基于多反转脉冲空间标记技术的非对比剂增强磁共振血管成像序列在评估移植肾血管解剖方面的研究

目的：评估基于多反转脉冲空间标记技术（SLEEK）的非对比剂增强磁共振血管成像序列在显示移植肾血管解剖方面的价值,并和彩色多普勒超声（CDUS）及手术记录结果进行对照。方法：对75名肾移植术后需要排除血管并发症的患者进行CDUS及SLEEK扫描,所有患者均签署知情同意书。由两名放射科专家对SLEEK 显示移植肾血管解剖结构进行评估,并将SLEEK结果与CDUS及手术记录进行对照。结果：75名肾移植患者均成功进行了 SLEEK 扫描及CDUS扫描。3名患者移植了2个肾脏,总共有78个移植肾进行了图像评估,所有患者的图像质量都是可以接受的。图像质量评分为优秀的占85％（66／78）,良好的占10％（8／78）,一般的占5％（4／78）。在检查移植肾血管吻合方式方面, SLEEK检查结果与手术记录完全吻合,发现72个肾脏被移植在右侧髂窝,6个肾脏被移植在左侧髂窝。移植肾动脉与髂外动脉端侧吻合的有43个,移植肾动脉与髂内动脉端端吻合的有35个,所有78个移植肾静脉均与髂外静脉端侧吻合,结果与CDUS间差异无统计学意义（P＞0．05）。手术记录显示78个移植肾中有9个有副肾动脉,SLEEK发现了其中的8例,超声只发现了2例,SLEEK在检出副肾动脉方面明显优于CDUS（P＜0．05）。结论：基于SLEEK 的非对比剂增强磁共振血管成像被证明是显示移植肾血管解剖的一种可靠方法。SLEEK 可以作为评估移植肾血管的方法,尤其适用于肾功能不良的患者。     

非对比剂磁共振血管成像评估胡桃夹综合征的可行性研究

目的探讨非对比剂磁共振血管成像(NC-MRA)评估肠系膜上动脉(SMA)、腹主动脉(AA)和肾静脉(RV)的解剖关系及左肾静脉(LRV)受压情况的可行性研究。资料与方法搜集MSCTA或CE-MRA诊断为胡桃夹综合征的9例患者,在1.5TMRI上采用多翻转恢复空间标记脉冲(SLEEK)标记动脉血、静脉血分别显示动脉系统(SMA与AA)和静脉系统(RV),最后移除所有翻转带扫描同时显示SMA、AA和RV。由两名放射科主任医师评估NC-MRA的图像质量及SMA、AA和RV解剖关系;LRV受压情况。测量SMA与AA之间的夹角(a),在LRV横断面上分别测量SMA和AA间隙内LRV的最小面积(S1)及近左肾侧LRV的最大面积(S2),并计算S2和S1的比值(q),与MSCTA及CE-MRA对照,并进行统计学分析。结果 NC-MRA在显示SMA、AA和RV的解剖关系及LRV受压情况与MSCTA和CE-MRA具有很好的相关性。NC-MRA测量SMA与AA的夹角(a)平均值,S2和S1及S2与S1比值(q)的平均值分别为22.19、(0.23±0.10)cm2、(0.89±0.29)cm2、4.30;而MSCTA和CE-MR...     

高分辨率对比增强磁共振血管成像技术

磁共振血管成像技术开始于 2 0世纪 80年代 ,由初期采用非增强的飞越时间和相位对比方法发展到增强法磁共振血管成像技术 ,目前常规磁共振血管成像术作为一种非创伤性血管成像技术已被广泛应用于临床实践。基本原理常规对比增强磁共振血管成像是通过静脉内注射顺磁性对比剂 ,利     

非对比剂增强MR血管成像技术在肝动脉血管成像中的应用价值

【摘要】目的：以CTA为对照,探讨基于多反转空间标记脉冲技术的非对比剂增强MR血管成像技术（SLEEK-MRA）在肝动脉血管成像中的应用价值。方法：37例同时行CTA及SLEEK-MRA检查的临床怀疑肝脏占位患者纳入研究,CTA检查后7天内行SLEEK-MRA检查。由两位腹部影像诊断医师分别对CTA和SLEEK-MRA图像进行独立评估,评估内容包括四分法图像质量主观评价及最大显示分支级别评估。比较CTA与SLEEK-MRA在肝动脉成像图像质量及最大显示分支级别上的差异。结果：两位医师对CTA及SLEEK-MRA图像质量评分的一致性均为良好及以上（Kappa值:CTA为0.645~0.814;SLEEK-MRA为0.633~0.877）。除肝左动脉一级分支和肝右动脉一级分支外,SLEEK-MRA与CTA两种方法在肝总动脉、肝固有动脉、肝左动脉及肝右动脉血管成像图像质量评分上差异均无统计学意义（P值均>0.05）。CTA显示最大分支级别的能力优于SLEEK-MRA（P=0.020）。37例病例中,CTA显示有7例出现肝动脉变异,SLEEK-MRA显示了其中6例。结论：SLEEK-MRA作为一种无创、无辐射、无需使用对比剂的血管成像方法,在肝动脉血管成像上具有一定的应用价值。     

非对比剂增强MR血管成像技术在门静脉成像中的应用

目的：探讨非对比剂增强磁共振血管成像（NCE-MRA）在评估肝脏门静脉解剖中的临床价值,并与 MSCT门静脉成像（MSCTP）进行对照。方法：选择30例受试者分别行 SLEEK 序列 NCE-MRA 和 MSCTA 门静脉成像检查,其中肝硬化10例,肝癌10例,健康体检者10例。由两位医师分别对所有患者的 NCE-MRA 和 MSCTP 门静脉成像质量进行评分（4级评分法）并进行统计学分析。结果：NCE-MRA 组和 MSCTP 组中,门静脉成像质量评分在2分以上者分别占93．3％（28／30）和96．7％（29／30）。两种方法均能显示所有受试者的3级及3级以下的肝内门静脉,符合率为100％（30／30）。2例（6．7％）健康志愿者的门静脉第6级分支在 NCE-MRA 上未显示,而在 CTP 上可以显示;3例（10％）肝硬化门静脉高压患者的门静脉第5级分支在 CTP 上未显示,而在 NCE-MRA 上可以显示;2例（6．7％）肝肿瘤患者门静脉的部分第4级分支在 CTP 上未显示,而在 NCE-MRA 上可以显示。两种方法的门静脉图像质量评分的差异无统计学意义（P ＜0．05）,两位诊断医师对 NCE-MRA 门静脉成像质量评分的一致性较高,Kappa 值为0．95。结论：SLEEK 序列 NCE-MRA是一种无需使用对比剂的非侵入性血管成像方法,能有效地对肝脏门静脉进行评估。     

肾动脉三维对比增强磁共振血管成像的研究进展

肾动脉3DCE—MRA已在高场MR设备下得到广泛应用，是筛选肾动脉狭窄的可靠方法；对于活体供肾者，其可为外科医师提供所需要的有价值信息，但可能漏检小直径血管。从与血管轴正交截面观察可提高MRA对肾动脉狭窄程度评估的准确度，降低阅片者间差异度。MRA可对铂合金支架腔内成像。尚缺乏采用平行采集技术利用3．0TMR设备对活体供肾者进行的评价研究。应用低剂量对比剂降低MRA费用是发展趋势。血池对比剂有潜力使MRA更上新台阶。     

非对比增强MR血管成像技术发展及应用

近年来,随着MR设备的发展和新序列的开发,非对比增强MR血管成像(NCE-MRA)技术发展迅速,除传统的时间飞跃法和相位对比法外,许多新方法已可用于全身各部位血管成像。NCE-MRA包括血流依赖和非血流依赖两大类成像技术,这些技术联合应用于不同的成像序列。为了提高对NCE-MRA技术的认识,促进该类技术的开发应用,对多种NCE-MRA方法的成像机制、优缺点和临床应用作一综述。     

非对比剂增强的MRA技术对肾动脉的评估价值

目的 评价非对比剂增强的磁共振血管成像(NCE-MRA)技术对肾动脉解剖变异的临床诊断价值.资料与方法 30例患者先后使用同一设备进行NCE-MRA和对比剂增强磁共振血管成像(CE-MRA)扫描后获取肾动脉血管的影像解剖图像,分别由两位医师对每例图像质量进行技术评分,然后评价两种方法对于血管的显示价值.结果 NCE-MRA组和CE-MRA组中,图像质量为3分以上者分别占93.3%(28/30)和96.7%(29/30);两者显示共60个单肾的肾动脉血管的符合率为97%(57/60),均没有出现假阳性病例,NCE-MRA方法出现假阴性3个.两种方法差异无统计学意义(P＞0.05),并且两位诊断医师的一致性较高,Kappa值均＞0.75.结论 NCE-MRA是一种无需使用对比剂、非侵人性的MRA技术,可以有效地用于肾动脉评估.     

SLEEK序列显示移植肾动脉的价值及扫描参数的优化选择

目的 评估基于多翻转脉冲空间标记(SLEEK)序列的非对比剂增强磁共振血管成像(MEC-MRA)在移植肾动脉成像的价值及扫描参数优化.方法 对75例接受了肾移植的患者,应用1.5 TMR扫描仪分别进行血液抑制翻转时间(BSP TI)为500、800、1100、1400 ms扫描,比较不同BSP TI下移植肾动脉主干、分支与肾实质的相对信号强度.结果 75例患者均成功实现了非对比剂移植肾动脉血管成像.BSP TI由500 ～ 1400 ms,移植肾动脉远端分支的信号强度逐渐增强.在BSP TI为800 ms或1100 ms时,移植肾动脉与移植肾实质之间的相对信号强度最高.结论 基于SLEEK的MEC-MRA在显示移植肾血管解剖方面是一种可靠的方法.在血流正常情况下BSPTI为800 ms或1100 ms时成像效果较好.     

移植肾磁共振成像特征的探讨

目的:探讨移植肾的MRI表现、材料与方法:对35例移植肾进行MRI检查,根据临床症状及生化资料将其分成三组,即非排斥组22例;排斥组(急性、慢性)5例;少尿、无尿组8例。MRI观察项目:(1)移植肾大小,(2)移植肾皮髓质分辨率(四级),(3)移植肾血管能见度(四度)。结果:非排斥组,肾脏外形无增大,皮髓质分辨率Ⅱ级以上达95％,血管能见度Ⅱ度以上达95％,排斥组,急性:肾脏外形均增大,皮髓质分辩模糊均在Ⅱ级以下,血管能见度在1～0度范围;慢性:肾脏稍偏小,皮髓质分辨率及血管能见度均在Ⅱ～Ⅰ级(度)范围。少尿、无尿组,早期肾脏无增大,皮髓质分辨清楚,Ⅱ级达75％,而血管能见度差,Ⅰ度达75％。本文重点讨论少尿、无尿组的病因,MRI特征及血管能见度改变的临床意义。结论:MRI能较好地显示移植肾的变化,并对其CMD和PVV级别进行判断。     

Role of high resolution contrast-enhanced magnetic resonance angiography (HR CeMRA) in management of arterial complications of the renal transplant

Introduction

Transplant renal artery (RA) stenosis (TRAS) is the most frequent posttransplantation vascular complication. Contrast enhanced magnetic resonance (CeMRA) angiography has been established as the preferred imaging technique for the evaluation of TRAS because it does not require the use of iodinated contrast material and does not expose the patient to ionizing radiation. Digital subtraction angiography (DSA) is the gold standard in the evaluation of arterial tree of the renal allograft.

Aim of the work

This study was carried out to assess the accuracy of CeMRA in the detection of arterial complications after renal transplantation.

Patients and methods

Thirty renal transplant patients with suspected arterial complications in which both CeMRA and DSA were performed were included in the study. The HR CeMRA shows 93.7% sensitivity, 80% specificity, 88.2% positive predictive value, 88.9% negative predictive value and 88.5% accuracy.

Conclusion

HR CeMRA is an accurate reliable tool in the assessment of arterial complications after renal transplantation. It may replace DSA as a diagnostic modality with reservation of interventional techniques for endovascular treatment of suitable cases.     

HYPR TOF: time-resolved contrast-enhanced intracranial MR angiography using time-of-flight as the spatial constraint

Purpose

To investigate the feasibility of using time‐of‐flight (TOF) images as a constraint in the reconstruction of a series of highly undersampled time‐resolved contrast‐enhanced MR images (HYPR TOF), to allow simultaneously high temporal and spatial resolution and increased SNR.

Materials and Methods

Ten healthy volunteers and three patients with aneurysms underwent a HYPR TOF study, which includes a clinical routine TOF scan followed by a first pass time‐resolved contrast‐enhanced exam using an undersampled three‐dimensional (3D) projection trajectory (VIPR). Image quality, waveform fidelity and signal to background variation ratio measurements were compared between HYPR TOF images and VIPR images without HYPR reconstruction.

Results

Volunteer results demonstrated the feasibility of using the clinical routine TOF as the spatial constraint to reconstruct the first pass time‐resolved contrast‐enhanced MRA acquired using highly undersampled 3D projection trajectory (VIPR). All the HYPR TOF images are superior to the corresponding VIPR images with the same temporal reconstruction window on both spatial resolution and SNR.

Conclusion

HYPR TOF improves the spatial resolution and SNR of the rapidly acquired dynamic images without losing the temporal information. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Non‐contrast‐enhanced renal and abdominal MR angiography using velocity‐selective inversion preparation

Non‐contrast‐enhanced MR angiography is a promising alternative to the established contrast‐enhanced approach as it reduces patient discomfort and examination costs and avoids the risk of nephrogenic systemic fibrosis. Inflow‐sensitive slab‐selective inversion recovery imaging has been used with great promise, particularly for abdominal applications, but has limited craniocaudal coverage due to inflow time constraints. In this work, a new non‐contrast‐enhanced MR angiography method using velocity‐selective inversion preparation is developed and applied to renal and abdominal angiography. Based on the excitation k‐space formalism and Shinnar‐Le‐Roux transform, a velocity‐selective excitation pulse is designed that inverts stationary tissues and venous blood while preserving inferiorly flowing arterial blood. As the magnetization of the arterial blood in the abdominal aorta and iliac arteries is well preserved during the magnetization preparation, artery visualization over a large abdominal field of view is achievable with an inversion delay time that is chosen for optimal background suppression. Healthy volunteer tests demonstrate that the proposed method significantly increases the extent of visible arteries compared with the slab‐selective approach, covering renal arteries through iliac arteries over a craniocaudal field of view of 340 mm. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Non-enhanced MR angiography of renal artery using inflow-sensitive inversion recovery pulse sequence: A prospective comparison with enhanced CT angiography

Purpose

To prospectively evaluate the diagnostic value of non-enhanced inflow-sensitive inversion recovery (IFIR) MR angiography for the detection of renal artery stenosis (RAS), with enhanced CT angiography performed as the reference standard.

Materials and methods

Sixty consecutive patients suspected of RAS underwent both of IFIR MR and enhanced CT angiography. Subjective image quality, renal artery depiction and renal artery grading were all evaluated on artery-by-artery basis. Spearman rank correlation analysis was used to assess agreement between the two techniques. The diagnostic sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for RAS detection at IFIR MR angiography were calculated.

Results

One hundred twenty-six main renal arteries were visualized on enhanced CT and non-enhanced MR angiographic images, respectively. The Spearman rank correlation was 0.773 (P < .001) for renal artery depiction, 0.998 (P < .001) for renal arteries grading and 0.833 (P < .001) for RAS detection between the two modalities. The sensitivity, specificity, PPV and NPV of IFIR MR angiography for RAS detection demonstrated 100%, 99.0%, 92.0% and 100%, respectively.

Conclusion

Non-enhanced IFIR MR angiography had high sensitivity, specificity, PPV and NPV for RAS detection. It could be the first choice of renal artery imaging methods to avoid ionizing irradiation and renal toxicity from contrast media.     

Time-resolved MR angiography of renal artery stenosis in a swine model at 3 Tesla using gadobutrol with digital subtraction angiography correlation

Purpose:

To establish the minimum dose required for detection of renal artery stenosis using high temporal resolution, contrast enhanced MR angiography (MRA) in a porcine model.

Materials and Methods:

Surgically created renal artery stenoses were imaged with 3 Tesla MR and digital subtraction angiography (DSA) in 12 swine in this IACUC approved protocol. Gadobutrol was injected intravenously at doses of 0.5, 1, 2, and 4 mL for time‐resolved MRA (1.5 × 1.5 mm² spatial resolution). Region of interest analysis was performed together with stenosis assessment and qualitative evaluation by two blinded readers.

Results:

Mean signal to noise ratio (SNR) and contrast to noise ratio (CNR) values were statistically significantly less with the 0.5‐mL protocol (P < 0.001). There were no statistically significant differences among the other evaluated doses. Both readers found 10/12 cases with the 0.5‐mL protocol to be of inadequate diagnostic quality (κ = 1.0). All other scans were found to be adequate for diagnosis. Accuracies in distinguishing between mild/insignificant (<50%) and higher grade stenoses (>50%) were comparable among the higher‐dose protocols (sensitivities 73–93%, specificities 62–100%).

Conclusion:

Renal artery stenosis can be assessed with very low doses (～0.025 mmol/kg bodyweight) of a high concentration, high relaxivity gadolinium chelate formulation in a swine model, results which are promising with respect to limiting exposure to gadolinium based contrast agents. J. Magn. Reson. Imaging 2012;36:704–713. © 2012 Wiley Periodicals, Inc.     

Nonenhanced extracranial carotid MR angiography using arterial spin labeling: improved performance with pseudocontinuous tagging

Purpose:

To compare pulsed arterial spin labeling (PASL) and pseudocontinuous arterial spin labeling (PCASL) for nonenhanced extracranial carotid MR angiography (MRA).

Materials and Methods:

Parametric signal equations for PASL and PCASL MRA were formulated and compared. Volunteer imaging (n = 7) at 1.5 Tesla was performed to compare the methods over a broad range of repetition and labeling times. Empirical results were compared with theoretical predictions. The feasibility of the optimal method was investigated in patients (n = 2) with sonographically documented carotid artery disease.

Results:

In volunteers, PCASL provided significantly improved signal than PASL (range: 32–255% improvement; P < 0.01), and better supported the use of long labeling times and short repetition times. Excellent agreement between theory and experiment was found (intraclass correlation coefficient = 0.966; P < 0.001). PCASL provided excellent depiction of the carotid arteries in initial patient studies.

Conclusion:

Compared with pulsed tagging, pseudocontinuous tagging provides improved performance for nonenhanced extracranial carotid MRA and warrants further clinical investigation. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Contrast-enhanced MR angiography (CE-MRA) in the evaluation of vascular complications of renal transplantation

Vascular complications associated with renal transplantation merit urgent investigation since they are often correctable, and timely intervention can help salvage the graft kidney. Contrast-enhanced MR angiography (CE-MRA) is a promising non-invasive technique, uses relatively non-nephrotoxic contrast agents and can rapidly demonstrate the underlying lesion in most instances. In this pictorial review we present the spectrum of abnormalities, as well as the pitfalls of interpretation of CE-MRA, that we encountered in 41 cases where there was clinical suspicion of vascular complications of renal transplantation. We believe that CE-MRA is a valuable, non-invasive screening technique in these cases, and further investigation and management of these patients can be confidently tailored to the results of the CE-MRA study.     

Three-dimensional time-of-flight MR angiography using selective inversion recovery RAGE with fat saturation and ECG-triggering: Application to renal arteries

A three-dimensional (3D), ECG-triggered, selective inversion recovery (SIR) rapid gradient-echo (RAGE) technique is proposed to obtain MR angiograms of the main renal arteries. By using the selective inversion recovery and fat saturation, the background is significantly suppressed while blood maintains a high signal intensity as compared with conventional 3D time-of-flight (TOF) MR angiography. The sequence is ECG-triggered so that blood in-flow is maximized during systole, and intravoxel dephasing and pulsatile flow artifacts are minimized by collecting data during diastole. As a result, vessel boundary blurring and ghosting artifacts due to background motion are dramatically reduced, and the conspicuity and lumen definition of the arteries are significantly improved. High-quality MR angiograms of the main renal arteries with excellent blood/tissue contrast and suppression of motion artifacts have been consistently obtained for normal volunteers, with the length of visualization being 51 ± 07 mm for the left, and 57 ± 06 mm for the right renal arteries, significantly greater than using conventional 3D TOF pulse sequences. Statistical analysis was performed by using a one-sided Student's t test. Key words: renal artery; MR angiography; three-dimensional MR imaging.