MRI对新型冠状病毒肺炎的应用价值初探

目的：探讨MRI对新型冠状病毒肺炎(新冠肺炎)的应用价值。方法：回顾性分析58例新冠肺炎患者的CT及MRI图像。MRI序列包括T₂WI、超短TE回波时间(UTE)序列、T₁WI。以CT检查结果为金标准,分析、比较MRI单一序列及联合序列对肺内不同性质病变(磨玻璃病变、实变影、条索影)的检出及显示情况,其中MRI序列所示肺内病变进行5分法评分,≥4分认为满足临床诊断需求。结果：58例患者中,CT共检出185个病灶,其中磨玻璃病变138个,实变影32个,条索影15个。T₂WI对病变的检出率为92.43%(171/185),与联合序列相等,略高于UTE序列[87.57%(162/185)],T₁WI检出率较低,仅59.46%(110/185),各序列比较,差异有统计学意义(P<0.001)。其中对于磨玻璃病变的检出,T₂WI与联合序列相等[89.86%(124/138)],稍优于UTE[83.33%(115/138)],T₁WI检出率较低,仅45.65%(...     

UTE-MRI常用技术在软骨定量研究中的应用进展

骨关节炎（OA）最初的病理生理变化主要发生在以短T₂成分为主的关节软骨,其信号衰减较快,因此常规MRI序列对早期OA的研究价值有限。MR超短回波时间（UTE）序列可以对软骨进行全面的定量评估。就UTE-T₂* mapping、UTE Adibatic-T_1ρ、UTE-磁化传递（MT）以及酸性化学交换饱和转移（acidoCEST）-UTE等软骨成分定量研究技术的基本原理、优缺点及其应用进展进行综述。     

UTE的基本原理及在骨关节系统中的应用进展

骨关节系统主要由短T_2组织构成,在常规MRI检查中常表现为低信号或无信号。超短回波时间(UTE)序列是研究短T_2组织最常用的成像技术,短T_2组织在UTE影像上表现为高信号。对UTE成像技术的基本原理进行介绍,并综述其在骨皮质、骨膜、肌腱和韧带、关节软骨和半月板中的具体应用。     

1.5 T磁敏感加权成像在新生儿颅内微出血中的应用

目的 探讨1.5 T磁敏感加权成像(SWI)在扫描新生儿颅内微出血中的应用价值。方法 本组研究收集500例临床表现怀疑有颅内损伤的患儿进行头颅磁共振成像(MRI)常规序列[T₁加权成像(T₁WI)、T₂加权成像(T₂WI)、T₂水抑制成像技术(T₂Flair)]和SWI序列的扫描。结果 500例新生儿中常规MRI序列扫描检出颅内出血83例,应用SWI序列扫描则检出116例;其中常规MRI序列扫描检出颅内微出血23例,而应用SWI序列扫描检出微出血50例。结论 1.5 T SWI对新生儿颅内微出血的检出率优于常规头颅MRI序列。     

MRI不同序列成像在高原藏族肛周感染性疾病诊断和分型中的应用价值

目的 分析MRI不同序列成像在高原藏族肛周感染性疾病诊断和分型中的应用价值。方法 搜集2016年1月至2020年1月于本院就诊的肛周脓肿或肛瘘的69例患者,所有患者于术前行MRI检查,检查序列为轴位T₁WI、T₂WI、T₂WI-抑脂(FS)扫描,冠状位T₂WI及T₂WI-FS扫描,轴位、冠状位、矢状位T₁WI-FS增强MRI扫描。与手术病理结果进行比较,分析不同序列成像诊断各类型脓肿、肛瘘及内口的正确率,采用受试者工作特征(ROC)曲线分析MRI在高原藏族肛周感染性疾病诊断的应用价值。结果 除矢状位序列的所有平扫及增强扫描序列诊断坐骨肛管间隙脓肿的正确率为100.00%。T₂WI-FS轴位平扫及增强扫描序列诊断括约肌间脓肿的正确率为100.00%。T₂WI冠状位及T₁WI-FS冠状位增强扫描序列诊断骨盆直肠间隙脓肿的正确率为100.00%。T₂WI-FS轴位平扫及T     

MRI常规序列、SWI序列及DWI在脑外伤微出血患者诊断中的应用研究

目的 探究MRI常规序列、SWI序列以及DWI序列在脑外伤微出血患者诊断中的应用价值。方法 选取2019年8月～2020年4月我院收治的71例脑外伤微出血患者作为观察对象,所有患者在入院3天后行头部MRI常规序列(T₁WI、T₂WI、T₂FLAIR)、扩散加权成像(DWI)序列及磁敏感加权成像(SWI)序列检查。观察脑外伤微出血病灶在不同扫描序列中的影像学表现,对比不同扫描序列对脑外伤微出血病灶的检出率。结果 微出血病灶在T₁WI序列中多表现为大小不等的斑片状、条状等、低信号影,T₂WI、T₂FLAIR序列中多为稍高信号或等信号,DWI序列中多表现为低信号或等信号。微出血病灶在SWI序列中多为点状、斑片状、类圆形或环形低信号影,与T₁WI、T₂WI、T₂FLAIR等MRI常规序列以及DWI序列相比,SWI对微出血病灶的显示更加明显,所显示的微出血病灶更多,病灶边缘更加清晰,病灶范围更大。71...     

磁共振超短回波时间序列在肺部的应用

【摘要】肺磁共振成像(MRI)具有极大的挑战性,因为肺实质的低质子密度,空气软组织交界面的磁化率伪影以及呼吸和心跳伪影的干扰,使用常规磁共振成像序列无法对肺组织进行成像。随着磁共振成像技术的发展,磁共振超短回波时间(UTE)序列的运用能使短T2组织如骨皮质、半月板、肺组织等成像。本文重点陈述UTE序列在肺部的应用进展并分析其在肺部的运用价值和前景。     

使用3.0T磁共振成像技术二维反转恢复超短回波时间和三维超短回波时间对半月板钙化形态和定量评价的可行性研究

摘要目的评价超短回波时间(UTE)MRI技术对不同类型半月板钙化的形态评估效果,将这些序列与标准的临床序列进行比较并测量半月板钙化的T2*值。方法该研究由机构审查委员会豁免,知情同意不是必需的。10具尸体的半月板行高空间分辨力X线摄影和3.0T的磁共振形态成像[T1加权快速自旋回波序列(FSE),T2加权FSE序列,质子密度加权(PD)的FSE序列,二维(2D)快速毁损梯度回波序列(FSPGR),三维(3D)FSPGR序列和3DUTE序列]以及定量成像[2D反转恢复(IR)UTE序列和3DUTE序列]。     

3.0 T MRI 3D-SPACE序列对膝关节半月板损伤的诊断价值

目的：探讨3.0 T MRI三维快速自旋回波序列（3D-SPACE）对膝关节半月板损伤的诊断价值。方法：收集经关节镜确诊的膝关节半月板损伤60例为研究对象，均行3.0 T MRI 3D-SPACE序列与2D-SPACE序列扫描。对2种检查方法诊断半月板损伤准确率及半月板和各种组织的对比噪声比进行比较。结果：3D-SPACE序列图像半月板与韧带的对比噪声比明显高于2D-SPACE序列（P<0.05）。3D-SPACE序列诊断半月板斜行撕裂的准确率明显高于2D-SPACE序列（P<0.05）。结论：3.0 T MRI3D-SPACE序列应用于膝关节半月板损伤的诊断中可有效提高半月板损伤的诊断准确性，具有一定的临床诊断价值。     

MAGiC技术在颈椎间盘退行性改变中的应用价值

目的:探讨MAGiC技术在颈椎间盘退行性改变中的临床应用价值。方法:前瞻性收集2021年3月至2021年12月于扬州大学附属医院接受颈椎MRI检查的患者40例(共200个颈椎间盘),患者均行常规颈椎MRI检查及T₂ MAP、MAGiC成像数据采集。由两位工作年限10年以上的医师对T₂WI图像的所有椎间盘进行Pfirrmann分级,分别对T₂ MAP和MAGiC序列的前、后纤维环及髓核进行定量值测定。结果:T₂ MAP序列与MAGiC序列的T₂值呈高度相关性(r均>0.8),T₂ MAP序列与MAGiC序列的T₂值均与年龄呈负相关,髓核区T₂值与Pfirrmann分级的负相关性最为显著(r=-0.950,P<0.01)。相邻Pfirrmann分级间MAGiC定量值分析结果显示,前纤维环的T₁、T₂、PD值在PfirrmannⅢ级与Ⅳ级间差异均有统计学意义(P&...     

影响短T2成分MR三维超短回波时间双回波脉冲序列成像质量因素的探讨

目的 探讨3D超短回波时间(UTE)舣回波脉冲序列成像的相关成像参数及后处理技术对图像质量的影响.方法 对主要含短T2成分的人于燥股骨标本及一组健康志愿者的胫骨、膝关节、踝部肌腱行MR 3D UTE舣回波脉冲序列成像.通过计算、比较图像的信噪比(SNR)或对比噪声比(CNR)及对图像伪影的分析,探讨系统内部不同轨道延迟时间(-6、-3、-2、-1、0、1、2、3 s)、不同反转角(4°、8°、12°、16°、20°、24°)、不同TE1(0.08、0.16、0.24、0.35 ms)及不同后处理技术(超短回波减影差异图、容积超短回波减影差异图)对图像质量的影响.结果 骨皮质、骨膜、半月板、肌腱、韧带等在UTE图像上表现为高信号.所设的不同轨道延迟时间中,获得最佳SNR的轨道延迟时阳间为2 s.活体人UTE成像的最佳反转角为8°～12°.不同TE1时间的图像质量不同,TE1为0.08 ms时,图像的CNR最佳.随TE1时阳延长,图像伪影逐渐增多.将原始双回波图经多平面重组后再相减(容积超短回波减影差异图),图像SNR明显增加.结论 短T2成分在3D UTE双回波脉冲序列成像上表现为高信号.通过改变反转角和将2次回波图像经MPR后再相减可增加图像SNR.缩短TE1时间可增加图像质量.

Abstract：

Objective To investigate the effect of imaging parameters and postprocessing methods on the quality of MR imaging of short T2 components with 3D ultrashort TE (UTE) double echo pulse sequence. Methods 3D UTE double echo pulse sequence was performed on dry human femoral specimen and the tibial diaphyses, knee joints, and tendons of ankles of a group of healthy volunteers. To investigate the effect of different trajectory delays of the imaging system(-6, -3, -2, - 1,0, 1,2, 3 s), different flip angles(4°, 8°, 12°, 16°, 20°, 24°), different TEs (0. 08, 0. 16, 0. 24, 0. 35 ms)and different postprocessing methods(difference imaging of subtracted volume and non-volume UTE)on the 3D UTE MR imaging quality, the SNR and CNR were calculated and compared, and the artifacts of the images were analysed. Results The cortical bone, periosteum, tendon and meniscus showed high signal intensity on the images of UTE pulse sequence. The best SNR was acquired with 2 s trajectory delay. The best flip angle was 8° to 12° for the human UTE imaging in vivo. The highest CNR was obtained from the TE of 0. 08 ms. The longer the TE was, the more artifacts appeared. The SNR of difference imagewas improved when image subtraction was performed afer multiplanar reconstruction (MPR) of the primary double echo images.Conclusions The short T2 components show high signal intensity on the MRI of 3D UTE double echo pulse sequence. The imaging quality can be improved by shortening TE, using appropriate flip angle and performing subtraction for difference image after MPR of the primary double echo images.     

Ultra‐short echo time (UTE) MR imaging of the lung: Comparison between normal and emphysematous lungs in mutant mice

Purpose:

To investigate the utility of ultra‐short echo time (UTE) sequence as pulmonary MRI to detect non‐uniform disruption of lung architecture that is typical of emphysema.

Materials and Methods:

MRI of the lungs was conducted with a three‐dimensional UTE sequence in transgenic mice with severe emphysema and their wild‐type littermates in a 3 Tesla clinical MR system. Measurements of the signal intensity (SI) and transverse relaxation time (T2*) of the lung parenchyma were performed with various echo times (TEs) ranging from 100 μs to 2 ms.

Results:

Much higher SI of the lung parenchyma was observed at an UTE of 100 μs compared with longer TEs. The emphysematous lungs had reduced SIs and T2* than the controls, in particular at end‐expiratory phase. The results suggested that both SI and T2* in lung parenchyma measured with the method represent fractional volume of lung tissue.

Conclusion:

The UTE imaging provided MR signal from the lung parenchyma. Moreover, the UTE sequence was sensitive to emphysematous changes and may provide a direct assessment of lung parenchyma. UTE imaging has the potential to assist detection of localized pathological destruction of lung tissue architecture in emphysema. J. Magn. Reson. Imaging 2010;32:326–333. © 2010 Wiley‐Liss, Inc.     

Validity and reliability of measurements of aponeurosis dimensions from magnetic resonance images

Muscle performance is closely related to the structure and function of tendons and aponeuroses, the sheet‐like, intramuscular parts of tendons. The architecture of aponeuroses has been difficult to study with magnetic resonance imaging (MRI) because these thin, collagen‐rich connective tissues have very short transverse relaxation (T2) times and therefore provide a weak signal with conventional MRI sequences. Here, we validated measurements of aponeurosis dimensions from two MRI sequences commonly used in muscle‐tendon research (mDixon and T1‐weighted images), and an ultrashort echo time (UTE) sequence designed for imaging tissues with short T2 times. MRI‐based measurements of aponeurosis width, length, and area of 20 sheep leg muscles were compared to direct measurements made with three‐dimensional (3D) quantitative microdissection. The errors in measurement of aponeurosis width relative to the mean width were 1.8% for UTE, 3.7% for T1, and 18.8% for mDixon. For aponeurosis length, the errors were 7.6% for UTE, 1.9% for T1, and 21.0% for mDixon. Measurements from T1 and UTE scans were unbiased, but mDixon scans systematically underestimated widths, lengths, and areas of the aponeuroses. Using the same methods, we then found high inter‐rater reliability (intraclass correlation coefficients >0.92 for all measures) of measurements of the dimensions of the central aponeurosis of the human tibialis anterior muscle from T1‐weighted scans. We conclude that valid and reliable measurements of aponeurosis dimensions can be obtained from UTE and from T1‐weighted scans. When the goal is to study the macroscopic architecture of aponeuroses, UTE does not hold an advantage over T1‐weighted imaging.     

Assessment of anterior cruciate ligament reconstruction using 3D ultrashort echo‐time MR imaging

This work demonstrates the potential of ultrashort TE (UTE) imaging for visualizing graft material and fixation elements after surgical repair of soft tissue trauma such as ligament or meniscal injury. Three asymptomatic patients with anterior cruciate ligament (ACL) reconstruction using different graft fixation methods were imaged at 1.5T using a 3D UTE sequence. Conventional multislice turbo spin‐echo (TSE) measurements were performed for comparison. 3D UTE imaging yields high signal from tendon graft material at isotropic spatial resolution, thus facilitating direct positive contrast graft visualization. Furthermore, metal and biopolymer graft fixation elements are clearly depicted due to the high contrast between the signal‐void implants and the graft material. Thus, the ability of UTE MRI to visualize short‐T₂ tissues such as tendons, ligaments, or tendon grafts can provide additional information about the status of the graft and its fixation in the situation after cruciate ligament repair. UTE MRI can therefore potentially support diagnosis when problems occur or persist after surgical procedures involving short‐T₂ tissues and implants. J. Magn. Reson. Imaging 2009;29:443–448. © 2009 Wiley‐Liss, Inc.     

Contrast-enhanced MRI of the menisci of the knee using ultrashort echo time (UTE) pulse sequences: imaging of the red and white zones

The objective of this study was to demonstrate the red and white zones of the meniscus of the knee using MRI. Ultrashort echo time (UTE) pulse sequences with an initial TE of 0.08 ms and later echoes at 5.95 ms, 11.08 ms and 17.70 ms were used to image the meniscus of the knee in two normal subjects before and after intravenous administration of gadodiamide. Difference images were formed by subtraction of later echo images from the first. The difference images showed obvious enhancement in an area consistent in location and dimensions with the red zone of the meniscus. Regions of interest placed within this area, central to it (corresponding to the white zone), and peripheral to it (corresponding to perimeniscal tissue) all showed increases in signal intensity after intravenous contrast administration. The greatest change in signal intensity in these regions of interest was seen with the shortest TE and in perimeniscal tissue on the original images. The increase in signal intensity was greatest in the red zone on the difference images. Using UTE pulse sequences and difference images derived from them, it is possible to visualize enhancement selectively in the red zone of the meniscus. Less obvious but significant changes in signal intensity were also present in the white zone.     

MRI不同序列在膝关节骨损伤中的应用

目的:评价自旋回波(SE)序列及梯度-短时反转回复(GE-STIR)序列对急性骨损伤的诊断价值.方法:回顾性分析50例膝关节外伤后行MRI检查的病例.所有病例均行SE序列矢状面T1WI及T2WI加权、GE-STIR序列矢状面扫描,分析不同序列显示骨挫伤的大小、范围、信号均匀性、边界以及伴随的半月板、软骨、韧带损伤及关节积液的表现,比较不同序列之间的差异.结果:50例病例中有45例显示有骨挫伤水肿,共有54处,其中6例伴有软骨损伤.伴有关节积液31例,半月板损伤23例,韧带损伤6例,其中前交叉韧带5列,外侧副韧带1例.在骨挫伤病例中,SE序列、T1WI显示43处,T2WI显示47处,GE-STIR序列显示54处.STIR序列在显示骨挫伤的大小、边界中敏感性均高于SE序列,两者之间差异有显著性意义(P＜0.05).在关节积液,半月板损伤、韧带损伤中,SE序列与GE-STIR序列比较,两者差异无显著性意义(P＞0.05).结论:GE-STIR序列在膝关节骨挫伤显示中有极大价值,明显优于SE序列.     

Three Dimensional Ultra-short Echo Time MRI Can Depict Cholesterol Components of Gallstones Bright

PurposeNon-calcified cholesterol stones that are small in size are hard to be depicted on CT or magnetic resonance cholangiopancreatography. This institutional review board (IRB)-approved retrospective in vitro study aims to characterize contrast behaviors of 3 main components of the gallstones, i.e., cholesterol component (CC), bilirubin calcium component (BC) and CaCO₃ (CO) on 3D radial scan with ultrashort TE (UTE) MRI, and to test the capability of depicting CC of gallstones as bright signals as compared to background saline.MethodsFourteen representative gallstones from 14 patients, including 15 CC, 6 BC and 4 CO, were enrolled. The gallstones underwent MRI including fat-saturated T1-weighted image (fs-T1WI) and UTE MRI with dual echoes. The contrast-to-noise ratio (CNR) and the chemical analysis for the 25 portions of the stones were compared.ResultsBC was bright on fs-T1WI, which did not change dramatically on UTE MRI and the signal did not remain on UTE subtraction image between dual echoes. Whereas the CC was negative or faintly positive signal on fs-T1WI, bright signal on UTE MRI and the contrast remained even higher on the UTE subtraction, which reflected their short T2 values. Median CNRs and standard errors of the segments on each imaging were as follows: on fs-T1WI, −10.2 ± 4.2 for CC, 149.7 ± 27.6 for BC and 37.9 ± 14.3 for CO; on UTE MRI first echo, 16.7 ± 3.3 for CC, 74.9 ± 21.3 for BC and 17.7 ± 8.4 for CO; on UTE subtraction image, 30.2 ±2.0 for CC, −11.2 ± 5.4 for BC and 17.8 ± 10.7 for CO. Linear correlations between CNRs and cholesterol concentrations were observed on fs-T1WI with r = −0.885, (P < 0.0001), UTE MRI first echo r = −0.524 (P = 0.0072) and UTE subtraction with r = 0.598 (P = 0.0016).ConclusionUTE MRI and UTE subtraction can depict CC bright.     

High-resolution ultrashort echo time (UTE) imaging on human knee with AWSOS sequence at 3.0 T

Purpose:

To demonstrate the technical feasibility of high‐resolution (0.28–0.14 mm) ultrashort echo time (UTE) imaging on human knee at 3T with the acquisition‐weighted stack of spirals (AWSOS) sequence.

Materials and Methods:

Nine human subjects were scanned on a 3T MRI scanner with an 8‐channel knee coil using the AWSOS sequence and isocenter positioning plus manual shimming.

Results:

High‐resolution UTE images were obtained on the subject knees at TE = 0.6 msec with total acquisition time of 5.12 minutes for 60 slices at an in‐plane resolution of 0.28 mm and 10.24 minutes for 40 slices at an in‐plane resolution of 0.14 mm. Isocenter positioning, manual shimming, and the 8‐channel array coil helped minimize image distortion and achieve high signal‐to‐noise ratio (SNR).

Conclusion:

It is technically feasible on a clinical 3T MRI scanner to perform UTE imaging on human knee at very high spatial resolutions (0.28–0.14 mm) within reasonable scan time (5–10 min) using the AWSOS sequence. J. Magn. Reson. Imaging 2012;35:204‐210. © 2011 Wiley Periodicals, Inc.     

k‐space water‐fat decomposition with T2* estimation and multifrequency fat spectrum modeling for ultrashort echo time imaging

Purpose:

To demonstrate the feasibility of combining a chemical shift‐based water‐fat separation method (IDEAL) with a 2D ultrashort echo time (UTE) sequence for imaging and quantification of the short T₂ tissues with robust fat suppression.

Materials and Methods:

A 2D multislice UTE data acquisition scheme was combined with IDEAL processing, including T₂* estimation, chemical shift artifacts correction, and multifrequency modeling of the fat spectrum to image short T₂ tissues such as the Achilles tendon and meniscus both in vitro and in vivo. The integration of an advanced field map estimation technique into this combined method, such as region growing (RG), is also investigated.

Results:

The combination of IDEAL with UTE imaging is feasible and excellent water‐fat separation can be achieved for the Achilles tendon and meniscus with simultaneous T₂* estimation and chemical shift artifact correction. Multifrequency modeling of the fat spectrum yields more complete water‐fat separation with more accurate correction for chemical shift artifacts. The RG scheme helps to avoid water‐fat swapping.

Conclusion:

The combination of UTE data acquisition with IDEAL has potential applications in imaging and quantifying short T₂ tissues, eliminating the necessity for fat suppression pulses that may directly suppress the short T₂ signals. J. Magn. Reson. Imaging 2010;31:1027–1034. ©2010 Wiley‐Liss, Inc.