房颤患者的64层CTCA:平均心率对图像质量和最佳重建期相的影响

目的:评价房颤患者64层螺旋CT冠状动脉成像中平均心率对最佳图像重建时相和图像质量的影响.方法:58例房颤患者行64层螺旋CT冠状动脉成像,扫描前均未服用美托洛尔.血管图像质量分为好、中等和差.分析平均心率和患者总体图像质量之间的相关性,采用判别分析法计算获得总体图像质量为好和中等的平均心率阈值和最佳重建时相在收缩末期的平均心率阈值.结果:平均心率和患者总体图像质量之间呈负相关(r=-0.43,P=0.001);患者总体图像质量为好和中等的平均心率阈值分别为80次/min和95次/min;最佳重建时相在收缩末期的平均心率阈值为85次/min.结论:控制患者平均心率在一定阈值以下并结合舒张中期蕈建.能保证房颤患者64层螺旋CT冠状动脉成像获得较高的图像质量.     

双源CT前瞻性和回顾性心电门控冠状动脉成像对比研究

目的:通过对双源CT前瞻性与回顾性心电门控冠状动脉成像的图像质量和辐射剂量等比较,探讨双源CT前瞻性触发序列扫描技术在冠状动脉成像中的应用价值.方法:将110例行双源CT冠状动脉血管成像检查的患者随机分为2组,A组60例行前瞻性触发序列门控扫描,B组50例行回顾性心电门控螺旋扫描.入组标准为心率75次/min(bpm)以下,心率相对规整(波动≤10bpm).管电压根据体重质量指数(BMI)调整:BM1≥25kg/m2,120kV;BMI＜25kg/m2,100kV.记录扫描中患者所接受辐射剂量,并对其图像质量进行评分.分别采用Wilcoxon秩检验和两独立样本t检验对两组的图像质量和辐射剂量进行统计学分析.结果:A组图像质量平均评分为(3.74±0.51)分,平均有效剂量为(2.38±0.83) mSv;B组图像质量平均评分为(3.68±0.58)分,平均有效剂量为(9.49±3.38)mSv.A、B两组图像质量评分差异无统计学意义(Z =-1.891,P=0.059);有效剂量差异有统计学意义(t=-14.522,P＜0.001),降低约75％.结论:双源CT在心率低且稳定的患者中行前瞻性触发序列扫描能够显著降低辐射剂量,并且可以获得满足临床诊断的图像质量.     

64排螺旋CT冠状动脉成像注射后延迟时间的影响因素

目的 探讨64排螺旋CT冠状动脉成像中心率、体重指数(BMI)、年龄、性别与冠状动脉CT血管造影(CTA)成像延迟扫描时间的相关性及与冠状动脉达峰CT值的相关性.资料与方法 150例可疑冠心病的受检者,男70例,女80例,年龄最大88岁,最小31岁,平均54岁.所有受检者均行timing bolus扫描技术预测冠状动脉CTA延迟扫描时间,然后行冠状动脉CTA扫描,记录冠状动脉达峰CT值、延迟扫描时间,分析性别、年龄、体重指数、心率与冠状动脉CTA延迟扫描时间及冠状动脉达峰CT值的相关性.结果 体重指数对冠状动脉达峰时间影响差异无统计学意义(P=0.157),性别的标准回归系数为-0.395,对冠状动脉达峰时间影响最大,其次是年龄,影响最小为心率;心率对冠状动脉达峰CT值影响差异无统计学意义(P=0.202),性别标准回归系数为0.462,对冠状动脉达峰CT值影响较大,其次为体重指数,影响最小为年龄.结论 当timing bolus扫描预测冠状动脉CTA达峰延迟扫描时间时,对老年、男性、心率较慢者,应综合考虑,适当增加延迟扫描时间.     

双源CT冠状动脉成像图像质量与影响因素的相关性分析

目的分析多种图像质量影响因素与图像质量的关系,探讨相应的解决方案。方法回顾性分析926例行双源CT(dual-source CT,DSCT)冠状动脉成像资料,分析其平均心率、心率变化、视野(FOV)、螺距(Pitch)值、采集心动周期数、对比剂注射流率、对比剂用量、触发阈值、触发时间等扫描参数与冠状动脉成像图像质量的相关性。结果影响因素中平均心率、心率变化及FOV与图像质量有统计学意义的相关关系。平均心率及心率变化与DSCT冠状动脉CTA图像质量呈负相关;FOV与图像质量呈正相关。心动周期、Pitch值、对比剂注射流率、对比剂用量、触发阈值、触发时间与图像质量无统计学意义的相关。结论冠状动脉CT成像图像质量受多种因素影响,其中心率、心率变化及FOV是影响图像质量的主要因素。     

320排容积CT冠状动脉血管成像前瞻性心电门控最佳重建时相的初步研究

目的 探讨320排容积CT(320-DVCT)冠状动脉血管成像前瞻性心电门控最佳重建时相,初步评价其对图像质量、曝光剂量及诊断准确性的影响.方法 对77例行DVCT心功能扫描的患者[平均扫描心率(70±13)次/min( bpm),范围46～ 102 bpm]做回顾性心电门控扫描,分析最佳重建时相与心率的关系.利用不同心率最佳重建时相作为前瞻性心电门控扫描曝光时相,对53例需接受冠状动脉导管造影的患者[平均扫描心率(75±11) bpm,范围57～114 bpm]同时行冠状动脉CT成像,评价曝光时相对图像质量、曝光剂量及诊断准确性的影响.图像质量评分随机区组多样本比较采用Friedman检验,双变量统计行直线回归分析及Spearman相关分析.结果 随着心率的增加,收缩期比例逐渐增高(r=0.78,P＜0.01).收缩期与舒张期最佳重建图像质量随着心率的增加明显下降(r分别为0.38、0.82,P均＜0.01).根据回归方程分析,最佳重建时相按心率分组如下:心率＜ 70 bpm,65％～80％;70～80 bpm,70％ ～85％;81 ～90 bpm,70％～90％;＞90 bpm,35％ ～ 50％.利用上述最佳重建时相行前瞻性心电门控扫描结果表明,前瞻性心电门控扫描较回顾性心电门控扫描明显降低辐射剂量[分别为(6.1±3.8)和(12.4±7.0) mSv,t=6.5,P＜0.01],对诊断准确性并无明显影响.但是随着心率的增加,前瞻性心电门控扫描辐射剂量仍会明显增加(r=0.64,P＜0.01).结论DVCT可在更宽心率范围内应用前瞻性心电门控扫描技术对冠状动脉进行准确诊断;但在高心率条件下需要多个心动周期扫描,辐射剂量明显增加,建议尽可能降低患者心率以降低辐射剂量.     

双源CT前瞻性心电触发序列扫描在房颤患者中的应用研究

目的应用双源CT前瞻性心电触发序列扫描对心房纤颤(atrial fibrillation,AF)患者行冠状动脉成像,并与回顾性心电门控螺旋扫描比较,评估二者的图像质量及放射剂量。方法对40例临床可疑冠心病的AF患者行二代128层双源CT增强扫描。随机分为两组:组1共21例(序列组),使用前瞻性心电触发序列扫描;组2共19例(螺旋组),使用回顾性心电门控螺旋扫描。基于AHA-15段冠状动脉分段法及4级评分法(1分-优秀至4分-差),由两位阅片者独立对所有冠状动脉按节段进行图像质量评价,比较两组患者的图像质量及有效放射剂量。结果序列组平均心率(94±25)次/min,心率波动(69±25)次/min;螺旋组平均心率(86±22)次/min,心率波动(65±22)次/min,组间平均心率(t=1.019,P=0.315)及心率波动(t=0.598,P=0.553)差异无统计学意义。序列组与螺旋组的图像质量优良,评分差异无统计学意义(1.29±0.55 vs 1.25±0.55;Z=-1.290,P=0.197);序列组的有效放射剂量较螺旋组显著降低(4.90±1.62 mSv vs 10.04±3.57 mSv;t=-5.988,P=0.000)。结论 AF患者双源CT冠状动脉成像中,前瞻性心电触发序列扫描与回顾性心电门控螺旋扫描相比,可以提供同样高质量的图像满足诊断需要,同时有效减低放射剂量。     

前瞻性门控技术在双源CT冠状动脉成像中的应用

目的 评价前瞻性门控扫描技术减低X线辐射的效能及前瞻性门控低剂量扫描冠状动脉CT成像技术的应用价值.方法 通过使用双源64排CT机,对50例心率≤70次/min患者行前瞻性门控,50例心率≤70次/min及50例心率＞70次/min患者行回顾性门控扫描模式下冠状动脉CT成像,对成像质量和X线剂量进行对比研究,经统计学处理分析2种扫描模式冠状动脉CT成像的图像质量差异及X线剂量差异.结果 2种扫描模式下冠状动脉CT成像的图像质量差异无统计学意义,前瞻性门控组中图像质量积分3分以上均达98%以上,全部病例图像质量均能满足诊断要求;2种扫描模式下X线剂量参数总剂量长度乘积值、总有效剂量差异有统计学意义(P＜0.001); 前瞻性门控扫描较回顾性门控扫描下心率＞70次/min及心率≤70次/min的X线总有效剂量分别下降75.15%及79.56%.结论 当受检者心率≤70次/min时,可选择时间窗为R-R间期70%前瞻性门控扫描,图像质量优良,并且能大幅度降低冠状动脉成像X线辐射剂量.     

16层螺旋CT冠状动脉成像图像质量相关影响因素分析及最佳扫描条件选择(心脏体模模拟实验)

目的 采用新型心脏动态体模,对16层螺旋CT冠状动脉成像图像质量相关影响因素进行分析,并探讨在不同心率下的扫描速度和重组算法选择.材料与方法 采用GE公司研制的新型心脏动态体模,心率设置为40～95次/min(间隔5次/min)共12组.采用GE LightSpeed 16 层螺旋CT,以心脏冠状动脉扫描模式对不同心率下的心脏体模进行扫描,X线球管转速(即扫描速度)设置为0.5 s/r和0.6 s/r.所有的扫描数据在R-R间期90%时相分别以单扇区(Snapshot segment)、双扇区(Burst-2)和四扇区重组(Burst-4)3种心脏重组算法进行重组.所有重组数据传至AW4.1工作站行后处理成像.后处理方法采用容积再现(VR)、多平面重组(MPR).分别对不同重组图像进行评分.统计学处理采用析因分析和多元线性回归分析.结果 (1)总模型具有统计学意义(F=11.15,P＜0.0001),不同心率(F=11.99,P＜0.0001)、不同转速(F=5.76,P=0.00196)、不同重组算法(F=9.21,P=0.0003)对图像质量有显著的影响,三者的交互作用均无显著差别(P＞0.05);(2)不同心率间比较,心率≤65次/min时图像质量评分较高(P＜0.05);(3)不同扫描速度比较,0.5 s/r时,图像质量评分较高(P＜0.05);(4)不同重组算法之间比较:重组算法为Burst-4和Burst-2时,图像质量评分较高(P＜0.05),但两者之间差异无统计学意义(P＞0.05);(5)心率、扫描速度及重组算法与图像质量间具有多元线性回归关系(标准化回归系数分别为-0.70794、-0.16449和0.27341,F=34.43,P＜0.0001),各回归系数具有显著性.结论 心率、扫描速度及重组算法等是影响16层螺旋CT冠状动脉成像图像质量的主要因素,可采用新型心脏动态体模进行评估.合理利用扫描参数能有效提高图像质量和检查的成功率.     

64层螺旋CT前门控冠状动脉横断面扫描低剂量技术的初步研究

目的 评价64层螺旋CT(MSCT)应用前瞻性心电门控横断面扫描技术低剂量冠状动脉成像的能力及图像质量.方法 连续选取77例临床拟行冠状动脉成像的患者(A组,平均体重指数24.6,心率＜70次/min)行前瞻性门控横断面扫描,根据患者体重指数选择管电流(230～740 mA),管电压120 kV;用同样扫描条件模拟固定参数螺旋扫描剂量并记录.同时比较行MSCT冠状动脉成像连续回顾性门控心电标记固定参数的30例患者(B组,平均体重指数23.9,心率＜70次/min)的扫描剂量,并对2组的图像质量进行评价(配对t检验,P＜0.05为差异有统计学意义).结果 A组前门控横断面扫描冠状动脉成像剂最平均为3.37 mSv,所获图像满足临床诊断需要,模拟固定参数螺旋扫描平均剂量为17.29 mSv;B组实际回顾性门控CT固定参数螺旋扫描冠状动脉成像平均剂量为18.13 mSv.B组与A组模拟固定参数螺旋扫描剂量差异无统计学意义(t=0.87,P＞0.05),与A组前瞻性门控横断面扫描有效剂量比较差异有统计学意义(t=18.50,P＜0.01),减少了约81.4%.结论 64层MSCT冠状动脉成像中前瞻性心电门控横断面扫描技术能够获得满足临床诊断需要的高质最图像,同时非常有效地降低了辐射剂量.     

256层螺旋CT无心率控制的成人112例冠状动脉成像应用

近年来,多层螺旋CT的问世使冠状动脉无创成像检查成为现实,256层螺旋CT的时间分辨率可达到34 ms,理论上可适应不同心率的冠脉成像.笔者总结了我院112例未进行心率控制的患者,行256层螺旋CT的成人冠状动脉成像的图像资料,以探讨图像质量与心率之间的关系.     

256层螺旋CT冠状动脉造影在心肌桥检测中的应用

目的:利用256层螺旋CT冠状动脉成像探讨心肌桥的出现率、好发部位.方法:连续收集临床诊断为冠心病且行256层螺旋CT冠状动脉成像的病例251例,回顾性地在线分析冠脉CT血管造影上心肌桥的出现率及其部位.结果:52例患者检出了心肌桥(52/251,20.7%),其中男性20例,女性22例,年龄60.27±11.36岁,共66段心肌桥.其中38例为单一壁冠状动脉,14例为两段受累,分别发生在前降支中段和钝缘支、前降支中段和右侧冠状动脉中段.心肌桥最常见于左前降支中段(48段,72.7%).结论:心肌桥常见,最常出现于左前降支,特别是左前降支中段,256层螺旋CT有效、无创且清晰地显示了心肌桥.     

Abolition of Respiratory-Motion Artifact in Computed Tomography Coronary Angiography with Ultrafast Examinations: A Comparison Between 64-row and 320-row Multidetector Scanners

Purpose

To compare the incidence of respiratory artifact in computed tomography (CT) coronary angiography performed with 64-row and 320-row multidetector scanners and to assess its effect on coronary evaluability.

Methods

A retrospective review of consecutive coronary angiograms performed on a 64-row multidetector CT from March to April 2007 (group 1: 115 patients, 63 men; mean age [standard deviation] 59.6 ± 12.8 years) and on a 320-row multidetector CT from March to April 2008 (group 2: 169 patients, 89 men; mean [SD] age 57.9 ± 11.6 years). Two cardiac radiologists assessed the occurrence of respiratory artifact and coronary evaluability in studies with respiratory artifacts. Unevaluable coronary segments because of motion at the same anatomical level of the respiratory artifact were considered unevaluable because of this artifact. The association between the occurrence of respiratory artifact and patient biometrics, medication, and scan parameters was examined.

Results

Respiratory artifacts were detected in 9 of the 115 patients from group 1 (7.8%) and in none of the 169 patients from group 2 (P < .001). Group 1 had longer scan times (median, 9.3 seconds; range, 7.5−14.4 seconds) compared with group 2 (median, 1.5 seconds; range, 1.1−3.5 seconds; P < .001). In group 1, 4 patients (3.5%) showed unevaluable coronary segments because of respiratory artifacts, and the CT coronary angiography was repeated in 1 patient (0.9%).

Conclusions

Respiratory artifacts are important in CT coronary angiography performed with 64-row multidetector scanners and impair the diagnostic utility of the examination in up to 3.5% of the studies. These artifacts can be virtually eliminated with a faster scan time provided by 320-row multidetector CT.     

Optimal timing of contrast enhancement in coronary CT angiography using the Bolus-tracking method

Negative product value for coronary artery disease is 98% to 99%. Therefore, the number of unnecessary cardiac catheterization procedures is reduced as the usefulness of CT systems for examination of the coronary arteries improves. In the bolus-tracking method, in which an ROI is placed in the ascending aorta to trigger scanning, scanning may not be performed at the optimal time of contrast enhancement depending on the patient. In addition to identifying the causes of this problem, we have developed a new method in which ROIs are placed in the right ventricle and left atrium to trigger scanning when the concentrations of contrast medium in the right ventricle and left atrium become equal. The two methods were then compared and evaluated. In the scan method, in which an ROI is placed in the ascending aorta, the reason for non-optimal scan timing is considered to be that the time required for contrast medium injected via an antecubital vein to reach the heart varies depending on the individual patient(approximately 3 times the variation of our method)followed by a delay of approximately 5 seconds between the scan trigger time and the actual scan start time. In the scan method in which scanning is triggered when the concentrations of contrast medium in the right ventricle and left atrium become equal, scanning can be performed at the time of peak enhancement regardless of differences in the time required for the injected contrast medium to reach the target region or differences in the injection rate, demonstrating the usefulness of this method.     

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.     

Clinical indications and utilization of 320-detector row CT in 2500 outpatients

Clinical indications and utilization patterns for 3963 CT scans on 2500 consecutive patents on a 320-detector row CT in an outpatient setting were retrospectively analyzed and compared with previously reported CT studies. The impact of the latest generation CT technology, including whole organ perfusion, on indications and utilization patterns during the study period was also assessed. The top five requested CT scan types were abdomen/pelvis, chest, head, sinuses, and coronary CT angiography. Indication and utilization rates were similar to prior studies for abdomen/pelvis, non-cardiac chest, and head CT scans. Abdominal pain and headaches were the most frequent indications for abdomen/pelvis and head CTs, respectively. The 7.3% cardiac CT scan utilization rate was not comparable to rates of up to 72% in self-referral outpatient settings. Whole organ volume CT imaging was utilized in 100% of coronary CT angiography and 22.7% of head CTs. The 320-row CT had fewer negative head and body CT findings as compared to prior reports. The availability of new technology, such as whole organ dynamic scans, appears to have influenced CT indications, utilization and finding rates with a decrease in negative brain and body results. Comparisons with previous outpatient CT studies were similar for multiple categories with the exception of cardiac CT utilization, which is heavily influenced by self-referral. Further study of outpatient imaging indications and utilization rates from multiple centers may benefit from a standardized categorization to improve understanding of the disparate outpatient imaging environment.     

Noninvasive assessment of coronary artery with substantial contrast volume reduction using 320-detector row computed tomography: a feasibility study

The recently introduced 320-detector row computed tomography (320-row CT) allows very fast volumetric acquisition of the entire heart. Because the total amount of contrast agent required for CT coronary angiography (CTCA) depends directly on the acquisition time, 320-row CTCA would substantially reduce the contrast agent dose. The objective of this retrospective study was to evaluate the feasibility of contrast volume reduction on 320-row CTCA compared with 64-detector row CTCA (64-row CTCA). We retrospectively reviewed consecutive 320- and 64-row CTCA data (16 eligible cases for each; administrated contrast volume, 20-24 ml for the former and 50-65 ml for latter) from a homogeneous patient population (age ≤ 81, body weight ≤ 67 kg, and heart rate ≤ 69 bpm). The two types of CTCA data were compared with respect to the successful rate of adequate intravascular contrast enhancement defined as the number of segments with attenuations of more than 250 HU divided by total number of coronary segments evaluated. Our dataset provided mean intravascular attenuation values of 320 and 404 HU on the 320- and 64-row CTCA, respectively. Although the attenuation values were statistically lower for the 320-row CTCA (P < 0.001), there was no significant difference in the successful rates of adequate intravascular contrast enhancement (rate of 0.98 for each; P > 0.05). We therefore conclude that 320-row CTCA is a feasible method of diagnostic imaging and is superior to 64-row CTCA because it uses less of the contrast medium.     

320排动态容积CT在冠心病筛查中的初步应用

目的探讨320排动态容积CT冠状动脉造影在冠状动脉粥样硬化性心脏病(冠心病)筛查中的应用。方法分析90例临床拟诊为冠心病患者的320排CT前瞻性心电门控全心容积扫描检查结果。对显示的冠状动脉主干及其主要分支进行分级评价,并对辐射剂量进行统计分析。结果本组90例,发现狭窄性病变70例,其中三支狭窄性病变10例,两支狭窄性病变25例,单支狭窄性病变35例;其中狭窄度≥50%35支(30.43%),<50%80支(69.57%)。90例冠状动脉成像质量1级80例(88.89%),2级9例(10%),3级1例(1.11%)。结论 320排CT冠状动脉成像速度快,图像质量高,辐射剂量低,是冠心病筛查的首选检查。     

16层螺旋CT冠状动脉成像扫描延迟时间及其相关因素的临床研究

目的探讨16层螺旋CT冠状动脉成像扫描延迟时间及其相关因素。方法对82例临床疑冠心病者进行MSCTA,其中A组47例为预扫描组,通过小剂量注射对比剂试验测定扫描延迟时间并对其数据进行统计学分析,B组35例为对照组,未进行预扫描,直接应用A组结果,进行A、B2组图像的评价。结果扫描延迟时间与患者年龄、体重、心功能等因素线性相关分析无明显相关;心率≤55次/min与扫描延迟时间有负相关(r=-0.596,P<0.05);心率≤55次/min组与55次以上组有显著性差异(P<0.05)。心率47～50次/min的延迟29s、28s扫描,心率51～55次/min延迟27s、26s,心率56～75次/min组延迟25s扫描。A、B2组图像评价无显著差异。结论直接扫描操作简便,工作效率高,有较高临床应用价值。     

Multidetektor-CT (MDCT) der Leber

Multidetector-row CT (MDCT) scanners have dramatically improved liver imaging. With the newest generation of 40-64 row scanners, true isotropic imaging with a z-axis resolution of 0,3-0.6 mm has become possible. Acquisition time for the scan has been shortened to a few seconds. To fully exploit the advantages of MDCT scanners in liver imaging, the examination protocols have to be optimized with regard to contrast material flow rate, scan delay, and the number of scans performed. The possible advantages of double arterial phase scans in the detection of HCC are discussed. The clinical value of 3D reconstructions, such as multiplanar reconstructions and curved planar reconstructions, for assessment of the vascular and biliary duct infiltration is demonstrated. Optimized MDCT imaging improves detection and characterization of focal liver lesions.