Performance Evaluation of a Multi-Slice CT System with 16-Slice Detector and Increased Gantry Rotation Speed for Isotropic Submillimeter Imaging of the Heart

Background: 4-slice CT scanners have shown limitations in clinical application for noninvasive coronary CT angiography (CTA). We evaluate advances in ECG-gated scanning of the heart and the coronary arteries with recently introduced 16-slice CT equipment (SOMATOM Sensation 16, Siemens, Forchheim, Germany). Materials and Methods: The technical principles of ECG-gated cardiac scanning, scan parameters, and detector design of the new scanner are presented. ECG-gated scan and image reconstruction techniques and ECG-controlled dose modulation ("ECG pulsing") for a reduction of the patient dose are described, key parameters for image quality and simulation results presented, and phantom studies and initial patient experience discussed. The impact of reduced gantry rotation time (0.42 s) on temporal resolution and initial estimations of the patient dose are presented. Results: Extensions of ECG-gated reconstruction algorithms used for 4-slice CT provide adequate image quality for up to 16 slices. For each detector collimation different slice widths are available for retrospective reconstruction with well-defined slice sensitivity profiles (SSPs). For coronary CTA the heart can be covered with 0.75 mm collimation within a 20-s breathhold. The best possible spatial resolution is 0.5 2 0.5 2 0.6 mm. For 0.42 s gantry rotation time, temporal resolution reaches its optimum (105 ms) at a heart rate of 81 bpm. Effective patient dose for coronary CTA is 4-5 mSv using ECG-pulsed acquisition. Conclusion: The clinical performance of coronary CTA by means of spatial resolution, temporal resolution and scan time is substantially improved with the evaluated 16-slice CT scanner. Also, display of smaller coronary segments and instent visualization are substantially improved. Hintergrund: Die Einführung der Mehrschicht-CT im Jahr 1998 stellte einen Durchbruch der mechanischen CT in der nichtinvasiven Bildgebung des Herzens dar. Klinische Studien zeigten jedoch Limitationen gängiger 4-Schicht-CT-Geräte, welche die breite klinische Anwendung der Methode einschränken. Material und Methoden: Die neue Generation von Mehrschicht-CT-Geräten bietet gleichzeitige Aufnahme von bis zu 16 Submillimeter-Schichten und verbesserte Zeitauflösung für Herzuntersuchungen durch Verringerung der Gantry-Rotationszeit auf 0,42 s. Diese Arbeit stellt die technischen Grundlagen und mögliche Applikationen dieser neuen Technologie in der Untersuchung des Herzens und der Koronargefäße am Beispiel eines neuartigen 16-Schicht-CT-Gerätes dar (SOMATOM Sensation 16, Siemens AG, Forchheim). Das neue Systemkonzept, Detektordesign und Dosiseffizienz sowie Datenaufnahme- und Bildrekonstruktionstechniken für die EKG-synchronisierte Untersuchung des Herzens werden diskutiert. Ergebnisse: Die Erweiterung gängiger Rekonstruktionstechniken von 4- auf 16-Schicht-Detektoren liefert eine diagnostisch adäquate Bildqualität. Die neuen Verfahren sind in der Lage, für jede kollimierte Schichtdicke Schichten verschiedener Dicke mit gut definierten Schichtempfindlichkeitsprofilen zu rekonstruieren. Basierend auf einer kollimierten Schichtdicke von 0,75 mm kann eine hochaufgelöste CT-Angiographie (CTA) des Herzens und der Koronargefäße in einer 20-sekündigen Atempause durchgeführt werden. Die bestmögliche räumliche Auflösung beträgt 0,5 2 0,5 2 0,6 mm. Mit einer Rotationszeit des Messsystems von 0,42 s wird die bestmögliche zeitliche Auflösung von 105 ms bei einer Herzfrequenz von 81 Schlägen/min erreicht. Unter Verwendung einer EKG-synchronisierten Röhrenstrommodulation ist für eine CTA des Herzens und der Herzkranzgefäße mit einer effektiven Patientendosis von 4-5 mSv zu rechnen. Schlussfolgerung: Mit den neuen 16-Schicht-CT-Systemen lassen sich bei reduzierter Untersuchungszeit sowohl die räumliche als auch zeitliche Auflösung für die CTA des Herzens und der Koronargefäße deutlich verbessern. Auch die Darstellung kleinerer Koronarsegmente und die In-Stent-Visualisierung werden ermöglicht.     

Klinischer Stellenwert der Cardio-CT-Koronarangiographie

As compared to conventional CT scanners, multi-slice spiral CT (MSCT) has improved temporal and spatial resolution. Dedicated image reconstruction algorithms permit to create cross-sectional images with a temporal resolution of approximately 150-250 ms, and a slice thickness of 0.75-1.3 mm (see Figure 1). In addition, image reconstruction can be synchronized to the ECG. This permits to use MSCT for visualization of the coronary artery lumen and detection of stenosis (see Figures 2 and 3). Various post-processing techniques can be used to display the coronary arteries. A low heart rate has been identified as an important prerequisite to obtain a sufficiently high image quality, and most authors recommend routine use of beta blocker premedication. Comparisons of 4-slice MSCT to invasive angiography concerning the detection of hemodynamically relevant coronary artery stenoses have resulted in sensitivities ranging from 72-93% and specificities ranging from 84-98%. However, up to 32% of all coronary segments had to be excluded from evaluation due to impaired image quality, in most cases due to severe calcification or insufficient suppression of motion artifacts. Initial results obtained with 16-slice MSCT scanners, which provide somewhat higher temporal and--through decreased slice thickness--improved spatial resolution, show promise that diagnostic accuracy may be increased while the number of coronary artery segments with nondiagnostic image quality may be reduced as compared to the prior generation of 4-slice scanners. Further studies are necessary to identify patient subgroups which might benefit from MSCT "noninvasive coronary angiography" in a clinical setting.     

64层CT冠状动脉成像的前瞻性与回顾性心电门控比较

目的 比较前瞻性心电门控和回顾性心电门控64层CT冠状动脉成像的辐射剂量和成像质量,探讨低剂量前瞻性心电门控CT冠状动脉成像的可行性.方法 两组心率≤65次/min各100例患者分别进行前瞻性和回顾性心电门控扫描,并采用多平面重组(MPR)、最大密度投影(MIP)、曲面重组(CPR)及容积再现(VR)多种重组技术显示冠状动脉,图像质量根据运动伪影影响分为优、良、差,使用剂量长度计算各自的有效辐射剂量,并进行统计学分析.结果 前瞻性组平均辐射剂量为(2.81±0.48)mSv明显低于回顾性组的(10.16±1.09)mSv(P＜0.01);前瞻性组诊断性冠状动脉节段和非诊断性冠状动脉节段为95.2%(1165/1224)和4.8%(59/1224),与回顾性组的94.1%(1186/1261)和5.9%(75/1261)比较,差异无统计学意义.结论 对于心率稳定在65次/min以下的患者,前瞻性心电门控64层CT冠状动脉成像,能以较低的辐射剂量达到回顾性心电门控诊断质量的影像,是切实町行的方法.     

Comparison of 16 slice multi-detector computed tomography and breath hold 3D magnetic resonance angiography in the detection of coronary stenosis

Objective To compare 16-slice multi-detector spiral computed tomography (MDCT) and breathhold 3D magnetic resonance (MR) coronary angiography in the visualization of coronary arteries and the accuracy of detecting significant (> 50%) coronary stenoses in patients with suspected coronary artery disease. Methods Forty patients were examined by 16-slice CT (GE, Lightspeed 16) and MR (GE,Twinspeed) within 3 days; 31 of them underwent conventional coronary angiography (CAG) within 2 weeks after CT and MR scan. CT was performed with 16×1.25 mm detector collimation, 0.5 s rotation time and images were reconstructed at 60%-75% of the cardiac cycle. MR was performed with breath hold 3D FIESTA (TR4.0 ms, TE1 .7 ms, flip angle 65, slice thickness 3 mm, FOV 280 mm, matrix 256×192). Mean heart rate was 63±5.8 bpm andβ-blocker was used in 24 patients. MR and CT image quality was evaluated in 9 coronary segments (RCA1, RCA2, RCA3, LM, LAD1, LAD2, LAD3, LCX1, LCX2) using a four-point grading scale. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated for detection of significant stenosis using CAG as the gold standard. Results 16-slice CT showed higher image quality in most coronary segments except RCA2. Forty-three segments were diagnosed as significant stenosis by CAG, 36 and 27 of these were correctly detected by CT and MR respectively. Sensitivity, specificity, positive predictive value, and negative predictive value of 16-slice CT and MR for detecting significant stenosis were 83%, 84%. 49%, 97%. and 63%, 90%, 55%, 93%, respectively. Conclusion Sixteen-slice CT showed higher image quality in most coronary segments excepted for middle RCA. 16-slice CT had higher sensitivity than MR for detection of coronary significant stenosis, whereas MR had higher specificity than CT. Both CT and MR showed high negative predictive value, which is useful for excluding coronary stenosis in symptomatic patients. (J Geriatr Cordial 2006; 3(1): 24-28)     

Esophagus imaging for radiofrequency ablation of atrial fibrillation using a dual-source computed tomography system: Preliminary observations

Objective The very recent introduction of dual-source computed tomography (DSCT) has significantly improved the temporal resolution of ECG-gated multidetector-row cardiac computed tomography (CT). The aim of the present study was to evaluate whether with a DSCT visualization of the esophagus is feasible without any use of contrast in the esophagus. Materials and methods A total of 20 patients were evaluated. Ten patients underwent examination with a DSCT scanner without a gastric tube. In another ten patients, which served as control group, a CT scan was performed with a radio-opaque gastric tube prior to circumferential pulmonary vein isolation (in seven patients with a 16-slice CT and in three patients with a DSCT). Results In the control group the gastric tube and the left atrium were reconstructed and were well visualized in all ten patients in the electro-anatomic mapping system, independently whether 16-row CT or DSCT scan was used. In the study group integration of the esophagus into the electro-anatomic mapping system was not feasible, due to the lacking contrast counterpart the surrounding tissue. Conclusions Even with the newest generation of DSCT scanner it is not possible to integrate the esophagus image into the 3-D electroanatomic mapping system without contrast by whatever means. However placing a conventional gastric tube before performing the CT scan allowed visualization and integration of the esophagus into the 3-D electro-anatomical map in all patients.     

Do Segmented Reconstruction Algorithms for Cardiac Multi-Slice Computed Tomography Improve Image Quality?

PURPOSE: To evaluate segmented reconstruction algorithms for spiral multi-slice computed tomography (MSCT) that use data from two cardiac cycles to improve temporal resolution (tau) for imaging of the heart. MATERIALS AND METHODS: An initial group of 78 cardiac patients (heart rates [HR] = 63-167 beats per minute [bpm]) were imaged on a 4-slice, 500 ms gantry rotation time scanner (scanner 1). Images were reconstructed with a single-segment algorithm using data from one cardiac cycle with a reconstruction window of fixed length (tau = 250 ms). Images were also reconstructed with two variants of a multi-segment algorithm using data from two cardiac cycles where only one end of the reconstruction window was fixed and the other end was freely moveable to allow adjustment of tau according to HR: (1) "2-segment fixed start" with fixed start of reconstruction, (2) "2-segment fixed end" with fixed end of reconstruction (for both, tau = 125-250 ms). The resulting image sets were ranked from best to worst (1-3, respectively) in a side-by-side, blinded comparison by two independent readers. A second group of 26 patients (HR = 74-90 bpm) were imaged on a 12-slice, 420 ms gantry rotation time scanner (scanner 2). Data were reconstructed with a single-segment algorithm (tau = 210 ms) and a "2-segment fixed start" algorithm (tau = 105-210 ms) and image sets were ranked from best to worst (1-2, respectively). RESULTS: There was no clear evidence that any one technique is superior for imaging on scanner 1. Reader 1 ranked single-segment images the highest for all HRs, but statistically significant differences among the three algorithms were only found for the lowest HRs (< 80 bpm), where reader 1 preferred single-segment over "2-segment fixed end" techniques (p = 0.048). The highest rankings given by reader 2 varied according to HR: single-segment images were superior for lowest HRs, while "2-segment fixed start" images were superior for HRs > 80 bpm; none of these comparisons reached statistical significance. Improved performance of 2-segment reconstruction was found with scanner 2. Both readers ranked "2-segment fixed start" images the highest (p < 0.01). CONCLUSIONS: The added value of 2-segment cardiac reconstruction algorithms for spiral MSCT was not demonstrated for a 4-slice, 500 ms gantry rotation time scanner but shown to be beneficial for a 12-slice, 420 ms gantry rotation time scanner in the crucial HR range of 74-90 bpm.     

Multislice computer tomography for detection of coronary artery disease

Multislice computer tomography has undergone substantial technological progress during the past years. Current 64-slice scanners with gantry rotation speeds of as little as 330 ms, and particularly the recently introduced dual source CT equipped with two X-ray tubes, provide a temporal and spatial resolution that is sufficient to allow reliable imaging of cardiac morphology and coronary arteries. Especially the ability to noninvasively visualize the coronary arteries, including the assessment and quantification of calcifications, as well as the detection of luminal obstruction and atherosclerotic plaque, constitutes an attractive addition to currently available diagnostic tools for the work-up of patients with known or suspected coronary artery disease. Besides the evaluation of coronary artery calcium and atherosclerotic plaques, this review focuses on the contrast-enhanced CT visualization of the coronary vessels, including native coronary arteries, bypass grafts, and coronary stonts. Thereby detailed information concerning the scan protocol, clinical data, possible indications, and limitations using up-to-date 64-slice technology is provided. Finally, the overview includes design and initial image examples of dual source CT technology as the newest development in the field.     

CT Coronary Angiography: 256-Slice and 320-Detector Row Scanners

Multidetector computed tomography (MDCT) has rapidly evolved from 4-detector row systems in 1998 to 256-slice and 320-detector row CT systems. With smaller detector element size and faster gantry rotation speed, spatial and temporal resolution of the 64-detector MDCT scanners have made coronary artery imaging a reliable clinical test. Wide-area coverage MDCT, such as the 256-slice and 320-detector row MDCT scanners, has enabled volumetric imaging of the entire heart free of stair-step artifacts at a single time point within one cardiac cycle. It is hoped that these improvements will be realized with greater diagnostic accuracy of CT coronary angiography. Such scanners hold promise in performing a rapid high quality “triple rule-out” test without high contrast load, improved myocardial perfusion imaging, and even four-dimensional CT subtraction angiography. These emerging technical advances and novel applications will continue to change the way we study coronary artery disease beyond detecting luminal stenosis.     

Visualization of coronary artery anomalies by contrast-enhanced multi-detector row spiral computed tomography

BACKGROUND: We investigated the potential of 16-slice multi-detector row spiral CT (MDCT) with retrospective ECG-gating for evaluation of coronary artery anomalies. METHODS: A total of 35 patients (23 men, 12 women, 19-81 years) in whom anomalous coronary arteries had been detected by invasive coronary angiography underwent MDCT (Sensation 16, Siemens, Germany). During one breathhold, a contrast-enhanced (90 ml, 5 ml/s) volume data set of the heart was acquired (16x0.75mm collimation, gantry rotation 375 ms). Images were reconstructed with a slice thickness of 1.0 mm in 0.5-mm intervals using retrospective ECG-gated reconstruction. The 35 data sets and 80 data sets of patients with angiographically normal coronary anatomy were analysed in random order concerning the origin and course of the coronary arteries. The results were compared to invasive coronary angiography. RESULTS: All patients with coronary artery anomalies and all controls with normal coronary anatomy were identified by MDCT. In addition, the origins and course concerning their anatomical relationship to adjacent cardiac structures were visualized in all patients, including right-sided origin of the left main (n=10), left anterior descending coronary artery (n=4) or left circumflex coronary artery (n=10); left-sided origin of the right coronary artery (n=6); four coronary fistula to the pulmonary artery (two from the left anterior descending, one from the right coronary artery, one from the left main), and one fistula from the circumflex coronary artery to the left atrium CONCLUSIONS: The study demonstrates that MDCT is a reliable noninvasive technique to identify and define anomalous coronary arteries and their course.     

前瞻性心电触发轴位扫描技术在64层螺旋CT中的应用

目的探讨在64层螺旋CT冠状动脉成像中采用前瞻性心电触发轴位扫描技术的图像质量和辐射剂量。方法选择采用前瞻性心电触发轴位扫描技术进行64层螺旋CT冠状动脉成像的患者160例作为前瞻组。将相同扫描参数输入回顾性心电门控螺旋扫描程序,获得扫描剂量数据作为回顾组。由2名放射科医师分别进行图像重建和图像质量评价。冠状动脉图像质量分级采用4级评分法。结果 2名放射科医师在图像重建和图像质量评价方面均有良好的一致性。160例患者除8例图像有严重血管错层伪影、2例冠状动脉严重钙化,共显示1449个冠状动脉节段。1～3分以上的1431个节段(98.76%)具有较好的图像质量,可以满足临床诊断要求。前瞻组与回顾组的平均有效剂量差异有统计学意义[(3.17±1.17)mSv vs (22.09±6.72)mSv,P0.01]。结论在64层螺旋CT冠状动脉成像中采用前瞻性心电触发轴位扫描技术可在保证图像质量的同时显著降低辐射剂量。     

Noninvasive visualization of coronary artery bypass grafts using 16-detector row computed tomography

OBJECTIVES: The aim of this study was to evaluate the diagnostic accuracy of a 16-detector row computed tomography (CT) scanner for the assessment of coronary artery bypass grafts. BACKGROUND: A new generation of multislice spiral CT scanners, equipped with more and thinner detector rows, allows for reliable noninvasive detection of obstructive coronary artery disease. METHODS: The study included 51 consecutive patients. Three patients had to be excluded from the study due to arrhythmias or fast heart rates despite beta-blockade. A total of 48 patients with 131 coronary artery bypass grafts (internal mammary artery, n = 40; venous grafts, n = 91) were examined by computed tomography angiography (CTA) and by invasive coronary angiography (ICA) using a 16-detector row CT scanner. For cardiac protocols, only the 12 inner detector rings are applied. All CT examinations were performed with retrospective electrocardiogram gating at a mean heart rate of 64 +/- 5 beats/min; 120 ml of Xenetix 300 (Guerbert GmbH, Sulzbach, Germany) were continuously injected. The bypass graft patency and the presence of stenoses as well as the proximal and distal anastomoses were evaluated by two experienced readers. RESULTS: All bypass grafts and 74% of the distal bypass anastomoses could be visualized by CTA; 21 bypass graft occlusions and 1 significant stenosis were detected by CTA and confirmed by ICA. Five false positive and one false negative finding resulted in a sensitivity of 96%, a specificity of 95%, a positive predictive value of 81%, and a negative predictive value of 99%. CONCLUSIONS: Sixteen-detector row CT scanner technology allows for the reliable visualization of coronary bypass grafts. Dysfunctional bypass grafts can be detected with high diagnostic accuracy. This technology can be used as a noninvasive test for patients with suspected graft dysfunction.     

256层CTA技术在冠状动脉硬化狭窄诊断中的应用价值

目的 探讨256层CT血管成像（CTA）技术在冠状动脉成像及其狭窄诊断中的应用价值.方法 选择临床拟诊或疑诊冠状动脉疾病者400例,均行CTA冠状动脉检查,其中53例行DSA冠状动脉造影;由2名医生对图像质量评价,采用分级评分法评价冠状动脉15节段.结果 CTA显示冠状动脉节段共5 793个,其中评分为4、5分5 691个（98.24％）;与DSA比较,CTA诊断冠状动脉狭窄的准确率为94.33％、特异性为93.75％、敏感性为94.59％.DSA与CTA两种检查方法诊断冠状动脉狭窄一致性较好,Kappa为0.868.256层CTA诊断冠状动脉狭窄,在不同心率患者间差异无统计学意义.结论 256层CTA冠状动脉成像质量较高,可清晰地显示冠状动脉主要节段影像,较为准确地诊断冠状动脉狭窄,特异性、敏感性较好,且不受心率影响.     

迭代重建技术在前门控结合体质量调节管电压管电流心脏CT成像的研究——降低辐射剂量及控制图像质量简

目的 探讨迭代重建技术（iDose4）在前瞻性心电门控结合体质量调节管电压管电流心脏螺旋计算机断层扫描（computerized tomography,CT）成像中降低辐射剂量及控制图像质量的应用价值.方法 选取实验猪10只,每只猪均进行以体质量调节管电压管电流为基础的常规剂量（A组）及在此基础上降低管电流[分别降低30％（B组）、50％（C组）、70％（D组）]的256层前瞻性心电门控心脏CT扫描,所有数据均分别采用滤波反投影（filtered back projection,FBP）和iDose4重建,计算猪接受的辐射剂量,测量升主动脉根部及左心室腔噪声、信噪比（SNR）、对比噪声比（CNR）,分别对总体图像质量和冠状动脉图像质量进行评分（5分法评分）,3分及以上为图像质量可满足诊断,并对两种重建方法处理后所得结果进行比较.结果 A、B、C、D组的有效辐射剂量（ED）分别为（3.13±0.63） mSv、（2.26±0.51） mSv、（1.61±0.36） mSv、（1.01±0.23）mSv.随着X线剂量降低,图像噪声增加,信噪比、对比噪声比降低,图像质量下降.各组内比较,iDose4重建的图像噪声均较FBP重建者明显降低,而信噪比及对比噪声明显提高,差异均有统计学意义（P均=0.000）.A、B、C、D各组内经FBP/iDose4重建后总体图像质量评分分别为（3.80±0.42）分/（4.60±0.52）分、（3.60±0.52）分/（4.40±0.52）分、（3.00±0.67）分/（3.80±0.42）分、（2.00±0.67）分/（3.40±0.52）分,各组内比较差异均有统计学意义（P＜0.05）.用FBP重建,A、B、C、D组近、远端冠状动脉的可诊断率分别为100％、95％、70％、20％和92％、72％、36％、0;经iDose4重建后,A、B、C组近、远端冠状动脉的可诊断率均大于经FBP重建后A组的可诊断率或与其相当（P＞0.05）,而D组的可诊断率明显低于FBP重建后A组的可诊断率,差异有统计学意义（P＜0.05）.结论 在前门控结合体质量调节管电压管电流心脏CT成像中,应用iDose4较FBP可显著降低图像噪声,提高信噪比及对比噪声比,提高图像质量;用iDose4重建可以在现有辐射剂量基础上降低50％的剂量进行扫描而图像质量保持不变.     

Pilot study of dynamic cine CT angiography for the evaluation of abdominal aortic aneurysms: implications for endograft treatment.

PURPOSE: To utilize 40-slice electrocardiographically (ECG)-gated cine computed tomographic angiography (CTA) to characterize normal aortic motion during the cardiac cycle at relevant anatomical landmarks in preoperative abdominal aortic aneurysm (AAA) patients. METHODS: In 10 consecutive preoperative AAA patients (10 men; mean age 78.8 years, range 69-86), an ECG-gated CTA dataset was acquired on a 40-slice CT scanner using a standard radiation dose. CTA quality was graded and scan time was measured. Pulsatility measurements at multiple relevant anatomical levels were performed in the axial plane. Changes in aortic circumference were determined for both the aortic wall and the luminal diameter. RESULTS: All 10 CT scans were of good quality. All patients could be scanned in 14 to 33 seconds (mean 21). At each anatomical level measured, there was a 2.2- to 3.4-mm increase in the aortic wall circumference per cardiac cycle. A similar increase was observed in luminal circumference, with a 2.4- to 3.6-mm increase per cycle. CONCLUSION: This study introduces the concept of dynamic cine CTA imaging of aortic motion, providing insight into the pathophysiology of abdominal aortic and iliac pulsations. Patients with AAAs selected for EVAR demonstrate changes in aortic circumference with each cardiac cycle that may have consequences for endograft sizing and future design. The potential for graft migration, intermittent type I endoleak, and poor patient outcome following EVAR can be anticipated. Complex aortic dynamics deserve increased scrutiny in an effort to prevent potential complications.     

心电门控320排容积CT在急性胸痛中应用价值的前瞻性研究

目的:探讨前瞻性心电门控320排容积CT对急性胸痛成像的可行性及诊断价值。方法:对连续61例急性胸痛患者不控制心率条件下行前瞻性心电门控wide-volume模式并强制在一个心动周期扫描,曝光时间窗根据心率不同预设在40%~50%R-R间期(心率≥70次/min)或70%~80%R-R间期(心率70次/min)。2个volume涵盖自胸廓入口至心膈面,对比剂采用三相注射法以便同时显示主动脉、冠状动脉、肺动脉三大血管床。评价三大血管床的图像质量及对胸痛病因的诊断能力。记录患者的有效辐射剂量、对比剂用量。结果:61例患者的三大血管床(主动脉、冠状动脉及肺动脉)均得到明显均匀强化。主动脉和肺动脉均获得良好的可诊断图像(可诊断率达100%,61/61)。2例患者因屏气不良冠状动脉图像无法评价,在其余59例患者的625个冠状动脉节段中,图像质量为1级的占94.2%(589/625),2级图像质量占3.2%(20/625),总的可评价率达97.4%。观察者之间总的一致性较好(k=0.83,95%CI:0.60~1.00)。平均有效辐射剂量为(5.44±1.15)mSv,对比剂总量平均为(75.7±4.35)mL。本扫描计划对胸痛病因阳性诊断率为82%(50/61),CTA诊断为阴性的18%(11/61)的患者中随诊一月内无不良并发症出现。结论:320排容积CT的前瞻心电门控wide-volume扫描模式在不控制心率情况下可低辐射剂量及低对比剂用量地对急性胸痛患者进行评价。     

Comparison of multidetector 64-slice computed tomographic angiography to coronary angiography to assess the patency of coronary artery bypass grafts

This study prospectively evaluated the diagnostic accuracy of 64-slice computed tomographic angiography (CTA) in assessing the patency of coronary artery bypass grafts compared with invasive coronary angiography. In total 147 bypass grafts (100 venous grafts and 47 mammary artery grafts) were evaluated in 50 consecutive patients. Contrast-enhanced 64-slice CTA was performed and compared with invasive angiography. The computed tomographic angiographic scan protocol used 64- x 0.5-mm slice collimation and 0.33-second gantry rotation time during simultaneous electrocardiographic gating. Patients with a heart rate >65 beats/min received beta blockers. Overall 145 of 147 bypass grafts (98.6%) were detected by CTA; 2 nonvisualized grafts were occluded at the time of invasive angiography. Of the grafts visualized, 28 were totally occluded, 103 were patent, and 14 had significant stenoses that were confirmed by invasive angiography. Ninety-five percent (111 of 117) of patent grafts demonstrated good run-off distal to anastomoses but without an ability to accurately evaluate the presence of retrograde flow; 83% (97 of 117) of distal anastomoses were adequately evaluated, whereas the remaining 17% (20 of 117) were not well visualized due to vascular clips and/or calcification artifacts. Two grafts were not demonstrated by invasive angiography but were detected by CTA and found to be widely patent. In conclusion, multidetector 64-slice CTA is a valuable tool for direct visualization of coronary bypass grafts and assessment of their patency. Dysfunctional bypass grafts can be detected with high diagnostic accuracy.     

64排螺旋CT在神经系统疾病诊断中的优势分析

目的 分析64排螺旋CT在神经系统疾病诊断中的应用优势.方法 选取经64排螺旋CT检查,怀疑有神经系统疾病的患者97例,其中常规头部CT扫描50例和横断面容积扫描冠状面重组20例,并与双螺旋CT检查70例相应病例的图像进行比较;头颈CT血管造影10例和全部脊柱CT血管造影7例,与数字减影血管造影和临床资料对照;10例13次脑灌注成像,分析其成像优势.结果 50例64排螺旋CT常规头部扫描未见或仅有轻微颅后窝伪影,而50例双螺旋CT中32例有明显的颅后窝骨伪影.20例64排螺旋CT头颅冠状重组图像质量优良,而双螺旋CT冠状扫描的20例,9例扫描角度不够,7例有伪影,增强者1例效果差.5例头颈CTA异常（4例头颈动脉狭窄或闭塞,1例脑内动静脉畸形）,4例脊柱CTA发现血管畸形（包括畸形血管位置、供血动脉和引流静脉）,均与DSA一致.10例（13次）脑灌注成像,7例短暂性脑缺血发作（TIA）表现有灌注时间延长,血流轻度减少或无减少,其中2例治疗后基本恢复正常;3例脑梗死灌注时间延长,血流明显减少.结论 64排螺旋CT能消除常规头部CT扫描时颅后窝伪影,平面重组可清楚显示颅底结构,可取代并且优于冠状位扫描;CTA能大范围准确显示头、颈和脊髓、脊柱血管病变;灌注成像范围显著扩大,准确度提高,可与静脉和同范围动脉CTA在一次增强后同时完成.     

Comprehensive cardiac CT study: evaluation of coronary arteries, left ventricular function, and myocardial perfusion--is it possible?

With advances in multidetector computed tomography (MDCT) technology, the new generation of 64-slice MDCT scanners with submillimeter collimation and a faster gantry rotation allows imaging of the entire heart in a single breath-hold with excellent temporal and spatial resolution. This potentially permits a comprehensive assessment of coronary anatomy, left ventricular function, and myocardial perfusion. As will be seen in this review of the current literature regarding 16- and 64-slice MDCT, there is great promise for a comprehensive cardiac computed tomography (CT) study. The available data support the notion that CT coronary angiography may be an alternative to invasive coronary angiography in symptomatic patients with a low to intermediate likelihood of having coronary artery disease. By use of the same data acquired for CT coronary angiography, evaluation of global and regional left ventricular function and myocardial perfusion can be added to the MDCT evaluation without additional exposure to contrast medium or radiation and may provide a more conclusive cardiac workup in these patients. The potential applications and limitations of coronary stenosis detection, global and regional left ventricular function, and myocardial perfusion assessment by MDCT will be reviewed. The full potential of cardiac MDCT is just beginning to be realized.     

两种方法控制64排螺旋CT冠状动脉成像中心率的比较

目的: 通过两组病例的对比研究,探讨控制患者检查前的心率和效果。方法: 基础心率大于70次/min的患者654例,分为药物干预组352例和心理干预组302例,进行不同的心率干预措施后行64排螺旋CT冠状动脉成像,将两组患者的心率控制效果,冠状动脉图像质量及图像后处理的时间进行比较。结果: 经过口服倍他乐克减慢和稳定心率后, 340例（96.6%）心率降至70次/min以下,12例（3.4%）口服倍他乐克者未降至目标心率。352例患者中有347例（98.8%）的整体图像能满足诊断要求。心理干预组127例（42.0%）经过给予心理护理后心率降至70次/min 以下,154例（58.0%）未降至目标心率。302例患者中266例（88%）能满足诊断要求。控制组图像后处理的平均时间为（12±5）min,对照组图像后处理的平均时间为（18±6）min。结论: 倍他乐克可降低心率明显提高冠状动脉CTA的成像质量,药物控制心率优于心理护理。     

Computed tomography for assessment of cardiac chambers, valves, myocardium and pericardium

The focus to date of MDCT has been primarily on CT applications for evaluating the coronary arteries, notably the measurement of coronary artery calcification, plaque characterization, and atherosclerotic lumen stenosis. This is because of the limited temporal resolution of CT, and the recent rapid improvements in MRI for cardiac applications. However, if the temporal resolution of MDCT can be improved, there will be a compelling argument for undertaking further CT validation studies. Feasibility of CT has already been established by EBT for general cardiac diagnosis. Modifications for MDCT include improved software methods for post processing ECG-gated scan data or higher speed CT hardware for faster image acquisition, both of which are being developed at this time. EBT is also evolving and continuously being refined so that the new generation of scanners have exposure times of 50 msec or less. There are many considerations in comparing the pros and cons of competing cardiac imaging modalities. Published diagnostic validations studies, convenience, procedure time, the comfort level (of patients and physicians), availability, and cost are all critical. The level of acceptance and the accuracy with which specific patient management questions can be appropriately answered are crucial issues in determining which diagnostic procedure to perform. However, the jury is still out regarding the ultimate role of CT in the diagnosis of heart disease; certainly the great potential of cardiac CT has not yet been fully realized.