Correlation of 3D MR coronary angiography with selective coronary angiography: feasibility of the motion-adapted gating technique

The aim of this study was to verify the feasibility of a respiratory motion compensation technique (motion-adapted gating, MAG) for visualization of coronary arteries (CA) by correlation with selective coronary angiography (SCA). Fifteen subjects (11 patients, mean age 61.3 years, age range 41-73 years; and 4 healthy volunteers, mean age 32.3 years, age range 31-35 years) were investigated. A Philips Gyroscan ACS-NT was used, operating at 1.5 T, was combined with the PowerTrak 6000 gradient system. An ECG-triggered, respiratory motion-gated 3D turbo field echo sequence was used. The real-time algorithm utilized the concept of k-space weighting in combination with automatic analysis of respiratory motion. The main CA were investigated. Qualitative analysis was performed by three blinded investigators. Visibility was graded on a five-point scale (0=not visualized, 1=insufficient, 2=sufficient, 3=good, 4=excellent). Segments graded 2-4 were defined as adequately visualized. Sixty-two of 88 assessable CA segments in patient, and 22 of 32 in volunteer group were adequately visualized. Visibility of CA was classified as excellent for proximal RCA (avg. 3.6+/-0.5), good for LM, proximal LAD, proximal LCX, middle RCA and sufficient for middle LAD. Sensitivity, specificity, positive and negative predictive values for coronary MRA in detection of CA stenoses with luminal narrowing >/=50% were 88, 94, 83, and 96%, respectively. Magnetic resonance imaging in combination with MAG has proven to be a promising technique for noninvasive imaging of CA due to good image quality and a patient convenient free-breathing technique.     

导航技术三维对比剂增强磁共振冠状动脉成像

目的评价导航技术三维对比剂增强磁共振冠状动脉成像的应用价值。方法应用导航技术三维对比剂增强磁共振血管成像方法,对20例受检者分别进行左、右冠状动脉成像,经后处理获得左、右冠状动脉血管图像。应用信噪比和对比噪声比评价增强前后的冠状动脉图像,并对冠状动脉主干及其主要分支的显示情况进行评价。结果(1)对获得成功的18例冠状动脉图像进行评价,增强前冠状动脉图像的信噪比为26.37±7.02,对比噪声比为14.76±6.97;增强后冠状动脉图像的信噪比为38.87±11.62,对比噪声比为33.72±10.80,经统计学比较,信噪比和对比噪声比增强前后的差异有统计学意义(t=2.91,4.62;P<0.05)。(2)对比剂增强后左、右及左回旋支冠状动脉近中段的显示率为100%,远侧段的显示率分别为94.4%、88.8%、77.8%。结论导航技术三维对比剂增强磁共振冠状动脉成像有较高的信噪比和对比噪声比,应用于临床尚需进一步的对照研究。     

Two-dimensional coronary MRA: limitations and artifacts

Our purpose was to assess image quality and interpretation problems of two-dimensional (2D) coronary MR angiograms. The coronary arteries of 27 subjects (12 normal volunteers and 15 patients) were evaluated with 2D coronary MR angiography (MRA). Coronary MRA was performed with a fat-suppressed electrocardiographically gated breath-hold gradient-echo sequence with k-space segmentation using a 1.5-T imager. Image quality throughout the study was occasionally degraded by: image ghosting (22%), ringing (19%), and/or blurring (22%) and incomplete fat-suppression (19%). Intermittent difficulties with breathholding were encountered in 44% of subjects. When limiting the analysis to those images with optimal image quality, interpretative difficulties were sometimes found: misregistration due to inconsistent breathholding (37%); difficulty in distinguishing veins from arteries (37%); obscured anatomy due to overlapping structures (26%); and poor visualization of portions of the left main coronary artery (59%). Two-dimensional coronary MRA studies have image quality and interpretive problems which need to be understood and addressed before routine clinical scanning is initiated.Correspondence to: A. J. Duerinckx     

3 T MR呼吸导航回波触发全心冠状动脉成像

目的探讨3TMR呼吸导航回波触发的全心冠状动脉MR成像（WH-CMRA）技术对冠状动脉的显示能力和图像质量。方法92名志愿者接受了3TMR呼吸导航回波触发的WH-CMRA检查，使用T2预备的快速梯度回波（TFE）序列采集。按目测法将图像质量分为0～Ⅳ级，并结合冠状动脉各主要分支的长度、直径和血管锐利度进行评判。分析呼吸、心率和导航回波的采集效率对成像质量的影响，评价呼吸导航回波触发WH-CMRA对冠状动脉主要分支的显示效果。结果92名受检者的图像质量评价为Ⅳ级28名，Ⅲ级53名，Ⅱ级9名，Ⅰ级2名，扫描成功率为88％（81／92）。心率≤75次／min，图像质量20名为Ⅳ级，锐利度为（48±11）％；心率〉75次／min，图像质量34名为Ⅲ级，锐利度为（33±15）％，心率的快慢和图像质量呈负相关（r=-0．726，P〈0．05）。呼吸模式和图像质量无明显相关性（r=0．215，P〉0．05）。结论3TWH-CMRA技术可以实现自由呼吸下的全心冠状动脉成像，但图像质量受到心率的限制。     

Image quality on dual-source computed-tomographic coronary angiography

Multi-detector CT reliably permits visualization of coronary arteries, but due to the occurrence of motion artefacts at heart rates >65 bpm caused by a temporal resolution of 165 ms, its utilisation has so far been limited to patients with a preferably low heart rate. We investigated the assessment of image quality on computed tomography of coronary arteries in a large series of patients without additional heart rate control using dual-source computed tomography (DSCT). DSCT (Siemens Somatom Definition, 83-ms temporal resolution) was performed in 165 consecutive patients (mean age 64 +/- 11.4 years) after injection of 60-80 ml of contrast. Data sets were reconstructed in 5% intervals of the cardiac cycle and evaluated by two readers in consensus concerning evaluability of the coronary arteries and presence of motion and beam-hardening artefacts using the AHA 16-segment coronary model. Mean heart rate during CT was 65 +/- 10.5 bpm; visualisation without artefacts was possible in 98.7% of 2,541 coronary segments. Only two segments were considered unevaluable due to cardiac motion; 30 segments were unassessable due to poor signal-to-noise ratio or coronary calcifications (both n = 15). Data reconstruction at 65-70% of the cardiac cycle provided for the best image quality. For heart rates >85 bpm, a systolic reconstruction at 45% revealed satisfactory results. Compared with earlier CT generations, DSCT provides for non-invasive coronary angiography with diagnostic image quality even at heart rates >65 bpm and thus may broaden the spectrum of patients that can be investigated non-invasively.     

3.0 T MR对比增强全心冠状血管成像对冠状静脉系统的解剖学研究

目的 探讨3.0 T MR对比增强全心冠状血管成像(CE CMRA)对冠状静脉解剖的研究价值.方法 43例受试者行3.0 T CE CMRA,采用自由呼吸导航门控、心电触发和非选择性反转恢复(IR)准备脉冲的3D扰相位梯度回波(FLASH)序列.采用32通道体部相控阵线圈进行数据获取.冠状静脉的图像质量由4分法进行评价.连续变量表达为(-x)±s,用配对t检验评价CS窦口前后径及上下径的差异.结果 40例受试者成功完成3.0 T CE CMRA检查,其中38例(95.0%)受试者的图像能够进行评价.左心室后静脉(PVLV)及左边缘静脉(LMV)距冠状窦(CS)窦口的距离分别为(3.34±0.90)及(6.12±1.02)cm.CS、后室间静脉(PIV)、PVLV、LMV及前室间静脉(AIV)的平均图像质量得分分别为(4.0±0.0)、(3.4±0.5)、(3.4±0.5)、(3.0±0.8)及(3.3±0.5)分.CS窦口的上下径[(1.10±0.26)cm]大于前后径[(0.83±0.19)cm],差异有统计学意义(t=-4.31,P<0.05).结论 3.0 T MR CE CMRA能够清晰地评价冠状静脉解剖.     

Fusion of MR coronary angiography and viability imaging: feasibility and clinical value for the assignment of myocardial infarctions

Purpose

To investigate the feasibility of image fusion of MR-coronary angiography (MRCA) and delayed gadolinium enhancement imaging (LGE) and to assign areas of myocardial infarction to the corresponding supplying coronary arteries.

Materials and methods

An interactive segmentation of the coronary arteries was performed in MRCA data sets (n = 25). The LGE slices were matched onto the vessel segmentation to perform a fused analysis of coronary artery anatomy and LGE. The results were compared to the segmental model recommended by the American Heart Association (AHA). Standard of reference was the identification of the culprit lesion in the invasive coronary angiography (CA) (n = 20).

Results

The fused analysis allowed the assignment of MI to the supplying coronary artery in 13/20 patients. The sensitivities/specificities for the assignment of MI to the three main vessels were: LAD 63%/100%, LCX 75%/100%, and RCA 56%/100%, respectively.Using the AHA segmental model the sensitivities/specificities for the correct assignment of MI to the three main vessels were: LAD 88%/58%, LCX 94%/75%, and RCA 77%/73%, respectively.

Conclusion

Fusion images of MRCA and LGE provides added diagnostic information in the effort to determine the epicardial vessels responsible for the postischemic myocardial injury and therefore might be helpful to establish appropriate future therapeutic steps.     

Appearance of the Normal Pericardium on Coronary MR Angiograms

We evaluated the appearance of the normal pericardium on breath-hold MR images used to visualize coronary arteries. A coronary MR angiogram was obtained in 23 subjects (17 healthy volunteers and six patients with no known pericardia! disease) using a breath-hold K-space segmented gradient-recalled echo sequence with fat suppression. Each coronary MR angiographic study included imaging planes equivalent to the following echocardiographic planes: four-chamber view, vertical two-chamber view, and two short-axis views (at base and mid ventricular level). The average pericardial thickness was 1.7 mm (range, 1.5–2.0 mm), and an average length of 60 mm (range, 20–110 mm) of pericardium was visualized. A significantly longer portion of the pericardium was seen in the vertical two-chamber view and the basal short-axis view than in the two other views (P <.001). Normal anatomic variations and overlapping structures and image artifacts can alter the appearance of the pericardium. Breath-hold MR imaging techniques used for coronary MR angiography allow routine, time-efficient evaluation of large portions of the pericardium.     

快速注射结合缓慢融入对比剂在冠状动脉MR血管成像中的应用

目的 评价快速注射结合缓慢融入对比剂Gd-DTPA对血池T1弛豫效果的影响.方法 对15例冠心病患者行冠状动脉MRA检查.先以1.50 ml/s流率注射对比剂Gd-DTPA 10 ml,再以0.05 ml/s流率注射20 ml,然后对冠状动脉同1支血管行2次扫描,获得注射对比剂后5和15 min的图像.计算增强前后图像的信噪比(SNR)和对比噪声比(CNR),并以t检验进行比较.结果 注射对比剂后5 min图像的SNR和CNR(35.37±6.84和21. 57±6.08)明显高于增强前图像的SNR和CNR(27.38±6.24和13.19±6.50).注射对比剂15 min后图像的SNR(33.81±9.43)高于增强前,但没有统计学意义(t=1.885,P=0.074),图像的CNR(21.20±7.65)明显高于增强前.注射对比剂后5和15 min图像的SNR和CNR没有明显的区别.结论 快速注射结合缓慢融入Gd-DTPA,可以获得延长短T1效应的采样时间,以适应冠状动脉MRA多期扫描的需求.     

3D MR angiography of intratumoral vasculature using a novel macromolecular MR contrast agent.

Noninvasive methods to visualize blood flow in the intratumoral vasculature have not previously been studied. In the present study, the use of a novel intravascular MR contrast agent with a generation-6 polyamidoamine dendrimer core (G6-(1B4M-Gd)192; MW: 175kD) was investigated, and the vasculature in experimental tumors was visualized using 3D MR angiography (MRA). Xenografted tumors in nude mice of two different histologies-KT005 (human osteogenic sarcoma) and LS180 (human colon carcinoma)-were used to obtain 3D MRA using G6-(1B4M-Gd)192 and Gd-DTPA. The contrast MR sectional images were correlated with the corresponding histological sections. The intratumoral vasculature in the KT005 tumor was clearly visualized by 3D MRA, which became more evident with the growth of the tumor xenograft. In contrast, the intratumoral vasculature in the LS180 tumor was sparser and much less developed than that in KT005 tumors. Blood vessels with a diameter as small as 100 microm based on histology were visualized using 0.033 mmol Gd/kg of G6-(1B4M-Gd)192. In conclusion, intratumoral vasculature with a 100-microm diameter was visualized better using 3D MRA with G6-(1B4M-Gd)192 than with Gd-DTPA.     

Coronary CT angiography: Comparison of a novel iterative reconstruction with filtered back projection for reconstruction of low-dose CT—Initial experience

Objective

To prospectively compare subjective and objective image quality in 20% tube current coronary CT angiography (cCTA) datasets between an iterative reconstruction algorithm (SAFIRE) and traditional filtered back projection (FBP).

Materials and methods

Twenty patients underwent a prospectively ECG-triggered dual-step cCTA protocol using 2nd generation dual-source CT (DSCT). CT raw data was reconstructed using standard FBP at full-dose (Group_1a) and 80% tube current reduced low-dose (Group_1b). The low-dose raw data was additionally reconstructed using iterative raw data reconstruction (Group_2). Attenuation and image noise were measured in three regions of interest and signal-to-noise-ratio (SNR) as well as contrast-to-noise-ratio (CNR) was calculated. Subjective diagnostic image quality was evaluated using a 4-point Likert scale.

Results

Mean image noise of group_2 was lowered by 22% on average when compared to group_1b (p < 0.0001–0.0033), while there were no significant differences in mean attenuation within the same anatomical regions. The lower image noise resulted in significantly higher SNR and CNR ratios in group_2 compared to group_1b (p < 0.0001–0.0232). Subjective image quality of group_2 (1.88 ± 0.63) was also rated significantly higher when compared to group_1b (1.58 ± 0.63, p = 0.004).

Conclusions

Image quality of 80% tube current reduced iteratively reconstructed cCTA raw data is significantly improved when compared to standard FBP and consequently may improve the diagnostic accuracy of cCTA.     

16层螺旋CT冠状动脉血管成像和传统冠状动脉血管造影的对比研究

目的评估16层螺旋CT血管成像（CTA）判断冠状动脉血液动力学相关性狭窄（≥50％）的价值。方法对同时接受16层CT冠状动脉成像和传统冠状动脉血管造影检查的26例患者进行回顾性分析。扫描时采用16排探测器，机架转速为2周／s，使用后心电门控进行横断面影像重建，结合三维重建影像评估冠状动脉狭窄程度。结果以冠状动脉血管造影为金标准，冠状动脉CTA影像判断血液动力学相关性冠状动脉狭窄（≥150％）的敏感度为90．0％，特异度为95．5％，准确度为94．7％，阳性预测值为77．6％，阴性预测值为98．2％。结论16层CTA判断冠状动脉血液动力学相关性狭窄（≥150％）有较高的临床诊断价值，对临床冠心病的诊断有较大指导意义。     

Coronary CT angiography for acute chest pain in the emergency department

Acute chest pain in the emergency department (ED) is a common and costly public health challenge. The traditional strategy of evaluating acute chest pain by hospital or ED observation over a period of several hours, serial electrocardiography and cardiac biomarkers, and subsequent diagnostic testing such as physiologic stress testing is safe and effective. Yet this approach has been criticized for being time intensive and costly. This review evaluates the current medical evidence which has demonstrated the potential for coronary CT angiography (CTA) assessment of acute chest pain to safely reduce ED cost, time to discharge, and rate of hospital admission. These benefits must be weighed against the risk of ionizing radiation exposure and the influence of ED testing on rates of downstream coronary angiography and revascularization. Efforts at radiation minimization have quickly evolved, implementing technology such as prospective electrocardiographic gating and high pitch acquisition to significantly reduce radiation exposure over just a few years. CTA in the ED has demonstrated accuracy, safety, and the ability to reduce ED cost and crowding although its big-picture effect on total hospital and health care system cost extends far beyond the ED. The net effect of CTA is dependent also on the prevalence of coronary artery disease (CAD) in the population where CTA is used, which significantly influences rates of post-CTA invasive procedures such as angiography and coronary revascularization. These potential costs and benefits will warrant careful consideration and prospective monitoring as additional hospitals continue to implement this important technology into their diagnostic regimen.     

Quantification of in-plane motion of the coronary arteries during the cardiac cycle: Implications for acquisition window duration for MR flow quantification

Motion of the coronary arteries during the heart cycle can result in image blurring and inaccurate flow quantification by MR. This condition applies particularly for longer acquisition windows that are typical of breath-hold coronary flow measurements. To determine the sensitivity of the technique to in-plane motion of different coronary arteries, the temporal variation in coronary position was measured in a plane perpendicular to the proximal portion of the vessel. The results indicated the presence of substantial displacement of the coronary arteries within the cardiac cycle, with a magnitude of motion approximately twice as large for the right as for the left coronary arteries. An estimation of the resulting vessel blurring was calculated, showing that the duration of the acquisition window for high spatial resolution coronary flow acquisitions should be less than 25 to 120 msec, depending on the specific coronary artery studied. In addition, these data specify optimal acquisition window placement for high resolution coronary angiography.     

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.     

Coronary CT angiography with dual source computed tomography in 170 patients

Introduction

In preliminary studies DSCT provides robust image quality over a wide range of heart rates and excludes CAD with high accuracy.The aim of the present study was to evaluate the reproducibility of these results in a large, unselected and consecutive group of patients scheduled for invasive coronary angiography (ICA).

Material and methods

170 patients (124 men, 46 women; mean age: 64 ± 9 years) with known CAD (101 patients) or suspected CAD (69 patients) scheduled for ICA were examined by coronary CTA prior to ICA. All coronary segments were assessed for image quality (1: excellent; 5: non-diagnostic). The presence of significant vessel stenosis (>50%) was calculated using ICA as standard of reference.

Results

A total of 680 vessels were analyzed. Despite of 45 arrythmic patients all analyzed coronary segments were diagnostically evaluable. Mean Agatston score equivalent was 686 (range 0-4950). ICA revealed 364 lesions with ≥50% diameter stenosis. DSCT correctly identified 336 of these lesions. 115 lesions with a diameter stenosis ≤50% were overestimated by DSCT and thus considered as false-positive findings. On a per-segment basis, sensitivity was 92%, specificity 93%, positive predictive value (PPV) was 75% and negative predictive value (NPV) 98%. On a per-vessel basis DSCT revealed a sensitivity of 93%, a specificity of 88%, a PPV of 78% and a NPV of 97%. On a per-patient basis sensitivity was 94%, specificity 79%, PPV 88% and NPV 90%.

Conclusions

Initial results of preliminary studies showing robust image quality and high accuracy in DSCT cardiac imaging could be approved with the present study enclosing a large consecutive population. However severe coronary calcifications and irregular heart rate still remain limiting factors for coronary CTA.Despite improved image quality and high accuracy of coronary DSCT angiography, proof of indication is necessary, due to still remaining limiting factors.     

宝石CT高清模式与标准模式冠状动脉支架成像质量比较

目的 比较高清模式和标准模式对宝石(HD) CT冠状动脉支架成像质量的影响及HDCT的诊断价值.资料与方法 连续选取22例冠状动脉支架术后复查的患者(置入支架50枚),行HDCT冠状动脉支架成像,分别用高清模式和标准模式进行重建,以支架原始数据为参照,对两种不同重建模式的图像质量进行评价.结果 两种模式重建支架内直径的测量值均小于实际值,高清模式重建测量支架内平均直径为2.36mm,标准模式重建测量支架内平均直径为2.06mm,两组之间差异有统计学意义(P＜0.05),高清模式重建支架内直径的测量值更接近于实际值.结论 HDCT空间分辨率的提高能有效改善冠状动脉支架内成像质量及支架测量的准确性.     

前瞻性心电门控在64层CT冠状动脉成像的初步应用

目的 评价前瞻性心电门控64层CT冠状动脉成像的可行性和临床应用价值.方法 60例患者进行前瞻性心电门控64层CT冠状动脉成像检查,分析有效辐射剂量,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)技术显示冠状动脉,评价其成像质量.结果 平均辐射剂量(2.7±0.2)mSv;符合诊断标准的冠状动脉节段为93.3%(720/772),44.2%(341/772)质量优秀,49.1%(379/772)质量中等,6.7%(52/772)质量较差.冠状动脉重度狭窄(＞75%)或闭塞5例(8.3%),中度狭窄(50%～75%)17例(28.4%),管腔不规则或轻度狭窄(＜50%)18例(30.0%),冠状动脉正常者20例(33.3%).结论 前瞻性心电门控64层CT冠状动脉成像的影像质量能达到诊断标准,大大降低了辐射剂量,具有很好的临床应用价值.