Practical choices of fast spin echo pulse sequence parameters: clinically useful proton density and T2-weighted contrasts

Summary With the development of fast spin echo (FSE) MRI techniques, T2-weighted images of the brain may be obtained much more quickly than when using conventional spin echo techniques (CSE), because made the individual echoes on the FSE pulse sequence are phase encoded, allowing acquisition of the same spatial information as in CSE with less excitations. The pulse sequence parameters (echo train length, bandwidth echo spacing) are discussed. Images were obtained on four volunteers using both CSE and FSE while varying repetition time, echo time and matrix. Comparison for signal intensity gray-white differentiation, fat and CSE signal, arifacts and vascular resolution showed that FSE images comparable in quality to those of CSE can be obtained in less than half the time. A practical choice of FSE parameters is recommended for clinical use. However, artifacts, possibly related to CSF and vascular pulsation, of which the radiologist should be aware, were identified on the FSE images.     

三维快速场回波序列在先心病患儿 气管支气管树MRI中的应用

目的 对比分析三维快速场回波（3D-TFE）序列、三维平衡快速场回波（3D b-TFE）序列以及对比增强MR血管成像（CE-MRA）3种序列在显示气道时影像质量,探讨3D-TFE序列在先心病患儿气管支气管树成像中的应用价值。方法 连续收集2016年9月-12月间我院62例经超声心电图确诊的先心病患儿,其中男32例,女30例,年龄2~141个月,中位年龄为12.7个月。在1.5 T MR扫描设备上进行常规心脏MRI检查,常规扫描序列3D b-TFE、CE-MRA主要显示大血管病变,3D TFE进行气管支气管成像,测量气管支气管影像信噪比（SNR）及信号强度（SI）,客观评价影像质量及气管边界清晰度。由2位医生采用双盲5分法评价影像噪声及影像质量,并采用Kappa分析对2位医生的评分结果行一致性评价。采用单因素方差分析比较3种序列影像的SNR、SI、气管边界清晰度和影像质量主观评分。结果 3D-TFE序列在显示气道的SNR、SI、气管边界清晰度及其影像质量主观评分均分别高于3D b-TFE和 CE-MRA序列（均P<0.05）。2位医生对3种序列影像质量的主观评分的结果一致性极好,κ值均>0.80。结论 3D-TFE序列显示气管支气管树的影像质量优于3D b-TFE和 CE-MRA序列,可应用于心脏MRI检查时辅助观察有无先心病伴随的气道异常,是先心病心脏MRI检查中不可缺少的辅助序列,可为先心病患儿术前评估提供更多信息。     

Virtopsy—noninvasive detection of occult bone lesions in postmortem MRI: additional information for traffic accident reconstruction

In traffic accidents with pedestrians, cyclists or motorcyclists, patterned impact injuries as well as marks on clothes can be matched to the injury-causing vehicle structure in order to reconstruct the accident and identify the vehicle which has hit the person. Therefore, the differentiation of the primary impact injuries from other injuries is of great importance. Impact injuries can be identified on the external injuries of the skin, the injured subcutaneous and fat tissue, as well as the fractured bones. Another sign of impact is a bone bruise. The bone bruise, or occult bone lesion, means a bleeding in the subcortical bone marrow, which is presumed to be the result of micro-fractures of the medullar trabeculae. The aim of this study was to prove that bleeding in the subcortical bone marrow of the deceased can be detected using the postmortem noninvasive magnetic resonance imaging. This is demonstrated in five accident cases, four involving pedestrians and one a cyclist, where bone bruises were detected in different bones as a sign of impact occurring in the same location as the external and soft tissue impact injuries.     

扩散加权平面回波成像在肝占位性病变中的应用探讨

目的　探讨扩散加权平面回波成像在肝占位性病变中的应用,以及表面扩散系数（ＡＤＣ）评估肝占位病变的价值。方法　对４８ 例共有５８ 个肝占位病灶患者进行了扩散加权平面回波成像。５８ 个肝占位病灶中肝癌３０ 个,肝血管瘤１６ 个,肝囊肿１２ 个。应用不同梯度因子ｂ 值的扩散图像拟合出ＡＤＣ图,并获取ＡＤＣ值。结果　肝癌、肝血管瘤和肝囊肿的平均ＡＤＣ 值分别为：（１－２５±０－５１）×１０－ ３ ｍｍ２／ｓ、（１－７５ ±０－６０） ×１０－３ ｍｍ２／ｓ 和（３－１５ ±０－４３） ×１０－３ ｍｍ２／ｓ,三者存在着显著性差异（Ｐ＜０－０１） 。结论　扩散加权平面回波成像对肝癌、肝血管瘤和肝囊肿的鉴别诊断具有一定的价值,但不适宜对小病灶作定性诊断。     

Pitfall for systemic artery aneurysms evaluation using electrocardiogram-gated subtracted three-dimensional fast spin echo sequence of magnetic resonance imaging in patients with Kawasaki disease

Kawasaki disease (KD) is described as a syndrome that causes both coronary and systemic artery aneurysms (SAAs). This report describes the pitfall for SAAs’ evaluation when using electrocardiogram (ECG)-gated subtracted three-dimensional fast spin echo (3D FSE) sequence of magnetic resonance imaging in KD patients. A 12-year-old male was diagnosed with KD at 3 months of age. We acquired ECG-gated 3D FSE images in the diastole and systole phases with coronal sections. Subtraction was then performed from diastolic phase imaging to systolic phase imaging. A 15.5 mm right axillary artery aneurysm and an 8.0 mm left axillary artery aneurysm were identified with ECG-gated 3D FSE in the diastolic phase. However, we observed signal loss in the right axillary artery aneurysm when subtraction was performed to selectively detect arteries; further, the brachial artery was poorly detected. ECG-gated subtracted 3D FSE sequence of magnetic resonance imaging can compromise the image quality of both aneurysm and peripheral artery images when detecting SAAs.     

The clinical applications of echo planar imaging in Neuroradiology

Summary Ultra high speed echo-planar imaging gives an imaging time typically of the order of a few minutes, facilitating throughput, improving patient tolerance and allowing real time dynamic studies. A complete two dimensional image may be aquired in a single shot lasting between 64 and 128 ms. In echo planar imaging the whole of k-space is sampled as a continuous trajectory. By a rapidly switched G_y frequency encoding gradient, a train of gradient echoes is formed, each corresponding to a line in the k plane. Variable degrees at T2- or T1-weighting can be produced by methods outlined. High quality 128×128 transverse axial inversion recovery images of 5–10 mm thickness are obtained in 128 ms plus the inversion time.     

High-resolution proton density weighted three-dimensional fast spin echo (3D-FSE) of the knee with IDEAL at 1.5 Tesla: comparison with 3D-FSE and 2D-FSE--initial experience

Purpose:

To assess the feasibility of combining three‐dimensional fast spin echo (3D‐FSE) and Iterative‐decomposition‐of water‐and‐fat‐with‐echo asymmetry‐and‐least‐squares‐estimation (IDEAL) at 1.5 Tesla (T), generating a high‐resolution 3D isotropic proton density‐weighted image set with and without “fat‐suppression” (FS) in a single acquisition, and to compare with 2D‐FSE and 3D‐FSE (without IDEAL).

Materials and Methods:

Ten asymptomatic volunteers prospectively underwent sagittal 3D‐FSE‐IDEAL, 3D‐FSE, and 2D‐FSE sequences at 1.5T (slice thickness [ST]: 0.8 mm, 0.8 mm, and 3.5 mm, respectively). 3D‐FSE and 2D‐FSE were repeated with frequency‐selective FS. Fluid, cartilage, and muscle signal‐to‐noise ratio (SNR) and fluid‐cartilage contrast‐to‐noise ratio (CNR) were compared among sequences. Three blinded reviewers independently scored quality of menisci/cartilage depiction for all sequences. “Fat‐suppression” was qualitatively scored and compared among sequences.

Results:

3D‐FSE‐IDEAL fluid‐cartilage CNR was higher than in 2D‐FSE (P < 0.05), not different from 3D‐FSE (P = 0.31). There was no significant difference in fluid SNR among sequences. 2D‐FSE cartilage SNR was higher than in 3D FSE‐IDEAL (P < 0.05), not different to 3D‐FSE (P = 0.059). 2D‐FSE muscle SNR was higher than in 3D‐FSE‐IDEAL (P < 0.05) and 3D‐FSE (P < 0.05). Good or excellent depiction of menisci/cartilage was achieved using 3D‐FSE‐IDEAL in the acquired sagittal and reformatted planes. Excellent, homogeneous “fat‐suppression” was achieved using 3D‐FSE‐IDEAL, superior to FS‐3D‐FSE and FS‐2D‐FSE (P < 0.05).

Conclusion:

3D FSE‐IDEAL is a feasible approach to acquire multiplanar images of diagnostic quality, both with and without homogeneous “fat‐suppression” from a single acquisition. J. Magn. Reson. Imaging 2012;361‐369. © 2011 Wiley Periodicals, Inc.     

儿童心脏良性肿瘤的CMR影像特征分析

目的 研究儿童心脏良性肿瘤的心脏MR（CMR）特征及其对儿童良性肿瘤的诊断价值。方法 回顾性收集2006年9月-2018年3月于我院进行CMR检查的心脏肿瘤病例资料,共38例心脏良性肿瘤患儿纳入研究,其中男21例,女17例,年龄0.2~153.3个月,中位年龄13个月。分析各病理类型肿瘤在CMR上的特征,包括累及部位、大小、信号特点、血流动力学改变等,以及是否伴发心包和胸腔积液。通过与病理结果对照,计算CMR对心脏良性肿瘤诊断的敏感度和准确度。结果 肿瘤累及心肌、心腔、心包、心室流出道及纵隔,形态大小不一,临床症状与肿瘤发生部位有一定相关性而不具有特异性,但各类肿瘤具有一定的影像特征。所有的心脏肿瘤均被CMR清晰显示,CMR的诊断与病理结果相符的有32例,诊断的敏感度及准确度分别为100%（38/38）和84.21%（32/38）。结论 CMR能够同时提供心脏良性肿瘤的形态学特征及组织学信号特征,对心脏良性肿瘤诊断的敏感性及准确性均较高,是评估心脏肿瘤的重要检查方法。     

Reducing motion artefacts in diffusion-weighted MRI of the brain: efficacy of navigator echo correction and pulse triggering

Diffusion-weighted MRI (DWI) is extremely sensitive to motion of the object being examined. Pulse triggering and navigator echo correction are methods for reducing motion artefacts which can be combined with conventional DWI sequences. Implementation of these methods in imaging sequences with a readout of one, three, or five echoes is presented and imaging results compared in a study of five healthy volunteers. As an objective measure for motion-induced image artefacts, the “artefacticity” of an image is defined. Pulse triggering and navigator echo correction significantly improve image quality and provide a technique for high-quality DWI on standard imagers without improved gradient hardware. Received: 31 January 1999/Accepted: 12 July 1999     

Improved imaging of the spinal cord in multiple sclerosis using three-dimensional fast spin echo

We report assessment of a new three-dimensional fast spin echo (3D FSE) sequence in ten patients with clinically definite multiple sclerosis, comparing it with standard 2D FSE, and in ten normal controls. We saw 29 focal lesions on the 2D images and 53 on the 3D FSE imgages (P = 0.05); none were seen in controls. Lesion length was significantly smaller on the 3D FSE than on to the 2D FSE images (3D: 1.36; 2D 2,0; P = 0.03). This may relate in part to separation into several lesions on the 3D images of confluent abnormal signal seen on 2D and in part to detection of small lesions missed by the thicker 2D FSE slices (3 mm compared to 1.5 mm). The 3D FSE sequence looks promising in improving spinal cord imaging. Received: 1 June 1997 Accepted: 16 December 1997     

Quantitative proton spectroscopic imaging of the neurochemical profile in rat brain with microliter resolution at ultra-short echo times.

Proton spectroscopy allows the simultaneous quantification of a high number of metabolite concentrations termed the neurochemical profile. The spin echo full intensity acquired localization (SPECIAL) scheme with an echo time of 2.7 ms was used at 9.4T for excitation of a slab parallel to a home-built quadrature surface coil in conjunction with phase encoding in the two remaining spatial dimensions to yield an effective spatial resolution of 1.7 microL. The absolute concentrations of at least 10 metabolites were calculated from the spectra of individual voxels using LCModel analysis. The calculated concentrations were used for constructing quantitative metabolic maps of the neurochemical profile in normal and pathological rat brain. Summation of individual spectra was used to assess the neurochemical profile of unique brain regions, such as corpus callosum, in rat for the first time. Following focal ischemia in rat pups, imaging the neurochemical profile indicated increased choline groups in the ischemic core and increased glutamine in the penumbra, which is proposed to reflect glutamate excitotoxicity. We conclude that it is feasible to achieve a sensitivity that is sufficient for quantitative mapping of the neurochemical profile at microliter spatial resolution.     

低场强MR在妇科盆腔疾病诊断中的临床应用

目的探讨低场强MR在妇科盆腔疾病诊断中的临床应用价值。方法对16例患者行MR及超声检查,并与病理相对照,分析妇科盆腔疾病MRI表现,并与超声对照分析其影像特点。结果所有患者行MR及超声检查,盆腔MRI正确诊断的14例,2例与病理结果有差异,诊断符合率87%。结论 MRI由于具有优越的软组织分辨力和多方位成像的特点,当超声检查不能明确诊断时,可作为另一种首选检查方法,女性盆腔疾病在MRI上表现有一定的特异性,结合临床可以对女性盆腔疾病作出诊断及鉴别诊断。     

MR灌注成像的回波时间和对比剂剂量的选择

目的　研究回波时间 (TE)和对比剂剂量对MR灌注成像 (PWI)的图像质量和计算参数的影响作用 ,确定二者的最适值。方法　 35例健康志愿者 ,分别以TE =2 0、30、4 0ms和 0 1、0 2mmol/kg的钆喷替酸葡甲胺 (Gd DTPA)及TE =30ms、0 3mmol/kg的对比剂行PWI ,观察PWI图像的质量 ,计算脑白质的最大信号强度下降百分率 (SRRmax)和平均通过时间 (MTT)。结果　未用对比剂的PWI图像 ,TE =2 0、30、4 0ms时各组间脑白质信噪比差异有显著意义 (q2 0ms,3 0ms=18 3,q2 0ms,40ms=2 5 9,q3 0ms,40ms=7 5 ,P <0 0 1)。剂量相同或TE相同时各组白质的SRRmax间差异有显著意义 (F0 1mmol/kg=31 5 ,F0 2mmol/kg=131 5 ,F2 0ms=12 1 9,F3 0ms=4 6 9,F40ms=91 4 ,P <0 0 1) ,但MTT间差异无显著意义 (F =0 0 9,P >0 0 5 )。对比剂剂量为 0 3mmol/kg、TE =30ms时与 0 2mmol/kg、TE =30ms方案相比SRRmax差异无显著意义 (F =0 91,P >0 0 5 ) ,而MTT则差异有显著意义 (F =10 2 ,P <0 0 5 )。结论　TE =30ms和 0 2mmol/kg的对比剂剂量 ,可获得最优化的PWI结果     

Postmortem computed tomography for detecting causes of sudden death in infants and children: retrospective review of cases

Purpose The aim of this study was to investigate the usefulness of postmortem computed tomography (PMCT) in detecting causes of sudden death in infants and children. Materials and methods Our subjects were 15 nontraumatically deceased patients (nine boys and six girls, ranging in age from 20 days after birth to 12 years old, mean age 1.6 years), who had been in a state of cardiopulmonary arrest on arrival at our hospital. PMCT was performed within 2 h after certification of death: head (15 cases), chest (11 cases), and abdomen (12 cases). Blood was collected from 11 of the patients at the time of cardiopulmonary resuscitation. An autopsy was conducted on two. Results PMCT did not show any traumatic changes indicating child abuse. It was difficult to presume the cause of death with PMCT alone, but the cause of death in 14 of 15 cases could be presumed by combining information from their medical history, clinical course before death, PMCT findings, laboratory data, and bacterial culture. The remaining subject was classified as cause unknown. Conclusion The causes of sudden death in infants and children were detected at a high rate when we comprehensively investigated the PMCT and other examination findings. This article was presented at the Japan Radiology Congress, Yokohama, April 2005     

The role of dynamic contrast-enhanced and diffusion weighted magnetic resonance imaging in the female pelvis

Functional imaging by means of dynamic multiphase contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion weighted magnetic resonance imaging (DW-MRI) is now part of the standard imaging protocols for evaluation of the female pelvis. DCE-MRI and DW-MRI are important MR imaging techniques which enable the radiologist to move from morphological to functional assessment of diseases of the female pelvis. This is mainly due to the limitations of morphologic imaging, particularly in lesion characterization, accurate lymph node staging, assessment of tumour response and inability to differentiate post-treatment changes from tumour recurrence.DCE-MRI improves the accuracy of T2WI in staging of endometrial cancer. It also helps differentiate tumour recurrence from radiation fibrosis in patients with cervical cancer. DCE-MRI improves characterization of cystic adnexal lesions and detection of small peritoneal implants in patients with ovarian cancer.DW-MRI is valuable in preoperative staging of patients with endometrial and cervical cancer, especially in detection of extra-uterine disease. It does increase reader's confidence for detection of recurrent disease in gynaecological malignancies and improves detection of small peritoneal implants in patients with ovarian cancer.In this review article we give an overview of both DCE-MRI and DW-MRI techniques, concentrating on their main clinical application in the female pelvis, and present a practical approach of the added value of these techniques according to the main pathological conditions, highlighting the pearls and pitfalls of each technique.     

纹理分析在心脏MR成像中的研究进展

纹理分析可以挖掘肉眼无法观察的高通量医学影像定量特征,基于心脏MR（CMR）成像的纹理分析可以提高CMR对心脏疾病的诊断、预后及预测价值。近年纹理分析已应用于钆对比剂延迟强化、电影、T₁WI、T₁ mapping、T₂ mapping序列。综述CMR成像不同序列纹理分析的研究进展,以指导临床精准诊断及治疗。     

Three-dimensional gradient echo versus spin echo sequence in contrast-enhanced imaging of the pituitary gland at 3 T

Introduction

To clarify whether a three-dimensional-gradient echo (3D-GRE) or spin echo (SE) sequence is more useful for evaluating sellar lesions on contrast-enhanced T1-weighted MR imaging at 3.0 Tesla (T).

Methods

We retrospectively assessed contrast-enhanced T1-weighted images using 3D-GRE and SE sequences at 3.0 T obtained from 33 consecutive patients with clinically suspected sellar lesions. Two experienced neuroradiologists evaluated the images qualitatively in terms of the following criteria: boundary edge of the cavernous sinus and pituitary gland, border of sellar lesions, delineation of the optic nerve and cranial nerves within the cavernous sinus, susceptibility and flow artifacts, and overall image quality.

Results

At 3.0 T, 3D-GRE provided significantly better images than the SE sequence in terms of the border of sellar lesions, delineation of cranial nerves, and overall image quality; there was no significant difference regarding the boundary edge of the cavernous sinus and pituitary gland. In addition, the 3D-GRE sequence showed fewer pulsation artifacts but more susceptibility artifacts.

Conclusion

Our results indicate that 3D-GRE is the more suitable sequence for evaluating sellar lesions on contrast-enhanced T1-weighted imaging at 3.0 T.     

低场磁共振扩散加权成像在超急性期脑梗死的应用

目的：评价低场磁共振的扩散加权成像（DWI）在超急性期脑梗死诊断上的应用价值。方法：用低场磁共振扩散加权成像诊断超急性期脑梗死36例,分析不同时间的影像学特点,并与常规 MRI 平扫进行比较。结果：低场磁共振DWI 能显示所有患者超急性脑梗死病灶,而有11例患者在常规 MRI 平扫上未发现异常,其中7例为发病2 h 内,4例为2～4 h。此外,DWI 还可发现发病1 h 内的脑梗死高信号灶,而且 DWI 显示的病灶范围较常规 T2 WI 显示的范围更大、信号更高。结论：颅脑低场强磁共振扩散成像可以诊断超急性期脑梗死,比 T2 WI、T2 FLAIR 平扫能更早显示病变,在发现病变、确定病变部位、病变范围具有较高的价值,可为临床早期治疗提供可靠的诊断依据。     

低场强磁共振梯度回波在颈椎间盘突出中的应用价值

目的探讨低场强磁共振梯度回波在颈椎间盘突出中的应用价值。方法对176例患者颈部MRI资料回顾性分析,对比横断T1WI、T2WI、T2^＊WI对椎间盘突出的显示率并作统计学处理。结果176例中共有椎间盘突出416个,其中T1WI显示70个（占16．82％）,T2WI显示304个（占73．07％）,T2^＊WI显示406个（占97．59％）。结论低场强磁共振梯度回波能更好的显示颈椎间盘突出,可作为颈椎常规检查序列,以弥补自旋回波的不足。