein grafts (graft age, 15.6 +/- 2.3 years). The disease was nonobstructive in three (16%) of the 19 grafts. The course of the left internal mammary artery was median retrosternal (< 1 cm deep) in 33.3% of conventionally sutured grafts.

CONCLUSION

Sixty-four-slice CT angiography can be used for accurate exclusion of greater than 50% graft stenosis, but detection of distal anastomotic stenosis is limited, and the degree of stenosis can be overestimated. The advantages of CT, however, are that it is noninvasive, vein graft disease can be diagnosed at an early stage, and complementary evaluation of extracardiac anatomic features provides useful information before coronary artery bypass grafting is redone.

[Clinical development of cardiac CT diagnostics: clinical and scientific applications from the cardiologist's point of view]

The development of cardiac CT imaging has been extraordinary in the last few years. Due to excellent cooperation with our radiology departments we have been able to gain a very close insight into the newest clinical and technical improvements made in this field. The following article aims to highlight the relevant, practically orientated indications and applications of cardiac CT. Furthermore you will find a summary of clinically driven multicenter and interdisciplinary scientific work using this fascinating imaging modality.

Left main coronary artery stenosis: state-of-the-art

Patients with stenosis of the left main coronary artery present difficult challenges. The risks associated with this lesion have been known since the early days of angiography when patients were found to have increased mortality during follow-up. This information led to the general guidelines that surgical revascularization should be considered the treatment of choice in patients with significant left main coronary artery stenosis. Current advances in invasive cardiology have brought important information to the field. Intravascular ultrasound is now used routinely to evaluate angiographically indeterminate lesions with criteria now set forward as to what constitutes an indication for revascularization. Stents have even further dramatically changed the landscape. There are substantial issues, however, that need to addressed. These include the following: (1) the effect of specific lesion location on outcome - it is known that patients with distal bifurcation left main disease have worse outcome; (2) the potential for subacute thrombosis of the left main coronary artery; (3) the impact of left ventricular function and patient comorbidities irrespective of the degree and location of left main coronary artery stenosis; and (4) the risk-benefit ratio of stenting versus coronary artery bypass graft surgery. These issues are currently being addressed in two seminally important trials including the SYNTAX trial, which randomizes patients with left main and/or three-vessel disease to either coronary artery bypass graft surgery or a TAXUS drug-eluting stent. This trial is in the final stages of patient recruitment and will have important implications for the field. The other trial is the COMBAT trial, which is focused exclusively on left main coronary artery stenosis and randomizes patients with left main coronary artery disease either to a Sirolimus-eluting stent (Cypher, Johnson and Johnson Cordis, USA) or to coronary artery bypass graft surgery. The field of left main coronary artery disease continues to expand in terms of the evidence available for optimal patient evaluation and selection of treatment modalities.

Sixty-Four Slice CT Evaluation of Aortic Stenosis Using Planimetry of the Aortic Valve Area

OBJECTIVE

The purpose of our study was to evaluate planimetry of the aortic valve area with 64-slice CT in comparison with transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) in patients with aortic stenosis.

MATERIALS AND METHODS

Thirty-six patients with aortic valve disease referred for coronary 64-slice CT angiography were examined. Planimetry of the aortic valve area with 64-slice CT was compared with TTE using the Doppler continuity equation for calculation of the aortic valve area and with planimetric measurement of the aortic valve area using TEE.

RESULTS

Planimetry of the aortic valve area with CT (1.11 +/- 0.42 cm2) showed a good correlation with TTE (1.05 +/- 0.42 cm2) (r = 0.88, p < 0.001) in 32 patients and a good correlation with TEE (1.41 +/- 1.61 cm2) (r = 0.99, p < 0.0001) in 10 patients. The mean and maximum transvalvular pressure gradients were correlated with the aortic valve area as measured with CT (r = -0.68, p = 0.0001; and r = -0.67, p = 0.0001, respectively). Beta-blockers were not given (mean heart rate, 62.5 +/- 10.7 beats per minute).

CONCLUSION

MDCT allows accurate planimetry of the aortic valve area in patients with aortic stenosis. In patients referred for 64-slice CT coronary angiography, concomitant aortic stenosis can be identified and evaluated.

Image quality of the aortic and mitral valve with CT: relative versus absolute delay reconstruction

RATIONALE AND OBJECTIVE

The purpose of this study was to compare image quality and artifacts of 16-detector row CT imaging of the aortic and mitral valve when performing ECG-gated synchronization using relative and absolute reconstructions.

MATERIALS AND METHODS

Cardiac CT was performed in 22 consecutive patients; 20 data sets per RR interval were reconstructed with relative and absolute reconstructions. Mean and variability of heart rate during data acquisition were noted. Two readers assessed contrast media-related artifacts, calcification-related artifacts, ECG gating-related artifacts, and image quality in parallel and perpendicular planes.

RESULTS

Contrast media-related and calcification-related artifacts similarly occurred with both reconstruction techniques. ECG gating-related artifacts occurred in both valves more often with relative reconstructions than with absolute reconstructions (p = .001). Image quality was significantly better for absolute reconstructions for the open aortic cusp surface (p = .014) and edge (p = .008) in both planes, and of the closed mitral valve leaflets (p = .003) and apposition zone (p = .003) in perpendicular planes. Occurrence of ECG gating-related artifacts in both valves significantly correlated (p = .01) with heart rate variability for relative reconstructions, whereas no correlation was found using the absolute technique.

CONCLUSION

Absolute reconstructions allow CT imaging of the aortic and mitral valve with fewer artifacts and are less sensitive to heart rate variability as compared to relative reconstructions.

Chasing the heart: new developments for cardiac CT

With the latest generations of multidetector row computed tomography (CT) scanners, CT of the heart is about to fulfill its promise to become the premier noninvasive imaging modality for the cardiac assessment. The performance of this modality has been continuously improved to a point where CT, beyond mere feasibility studies, is firmly establishing its role in the diagnostic work-up of patients with suspected cardiac disease. This has been enabled by ongoing technical refinements, which are the topic of this contribution. This review traces the evolution of CT for cardiac applications, describes the current status of scanner technology with special emphasis on dual-source CT, and provides insights into potential future developments for further refinement of this technique.

The Simultaneous Assessment of Aortic Valve Area and Coronary Artery Stenosis Using 16-Slice Multidetector-Row Computed Tomography in Patients With Aortic StenosisComparison With Echocardiography

BACKGROUND

Recent advancements in 16-slice multidetector-row computed tomography (16-slice MDCT) provide for non-invasive assessment of not only coronary artery disease (CAD), but also myocardial properties and the anatomy of the whole heart. The purpose of the present study was to investigate whether the aortic valve area (AVA) in patients with aortic stenosis (AS) assessed by 16-slice MDCT corresponds to echocardiographic assessment and to evaluate simultaneously the clinical accuracy in detecting CAD with 16-slice MDCT.

METHODS AND RESULTS

The AVA of 29 consecutive AS patients with transthoracic echocardiography (TTE) and 16-slice MDCT were analyzed. The AVA was estimated by means of the continuity equation method in 2-dimensional echocardiography (DE) and the quantitative planimetric method after multi-planar reformation in 16-slice MDCT. Concomitantly, the severity of the coronary artery stenosis was assessed by 16-slice MDCT. In the present study, the AVA assessed by TTE and 16-slice MDCT was 1.34+/-0.32 cm(2) and 1.38+/-0.32 cm(2), respectively. Regression analysis showed that the AVA in patients with AS determined by 16-slice MDCT correlated well with those determined by 2-DE (r=0.96, p<0.001). Significant coronary artery stenosis of more than 50% diameter reduction was present in 48% of the study population.

CONCLUSIONS

In patients with AS, the analysis of the severity of the AVA by 16-slice MDCT provides a feasible and accurate estimation with the concomitant evaluation of CAD.

Electrocardiogram-Independent Image Reconstruction in Cardiac Multidetector Computed Tomography Using Retrospective Motion Synchronization

OBJECTIVE

We sought to evaluate an electrocardiogram (ECG)-independent image reconstruction technique for coronary computed tomography (CT)-angiography based on cardiac motion.

MATERIALS AND METHODS

The raw data from 20 patients was reconstructed with both an ECG-gated algorithm and a motion-dependent algorithm that calculates the cardiac motion-function directly from the CT raw data using a center of mass technique. Images were reconstructed in 5% steps over the R-R interval and the cardiac motion-cycle. For both approaches multiplanar reformations were created and the set of images with the least motion artifacts was used for the evaluation. Motion artifacts affecting the ascending aorta, the left main coronary artery and the entire course of the LAD, LCX and RCA were scored using a 5-point scale.

RESULTS

The mean optimal reconstruction window was at 60% of the R-R interval and 30% of the cardiac motion cycle. A total of 73 of 100 vascular regions showed no motion artifacts in ECG-gated images, with the motion-synchronized algorithm only 41 regions were free of motion artifacts. The mean motion-score was 1.4 (+/-0.6) and 2.4 (+/-1.2) respectively (P < 0.05).

CONCLUSION

In the currently implemented form the motion-gated algorithm is inferior to ECG-gated image reconstruction but can be used in patients with an incomplete or corrupt ECG-signal.

Cardiac CT: coronary arteries and beyond

Multi-detector-row computed tomography (MDCT) has emerged as a rapidly developing method for non-invasive imaging of the heart. An understanding of ECG synchronization, contrast material administration, patient preparation and image post-processing is needed to optimize image quality. The basic technical principles and essentials of these technical basics are described here. Correctly applied cardiac MDCT allows imaging of the coronary arteries including coronary anatomy and stenosis detection. The same is true for evaluation of coronary artery bypass grafts and, to some extent, coronary artery stents. While quantification of total calcified plaque burden has been long established, coronary MDCT allows assessing plaque morphology and constitution. Recent approaches go beyond the coronaries and include evaluation of left ventricular function at rest and myocardial viability. In combination with experimental approaches for assessing aortic valve function and myocardial perfusion imaging, cardiac MDCT offers the potential for a comprehensive examination of the heart using a single breath-hold examination.

Multidetector CT for visualization of coronary stents

Whereas the clinical diagnosis of in-stent thrombosis is straightforward, that of in-stent restenosis remains a problem, because although many patients experience chest pain after coronary stent placement, that symptom is secondary to ischemia in only a few. The use of a noninvasive technique to identify such patients for early invasive intervention versus more conservative management is thus highly desirable. Multidetector computed tomography (CT) performed with 16-section scanners recently emerged as such a technique and has overtaken modalities such as electron-beam CT and magnetic resonance imaging as an alternative to conventional angiography for the assessment of in-stent restenosis. The improved hardware design of the current 64-section CT scanners allows even better delineation of stent struts and lumen. The more reliable criterion of direct lumen visualization thus may be substituted for the presence of distal runoff, which lacks specificity for a determination of in-stent patency because of the possibility of collateral pathways. However, the capability to accurately visualize the in-stent lumen depends partly on knowledge of the causes of artifacts and how they can be compensated for with postprocessing and proper image display settings. In addition, an understanding of the major stent placement techniques used in the treatment of lesions at arterial bifurcations is helpful.

In vitro Evaluation of Metallic Coronary Artery Stents with Sub-Millimeter Multi-Slice Computed Tomography Using an ECG-Gated Cardiac Phantom: Relationship between In-Stent Visualization and Stent Type

The aim of this experimental study was to investigate visualization of various coronary artery stents with sub-millimeter multi-slice spiral computed tomography (MSCT) using a cardiac physical phantom. Four 3-mm stents of various designs were implanted in tubes with an inner diameter of 3 mm to simulate coronary artery. Stents were placed on a cardiac phantom and scanned at different heart rates. Retrospective ECG-gated adaptive segmental reconstruction technique was employed. Profile curves across longitudinal curved planar reconstruction images of the stents were generated. From the profile curve, the full width at half maximum was defined as the stent lumen index. The effect of heart rate and stent type on the stent lumen index was evaluated. Visual evaluation for each stent at various heart rates was also performed. The heart rate had no significant effect on in-stent visualization. However, in-stent visualization differed significantly for the various stent types for both profile curve analysis and visual evaluation (the Tukey-Kramer multiple comparisons test). Multiple regression analysis indicated that strut thickness, especially minimal strut thickness, was the significant influencing factor for the in-stent visualization. On the basis of four stent models examined it would appear that visualization of the coronary stent lumen varies depending on the stent type, but not on the heart rate. Stents with slim struts are preferable for in-stent evaluation with multi-slice spiral computed tomography.

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.

High iodine concentration contrast material for noninvasive multislice computed tomography coronary angiography: iopromide 370 versus iomeprol 400

OBJECTIVE

The objective of this study was to compare intracoronary attenuation on 16-row multislice computed tomography (16-MSCT) coronary angiography using 2 contrast materials (CM) with high iodine concentration.

MATERIAL AND METHODS

Forty consecutive patients (29 male, 11 female; mean age, 61+/-11 years) with suspected coronary artery disease were randomized to 2 groups to receive 100 mL of either iopromide 370 (group 1: Ultravist 370, 370 mg iodine/mL; Schering AG, Berlin, Germany) or iomeprol 400 (group 2: Iomeron 400, 400 mg iodine/mL; Bracco Imaging SpA, Milan, Italy). Both CM were administered at a rate of 4 mL/s. All patients underwent 16-MSCT coronary angiography (Sensation 16; Siemens, Germany) with collimation 16 x 0.75 mm and rotation time 375 ms. The attenuation in Hounsfield units (HU) achieved after each CM was determined at regions of interest (ROIs) placed at the origin of coronary arteries and on the ascending aorta, descending aorta, and pulmonary artery. Differences in mean attenuation in the coronary arteries and on the ascending aorta, descending aorta, and pulmonary artery were evaluated using Student t test.

RESULTS

The mean attenuation achieved at each anatomic site was consistently greater after iomeprol 400 than after iopromide 370. At the origin of coronary arteries, the mean attenuation after iomeprol 400 (340+/-53 HU) was greater (P<0.05) than that after iopromide 370 (313+/- 42 HU). Similar findings were noted for the mean attenuation in the ascending aorta, descending aorta, and pulmonary artery.

CONCLUSION

The intravenous administration of iomeprol 400 provides higher attenuation of the coronary arteries and of the great arteries of the thorax as compared with iopromide 370 using the same injection parameters.

Aortic Stenosis: Comparative Evaluation of 16–Detector Row CT and Echocardiography

PURPOSE

To prospectively evaluate whether planimetric measurements of aortic valve area (AVA) with 16-detector row computed tomography (CT) allow classification of aortic stenosis (AS).

MATERIALS AND METHODS

The study had institutional review board approval; patients gave informed consent. Twenty patients (11 men, nine women; mean age, 63 years) with AS and 20 patients (10 men, 10 women; mean age, 65 years) without underwent transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and retrospectively electrocardiographically gated 16-detector row CT. Twenty CT data sets were reconstructed in 5% steps of R-R interval; data analysis was performed with four-dimensional software. Maximum AVA in systole planimetrically measured with CT (AVA(CT)) was compared with AVA planimetrically measured with TEE (AVA(TEE)), AVA calculated with the continuity equation and TTE (AVA(TTE)), and transvalvular pressure gradients determined with the Bernoulli equation and TTE. Correlations among AVA(CT), AVA(TTE), AVA(TEE), and transvalvular pressure gradients were tested with bivariate regression analysis; agreement between methods was assessed with the Bland-Altman method.

RESULTS

In patients without AS, mean AVA(CT) was 3.56 cm2 +/- 0.66 and mean AVA(TEE) was 3.43 cm2 +/- 0.69. In patients with AS, mean AVA(CT) was 0.89 cm2 +/- 0.35; mean AVA(TEE), 0.86 cm2 +/- 0.35; and mean AVA(TTE), 0.83 cm2 +/- 0.33. Mean transvalvular pressure gradient was 51 mm Hg +/- 22. Significant correlations were present between AVA(CT) and AVA(TEE) (r = 0.99, P < .001), AVA(CT) and AVA(TTE) (r = 0.95, P < .001), and AVA(CT) and transvalvular pressure gradients (r = -0.74, P < .01). Mean differences were -0.08 cm2 (limits of agreement: -0.32, 0.16) for AVA(CT) versus AVA(TEE) and 0.06 cm2 (limits of agreement: -0.15, 0.26) for AVA(CT) versus AVA(TTE).

CONCLUSION

Planimetric measurements of AVA with retrospectively electrocardiographically gated 16-detector row CT allow classification of AS that is similar to that achieved with measurements by using echocardiographic methods.

Diagnostic Performance of MDCT for Detecting Aortic Valve Regurgitation

OBJECTIVE

This study evaluates whether ECG-gated 16-MDCT coronary angiography provides a reliable imaging technique for detecting aortic regurgitation (AR).

SUBJECTS AND METHODS

We examined 71 patients prospectively with 16-MDCT angiography using retrospective ECG gating during the mid-to-end diastolic phase. A visible central valvular leakage area was considered as a diagnostic criterion for AR. The central valvular leakage area was quantified in patients with positive transthoracic echocardiography (TTE). We compared 16-MDCT to Doppler TTE, the accepted diagnostic standard based on semiquantitative regurgitation jet analysis (grade 0-3+ for mild, moderate, and severe).

RESULTS

The overall sensitivity of 16-MDCT for the identification of patients with AR was 81%. The specificity was 91%, the negative predictive value was 70%, and the positive predictive value was 95%. Of the 71 patients, 48 had AR determined by TTE, and 16-MDCT correctly detected AR in 39 of those 48 patients. The sensitivity of 16-MDCT for the detection of patients with moderate and severe AR (grade > or = 1.5+) was 95%, and the specificity was 96% (20 of 21 patients). The sensitivity of 16-MDCT for identification of patients with mild AR (grade < or = 1+) was 70%, and the specificity was 92% (19 of 27 patients). Quantification of the central valvular leakage area was not possible in 50% of cases with AR by TTE because of valve calcifications.

CONCLUSION

Sixteen-MDCT coronary angiography provides an accurate, noninvasive imaging technique to detect moderate and severe aortic regurgitation (grade > or = 1.5+). However, severe valve calcifications and mild AR limit its results.

Synergy of MDCT and Cine MRI for the Evaluation of Cardiac Motility

OBJECTIVE

The objective of our study was to validate the feasibility of the synergistic use of cardiac MR and CT data sets for ventricular motility analysis and to correlate measurement variability with underlying heart rate.

SUBJECTS AND METHODS

Twenty patients underwent concurrent ECG-gated MDCT and MRI for evaluation of ventricular motility, expressed as ventricular wall thickening and motion. Initially, individual measurement repetition series were analyzed by determining intraobserver variability and detecting intraobserver bias related to heart rates. Subsequently, absolute measurement differences of CT or MR data were statistically evaluated. Finally, absolute measurement differences were correlated with underlying heart rates by curve estimation regression.

RESULTS

Analysis of measurement reproducibility proved that data variability was dependent on only the anatomic localization of the analyzed ventricular segment, not on the imaging technique used or underlying heart rate, in normofrequent patients. Comparing MR and CT image data sets, no statistically significant differences were identified when ventricular motility was evaluated based on data sets of either imaging technique in normofrequent patients. Tachycardic frequencies, above 100 beats per minute, led to exponential error propagation due to insufficient temporal resolution of the current CT technology.

CONCLUSION

This study proved that cardiac motility assessment based on ECG-gated CT and MR data sets resulted in comparable ventricular function results for normofrequent patients; however, the high spatial resolution of cardiac MDCT cannot compensate for the lack of temporal resolution in patients with tachycardia, thus emphasizing the necessity of reporting ventricular motility analysis results in combination with heart rate to allow consideration of this possible cause for measurement variation.

Sixteen-Channel Multidetector Row Computed Tomography versus Coronary Angiography in a Surgical View

BACKGROUND

Invasive coronary angiography (ICA) is the gold standard for the diagnosis of coronary artery disease and also for imaging procedures for preoperative planning of coronary artery bypass grafting (CABG). Sixteen-multidetector row computed tomography (MDCT) represents an alternative depiction of coronary vessels.

METHODS

Preoperative exams included ICA and MDCT in 50 patients. Two blinded surgical readers independently investigated both diagnostic modalities regarding location, severity, and morphology of the stenoses. The right coronary artery, left anterior descending branch, and circumflex branch--each divided in 3 sections--and the left main artery with a diameter (3) 1.5 mm were rated in both procedures, and the percentage of complete evaluations by MDCT was assessed.

RESULTS

Heart rate was 72 +/- 8 bpm. Forty-six percent of patients received a complete MDCT evaluation, and 54% received an incomplete MDCT evaluation. In 62% of these incompletely examined patients, 1 branch was not completely analyzable, in 31% 2 branches; and in 7% all 3 branches. In total, 9% of all segments were incompletely assessed. Investigators detected coronary stenoses in complete evaluations with a sensitivity of 94% and a specificity of 95%. Positive predictive value was 87% and negative predictive value was 98%. Plaque classification in soft and hard plaques was possible.

CONCLUSION

Sixteen-MDCT is not a viable alternative diagnostic tool at present. However, although the percentage of incomplete evaluated patients is more then 50%, only 9% of all segments were incompletely assessable. If this technology can be further improved, especially its software, it will become a valid diagnostic tool for coronary artery disease.

Nontraumatic Thoracic Emergencies

Acute chest pain is one of the most common complaints of patients who present to an emergency department, and accounts for up to 5% of all visits. It also is one of the most complex issues in an emergency setting because, although clinical signs and symptoms often are nonspecific, rapid diagnosis and therapy are of great importance. The chest radiograph remains an important component of the evaluation of chest pain, and usually is the first examination to be obtained. Nevertheless, cross-sectional imaging has added greatly to the ability to characterize the wide constellation of clinical findings into a distinct etiology. This article reviews how the various entities that can present as nontraumatic chest pain can manifest radiographically.

High-resolution 16-MDCT evaluation of radial artery for potential use as coronary artery bypass graft: a feasibility study

OBJECTIVE

The objective of our study was to assess the feasibility of using 16-MDCT angiography for the preoperative assessment of the radial and ulnar arteries and the palmar arches in patients scheduled for radial artery harvesting for coronary artery bypass graft (CABG) surgery.

CONCLUSION

Sixteen-MDCT angiography shows promise for the noninvasive preoperative assessment of the radial artery as a CABG donor site.

Mitral Regurgitation: Quantification with 16–Detector Row CT—Initial Experience

PURPOSE

To prospectively determine if retrospectively electrocardiographic (ECG)-gated multi-detector row computed tomography (CT) with a 16-detector row CT scanner can depict mitral regurgitation and enable quantification of the severity of the disease.

MATERIALS AND METHODS

The study had institutional review board approval, and patients gave informed consent. Nineteen patients with mitral regurgitation (10 men, nine women; mean age, 66 years +/- 9 [standard deviation]; range, 41-83 years) and 25 patients without mitral regurgitation (14 men, 11 women; mean age, 68 years +/- 9; range, 43-83 years) as determined with transesophageal color Doppler echocardiography and ventriculography underwent retrospectively ECG-gated 16-detector row CT. Twenty CT data sets covering the entire mitral valve apparatus were reconstructed in 5% steps of the R-R interval for each patient, and data analysis was performed with four-dimensional software. Using planimetry, two readers measured in consensus the area of the regurgitant orifice during systole. These measurements were compared with semiquantitative data from transesophageal echocardiography and ventriculography by using Spearman rank order correlation coefficients.

RESULTS

In the 25 patients without mitral regurgitation, no regurgitant orifice during systole could be detected with multi-detector row CT. In the 19 patients with mitral regurgitation, a regurgitant orifice could be visualized in all cases. The mean regurgitant orifice area at CT-45 mm(2) +/- 34 (range, 10-148 mm(2))-correlated significantly with the results at transesophageal echocardiography (r = 0.807, P < .001) and ventriculography (r = 0.922, P < .001).

CONCLUSION

Planimetric measurements of the regurgitant orifice area at retrospectively ECG-gated 16-detector row CT enable quantification of mitral regurgitation.

16-MDCT Aortography with a Low-Dose Contrast Material Protocol

OBJECTIVE

The objective of our study was to evaluate whether a low-dose contrast material (CM) protocol with a saline flush might provide sufficient contrast enhancement in aortoiliac 16-MDCT angiography.

SUBJECTS AND METHODS

Forty-five patients were divided into two groups on the basis of the CM (300 mg I/mL) administration protocol: group 1 (23 patients) received 100 mL of CM at 3.0 mL/sec; and group 2 (22 patients), 50 mL of CM at 3.0 mL/sec followed by a 20-mL saline flush at 3.0 mL/sec. All patients underwent 16-MDCT angiography of the entire aortoiliac region. Seven regions of interest (ROIs) were drawn from the ascending aorta (ROI 1) to the external iliac artery (ROI 7). Quantitative analysis was performed by calculating the mean aortoiliac attenuation and the mean difference between the maximum and minimum attenuation values. Vascular enhancement of the renal arteries was visually assessed using 2D and 3D postprocessing techniques.

RESULTS

The mean aortoiliac attenuation in group 1 was 314.3 +/- 45.9 H and that in group 2 was 306.1 +/- 35.0 H. The difference was not statistically significant. Adequate mean aortoiliac attenuation was achieved in 95.7% (22/23) and 95.5% (21/22) of patients in groups 1 and 2, respectively. The difference was not statistically significant. The mean difference between the maximum and minimum attenuation values was significantly smaller in group 1 (41.3 +/- 16.8 H) than in group 2 (57.2 +/- 25.3 H). The renal arteries were assessable in all patients in both groups.

CONCLUSION

This protocol of 50 mL of CM with a saline flush provides attenuation comparable to that obtained with the 100 mL of CM in aortoiliac 16-MDCT angiography.

When, Why, and How to Examine the Heart During Thoracic CT: Part 1, Basic Principles

OBJECTIVE

MDCT systems with fast scanning capabilities can acquire images of the thorax with reduced cardiac motion artifacts, enabling improved evaluation of the heart and surrounding structures in the course of routine thoracic CT. This article describes the principles of including an evaluation of the heart in the course of a chest CT examination in terms of both examination technique and image interpretation. In addition, both the normal appearances and some of the most common abnormal appearances of the cardiac structures will be described.

CONCLUSION

Details concerning the cardiac structures can inform interpretation of thoracic CT studies and can influence the patient's clinical management. Both unenhanced and contrast-enhanced scans can detect significant cardiac disorders that may otherwise go undetected. In certain situations, a CT examination of the entire chest, complemented by cardiac gating, can provide a more dedicated analysis of the heart and coronary arteries, providing both morphologic and functional information.

Detection of Pulmonary Embolism Using 16-Slice Multidetector-Row Computed Tomography

OBJECTIVE

To compare different image reconstruction parameters for detecting emboli of the pulmonary arteries according to anatomic levels using 16-slice multidetector-row computed tomography in patients suspected of having an acute pulmonary embolism (PE).

METHODS

Sixty-two patients (33 male and 29 female) with a clinically suspected acute PE were included in the present study. Multidetector-row computed tomography scans were performed using 16-mmx0.75-mm collimation. Based on the computed tomography data set, different image reconstruction parameters were used for each patient: axial slice thicknesses (STs) of 0.75, 2, 4, and 6 mm; axial maximum intensity projection (MIP) STs of 4 mm; and coronal STs of 2 and 4 mm. In joint reading fashion, 2 experienced radiologists reviewed examination findings regarding the presence and/or absence of a PE. The reference standard for visualization and detection of PEs was defined using the axial images with a 0.75-mm ST.

RESULTS

In 23 of 62 patients, a PE was diagnosed. For main and lobar pulmonary arteries, the sensitivities and specificities were as follows: axial 2-mm images, 1.0/1.0; axial 4-mm images, 1.0/1.0; axial 6-mm images, 0.97/0.99; MIP 4-mm images, 0.95/0.99; coronal 2-mm images, 1.0/1.0; and coronal 4-mm images, 1.0/1.0. Regarding segmental and subsegmental pulmonary arteries, sensitivity and specificity varied: axial 2-mm images, 0.97/1.0; axial 4-mm images, 0.81/0.99; axial 6-mm images, 0.65/0.99; axial MIP 4-mm images, 0.63/0.99; coronal 2-mm images, 0.91/0.99; and coronal 4-mm images, 0.74/0.99.

CONCLUSIONS

In detecting segmental and subsegmental PEs, only the axial images with an ST of 2 mm proved to have results comparable with the axial 0.75-mm images. Therefore, thin-slice collimation and ST are mandatory for visualization of segmental and subsegmental PEs in patients suspected of having an acute PE.

Usefulness of 4-, 8-, and 16-slice computed tomography for detection of graft occlusion or patency after coronary artery bypass grafting

The sensitivity and specificity of computed tomographic angiography for the evaluation of coronary artery bypass grafts (CABGs) was reviewed. A search of published studies in all languages was performed, incorporating electronic and manual components. A total of 985 patients with 2,200 CABGs participated in investigations with single-detector computed tomography (CT), 441 patients (1,246 CABGs) with 4-slice CT, none with 8-slice CT, and 144 patients (416 grafts) with 16-slice CT. Pooled data showed a sensitivity for the detection of complete occlusion with single-slice CT of 81% (402 of 494 patients), with 4-slice CT of 93% (293 of 315 patients), and with 16-slice CT of 99% (75 of 76 patients). The specificity, based on pooled data, using single-slice CT was 89% (1,507 of 1,697 patients), with 4-slice CT was 96% (878 of 915 patients), and with 16-slice CT was 98% (301 of 306 patients). The detection of complete occlusion and the detection of patency in saphenous vein bypass grafts and arterial bypass grafts were similar with multislice CT. Limited data were available on the detection of significant stenosis, exclusive of complete occlusion. With 4-slice CT, the sensitivity was 74% (23 of 31 patients) and was 88% (21 of 24 patients) with 16-slice CT. In conclusion, single-detector CT was able to detect graft patency, but it was not sensitive for graft occlusion. The data suggest that 4- and 16-slice CT can be used for the detection of complete graft occlusion or graft patency of CABGs. Significant stenosis was better assessed with 16-slice CT than with 4-slice CT.

First performance evaluation of a dual-source CT (DSCT) system

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

First performance evaluation of a dual-source CT (DSCT) system

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

Assessment of left ventricular myocardial function using 16-slice multidetector-row computed tomography: comparison with magnetic resonance imaging and echocardiography

OBJECTIVE

To assess functional parameters using multidetector-row computed tomography (MDCT) and echocardiography and to compare the results with magnetic resonance imaging (MRI).

MATERIALS AND METHODS

End-diastolic-volume (EDV), end-systolic-volume (ESV), stroke-volume (SV), ejection-fraction (EF), and myocardial mass (MM) were calculated based on CT data sets from 52 patients. Echocardiography was performed in 24 of the 52 patients. The results from MDCT and echocardiography were compared with MRI.

RESULTS

A strong correlation between MDCT and MRI (r=0.66-0.90) was found for all parameters. Echocardiography revealed a low or moderate correlation (0.05-0.59). Compared to MRI the average differences with MDCT were for EDV 15.1 ml, ESV 10.6 ml, SV 4.5 ml, EF 1.8%, and MM 8.2 g, for EDV determined by echocardiography 36.2 ml, ESV 6.8 ml, and EF 13.9%. Bland-Altman analysis revealed acceptable limits of agreement between MRI and MDCT.

CONCLUSIONS

MDCT enables reliable quantification of left ventricular function. Echocardiography was found to have only a moderate agreement of functional parameters with MRI.