The influence of heart rate, slice thickness, and calcification density on calcium scores using 64-slice multidetector computed tomography: a systematic phantom study

OBJECTIVE: The purpose of this study was to investigate the influence of heart rate, slice thickness, and calcification density on absolute value and variability of calcium score using 64-slice multidetector computed tomography (MDCT). METHODS AND MATERIALS: Three artificial arteries containing each 3 lesions with varying density were scanned using a moving cardiac phantom at rest and at 50 to 110 beats per minute (bpm) at 10-bpm intervals on a 64-slice MDCT. Images were reconstructed at slice thicknesses (increment) of 0.6 (0.4), 0.75 (0.5), 1.5 (1.5), and 3.0 (3.0) mm. The amount of calcium was expressed as an Agatston score, volume score, and equivalent mass. RESULTS: Absolute coronary artery calcium (CAC) scores decreased [average -37% for low density calcification (LDC)] or increased [average +32% for high density calcification (HDC)] at heart rates over 60 bpm depending on slice thickness and scoring method. Thinner slice thicknesses yielded higher CAC scores. Variability of the CAC scores increased with increasing heart rates especially for low density calcifications (8% at rest vs. 50% at 110 bpm). Variability also increased for thicker slices (average 6% for 0.6 mm vs. 18% for 3.0 mm). Variability was lower for HDC compared with LDC (approximately 5% for HDC vs. 27% for LDC at 70 bpm, averaged over all methods and slice thicknesses). CONCLUSION: CAC-scoring is strongly influenced by cardiac motion, calcification density, and slice thickness. CAC scores increase for high density calcifications and decrease for low density calcifications at increasing heart rates. Heart rate should be reduced on 64-slice MDCT to obtain a lower degree of variability of CAC-scoring, preferably below 70 bpm. A thinner slice thickness further enhances the reproducibility.     

The importance of end-systole for optimal reconstruction protocol of coronary angiography with 16-slice multidetector computed tomography

OBJECTIVES: Multidetector-row computed tomography coronary images are usually analyzed in mid-diastole (MD). Because of slow coronary motion also in end-systole (ES), we evaluated the impact on image quality of including ES images and defined an efficient reconstruction protocol. MATERIAL AND METHODS: In 50 coronary multidetector-row computed tomography studies, 9 reconstructions (at 10% increments of the RR interval) were graded for image quality. Multiple combinations of reconstructions were compared. RESULTS: MD (60-70% of the RR interval) offered the best image quality. In 44% patients, the best reconstruction for >or=1 coronary was found in ES (20-30%). Their heart rate was higher (68.2+/-9.9 bpm vs. 59.2+/-8.8 bpm, P=0.0014). Combining ES and MD consistently offered superior image quality and less nonevaluable vessels than even larger numbers of diastolic reconstructions alone. A combination of 2-3 reconstructions was most efficient. Adding more reconstructions did not significantly improve results. CONCLUSIONS: Combining ES and MD reconstructions reduces nonevaluable coronary arteries, particularly with higher heart rates. A protocol including 2-3 reconstructions is the most efficient.     

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.     

320层容积CT无心率(律)控制的冠状动脉血管成像在冠心病高危人群中的初步应用

目的 探讨在无心率(律)控制条件下,320层容积CT冠状动脉血管成像(VCTA)诊断冠心病高危人群冠状动脉狭窄的准确性.方法 对30例有冠心病高危因素的患者,以冠状动脉导管造影(ICA)为金标准,评价VCTA诊断冠状动脉节段狭窄率≥50%的敏感度、特异度、阳性预测值(PPV)、阴性预测值(NPV)及Youden指数;同时采用卡方检验分析心率快慢及钙化程度对2种检查方法诊断一致率的影响.结果 30例患者平均心率(73.7±15.4)次/min(bpm),420个可分析节段的平均Agatston钙化积分中位数为45.6分(OR=181).心率＜70和≥70 bpm分别显示242和169段,诊断一致率差异无统计学意义(P＞0.05);Agatston钙化积分≥100分的图像质量和诊断一致率低于Agatston钙化积分＜100分的节段,但VCTA与ICA结果仍具有良好吻合性(P＞0.05).结论 在无心率(律)控制情况下,VCTA对冠心病高危人群的冠状动脉狭窄诊断具有很高的准确性.     

High-pitch versus sequential mode for coronary calcium in individuals with a high heart rate: Potential for dose reduction

BackgroundTo determine the impact of high-pitch spiral acquisition on radiation dose and cardiovascular disease (CVD) risk stratification by coronary artery calcium (CAC) assessment with computed tomography in individuals with a high heart rate.MethodsOf the ROBINSCA trial, 1990 participants with regular rhythm and heart rates >65 beats per minute (bpm) were included. As reference, 390 participants with regular heart rates ≤65 bpm were used. All participants underwent prospectively electrocardiographically(ECG)-triggered imaging of the coronary arteries using dual source CT at 120 kVp, 80 ref mAs using both high-pitch spiral mode and sequential mode. Radiation dose, Agatston score, number of positive scores, as well as median absolute difference of the Agatston score were determined and participants were stratified into CVD risk categories.ResultsA similar percentage of participants with low heart rates and high heart rates had a positive CAC score in data sets acquired in high-pitch spiral (low heart rate: 57.7%, high heart rate: 55.8%) and sequential mode (58.0%, 54.7%, p = n.s.). The median absolute difference in Agatston scores between acquisition modes was 14.2% and 9.2%, for the high and low heart rate groups, respectively. Excellent agreement for risk categorization between the two data acquisition modes was found for the high (κ = 0.927) and low (κ = 0.946) heart rate groups. Radiation dose was 48% lower for high-pitch spiral versus sequential acquisitions.ConclusionRadiation dose for the quantification of coronary calcium can be reduced by 48% when using the high-pitch spiral acquisition mode compared to the sequential mode in participants with a regular high heart rate. CVD risk stratification agreement between the two modes of data acquisition is excellent.     

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。     

Evidence for lower variability of coronary artery calcium mineral mass measurements by multi-detector computed tomography in a community-based cohort--consequences for progression studies

PURPOSE: To compare the measurement variability for coronary artery calcium (CAC) measurements using mineral mass compared with a modified Agatston score (AS) or volume score (VS) with multi-detector CT (MDCT) scanning, and to estimate the potential impact of these methods on the design of CAC progression studies. MATERIALS AND METHODS: We studied 162 consecutive subjects (83 women, 79 men, mean age 51 +/- 11 years) from a general Caucasian community-based cohort (Framingham Heart Study) with duplicate runs of prospective electrocardiographically-triggered MDCT scanning. Each scan was independently evaluated for the presence of CAC by four experienced observers who determined a "modified" AS, VS and mineral mass. RESULTS: Of the 162 subjects, CAC was detected in both scans in 69 (42%) and no CAC was detected in either scan in 72 (45%). Calcium scores were low in the 21/162 subjects (12%) for whom CAC was present in one but not the other scan (modified AS < 20 in 20/21 subjects, mean AS 4.6 +/- 1.9). For all three quantification algorithms, the inter- and intraobserver correlation were excellent (r > 0.96). However, the mean interscan variability was significantly different between mineral mass, modified AS, and VS (coefficient of variation 26 +/- 19%, 41 +/- 28% and 34 +/- 25%, respectively; p < 0.04), with significantly smaller mean differences in pair-wise comparisons for mineral mass compared with modified AS (p < 0.002) or with VS (p < 0.03). The amount of CAC but not heart rate was an independent predictor of interscan variability (r = -0.638, -0.614 and -0.577 for AS, VS, and mineral mass, respectively; all p < 0.0001). The decreased interscan variability of mineral mass would allow a sample size reduction of 5.5% compared with modified AS for observational studies of CAC progression and for randomized clinical trials. CONCLUSION: There is significantly reduced interscan variability of CAC measurements with mineral mass compared with the modified AS or VS. However, the measurement variability of all quantification methods is predicted by the amount of CAC and is inversely correlated to the extent of partial volume artifacts. Moreover, the improvement of measurement reproducibility leads to a modest reduction in sample size for observational epidemiological studies or randomized clinical trials to assess the progression of CAC.     

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。     

Effect of Heart Rate and Coronary Calcification on the Diagnostic Accuracy of the Dual-Source CT Coronary Angiography in Patients with Suspected Coronary Artery Disease

Objective

To evaluate the diagnostic accuracy of a dual-source computed tomography (DSCT) coronary angiography, with a particular focus on the effect of heart rate and calcifications.

Materials and Methods

One hundred and nine patients with suspected coronary disease were divided into 2 groups according to a mean heart rate (< 70 bpm and ≥ 70 bpm) and into 3 groups according to the mean Agatston calcium scores (≤ 100, 101-400, and > 400). Next, the effect of heart rate and calcification on the accuracy of coronary artery stenosis detection was analyzed by using an invasive coronary angiography as a reference standard. Coronary segments of less than 1.5 mm in diameter in an American Heart Association (AHA) 15-segment model were independently assessed.

Results

The mean heart rate during the scan was 71.8 bpm, whereas the mean Agatston score was 226.5. Of the 1,588 segments examined, 1,533 (97%) were assessable. A total of 17 patients had calcium scores above 400 Agatston U, whereas 50 had heart rates ≥ 70 bpm. Overall the sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV) for significant stenoses were: 95%, 91%, 65%, and 99% (by segment), respectively and 97%, 90%, 81%, and 91% (by artery), respectively (n = 475). Heart rate showed no significant impact on lesion detection; however, vessel calcification did show a significant impact on accuracy of assessment for coronary segments. The specificity, PPV and accuracy were 96%, 80%, and 96% (by segment), respectively for an Agatston score less than 100% and 99%, 96% and 98% (by artery). For an Agatston score of greater to or equal to 400 the specificity, PPV and accuracy were reduced to 79%, 55%, and 83% (by segment), respectively and to 79%, 69%, and 85% (by artery), respectively.

Conclusion

The DSCT provides a high rate of accuracy for the detection of significant coronary artery disease, even in patients with high heart rates and evidence of coronary calcification. However, patients with severe coronary calcification (> 400 U) remain a challenge to diagnose.     

Improved reproducibility of coronary artery calcium scoring by electron beam tomography with a new electrocardiographic trigger method

RATIONALE AND OBJECTIVES: To improve the interscan reproducibility with electron beam tomography (EBT) by choosing an optimal electrocardiographic (ECG) trigger time. METHODS: Two hundred fourteen asymptomatic subjects found to have coronary artery calcium (CAC) on EBT were rescanned immediately to measure the interscan variability. Subjects were randomized to one of two different ECG trigger interval groups: the new trigger method (group 1) and the 80% R-R interval trigger method (group 2). The new trigger method was derived from a previous study of motion in the coronary arteries. In group 1 (new trigger method), the ECG trigger was programmed for a certain time (in ms) after the R wave, based on the resting heart rate. The triggers for group 1 were 360 (heart rate <50 beats per minute [bpm]), 340 (51--60 bpm), 314 (61--70 bpm), 300 (71--80 bpm), 290 (81--90 bpm), 280 (91--100 bpm), and 270 ms (>100 bpm). The interscan variation (CAC area and Agatston score) was compared between the two groups. RESULTS: The interscan variability was significantly reduced using the new trigger method for both CAC area and score compared with the 80% trigger method. The individual lesion variation was also significantly reduced by the new trigger method compared with the 80% trigger method. Area measure had a significantly lower variability compared with the Agatston score. CONCLUSIONS: These results strongly support the use of this new ECG trigger that relies on a rate-adjusted millisecond delay after the R wave instead of the more commonly used 80% R-R interval in EBT calcium studies.     

The impact of motion artifacts on the reproducibility of repeated coronary artery calcium measurements

The purpose of this study is, using a 16-section multidetector-row helical computed tomography (MDCT) scanner with retrospective reconstruction, to compare variability in repeated coronary calcium scoring and qualitative scores of the motion artifacts. One hundred forty-four patients underwent two subsequent scans using MDCT. According to Agatston and volume algorithms, the coronary calcium scores during mid-diastole (the center corresponding to 70% of the R-R cycle) were calculated and the inter-scan variability was obtained. Motion artifacts from coronary artery calcium were subjectively evaluated and classified using a 5-point scale: 1, excellent; no motion artifacts; 2, fine, minor motion artifacts; 3, moderate, mild motion artifacts; 4, bad, severe motion artifacts; 5, poor, doubling or discontinuity. Each reading was done by vessels (left main, left descending, left circumflex and right coronary arteries) and the motion artifact score (mean of the scales) was determined per patient. The variability in the low (1.2+/-0.2) and high (2.4+/-0.6) motion artifact score groups was 7+/-6 (median, 6)% and 19+/-15 (16)% on the Agatston score (P<0.01) and 7+/-7 (6)% and 16+/-13 (14)% on the volume score (P<0.01), respectively. In conclusion, motion has a significant impact on the reproducibility of coronary calcium scoring.     

A comparison of the efficacy and safety of iopamidol-370 and iodixanol-320 in patients undergoing multidetector-row computed tomography

OBJECTIVES: To prospectively compare the effects on heart rate (HR) and contrast enhancement efficacy of iopamidol-370 and iodixanol-320 in contrast-enhanced, multidetector-row computed tomography (CE-MDCT). METHODS: IMPACT is a multicenter, double-blind study involving 166 patients undergoing CE-MDCT of the liver (n = 121) or peripheral arteries (n = 45) randomized to receive equi-iodine doses (40 gI) of iopamidol-370 or iodixanol-320 intravenous at 4 mL/s. CE-MDCT was performed using 16-MDCT scanners according to predefined imaging protocols. HR was measured with the patient in the supine position before and continuously for 5 minutes after contrast medium administration. Mean and peak increases in HR and the proportion of subjects with predefined HR increases (>5 to <10, 10 to <15, 15 to <20, >20 bpm) were compared in the 2 populations. Liver images were assessed by 2 independent, blinded readers for contrast enhancement [Hounsfield unit (HU)], using predefined regions-of-interest during the arterial and portal-venous phase of enhancement. RESULTS: Effects on HR: Eighty-four subjects received iopamidol-370 whereas 82 received iodixanol-320. Mean age, gender distribution, weight, total iodine dose, dose/body weight, concomitant medications and use of beta-blockers were comparable in the 2 groups. Mean baseline HR was similar in the 2 groups (iopamidol-370: 72.3 +/- 12.5 bpm; iodixanol-320: 74.5 +/- 11.9 bpm). Mean changes from baseline to peak postdose were similar in the 2 groups (8.0 +/- 9.3 bpm after iopamidol-370 and 8.4 +/- 14.7 after iodixanol-320, P = 0.72). The proportion of subjects in each group having increases of <5, >5 to <10, 10 to <15, 15 to <20, or >20 bpm was comparable (P = 0.87). Two subjects experienced postcontrast tachycardia (HR increase >70 bpm, peak HR of 146 and 164 bpm), both in the iodixanol-320 group (2.4%). Contrast Enhancement: Of the 121 patients undergoing liver CT, 60 received iopamidol-370 whereas 61 received iodixanol-320. Mean age, gender distribution, weight, total iodine dose, and dose/body weight were comparable in the 2 groups. Iopamidol-370 provided significantly higher HU values in abdominal aorta during the arterial phase of enhancement for both readers [R1: 301.3 +/- 80.2 vs. 273.6 +/- 65.9 HU, 95% confidence interval (6.1-56.8), P = 0.02; R2: 302.0 +/- 73.6 vs. 275.1 +/- 62.9 HU, 95% confidence interval (2.3-51.3), P = 0.03]. No significant difference was observed between the 2 contrast medium during the portal venous phase of enhancement. CONCLUSIONS: When the same injection rate and iodine dose is used, the effects on HR of bolus intravenous injections of iopamidol-370 and iodixanol-320 were similar. Iopamidol-370 provides significantly greater enhancement during the arterial phase and similar enhancement during the portal venous phase compared with iodixanol-320.     

Automatic selection of optimal cardiac-phase in coronary CT angiography--its clinical usefulness for patients with atrial fibrillation

The optimal cardiac phases for coronary CT angiography (CTA) are end-systole and mid-diastole, in which cardiac movement is slow. In conventional methods, these cardiac phases are determined by visual selection. We have compared the images in the optimal cardiac phases that were selected by the conventional method and cardiac-phase search software (Phase Navi), and examined the clinical usefulness of Phase Navi in patients with atrial fibrillation. The subjects were 38 patients (regular rhythm: 20, atrial fibrillation: 18). The continuity scores of patients with regular rhythm (Phase Navi, conventional methods) were 2.4+/-0.3-2.5+/-0.3 in end-systole and 2.4+/-0.5-2.4+/-0.4 in mid-diastole. The scores of patients with atrial fibrillation (Phase Navi, conventional methods) were 2.3+/-0.4-2.3+/-0.4 in end-systole, and 2.2+/-0.5-2.1+/-0.6 in mid-diastole. Because the continuity scores of the optimal images from Phase Navi were similar to those from the conventional method, Phase Navi had clinical usefulness in patients with atrial fibrillation.     

Dose performance and image quality: dual source CT versus single source CT in cardiac CT angiography

Objective

To evaluate dose performance and image quality of 64-slice dual source CT (DSCT) in comparison to 64-slice single source CT (SSCT) in cardiac CT angiography (CTA).

Methods

100 patients examined by DSCT and 60 patients scanned by SSCT were included in this study. Objective indices such as image noise, contrast-to-noise ratio and signal-to-noise ratio were analyzed. Subjective image quality was assessed by two cardiovascular radiologists in consensus using a four-point scale (1 = excellent to 4 = not acceptable). Estimation of effective dose was performed on the basis of dose length product (DLP).

Results

At low heart rates (<70 bpm), image quality of SSCT was equivalent to that of DSCT (P > 0.05), but, at high heart rates (>70 bpm), DSCT provided robust image quality (P < 0.05). The average effective dose of SSCT was 9.3 ± 0.9 mSv at low heart rates (<70 bpm) while, the average estimated effective doses of DSCT were 9.1 ± 1.3 mSv, 8.3 ± 1.1 mSv, 7.9 ± 1.1 mSv, 6.9 ± 0.7 mSv, and 5.9 ± 1.3 mSv, corresponding to heart rates of 50-59 bpm, 60-69 bpm, 70-79 bpm, 80-89 bpm, and 90-100 bpm.

Conclusion

For cardiac CTA, both DSCT and SSCT can get good image quality at low heart rates (<70 bpm) with a similar radiation dose, but, at high heart rates (>70 bpm), DSCT is able to provide robust diagnostic image quality at doses far below that of SSCT.     

第二代双源CT前门控FLASH扫描与序列扫描冠状动脉成像比较

目的:比较第二代双源CT前门控大螺距螺旋扫描(FLASH扫描)与序列扫描模式在冠状动脉CT成像中的图像质量及辐射剂量。方法:回顾性分析采用第二代双源CT行前门控FIASH扫描(A组)与序列扫描(B组)冠状动脉CTA连续各50例患者,入组标准为心率70次/min以下,窦性心律,心率波动范围在10次/min以内。评价这2种成像模式的图像质量及辐射剂量。扫描参数:2组均采用Z轴飞焦点技术采集,探测器准直宽度0.6 mm,重建层厚0.75 mm,扫描时间0.28 s/r,单扇区时间分辨率75 ms,根据患者体质量指数(BMI)值设定管电压:100kV(BMI<24 kg/m~2)、120 kV(BMI≥24 kg/m~2),参考管电流370 mAs,采用管电流调制方案;FLASH扫描前门控心电触发选在60%R-R间期,螺距3.4;序列扫描采集时相为35%～75%R-R间期,步进采集宽度34.5 mm。冠状动脉图像质量分为4级(1级为优异,1～3级为可评价血管,4级为不可评价血管),相应评为1～4分。应用秩和检验比较2组患者冠状动脉段图像质量评分,应用两独立样本t检验比较2组患者所接受的辐射剂量。结果:A、B 2组患者的年龄及BMI差异无统计学意义。A、B 2组可评价的冠状动脉节段百分比分别为98.21%和98.56%,差异无统计学意义(χ~2=0.244,P=0.621),平均图像质量评分分别为1.30±0.60和1.28±0.56,差异无统计学意义(Z=-0.489,P=0.625)。A、B 2组扫描的平均有效辐射剂量分别为(0.99±0.34)mSv和(4.80±2.21)mSv,差异有统计学意义(t=-12.048,P=0.000),FLASH扫描剂量明显低于序列扫描。结论:在心率低于70次/min、心律稳定的情况下,第二代双源CT前门控FLASH扫描可获得与序列扫描相似的高质量图像,但辐射剂量明显降低。     

双源CT冠状动脉成像的图像质量及重组时相与心率的关系

目的 探讨双源CT冠状动脉成像的图像质量和重组时相与心率的关系.方法 对95例临床可疑冠心病患者进行双源CT增强扫描,检查前均不使用β受体阻滞剂控制心率.按扫描时心率分为3组:低心率组(≤70 次/min)26例,中心率组(71～90 次/min)37例,高心率组(t≥91 次/min)32例.利用回顾性心电门控重建出10%～100% R-R时相的图像,分析不同R-R时相冠状动脉的图像质量情况及其与心率的关系.结果 低、中、高心率3组图像质量评分分别为(1.08±0.27)、(1.32±0.58)、(1.47±0.61)分,低心率和中心率组图像质量评分差异无统计学意义(P＞0.05),低心率组图像质量评分显著优于高心率组(P＜0.05),中心率组和高心率组图像质量评分差异无统计学意义(P＞0.05).只有1.4%(19/1386)的冠状动脉节段不可评价.74例患者(77.9%)可在单一重组时相获得冠状动脉各段最佳图像质量.低心率组23例(88.5%)最佳重组时相在舒张中晚期;高心率组27例(84.4%)的最佳重组时相前移至舒张早期和收缩末期.结论 双源CT能够在相当宽的心率范围内提供优良的图像质量;多数患者可在单一时相获得各支冠状动脉最佳质量图像,随着心率的增快最佳重组时相从舒张中晚期前移至舒张早期和收缩末期.     

256层螺旋CT低剂量冠状动脉成像研究

目的：评价256层CT前瞻性心电门控冠状动脉成像的图像质量与辐射剂量,并与回顾性心电门控对照分析。方法 共200例患者纳入研究。100例行前瞻性心电门控的患者分为2组：(1)心率≤70次/min( bpm )50例,数据采集时间窗设在心动周期的75％期相（A组）;(2)心率＞70 bpm 50例,数据采集时间窗设在心动周期的45％期相,包含5％宽容度（B组）。另外100例行回顾性心电门控的患者亦分为2组：(3)心率≤70 bpm 50例,最大管电流输出设在75％期相（C组）;(4)心率＞ 70 bpm 50例,最大管电流输出设在45％与75％期相（D组）。所有患者由数字表法随机分组。采用4分法半定量分析冠状动脉节段及整体评分。采用Mann-Whitney U检验比较组间图像质量,采用t检验比较组间的辐射剂量;并对100例前瞻性心电门控检查者冠状动脉图像质量与平均心率进行ROC分析及相关分析。结果 在共2338个冠状动脉节段中,图像质量优秀或良好（评分1或2分）者A组中达到96.5％( 585/606),B组为77.7％(445/573),C组为96.1％( 548/570),D组为85.7％ (505/589),冠状动脉节段图像质量A组与C组比较差异无统计学意义（Z＝ -1.351,P＞0.05）;B组和D组差异有统计学意义（Z＝-2.236,P＜0.05）。前瞻性心电门控检查ROC分析及相关分析显示,平均心率与冠状动脉图像质量密切相关(r＝0.577,P＜0.01),平均心率78 bpm可做为满足诊断图像的最高临界点心率（ROC曲线下面积为0.827,P＜0.05）。A组[(2.6±0.5)mSv]相对C组[(10.6 ±2.3) mSy]平均辐射剂量减少75％,B组[(4.0 ±0.7) mSy]相对D组[ (13.0±1.4) mSy]平均辐射剂量减少69％。结论 256层CT低剂量前瞻性心电门控成像可获得与回顾性心电门控相似的满足诊断需要的图像质量,并可应用于高心率检查者。     

Variability of aortic valve calcification measurement with multislice spiral computed tomography

OBJECTIVES: We sought to assess the variability of aortic valve calcifications (AVCs) regarding the reconstruction window at different heart phases using multislice-spiral computed tomography. MATERIALS AND METHODS: A total of 46 patients (26 men; mean age. 65 years) underwent AVC scoring with multislice-spiral computed tomography (12 x 0.75 mm, 120 kV, 133 mAseff). Image reconstruction was performed every 10% of the RR-interval (0-90%). AVC was quantified using Agatston score, calcium volume, and calcium mass. Images were assessed for least motion artifacts. Coefficients of variation and Wilcoxon test were calculated. RESULTS: AVC scores are lowest at 60% and highest at 0% of the RR-interval (P < 0.001). Mean coefficients of variation were 36.2% (Agatston score), 38.7% (calcium volume), and 32.9% (calcium mass). At 60% (50-70%). minimal motion artifacts and the lowest variability of the scores were found. CONCLUSIONS: AVC scores show large variability depending on the point of image reconstruction. Diastolic image reconstruction at 60% of the RR-interval is recommended.     

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.     

Optimal image reconstruction intervals for non-invasive coronary angiography with 64-slice CT

The reconstruction intervals providing best image quality for non-invasive coronary angiography with 64-slice computed tomography (CT) were evaluated. Contrast-enhanced, retrospectively electrocardiography (ECG)-gated 64-slice CT coronary angiography was performed in 80 patients (47 male, 33 female; mean age 62.1±10.6 years). Thirteen data sets were reconstructed in 5% increments from 20 to 80% of the R-R interval. Depending on the average heart rate during scanning, patients were grouped as <65 bpm (n=49) and ≥65 bpm (n=31). Two blinded and independent readers assessed the image quality of each coronary segment with a diameter ≥1.5 mm using the following scores: 1, no motion artifacts; 2, minor artifacts; 3, moderate artifacts; 4, severe artifacts; and 5, not evaluative. The average heart rate was 63.3±13.1 bpm (range 38–102). Acceptable image quality (scores 1–3) was achieved in 99.1% of all coronary segments (1,162/1,172; mean image quality score 1.55±0.77) in the best reconstruction interval. Best image quality was found at 60% and 65% of the R-R interval for all patients and for each heart rate subgroup, whereas motion artifacts occurred significantly more often (P<0.01) at other reconstruction intervals. At heart rates <65 bpm, acceptable image quality was found in all coronary segments at 60%. At heart rates ≥65 bpm, the whole coronary artery tree could be visualized with acceptable image quality in 87% (27/31) of the patients at 60%, while ten segments in four patients were rated as non-diagnostic (scores 4–5) at any reconstruction interval. In conclusion, 64-slice CT coronary angiography provides best overall image quality in mid-diastole. At heart rates <65 bpm, diagnostic image quality of all coronary segments can be obtained at a single reconstruction interval of 60%.