Curved multiplanar reconstructions for the evaluation of contrast-enhanced electron beam CT of the coronary arteries

Imaging in urethral stricture disease: an educational review of current techniques with a focus on MRI

Urethral stricture disease refers to narrowing of the urethral lumen obstructing the flow of urine. Urethral strictures can significantly impact daily life due to incontinence, incomplete emptying, hesitancy, and increased risk of urinary tract infections. Imaging is central to the evaluation of suspected urethral stricture, as assessment of stricture length and severity is crucial for guidance of surgical management. The currently employed modalities include radiography, chiefly retrograde urethrography (RUG) and voiding cystourethrography (VCUG); magnetic resonance urethrography (MRU); and sonourethrography (SUG). MRU has become a recent focus of research as it provides high spatial resolution, multiplanar capacity, and soft tissue type differentiation for evaluation of periurethral compartments and concurrent soft tissue defects. The protocol for MRU has evolved over the years to now include dynamic micturition imaging and image reconstruction options. In this review, we discuss each of the imaging modalities used in the diagnosis and evaluation of urethral stricture and provide an overview of literature on MRU over the last decade, including suggested indications that have not yet been incorporated into current guidelines. We delineate scenarios where special diagnostic imaging beyond radiography is beneficial, providing examples from our practice and description of our techniques for each modality.

The effect of the surgical approach and cochlear implant electrode on the structural integrity of the cochlea in human temporal bones

Cochlear implants (CI) restore hearing of severely hearing-impaired patients. Although this auditory prosthesis is widely considered to be very successful, structural cochlear trauma during cochlear implantation is an important problem, reductions of which could help to improve hearing outcomes and to broaden selection criteria. The surgical approach in cochlear implantation, i.e. round window (RW) or cochleostomy (CO), and type of electrode-array, perimodiolar (PM) or lateral wall (LW), are variables that might influence the probability of severe trauma. We investigated the effect of these two variables on scalar translocation (STL), a specific type of severe trauma. Thirty-two fresh frozen human cadaveric ears were evenly distributed over four groups receiving either RW or CO approach, and either LW or PM array. Conventional radiological multiplanar reconstruction (MPR) was compared with a reconstruction method that uncoils the spiral shape of the cochlea (UCR). Histological analysis showed that RW with PM array had STL rate of 87% (7/8), CO approach with LW array 75% (6/8), RW approach with LW array 50% (4/8) and CO approach with PM array 29% (2/7). STL assessment using UCR showed a higher inter-observer and histological agreement (91 and 94% respectively), than that using MPR (69 and 74% respectively). In particular, LW array positions were difficult to assess with MPR. In conclusion, the interaction between surgical approach and type of array should be preoperatively considered in cochlear implant surgery. UCR technique is advised for radiological assessment of CI positions, and in general it might be useful for pathologies involving the inner ear or other complex shaped bony tubular structures.

Post-mortem computed tomography: Technical principles and recommended parameter settings for high-resolution imaging

Post-mortem computed tomography (PMCT) has become a standard procedure in many forensic institutes worldwide. However, the standard scan protocols offered by vendors are optimised for clinical radiology and its main considerations regarding computed tomography (CT), namely, radiation exposure and motion artefacts. Thus, these protocols aim at low-dose imaging and fast imaging techniques. However, these considerations are negligible in post-mortem imaging, which allows for significantly increased image quality. Therefore, the parameters have to be adjusted to achieve the best image quality. Several parameters affect the image quality differently and have to be weighed against each other to achieve the best image quality for different diagnostic interests. There are two main groups of parameters that are adjustable by the user: acquisition parameters and reconstruction parameters. Acquisition parameters have to be selected prior to scanning and affect the raw data composition. In contrast, reconstruction parameters affect the calculation of the slice stacks from the raw data. This article describes the CT principles from acquiring image data to post-processing and provides an overview of the significant parameters for increasing the image quality in PMCT. Based on the CT principles, the effects of these parameters on the contrast, noise, resolution and frequently occurring artefacts are described. This article provides a guide for the performance of PMCT in morgues, clinical facilities or private practices.

Multipath Curved Planar Reformations of Peripheral CT Angiography: Diagnostic Accuracy and Time Efficiency

Objectives

To compare diagnostic performance and time efficiency between 3D multipath curved planar reformations (mpCPRs) and axial images of CT angiography for the pre-interventional assessment of peripheral arterial disease (PAD), with digital subtraction angiography as the standard of reference.

Methods

Forty patients (10 females, mean age 72 years), referred to CTA prior to endovascular treatment of PAD, were prospectively included and underwent peripheral CT angiography. A semiautomated toolbox was used to render mpCPRs. Twenty-one arterial segments were defined in each leg; for each segment, the presence of stenosis > 70% was assessed on mpCPRs and axial images by two readers, independently, with digital subtraction angiography as gold standard.

Results

Both readers reached lower sensitivity (Reader 1: 91 vs. 94%, p = 0.08; Reader 2: 89 vs. 93%, p = 0.03) but significantly higher specificity (Reader 1: 94 vs. 89%, p < 0.01; Reader 2: 96 vs. 95%, p = 0.01) with mpCPRs than with axial images. Reader 1 achieved significantly higher accuracy with mpCPRs (93 vs. 91%, p = 0.02), and Reader 2 had similar overall accuracy in both evaluations (94 vs. 94%, p = 0.96). Both readers read mpCPRs significantly faster than axial images (Reader 1: 5′45″ based on mpCPRs vs. 7′40″ based on axial images; Reader 2: 4′41″ based on mpCPRs vs. 6′57″ based on axial images; p < 0.01).

Conclusions

mpCPRs are a promising 3D reformation technique that facilitates a fast assessment of PAD with high diagnostic accuracy.

Electronic supplementary material

The online version of this article (10.1007/s00270-017-1846-3) contains supplementary material, which is available to authorized users.

Coronary artery analysis: Computer-assisted selection of best-quality segments in multiple-phase coronary CT angiography

PURPOSE

The authors are developing an automated method to identify the best-quality coronary arterial segment from multiple-phase coronary CT angiography (cCTA) acquisitions, which may be used by either interpreting physicians or computer-aided detection systems to optimally and efficiently utilize the diagnostic information available in multiple-phase cCTA for the detection of coronary artery disease.

METHODS

After initialization with a manually identified seed point, each coronary artery tree is automatically extracted from multiple cCTA phases using our multiscale coronary artery response enhancement and 3D rolling balloon region growing vessel segmentation and tracking method. The coronary artery trees from multiple phases are then aligned by a global registration using an affine transformation with quadratic terms and nonlinear simplex optimization, followed by a local registration using a cubic B-spline method with fast localized optimization. The corresponding coronary arteries among the available phases are identified using a recursive coronary segment matching method. Each of the identified vessel segments is transformed by the curved planar reformation (CPR) method. Four features are extracted from each corresponding segment as quality indicators in the original computed tomography volume and the straightened CPR volume, and each quality indicator is used as a voting classifier for the arterial segment. A weighted voting ensemble (WVE) classifier is designed to combine the votes of the four voting classifiers for each corresponding segment. The segment with the highest WVE vote is then selected as the best-quality segment. In this study, the training and test sets consisted of 6 and 20 cCTA cases, respectively, each with 6 phases, containing a total of 156 cCTA volumes and 312 coronary artery trees. An observer preference study was also conducted with one expert cardiothoracic radiologist and four nonradiologist readers to visually rank vessel segment quality. The performance of our automated method was evaluated by comparing the automatically identified best-quality segments identified by the computer to those selected by the observers.

RESULTS

For the 20 test cases, 254 groups of corresponding vessel segments were identified after multiple phase registration and recursive matching. The AI-BQ segments agreed with the radiologist's top 2 ranked segments in 78.3% of the 254 groups (Cohen's kappa 0.60), and with the 4 nonradiologist observers in 76.8%, 84.3%, 83.9%, and 85.8% of the 254 groups. In addition, 89.4% of the AI-BQ segments agreed with at least two observers' top 2 rankings, and 96.5% agreed with at least one observer's top 2 rankings. In comparison, agreement between the four observers' top ranked segment and the radiologist's top 2 ranked segments were 79.9%, 80.7%, 82.3%, and 76.8%, respectively, with kappa values ranging from 0.56 to 0.68.

CONCLUSIONS

The performance of our automated method for selecting the best-quality coronary segments from a multiple-phase cCTA acquisition was comparable to the selection made by human observers. This study demonstrates the potential usefulness of the automated method in clinical practice, enabling interpreting physicians to fully utilize the best available information in cCTA for diagnosis of coronary disease, without requiring manual search through the multiple phases and minimizing the variability in image phase selection for evaluation of coronary artery segments across the diversity of human readers with variations in expertise.

Noninvasive coronary angiography using computed tomography

While noninvasive imaging of the coronary lumen remains challenging, great strides have been made with computed tomography. Two variations of computed tomography are used in the study of the coronary tree: multislice or multidetector computed tomography and electron-beam computed tomography. Both have high spatial and temporal resolutions as well as excellent signal-to-noise ratios, which allows major branches of the coronary tree to be depicted. Impaired image quality, due to dense calcifications and multiple image artifacts including coronary artery motion and breathing artifacts, limits the clinical utility of noninvasive coronary angiography. Early studies with electron-beam angiography demonstrated an overall sensitivity of 85% and specificity of 89% for the detection of obstructive coronary artery disease. With early diastolic imaging, the sensitivity and specificity increases to 92 and 93%, respectively (rather than 80% of the cardiac interbeat interval, where coronary motion is more pronounced). Multidetector computed tomography, with improved spatial resolution but decreased temporal resolution, produces results that vary depending on the equipment. Four-slice scanners have an average sensitivity of only 61%, and only 38% of patients have all four vessels or 15 segments available for analysis, due to both cardiac motion and calcification. Thinner slice collimation with eight and 16 slices have allowed for improved detection. Sensitivity and specificity improve to 80 and 86%, respectively. Furthermore, the number of assessable segments with eight-to 16-slice scanners improves significantly, compared with four-slice scanners (85 vs. 73%; p<0.001). If only assessable segments are included in analysis, sensitivity and specificity for multidetector-row computed tomography improves to nearly 90%. Compared with magnetic resonance imaging, with a reported accuracy of 72% in the only multicenter study, computed tomography has great promise to become the primary method of noninvasive coronary angiography.

Interactive navigation of segmented MR angiograms using simultaneous curved planar and volume visualizations

PURPOSE

Interactive visualization is required to inspect and monitor the automatic segmentation of vessels derived from contrast-enhanced magnetic resonance angiography (CE-MRA). A dual-view visualization scheme consisting of curved planar reformation (CPR) and direct volume rendering (DVR) was developed for this purpose and tested.

METHODS

A dual view visualization scheme was developed using the vessel pathline for both camera position and rotation in 3D, greatly reducing the degrees of freedom (DOF) required for navigation. Pathline-based navigation facilitates coupling of the CPR and DVR views, as local position and orientation can be matched precisely. The new technique was compared to traditional techniques in a user study. Layperson users were required to perform a visual search task that involves checking for (minor) errors in segmentations of MRA data from a software phantom. The task requires the user to examine both views.

RESULTS

Pathline-based navigation and coupling of CPR and DVR provide user speed performance improvements in a vessel inspection task. Interactive MRA visualization with this method, where rotational degrees of freedom were reduced, had no negative effect.

CONCLUSIONS

The DOF reduction achieved by the new navigation technique is beneficial to user performance. The technique is promising and merits comprehensive evaluation in a realistic clinical setting.

Diagnostic accuracy of angiographic view image for the detection of coronary artery stenoses by 64-detector row CT: a pilot study comparison with conventional post-processing methods and axial images alone

BACKGROUND

The angiographic view (AGV) image is a new post-processing method that is similar to conventional coronary angiography (CAG). The purpose of this study was to evaluate its accuracy for coronary stenosis detection by 64-detector row computed tomography (CT).

METHODS AND RESULTS

CT evaluation results of 17 patients were compared with the results of invasive CAG on a coronary segment basis concerning the presence of stenoses>50% diameter reduction. All images of the 3 viewing methods (combination of conventional methods, AGV image alone, and axial images alone) were evaluated in consensus by 3 cardiovascular radiologists. Among 196 assessable segments, invasive CAG showed significant coronary artery stenoses in 44 segments. 43 of 44 lesions were detected with the AGV image, and absence of significant stenosis was correctly identified in 135 of 152 segments (sensitivity 98%; specificity 89%; accuracy 91%; positive predictive value 72%, negative predictive value 99%). The sensitivity of the AGV image was the same as that of conventional methods (98%). There was no significant difference in accuracy between the AGV image (91%) and conventional methods (94%). The accuracy of the AGV image was significantly higher than the axial images alone (78%).

CONCLUSIONS

AGV image shows promise as a post-processing method for identifying coronary artery stenosis with high accuracy.

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).

Diagnostic Accuracy of Image Postprocessing Methods for the Detection of Coronary Artery Stenoses by Using Multidetector CT1

PURPOSE

To retrospectively evaluate the diagnostic accuracy of multidetector computed tomography (CT) coronary angiography for detection of hemodynamically significant (>or=50%) stenoses by using various image postprocessing methods, with conventional coronary angiography as the reference standard.

MATERIALS AND METHODS

The analysis used data from previous studies, use of which had been approved by the Institutional Review Board. Sixteen-section multidetector CT data sets for 40 patients (30 men, 10 women; mean age 56 years +/- 8; mean heart rate, 61 beats per minute +/- 6) were evaluated. Six independent investigators evaluated the data sets for the presence of stenoses with diameter reduction of 50% or more, by using either exclusively transverse images, free oblique multiplanar reconstructions (MPRs), free oblique maximum intensity projections (MIPs, 5 mm thick), prerendered curved MPRs, prerendered curved MIPs, or prerendered three-dimensional volume rendered reconstructions (VRTs). Evaluation results were compared with conventional coronary angiography for each artery in a blinded fashion (chi(2) test).

RESULTS

Overall, 35 coronary artery stenoses were present. Percentage of evaluable arteries and accuracy for detecting stenosis (percentages of accurately classified arteries were, respectively, 99% and 88% for transverse, 99% and 91% for oblique MPR, 94% and 86% for oblique MIP, 94% and 83% for curved MIP, 93% and 81% for curved MPR, and 91% and 73% for VRT). Accuracy was significantly higher for oblique MPR than for curved MPR (P=.01), curved MIP (P=.03), and VRT (P<.001).

CONCLUSION

The evaluation of multidetector CT coronary angiography with interactive image display methods, especially interactive oblique MPRs, permits higher diagnostic accuracy than evaluation of prerendered images (curved MPR, curved MIP, or VRT images).

Multipath curved planar reformation of the peripheral arterial tree in CT angiography

The study was approved by the institutional review board, and informed consent was obtained. The purpose of the study was to prospectively quantify the angular visibility range, determine the existence of orthogonal viewing pairs, and characterize the conditions that cause artifacts in multipath curved planar reformations (MPCPRs) of the peripheral arterial tree in 10 patients (eight men and two women; mean age, 69 years; range, 54-80 years) with peripheral arterial occlusive disease. Percentage of segments with the maximal possible visibility score of 1 was significantly greater (odds ratio, 1.42; P<.001) for MPCPRs than for maximum intensity projections. One or more orthogonal viewing pairs were identified for all above-knee arterial segments, and artifactual vessel distortion was observed when the vessel axis approached a horizontal course in MPCPRs.

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.

Coronary imaging quality in routine ECG-gated multidetector CT examinations of the entire thorax: preliminary experience with a 64-slice CT system in 133 patients

To evaluate image quality in the assessment of the coronary arteries during routine ECG-gated multidetector CT (MDCT) of the chest. One hundred and thirty three patients in sinus rhythm underwent an ECG-gated CT angiographic examination of the entire chest without beta-blockers with a 64-slice CT system. In 127 patients (95%), it was possible to assess the coronary arteries partially or totally; coronary artery imaging failed in six patients (5%), leading to a detailed description of the coronary arteries in 127 patients. Considering ten coronary artery segments per patient, 75% of coronary segments were assessable (948/1270 segments). When the distal segments were excluded from the analysis (i.e., seven coronary segments evaluated per patient), the percentage of assessable segments was 86% (768/889 proximal and mid coronary segments) and reached 93% (474/508) when assessing proximal segments exclusively. The mean number of assessable segments was significantly higher in patients with a heart rate < or =80 bpm (n=95) than in patients with a heart rate >80 bpm (n=38) (p<0.002). Proximal and mid-coronary segments can be adequately assessed during a whole-chest ECG-gated CT angiographic examination without administration of beta-blockers in patients with a heart rate below 80 bpm.

Contrast enhancement in electron beam tomography of the heart: comparison of a monomeric and a dimeric iodinated contrast agent in 59 patients

RATIONALE AND OBJECTIVES

The aim of the study is to determine whether intravascular time-density course and visualization of the coronary arteries differ with use of a hyperosmolar monomeric versus an iso-osmolar dimeric contrast agent in electron beam tomography (EBT) of the heart.

MATERIALS AND METHODS

Fifty-nine patients underwent EBT of the coronary arteries using the monomeric ioversol or the dimeric iodixanol at the same concentration of 320 mg I/mL. Contrast volume was determined relative to body surface area and injected over 40 seconds. Intravascular time-density curves were created for quantitative analysis. For qualitative assessment, visualization of coronary arteries on axial scans and three-dimensional reconstructions was scored. Patients were matched for contrast flow, transit time, and mean pulse rate for statistical analysis.

RESULTS

Ioversol produced a significantly greater increase in intravascular density for up to 30 seconds after injection (P < .01) compared with iodixanol. No difference between the two contrast media was seen in the qualitative assessment.

CONCLUSION

Monomeric and dimeric contrast media differ in their time-density curves at coronary EBT, a reason for which is not apparent. Qualitative evaluation of coronary arteries is not affected by this difference.

16-MDCT Coronary Angiography Versus Invasive Coronary Angiography in Acute Chest Pain Syndrome: A Blinded Prospective Study

OBJECTIVE

The purpose of our study was to prospectively evaluate the usefulness of CT coronary angiography versus invasive coronary angiography for the detection of clinically significant coronary artery disease in patients hospitalized for acute chest pain syndrome.

SUBJECTS AND METHODS

Sixty-six consecutive patients (52 men and 14 women; average age, 57 +/- 11 [SD] years) who were hospitalized for acute chest pain syndrome underwent CT coronary angiography and invasive coronary angiography within an average time interval of 4 days. ECG-gated CT coronary angiography was performed with a 16-MDCT scanner (0.42-sec rotation time, 16 x 0.75 mm detector collimation). Beta-blockers were not administered routinely, and thus the average heart rate was 71 +/- 11 beats per minute. CT coronary angiographic images were evaluated concurrently by two radiologists, who were blinded to invasive coronary angiography results, for stenoses having a diameter of 50% or more, using a 15-segment classification, including all segments 2 mm or more in diameter. The consensus interpretation was compared with results of invasive coronary angiography.

RESULTS

CT coronary angiography was technically successful in 59 patients (89%). After exclusion of 20 (3.1%) of 649 coronary segments, which were classified as nonevaluable by CT coronary angiography, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CT coronary angiography for identifying significant coronary artery disease in the remaining 629 coronary segments were 80% (68/85), 89% (482/544), 52% (68/130), 97% (482/499), and 87% (550/629), respectively. The overall accuracy for the main vessels (left main, left anterior descending, left circumflex, and right coronary arteries) was 93%, 88%, 86%, and 86%, respectively.

CONCLUSION

CT coronary angiography using a 16-MDCT scanner enables accurate noninvasive detection of significant coronary artery disease in patients hospitalized for acute chest pain syndrome. Furthermore, relative high sensitivity and specificity of CT coronary angiography can be achieved without pharmacologic manipulation of patient heart rates.

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.

MDCT Evaluation of the Coronary Arteries, 2004: How We Do It—Data Acquisition, Postprocessing, Display, and Interpretation

OBJECTIVE

Cardiac CT is rapidly becoming part of clinical practice. The objective of this article is to discuss and illustrate the current practice of coronary artery MDCT, including data acquisition, postprocessing, image display, and interpretation. The practice described reflects our experience with a series of patients referred in routine clinical practice.

CONCLUSION

The reader should gain an insight into the current clinical application of coronary artery CT.

Methodology for improved detection of coronary stenoses with computed tomographic angiography

BACKGROUND

Noninvasive angiography is a promising technique for visualization of the coronary lumen; however, current methodologies lead to limited accuracy. We assessed the accuracy of electron beam computed tomographic angiography (EBA) for detection of coronary stenoses, using improved triggering techniques and thinner slice collimation.

METHODS

Eighty-six patients with suspected coronary disease were studied with EBA and conventional invasive coronary angiography. Electrocardiographic triggering was performed at a fixed time in end systole to reduce cardiac motion. Thin (1.5 mm) slices were obtained with 1.5 mm table incrementation. In axial (2-dimensional) EBA images and 3-dimensional reconstructions, all coronary arteries and side branches with a diameter of >or=1.5 mm were assessed for the presence of stenoses with >50% diameter reduction. Both EBA and invasive angiographic images were assessed in a blinded manner.

RESULTS

In comparison to invasive coronary angiography, EBA correctly classified 49 of 53 patients (92%) as having at least 1 coronary stenosis. Overall, 103 stenoses with >50% diameter reduction were present, and 93 of these lesions were correctly detected by EBA (sensitivity 90%, specificity 93%, positive predictive value 84%, and negative predictive value 96%). Only 5% of vessels could not be assessed, predominantly due to significant calcification.

CONCLUSIONS

Thinner slice collimation and end-systolic electrocardiographic triggering improves accuracy and assessment of coronary EBA for the detection of obstructive coronary artery disease, making this study clinically useful in the evaluation of obstructive coronary artery disease.

Noninvasive coronary angiography with 16-detector row CT: effect of heart rate

PURPOSE

To evaluate the effect of heart rate on the quality of coronary angiograms obtained with 16-detector row computed tomography (CT) by using temporally enhanced three-dimensional (3D) approaches.

MATERIALS AND METHODS

The local ethics committee approved the study, and informed consent was obtained from all patients. Fifty patients underwent coronary CT angiography (heart rate range, 45-103 beats per minute). Raw data from helical CT and electrocardiography (ECG) were saved in a combined data set. Retrospectively ECG-gated images were reconstructed at preselected phases (50% and 80%) of the cardiac cycle. A 3D voxel-based approach with cardiac phase weighting was used for reconstruction. Testing for correlation between heart rate, cardiac phase reconstruction window, and image quality was performed with Kruskal-Wallis analysis. Image quality (freedom from cardiac motion-related artifacts) was referenced against findings at conventional angiography in a secondary evaluation step. Regression analysis was performed to calculate heart rate thresholds for future beta-blocker application.

RESULTS

A significant negative correlation was observed between heart rate and image quality (r = 0.80, P < .001). Motion artifact-free images were available for 44 (88%) patients and were achieved consistently at a heart rate of 80 or fewer beats per minute (n = 39). Best image quality was achieved at 75 or fewer beats per minute. Segmental analysis revealed that 97% of arterial segments (diameter > or = 1.5 mm according to conventional angiography) were assessable at 80 or fewer beats per minute. Premature ventricular contractions and rate-contained arrhythmia did not impede diagnostic assessment of the coronary arteries in 10 (83%) of the 12 patients affected.

CONCLUSION

Motion-free coronary angiograms can be obtained consistently with 16-detector row CT scanners and adaptive multicyclic reconstruction algorithms in patients with heart rates of less than 80 beats per minute.

Baseline Heart Rate–adjusted Electrocardiographic Triggering for Coronary Artery Electron-Beam CT Angiography

Conventional electrocardiographic (ECG) triggering (group 1, 53 patients) was compared with baseline heart rate-adjusted ECG triggering (group 2, 54 patients) for coronary artery electron-beam computed tomographic (CT) angiography. CT angiographic data sets were compared blindly with conventional angiograms according to segment. Nonassessability of coronary artery segments was reduced from 35% in group 1 to 13% in group 2 (P < .001). More motion-free coronary artery images were obtained in group 2 than in group 1, especially in the right coronary artery (95% vs 67%, P < .001). Overall sensitivity and specificity for luminal stenosis (> or =50%) were 69% and 82% (group 1) and 76% and 92% (group 2) (P > .05 and P < .001, respectively). Baseline heart rate-adjusted ECG triggering improves image quality at coronary artery CT angiography for detection of coronary artery disease.

Role of curved planar reformations using multidetector spiral CT in diagnosis of pancreatic and peripancreatic diseases

AIM: To investigate the role of curved planar reformations using multidetector spiral CT (MSCT) in diagnosis of pancreatic and peripancreatic diseases.

METHODS: From October 2001 to September 2003, 47 consecutive patients with pancreatic or peripancreatic diseases, which were confirmed by operation, endoscopic retrograde cholangiopancreatography and clinical follow-up, were enrolled in this study. CT scanning was performed at a MSCT with four rows of detector. A set of images with an effective thickness of 1.0-2.0 mm and a gap of 0.5-1.0 mm (50% overlap) were acquired in all patients for post-processing. Curved planar reformations were carried out by drawing a curved line on transverse source images, coronal or sagittal multiplanar reformations according to certain anatomic structures (such as cholangiopancreatic ducts or peripancreatic vessels) and the position of lesion.

RESULTS: With thin collimation, MSCT could acquire high-quality curved planar reformations to display the profile of the whole pancreas, to trace the cholangiopancreatic ducts and peripancreatic vessels, and to show the relationship of lesions with pancreas and peripancreatic anatomic structures in one curved plane, which facilitates diagnosis and rapid communication of diagnostic information with referring physicians.

CONCLUSION: MSCT with thin collimation could be used to create high-quality curved planar reformations in evaluating pancreatic and peripancreatic diseases with pertinent anatomic information and relative pathologic signs to facilitate the diagnosis and enhance communication with the referring physician. Curved planar reformations can serve as supplements for transverse images in diagnosis and management of pancreatic and peripancreatic diseases.

Improved Accuracy of Noninvasive Electron Beam Coronary Angiography

OBJECTIVES

We investigated the effect of electrocardiographic (ECG) triggering on the accuracy of coronary electron-beam angiography (EBA) as compared with invasive angiography.

METHODS

One hundred thirty-three patients with suspected coronary disease were studied with intravenous coronary EBA and conventional coronary angiography. Patients were divided into 2 groups based upon ECG triggering on the EBA study. Patients were divided into 2 groups based upon different ECG triggering used: 80% R-R interval trigger method (group 1, n = 53) and end-systolic triggering (group 2, n = 80). End-systolic ECG triggering, which started at the end of the T wave in each study, was based on baseline heart rate.

RESULTS

Overall sensitivity to detect a > or = 50% luminal stenosis was 69% in group 1 and 91% in group 2 (P = 0.002); specificity was 82% and 94% in group 1 and group 2, respectively (P < 0.001). Using newer triggering techniques (group 2) with EBA, the sensitivity, specificity, and accuracy for patients with disease of the left main coronary artery or 3 vessel disease was 100%, 94%, and 98%, respectively. Nonassessability of coronary segments on 3D-EBA images was reduced from 35% in group 1 to 9% in group 2 patients (P < 0.001). The number of motion-free coronary images increased from 67% to 95% from group 1 to group 2 (P < 0.0001).

CONCLUSION

End-systolic ECG triggering improves accuracy, image quality, and assessability of segments of coronary EBA for the detection of angiographic coronary artery disease.

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.

Advances in cardiac imaging with 16-section CT systems

RATIONALE AND OBJECTIVES

The authors present advances in electrocardiographically (ECG) gated cardiac spiral scanning with recently introduced 16-section computed tomographic (CT) equipment.

MATERIALS AND METHODS

The authors discuss the technical principles of ECG-gated cardiac scanning. They give an overview on system properties and on the detector design. They describe ECG-gated scan- and image-reconstruction techniques and ECG-controlled dose modulation ("ECG pulsing") for a reduction of the patient dose. They discuss key parameters for image quality and present simulation and phantom studies and they give preliminary values for the patient dose.

RESULTS

An extension of the adaptive cardiac volume reconstruction for ECG-gated spiral CT provides adequate image quality for up to 16 sections. With the smallest reconstructed section width (about 0.83 mm) and overlapping image reconstruction, cylindrical holes 0.6-0.7 mm in diameter can be resolved in a transverse resolution phantom independent of the heart rate. For coronary CT angiography, the influence of transverse resolution is most pronounced for coronary segments that are only slightly tilted relative to the scan plane. In this case, visualization of stents and plaques is considerably improved with 1.0-mm or smaller section width. For 0.42-second gantry rotation time, temporal resolution reaches its optimum (105 msec) at a heart rate of 81 beats per minute. Effective patient dose for the standard protocols recommended by the manufacturer ranges from 0.45 mSv (male) for ECG-triggered calcium scoring to 7.1 mSv (male) for high-resolution ECG-gated coronary CT angiography. With ECG pulsing, the dose is reduced by 30%-50% depending on the patient's heart rate.

CONCLUSION

Clinical experience will be needed to evaluate fully the potential of 16-section technology for cardiac imaging.

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.

Coronary artery: quantitative evaluation of normal diameter determined with electron-beam CT compared with cine coronary angiography initial experience

Eight male heart transplant recipients underwent contrast material-enhanced electron-beam computed tomographic angiography. Coronary artery diameters measured with fixed thresholds and adaptive line density profile (LDP) methods were calculated relative to findings at quantitative coronary angiography. Variation with fixed-threshold methods was significantly greater than that with LDP methods because of variations in vessel enhancement. Thus, more accurate measurements of vessel diameter were obtained with LDP methods.

Technical innovation of cardiac multirow detector CT using multisector reconstruction

Multisector reconstruction is a newly developed algorithm for multirow detector CT in cardiac study. Using volume data sets obtained by ECG-gated scanning, we can reconstruct cardiac images at any desired phase of the cardiac cycle retrospectively. In retro-processing multiplanar and three-dimensional images, thin-slice images with overlapping increment have a great advantage due to increasing z-axis resolution. In this article, we present principles of the algorithm, a phantom study, clinical applications and perspectives for the future.

Modified Blalock-Taussig shunt patency for pulmonary atresia: assessment with electron beam CT

PURPOSE

The purpose of this work was to evaluate electron beam CT (EBCT) for the noninvasive assessment of modified Blalock-Taussig (BT) shunt patency in patients with pulmonary atresia.

METHOD

Five infants and children with pulmonary atresia and modified BT shunts underwent contrast-enhanced EBCT. Modified BT shunts from the subclavian artery to the pulmonary artery were performed to improve the pulmonary blood flow. Electrocardiogram (ECG)-triggered EBCT was obtained with a 100 ms exposure, 3 mm section thickness, and 2 mm table feed after intravenous administration of contrast material. Three-dimensional (3D) or maximum intensity projection (MIP) EBCT images were compared with conventional angiography. The visibility of modified BT shunts was graded and recorded with use of a four-point scale.

RESULTS

Satisfactory visualization was achieved in both 3D and MIP EBCT images to evaluate modified BT shunt patency.

CONCLUSION

Contrast-enhanced 3D or MIP EBCT imaging with ECG trigger may be used as an effective substitute to evaluate modified BT shunts with low radiation dose exposure.

Automated generation of curved planar reformations from volume data: method and evaluation

The authors developed and evaluated a method to automatically create interactive vascular curved planar reformations with computed tomographic (CT) angiographic data. The method decreased user interaction time by 86%, from 15 to 2 minutes. Expert reviewers were asked to indicate their confidence in differentiating automatically created images from clinical-quality manually produced images. The area under the receiver operating characteristic curve was 0.45 (95% CI: 0.39, 0.51), and a test of equivalency indicated that reviewers could not distinguish between images. They also graded image quality as equivalent to that with manual methods and found fewer artifacts on automatically created images. Automatic methods rapidly produce curved planar reformations of equivalent quality with reduced time and effort.

Ethical considerations in image-based screening for coronary artery disease

Despite marked advances in the treatment and prevention of coronary artery disease (CAD) during the last decade, CAD and its complications continue to account for 20% of all deaths in the United States, more than other cause of death. Moreover, half of those who die suddenly of an acute myocardial infarction have no prior symptoms or overt manifestations of their underlying CAD. As our understanding of the pathophysiology of coronary atherosclerosis improves, diagnostic tests utilizing magnetic resonance (MR) imaging and gated computed tomography are being developed to screen for significant CAD in symptomatic individuals and in those who are preclinical or asymptomatic. Patients with known or suspected CAD might be candidates for MR studies of myocardial perfusion, myocardial contraction under stress, MR coronary arteriography, and plaque characterization. One rationale would be to uncover patients before they have a silent heart attack to institute preventative therapies. Although clinical studies have not definitively demonstrated the efficacy of these modalities, screening sites are proliferating and patients are demanding screening tests for CAD. Radiologists interpreting these tests should understand their underlying rationale, the data referenced to substantiate their use, and their responsibility to inform the patient of the results. This review describes current concepts of the pathophysiology of CAD, the rationale for the various screening tests for CAD that are in use or in development, and the potential value of the results of screening to individual patients. The ethical issues embodied in the performance of screening tests for CAD are placed in the context of the appropriate role of the radiologist as a physician interacting directly with a patient.

Image quality of three-dimensional electron beam coronary angiography

PURPOSE

This study identifies reasons for poor image quality and nonassessability of coronary artery segments and compares results between early and late diastolic triggering on coronary electron beam angiography (EBA).

METHOD

One hundred patients referred for EBA were studied. Contrast-enhanced transaxial coronary images were acquired using electrocardiographic (ECG) triggering and reconstructed three dimensionally using volume-rendering techniques. The image quality of coronary segments and image artifacts were analyzed statistically.

RESULTS

Volume rendering failed in seven patients (7%) owing to cardiac and breathing motions. Image quality was the best with the left main (LM) and worst with the left circumflex (LCX) coronary arteries (p < 0.001). The image quality decreased systematically from proximal to distal within each coronary artery (p < 0.001). Forty percent R-R interval triggering on ECG was better than 80% for image quality. The nonassessable segments occurred in 3% of LM, 2, 8, and 5% of proximal, 24, 22, and 12% of mid, and 64, 45, and 20% of distal segments of the left anterior descending, LCX, and right coronary arteries, respectively (p < 0.05).

CONCLUSION

The major limitations of coronary EBA were suboptimal spatial resolution and image artifacts. The image quality could be improved by using optimal ECG triggering.

Progression of coronary atherosclerosis quantified by analysis of 3-D reconstruction of left coronary arteries

OBJECTIVES

Quantitative measurements on three-dimensional (3-D) reconstructed coronary trees permit accurate evaluation of vascular volumes, lengths and diameters. We applied this technique to investigate diffuse luminal narrowing in patients with the clinical manifestation of progressive atherosclerosis.

METHODS

In 13 patients who presented repeatedly for coronary angioplasty (at least 4 years of invasive follow-up), left coronary arteries were reconstructed in 3-D from biplane coronary angiograms. Mean diameter, cross-sectional areas, total length, and volume were calculated for segments and branches. Five patients without coronary artery disease served as controls.

RESULTS

Patients with progressive coronary atherosclerosis demonstrated a significant reduction of total vascular volumes, mean diameters and cross-sectional areas at the initial investigation when compared with controls. Progressive luminal shrinkage occurred during follow-up (-0.04+/-0.13 mm per year and per segmental diameter). The progress of luminal narrowing in patients with coronary artery disease is related to the number of coronary risk factors and the duration of follow-up.

CONCLUSION

Quantitative measurements on 3-D reconstructed coronary trees are a useful investigative tool for the assessment of progression of coronary atherosclerosis.

Heart rate adaptive optimization of spatial and temporal resolution for electrocardiogram-gated multislice spiral CT of the heart

PURPOSE

We introduce a reconstruction method for electrocardiogram (ECG)-gated multislice spiral computed tomography (CT) examinations of the heart [adaptive cardio volume (ACV) reconstruction]. It is evaluated for a four-slice CT system (Siemens Somatom VolumeZoom).

METHOD

State-of-the-art reconstruction techniques for ECG-gated multislice spiral CT use scan data from N consecutive heart cycles for image reconstruction. With increased N, the temporal resolution improves up to t rot /(2 N ) ( t rot is the 360 degrees rotation time of the scanner) but at the expense of insufficient volume coverage or loss of longitudinal resolution, especially at low heart rates. With the ACV technique, the number N of consecutive heart cycles used for image reconstruction is automatically adapted to the momentary heart rate of the patient, ranging from N = 1 at very low heart rates up to N = 3 at high heart rates, to maintain both high z resolution (reconstructed slice width close to the collimated slice width) and adequate temporal resolution. We evaluated slice sensitivity profiles and investigated 10 patients with different heart rates ranging from 55 to 110 beats/min for CT angiography (CTA) studies of the coronary arteries and compared the results with those from a reconstruction with fixed N ( N = 1 and N = 2). Axial images as well as multiplanar reformations were used for an evaluation of image quality.

RESULTS

With the ACV approach, the complete heart may be scanned at 1 mm slice width within 25-35 s. A narrow slice sensitivity profile (full width at half-maximum of approximately 1.3 mm) is maintained for all heart rates. Diagnostic results can be obtained for heart rates up to about 95 beats/min by individual patient optimization of the ECG gating parameters. Improved temporal resolution at the expense of reduced longitudinal resolution may degrade the image quality of CTA studies at low heart rates by blurring plaques and stenoses.

CONCLUSION

The results indicate the potential of the ACV reconstruction technique for high-resolution coronary CTA in a wide range of heart rates.

Medial axis reformation: a new visualization method for CT angiography

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate a new method (medial axis reformation [MAR]) for visualizing three-dimensional vascular data at electron-beam computed tomographic (CT) angiography.

MATERIALS AND METHODS

MAR was performed automatically with a personal computer-based workstation. After the region of interest was edited, voxels were divided into groups according to their path lengths. Centroids of groups were connected to form the medial axis. Then, the medial axis was refined with multiscale medial response. Bifurcations were also detected and refined. Finally, curved sections were generated through the branches and laid out onto a single image by using a splitting method. The authors performed MAR during electron-beam CT angiography of coronary arteries, common carotid arteries, and iliac arteries.

RESULTS

MAR displayed curved sections of branched vessels on one image, cut through the axis of vessels to show the vessel diameter objectively, and allowed the viewing direction to be altered arbitrarily.

CONCLUSION

Results of preliminary applications demonstrate that MAR is a valuable new visualization method for CT angiography.

Effects of window and threshold levels on the accuracy of three-dimensional rendering techniques in coronary artery electron-beam CT angiography

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate the effect of window level and gray-scale threshold on the demonstration of coronary artery lumina at three-dimensional electron-beam computed tomographic (CT) angiography.

MATERIALS AND METHODS

Forty-four coronary artery branches in postmortem pigs were evaluated with electron-beam CT angiography, and the findings were compared with those from conventional angiography. Images from electron-beam CT angiography were reconstructed with maximal intensity projection (MIP), multiplanar reformation (MPR), and shaded-surface display (SSD). Four categories of window level and gray-scale threshold were evaluated.

RESULTS

Three-dimensional electron-beam CT angiography accurately depicted the luminal diameters of the coronary arteries compared with conventional angiography (r = 0.83-0.90, P < .0001). The length of lumina visualized at electron-beam CT angiography was significantly shorter than that visualized with conventional angiography (P < .001). The use of MPR enabled visualization of longer segments of coronary arteries than did the use of MIP or SSD (P < .05). The higher the window level and gray-scale threshold used, the smaller the coronary luminal diameters measured (P < .05). The most accurate window level and gray-scale threshold (82.6 HU +/- 29.8 and 89.5 HU +/- 29.7, respectively) were found to correspond to the attenuation of the lumina (275.8 HU +/- 58.8). Results of simple linear regression showed a strong correlation between luminal attenuation and window level (r = 0.89, P < .0001) or gray-scale threshold (r = 0.95, P < .0001).

CONCLUSION

Electron-beam CT angiography shows promise in the visualization of coronary artery lumina. For accurate display of lumina, a proper window level and gray-scale threshold for three-dimensional rendering techniques should be determined and used on the basis of the attenuation of the target vessel.

Usefulness of calcium scoring using electron beam computed tomography and noninvasive coronary angiography in patients with suspected coronary artery disease

The aim of this study was to investigate the reliability of calcium scoring (CS) and electron beam computed tomographic angiography (EBCTA) as a noninvasive tool in the diagnosis of coronary artery disease (CAD): 93 consecutive patients (aged 59 +/- 9 years) with symptoms suspicious for CAD underwent CS. In 87 of these subjects, an additional EBCTA investigation was performed. Using receiver-operating characteristic curve analysis, we determined a calcium score cut point providing an overall sensitivity of 80% and a specificity of 72% in detecting patients with CAD. For clinical purposes the use of cut points is difficult. We therefore determined score ranges providing >80% specificity (high score range) and >85% sensitivity (low score range) and determined the scores between these ranges as equivocal borderline scores. Calculated on a per-segment basis in assessable proximal and midcoronary segments, the sensitivity for detecting coronary stenoses >50% was 78%, and the specificity was 93%. Thus, 32 of 44 patients with significant CAD and 24 of 49 patients without CAD were correctly classified. The combination of CS and EBCTA predicted CAD in 77% (72 of 93) of patients. No or low calcium scores provided high specificity for ruling out CAD. The addition of EBCTA in those patients improved sensitivity. In patients with high calcium scores, accuracy of EBCTA was not significantly different from CS alone (72% vs 83%), whereas in patients with borderline scores it was significantly superior (80% vs 58%, p <0.03). Thus, the complementary use of CS and EBCTA appears beneficial, particularly in patients with borderline scores, and could improve sensitivity in the low score range. In the presence of high scores, no major diagnostic gain from an additional EBCTA versus CS alone could be observed.

Coronary artery stenoses: a phantom study using contrast enhanced three-dimensional electron beam tomography

This paper evaluated the accuracy of electron beam tomographic angiography (EBA) with conventional coronary arteriography (CCA) using four graded artificial stenoses in a postmortem swine coronary phantom model. The sensitivity, specificity, and accuracy of EBA for diagnosing significant stenosis (> or =50% stenosis) were 94.3%, 96.7%, and 95.8%, respectively. The diagnostic accuracy of EBA had no significant difference with CCA (chi(2)=0.0162; P>.05). EBA three-dimensional (3D) procedures had high interobserver reproducibility (k=.92-.95, P>.05). Maximum intensity projection (MIP) was the most sensitive and curved planar reformation (CPR) was the most accurate 3D procedure for quantitatively identifying coronary stenosis. EBA yields promising results concerning the visualization of coronary artery stenosis with high accuracy for stenoses >50%.

Optimal electrocardiographically triggered phase for reducing motion artifact at electron-beam CT in the coronary artery

RATIONALE AND OBJECTIVES

The authors performed this study to (a) investigate coronary movement with electron-beam computed tomography (CT) and (b) find the optimal electrocardiographic (ECG) triggering phase for eliminating motion artifact.

MATERIALS AND METHODS

One hundred fifty-one patients without arrhythmia were examined with electron-beam CT. First, movie scans were obtained to create displacement and velocity graphs of coronary artery movement. Then, a volume scan with an exposure time of 100 msec was obtained with various ECG trigger settings.

RESULTS

Movement patterns of coronary arteries varied with heart rate. Optimal triggering phase was before atrial systole (near 71% of the R-R interval) when heart rate was slower than 68 beats per minute and at ventricular end systole when heart rate was fast. Rate of severe motion artifacts decreased from 43% to 0% when triggering was altered from 80% of the R-R interval to the individual optimal value. Experimental values of the optimal phase at different heart rates were derived, and severe motion artifact was only 3.0% with these values.

CONCLUSION

ECG triggering set according to the heart rate enables a great reduction in motion artifacts at electron-beam CT with a 100-msec exposure time. The results may have implications for magnetic resonance imaging of the coronary artery.

Noninvasive coronary angiography by retrospectively ECG-gated multislice spiral CT

BACKGROUND

We investigated the applicability and image quality of contrast-enhanced coronary artery visualization by multislice spiral CT using retrospective ECG gating.

METHODS AND RESULTS

Twenty-five patients in sinus rhythm (significant coronary artery stenoses ruled out by invasive angiography) were studied with a multislice spiral CT (Siemens SOMATOM Volume Zoom). In inspiration (mean breath-hold, 37 seconds), a volume data set of the heart was acquired (intravenous contrast agent; 4 x 1-mm slice thickness; 500-ms rotation; table feed, 1.5 mm/360 degrees ). Simultaneous recording of the ECG permitted retrospective reconstruction of contiguous cross sections in intervals of 1 mm at any desired interval of the cardiac cycle. The mean duration of the image reconstruction window was 185 ms. Next to 3-dimensional reconstructions of the heart and coronary arteries, multiplanar reconstructions were rendered to determine the visualized length of the coronary arteries, the contrast-to-noise ratio, and the correlation of coronary artery diameters to quantitative coronary angiography.

CONCLUSIONS

The coronary arteries could be visualized over long segments (left main, 9+/-4 mm; left anterior descending, 112+/-34 mm; left circumflex, 80+/-29 mm; right coronary artery, 116+/-33 mm). On average, 78+/-16% of these distances were visualized free of motion artifacts. The mean contrast-to-noise ratio was 9.3+/-3.3. Coronary artery diameters in multislice spiral CT showed close correlation to quantitative coronary angiography (CT, 3.3+/-1.0 mm; angiography, 3. 2+/-0.9 mm; mean difference, 0.38 mm; r=0.86). Contrast-enhanced multislice spiral CT permits visualization of the coronary artery lumen. Further studies are necessary to determine whether image quality is sufficient to reliably detect coronary artery stenoses.

Effects of scanning and reconstruction parameters on image quality in electron-beam CT angiography: coronary artery phantom study

RATIONALE AND OBJECTIVES

This study compared the image quality obtained with different scanning and reconstruction parameters for electron-beam computed tomographic (CT) angiography and sought optimal methods for visualizing the coronary artery lumen.

MATERIALS AND METHODS

Electron-beam CT angiography with contrast material enhancement was used to image 35 branches of fresh postmortem swine coronary arteries. Different collimation widths, fields of view (FOVs), reconstruction kernels, and algorithms were employed to reconstruct the acquired raw data into CT angiographic images. Image quality was compared and analyzed.

RESULTS

The contrast-to-noise ratios (C/Ns) for 1.5-, 2-, and 3-mm section thickness were 28.4 +/- 15.2, 31.9 +/- 9.3, and 33.8 +/- 14.5, respectively (P < .05). The lengths of visualized coronary artery lumina were significantly longer for 1.5-mm scanning (71.6 mm +/- 4.3) than for 2-mm (58.3 mm +/- 5.5) and 3-mm scanning (59.0 mm +/- 8.0) (P < .01). The C/Ns for 12.7-, 18.0-, and 26.0-cm FOV reconstruction were 32.8 +/- 9.9, 28.9 +/- 8.2, and 27.1 +/- 8.2, respectively (not significant), and the visualized luminal lengths were 76.1 mm +/- 12.5, 71.7 mm +/- 14.6, and 65.4 mm +/- 13.1, respectively (not significant). The highest C/N (48.2 +/- 13.3) was achieved with smooth kernels and a cone-beam algorithm, and the lowest (14.7 +/- 3.4) with very sharp kernels and a normal algorithm. Cone-beam algorithm images had significantly higher C/Ns than did normal algorithm images (P < .001), and they demonstrated longer coronary artery lumina (P < .01).

CONCLUSION

Collimation width, FOV, reconstruction kernels, and algorithms are important in the processing of high-quality electron-beam coronary angiograms. A 1.5-mm collimation width, 12.7-cm FOV, cone-beam reconstruction algorithm, and very sharp kernels should help in obtaining the best image quality and depicting the longest segments of coronary artery lumen.

Cardiac imaging by means of electrocardiographically gated multisection spiral CT: initial experience

The authors introduce a method for cardiac investigations by using electrocardiographically gated spiral scanning with a four-section computed tomographic system. Three-dimensional images were reconstructed by means of a 250-msec temporal resolution and continuous volume coverage by using a dedicated multisection cardiac volume reconstruction algorithm. Motion-free thin-section volume images were acquired with thin sections and overlapping image increments within a single breath hold. Data segment shifts in time allowed for multiphase imaging.

Coronary artery bypass grafts: improved electron-beam tomography by prolonging breath holds with preoxygenation

In 45 patients with coronary bypass grafts, the breath-hold interval with and that without preoxygenation was measured. Its effect on depiction of the distal graft anastomosis at electron-beam tomography was evaluated. Preoxygenation prolonged the breath-hold interval in most patients, thereby allowing greater anatomic coverage including more distal anastomoses. Preoxygenation may improve scanning of coronary bypass grafts and increase detectability of graft stenoses.