心率对64层螺旋CT冠状动脉成像图像质量的影响

目的:评价心率对64层螺旋CT冠状动脉成像图像质量的影响.方法:采用GE Light speed 64层螺旋VCT,以心脏扫描模式对心脏动态体模进行扫描.心脏动态体模由3个部分组成:动力部分、解剖结构模拟部分和控制部分.心脏动态体模的心率设置为40、45、50、55、60、65、70、75、80、85、90、95、100、105、110和115次/min,心律齐.以球管转速0.35 s对不同心率下的心脏动态体模进行冠状动脉成像扫描.所有扫描数据在R-R间期90%时相分别进行单扇区和多扇区重建.重建数据传至工作站后处理成像.后处理方法采用VR、MPR重组模式.分别对重建图像进行评分.结果:①心率与图像质量呈负相关(P＜0.01);随着心率的增加,图像质量评分呈下降趋势;②在同一条件下多扇区重建算法较单扇区重建算法提高了图像质量评分.结论:采用心脏动态体模评价心率对64层螺旋CT冠状动脉成像图像质量的影响,对临床研究和应用有着重要价值.     

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心脏冠状动脉检查质量控制和扫描参数优化研究

目的 分析影响64层螺旋CT冠状动脉成像质量的各种因素，对扫描方法进行质量控制和优化。方法 对78例怀疑冠心病或冠心病复查患者进行64层螺旋CT冠状动脉检查，回顾性分析成像质量，探讨心率替代（override）功能的应用价值，分组分析扇区选择与心率对图像质量的影响以及心率与对比剂增强效果的相关性，优化扫描参数。结果 （1）心率替代功能的合理使用可以提高CT冠状动脉的成像质量；（2）心率70次／min以下的单扇区重组图像质量可以满足要求；70-79次／min之间的心率，选择双扇区重组图像的评分要高于单扇区；（3）预测对比剂总量70m1组的平均心率为60．7次／min，65．7％（23／35）的患者增强药量稍显不足；总量为60ml组的平均心率为71．1次／min，52．9％（18／34）的患者增强效果良好。结论 根据心率选择心率替代功能的使用，适当的扇区扫描模式和对比剂总量可以提高图像质量和冠状动脉检查的可靠性。     

心率波动对16层CT冠脉成像图像质量的影响及对策(心脏体模模拟实验)

目的 研究心率波动对16层螺旋CT冠状动脉成像质量的影响及心率波动情况下最佳扫描条件.方法 采用GE Light-Speed 16层螺旋CT,以心脏冠脉扫描模式对心脏体模进行扫描.心率设置为以60次/min、85次/min为中心上下波动2组,每组分别设置波幅为2.5次/min、5次/min和10次/min各3小组,分别对6组心率波动情况下的心脏体模以心脏冠脉扫描模式进行扫描,所有扫描数据在R-R间期5%、15%、25%、35%、45%、55%、65%、75%、85%、95%相位分别进行单扇区(Segment)、双扇区(Burst-2)和四扇区重建(Burst-4).重建数据传至AW4.1工作站后处理成像.后处理方法采用容积再现(VR)、多平面重组(MPR)模式.由1名高年资医师和1名技师分别对不同重组图像进行评分.统计学处理采用析因分析.结果 (1)方差分析显示,总模型具有显著意义(F=22.58,P《0.0001),各变量(心率、波幅、算法和相位)具有显著意义,均对冠状动脉成像质量有影响;(2)不同心率之间比较心率为60次/min者图像质量评分均数显著高于心率为85次/min者(P《0.05);(3)不同波动范围之间比较波幅为2.5次/min和5次/min者,图像质量评分均数高于波幅为10次/min者(P《0.05),但波幅为2.5次/min和5次/min无显著差异(P》0.05);(4)不同重建算法之间比较算法为Burst-4和Burst-2者图像质量评分均数显著高于算法为Segment(P《0.05),但Burst-4和Burst-2之间无显著差异(P》0.05);(5)不同相位之间比较相位为45%,95%显著高于其他相位(P《0.05),但上述二者相位之间无显著差异(P》0.05).相位为15%者,图像质量最差.结论 新型心脏动态体模评价心率波动对16层螺旋CT冠状动脉成像质量的影响及心率波动情况下最佳扫描条件分析,能够为临床应用和基础研究提供帮助.     

64层螺旋CT冠状动脉成像:不同心率下最优相位窗的探讨

目的:探讨64层螺旋CT冠状动脉成像在不同心率下最优成像相位窗.方法:对112例病例行64层螺旋CT冠状动脉成像,扫描后数据分别按R-R间期10%、20%、30%、40%、50%、60%、70%、80%及90%的相位进行后处理重组,对后处理图像按5级评分,记录扫描期间心率,112例患者心率＜60次/min者为Ⅰ组,60～69次/min为Ⅱ组,70～79次/min为Ⅲ组,≥80次/min为Ⅳ组,绘制不同心率组的冠状动脉成像质量评分随时相位变化的线图,分析观察不同心率组的各时相冠状动脉评分趋势.结果:Ⅰ、Ⅱ、Ⅲ组80%相位图像质量最优,Ⅳ组RCA最优的相位窗为50%相位,LMA、LAD、LCX最优的相位窗为40%,Pearson相关分析在R-R 40%相位,冠状动脉的图像质量评分与心率无显著相关性.结论:在不同心率下,64层螺旋CT冠状动脉成像各相位的图像质量有差别,高心率下,可用40%、50%相位的图像来用于诊断.     

64层探测器CT冠状动脉成像依据不同心率的最佳重建方案

目的:探讨64层螺旋CT冠状动脉成像不同心率下冠状动脉各节段血管的最佳重建时相。方法:对61例患者行64层螺旋CT冠状动脉成像,扫描后原始数据分别按R-R间期30%、35%、40%、45%、50%、60%、70%、75%的相位进行后处理重组,按扫描期间平均心率分组,Ⅰ组30例,心率70次/min;Ⅱ组31例,心率≥70次/min。分析不同心率组不同R-R时相对各支冠状动脉血管的显示情况。结果:Ⅰ组的所有的冠状动脉节段可以在单一的75%相位上获得最佳图像质量;Ⅱ组的所有冠状动脉可以在单一的45%或40%的相位上获得最佳图像质量,多时相重建并不能显著提高图像质量。结论:随着64层螺旋CT时间分辨率的充分发展,所有冠状动脉节段能在一个重建时相得到有诊断价值的图像,多时相重建并不能显著提高图像质量。     

64层螺旋CT冠状动脉成像初步研究

目的 探讨64层螺旋CT冠状动脉成像的图像质量和诊断冠状动脉狭窄的准确性。方法 对120例临床可疑冠心病患者进行64层螺旋CT回顾性心电门控增强扫描，用多平面重组（MPR）、最大密度投影（MIP）及容积再现技术（VRT）重组图像，其中60例患者有常规X线冠状动脉成像作对照。结果 以VRT重组像评价图像质量，92例（77％）为1级，22例（18％）为2级，6例（5％）为3级。MPR、MIP及VRT重组像能显示冠状动脉的所有1级、大部分2、3级以及部分4级分支。64层螺旋CT冠状动脉成像诊断冠状动脉≥50％狭窄的敏感性为93％，特异性为98％。结论 64层螺旋CT冠状动脉成像是一种无创、快速的成像方法，对诊断冠状动脉≥50％狭窄有较高的敏感性和特异性。     

双源CT冠状动脉成像的初步研究

目的初步探讨无需口服控制心率药物准备的双源CT冠状动脉成像的扫描技术和图像质量。方法对215例临床怀疑冠心病或冠状动脉早期病变患者进行无需口服控制心率药物准备的双源CT冠状动脉成像。扫描步骤包括平扫和增强扫描。用平扫图像行冠状动脉钙化积分，用增强扫描图像行多平面重组（MPR）、最大密度投影（MIP）及容积再现技术（VRT）重组。总结双源CT冠状动脉成像的扫描技术和后处理方法。将图像质量分为3级，按冠状动脉分段标准评价各个节段的图像质量。结果215例患者钙化积分值中位数为82．2（2．3～1827．9）。增强扫描平均心率为（80．6±15．3）（57～139）次／min，尽可能使冠状动脉良好显示的后处理方法有：（1）多个时相筛选法；（2）2个或多个时相补充法；（3）早搏去除法和心律不齐移位法。共评价3026个冠状动脉节段，其中图像质量为1级者占97．5％（2951／3026），2级者占2．0％（62／3026），为3级者占0．5％（13／3026）；图像质量为2级和3级的节段多由于呼吸伪影所致。215例患者共91例冠状动脉各节段均未见斑块或狭窄，共诊断〈50％冠状动脉狭窄节段112个，≥50％冠状动脉狭窄节段213个。结论双源CT冠状动脉成像在无需口服控制心率药物准备的情况下可获得非常好的冠状动脉各节段图像，心率不再是影响图像质量的关键因素，通过单时相或多时相重组可良好显示冠状动脉主干及分支。     

64层容积CT冠状动脉成像技术及影响因素的分析

目的探讨64层容积CT冠状动脉成像技术及影响图像质量的因素。资料与方法对254例患者进行64层容积CT心脏扫描,以容积再现（VR）、最大密度投影（MIP）和曲面重组（CPR）等技术行冠状动脉三维成像．以心率≤60次／min、61～69次／min、70～75次／min及≥76次／min分为4组评价图像质量,分析其影响因素。结果（1）心率≤60次／min、61～69次／min、70～75次／min3组间冠状动脉成像优良率差异无统计学意义;（2）心率≤75次／min组出现差片的概率明显低于心率≥76次／min组（P＜0．05）．优等片的概率明显高于心率≥76次／min组（P＜0．05）;（3）影响冠状动脉管腔评价的技术性因素主要是扫描过程中发生心率、心律变化或对比剂延迟时间不当等造成的移动伪影、血管错位和边缘模糊;非技术性因素为冠状动脉管壁的弥漫性钙化导致的高密度及其伪影。结论影响64层容积CT冠状动脉成像质量的主要因素是心率或心律的变化、延迟时间不当和广泛钙化。适当控制心率,避免心律不齐的发生可明显改善冠状动脉的成像质量,提高可评估率。     

64层螺旋CT冠状动脉图像质量控制研究:最佳重组时相与心率关系

目的量化评估64层螺旋CT冠状动脉各分支不同重组时相图像质量,探讨冠状动脉CT成像最佳重组时相与心率关系。资料与方法102例患者均采用64层螺旋CT回顾性心电门控冠状动脉成像,男68例,女34例,平均年龄(58.1±9.7)岁,平均心率(66.4±11.5)次/min。心率<65次/min(n=43)为Ⅰ组,65～75次/min(n=34)为Ⅱ组,>75次/min(n=25)为Ⅲ组,每例患者的4支冠状动脉(左主干、左前降支、左回旋支、右冠状动脉)共分为12个节段用于图像质量分析。扫描原始数据以间隔5%在20%～80%时相分别回顾性重组冠状动脉图像,采用横断位、曲面重组、容积再现等方法对图像质量综合评分。结果Ⅰ组60%、65%和70%为最佳时相,Ⅱ组60%、65%时相为最佳时相,Ⅲ组右冠状动脉较优时相为35%、40%,左冠状动脉较优时相为60%、65%。结论心率和重组时相的选择是决定冠状动脉图像质量的重要因素。平均心率≤75次/min,冠状动脉各分支图像质量在心脏运动的舒张中期(60%、65%)最佳;>75次/min时,左右冠状动脉分别进行重组能明显提高冠状动脉的成像质量。     

Improving coronary artery imaging quality in the high heart rate region and on MDCT using a pulsating cardiac phantom

The multi-sector reconstruction (MSR) algorithm and cardiac half-reconstruction (CHR) algorithm are the main algorithms used in cardiac reconstruction. Analysis of effective temporal resolution (TR) confirmed that optimal rotation speed depends on different heart rates when using MSR. During visualization (3D/MPR image) and quantitative (EF: ejection fraction) evaluations, it was found that image quality and measurement accuracy are well correlated with effective temporal resolution (TR) by the different algorithms. The CHR algorithm resulted in less desirable image quality at TR 250 ms than that from MSR at high heart rates (>75 bpm) in the phantom experiment. We determined that the combination of the MSR algorithm and the optimal selection of gantry rotation speed is important for obtaining high-quality cardiac imaging in the high heart rate region.     

Correlation of effective temporal resolution and accuracy of volume ejection fraction on the ECG-gated cardiac MDCT

PURPOSE: ECG-gated cardiac MDCT offers many cardiac clinical applications. The goals of this report are 1) to introduce a new concept of effective reliability (ER) from effective temporal resolution for the evaluation of ejection fraction (EF) and evaluation of image quality (IQ) of coronary arteries, and 2) to show the correlation of ER and the accuracy of EF with different cardiac reconstruction algorithms and different rotation speeds. METHODS AND MATERIALS: To assess the accuracy of EF, helical scanning was performed with a gated cardiac MDCT (GE LightSpeed, 8/16 slice) on pulsating cardiac coronary phantoms (0.5 and 0.6 sec rotation speed for each 50-110 bpm, 5-bpm step). We define effective reliability (ER) from effective temporal resolution (%) as follows: ER= (1-TR/HC) x 100; TR: Effective temporal resolution, HC: time of heart cycle in each bpm. RESULTS: From the results of the EF measurement and calculated ER, high accuracy was obtained by using optimal scan conditions (optimal rotation speed and cardiac reconstruction algorithm) in a wide range of heart rates (heart rate<90: EF & ER>81%; heart rate<110 bpm: EF & ER>73%). Results showed that the calculated ER is closely correlated with the measurement results of EF based on the phantom experiment (R2=0.901+/-0.075; Max: 0.994, Min: 0.738). Optimal reconstruction thickness can reduce total image number for the evaluation of EF. CONCLUSION: We concluded that the ER is useful to evaluate EF accuracy and the IQ of images of coronary arteries.     

64层VCT冠脉成像单扇区图像重建算法与相位窗的优选

目的评价单扇区图像重建算法的相位窗优选。方法102例患者行64层VCT冠状动脉成像检查，采用回顾性心电门控、0.35s容积扫描、单扇区重建算法，静脉注射对比剂。在8个相位窗（心动周期的R波后45%、50%、55%、65%、70%、75%、80%和90%）上对冠状动脉进行CT图像重组。结果在冠状动脉内径大于1.6mm的1286个节段中，823个节段（占63.9%）在75%相位窗上显示最佳，267个节段（占20.8%）在70%相位窗上显示最佳，109个节段（占8.4%）在50%相位窗上显示最佳，31个节段（占2.4%）在80%相位窗上显示最佳，23个节段（占1.7%）在45%相位窗上显示最佳，15个节段（占1.1%）在55%相位窗上显示最佳，11个节段（占0.9%）在90%相位窗上显示最佳，7个节段（占0.5%）在65%相位窗上显示最佳。结论采用单扇区重建算法，冠状动脉多数在心动周期的R波后75%相位窗上显示最佳，其次为70%和50%相位窗。     

心电图调制电流对于容积CT心脏扫描图像质量及曝光剂量影响的评估

目的评估容积CT（VCT）心脏扫描时，开启或关闭心电图（ECG）调制电流（mA）技术对图像质量是否有影响，并判断ECG调制mA技术是否能有效降低曝光剂量。方法将跳动心脏模具设定为高、中、低不同速率的稳定心率，采用与不同速率稳定心率相匹配的重组算法，开启ECG调制mA，对心脏模具进行扫描，扫描同时记录各扫描序列的曝光剂量，在采集到的图像中选取结构均匀的部位，测量该部位的CT值及不同部位CT值的差值，并记录图像测量部位的标准差（s）值；关闭ECG调制mA，重复上述扫描并记录曝光剂量，对采集到的图像进行相同测量和记录。将2次扫描所测得的数据进行统计学分析。结果在同样心率条件下，ECG调制开启时比关闭时曝光剂量有明显减低，在每分钟搏动数（bpm）为50、60、75和95的4种心率条件下，曝光剂量分别减少了48．0％、44．0％、37．0％和37．7％；2组图像的数据分析差异无统计学意义（P〉0．05）。结论VCT心脏扫描时，开启ECG调制mA技术能够有效降低曝光剂量，同时对图像质量无明显影响。     

Study on motion artifacts in coronary arteries with an anthropomorphic moving heart phantom on an ECG-gated multidetector computed tomography unit

Acquisition time plays a key role in the quality of cardiac multidetector computed tomography (MDCT) and is directly related to the rotation time of the scanner. The purpose of this study is to examine the influence of heart rate and a multisector reconstruction algorithm on the image quality of coronary arteries of an anthropomorphic adjustable moving heart phantom on an ECG-gated MDCT unit. The heart phantom and a coronary artery phantom were used on a MDCT unit with a rotation time of 500 ms. The movement of the heart was determined by analysis of the images taken at different phases. The results indicate that the movement of the coronary arteries on the heart phantom is comparable to that in a clinical setting. The influence of the heart rate on image quality and artifacts was determined by analysis of several heart rates between 40 and 80 bpm where the movement of the heart was synchronized using a retrospective ECG-gated acquisition protocol. The resulting reformatted volume rendering images of the moving heart and the coronary arteries were qualitatively compared as a result of the heart rate. The evaluation was performed on three independent series by two independent radiologists for the image quality of the coronary arteries and the presence of artifacts. The evaluation shows that at heart rates above 50 bpm the influence of motion artifacts in the coronary arteries becomes apparent. In addition the influence of a dedicated multisector reconstruction technique on image quality was determined. The results show that the image quality of the coronary arteries is not only related to the heart rate and that the influence of the multisector reconstruction technique becomes significant above 70 bpm. Therefore, this study proves that from the actual acquisition time per heart cycle one cannot determine an actual acquisition time, but only a mathematical acquisition time.     

Evaluation of spatial and temporal resolution for ECG-gated 16-row multidetector CT using a dynamic cardiac phantom

Measurements of spatial and temporal resolution for ECG-gated scanning of a stationary and moving heart phantom with a 16-row MDCT were performed. A resolution phantom with cylindrical holes from 0.4 to 3.0 mm diameter was mounted to a cardiac phantom, which simulates the motion of a beating heart. Data acquisition was performed with 16×0.75 mm at various heart rates (HR, 60–120 bpm), pitches (0.15–0.30) and scanner rotation times (RT, 0.42 and 0.50 s). Raw data were reconstructed using a multi-cycle real cone-beam reconstruction algorithm at multiple phases of the RR interval. Multi-planar reformations (MPR) were generated and analyzed. Temporal resolution and cardiac cycles used for image reconstruction were calculated. In 97.2% (243/250) of data obtained with the stationary phantom, the complete row of holes with 0.6 mm was visible. These results were independent of heart rate, pitch, scanner rotation time and phase point of reconstruction. For the dynamic phantom, spatial resolution was determined during phases of minimal motion (116/250). In 40.5% (47/116), the resolution was 0.6 mm and in 37.1% (43/116) 0.7 mm. Temporal resolution varied between 63 and 205 ms, using 1.5–4.37 cardiac cycles for image reconstruction.This revised version was published online in March 2005 with corrections to the authors affiliations.     

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.