敏感性编码技术在腹部磁共振快速成像中的应用

目的　研究敏感性编码 (SENSE)技术在腹部快速MRI检查中的临床应用。方法　对 15例患者的腹部进行常规快速自旋回波 (TSE)序列T2 加权成像 (T2 WI)、选择性部分反转恢复 (SPIR)序列T2 WI、快速场回波 (FFE)序列T1加权成像 (T1WI)以及在保持参数不变时联合应用SENSE成像。观察应用SENSE后 ,扫描时间的缩短情况以及图像的对比度变化情况。结果　应用SENSE成像当缩减因子为 2 .0时 ,腹部每个序列扫描时间缩短约 43 %～ 5 0 % ,而图像的对比度不变。结论　联合应用SENSE技术能显著缩短扫描时间 ,而保持图像对比度基本不变。SENSE技术在磁共振快速成像中的应用前景广阔。     

SENSE技术在下肢静脉成像中的应用

目的：探讨磁共振SENSE技术在下肢静脉成像中的应用价值。方法：不用造影剂，采用非SENSE线圈及技术，SENSE线圈及技术对34例临床怀疑下肢静脉病变的患者同时进行磁共振静脉成像并分析其应用价值。结果：所有病例均较清晰显示下肢静脉，应用SENSE技术的下肢静脉图像与非SENSE技术的图像质量相同，扫描时间减少一半。在扫描范围及时间不变时提高分辨率的参数，可明显提高图像质量。结论：SENSE技术是一种可以大大减少扫描时间，不影响空间分辨率的新方法，在磁共振快速成像及临床中的应用前景广阔。     

关于MRI成像过程若干技术问题的探讨

本文论述了MRI成像过程中，梯度磁场的空间编码、K空间填充及信号采集方式。重点讨论了螺旋桨扫描技术（PEOPELLER）及灵敏度编码技术（SENSE）两种成像方法的原理及特征。SENSE技术利用阵列线圈并行采集信号，可在图像的空间分辨率不变的情况下，缩短扫描时间，加快成像速度。PEOPELLER技术利用其独特的K空间填充方式，在头部扫描中通过各种校正，消除患者因头部运动产生的伪影，得到具有诊断意义的T2WI、DWI图像。     

乳腺磁共振检查技术的应用与探讨

目的探讨乳腺磁共振(MRI)检查技术中成像序列、参数、扫描方位的选择及其应用价值。方法 回顾性分析32例乳腺MRI检查资料,对进行检查所选用的扫描方法、序列、参数做出总结分析。结果 32例研究对象乳腺MRI图像均显示良好,乳腺结构和周围组织清晰,未见有变形情况。结论 MRI检查中,采用恰当的扫描序列、参数及进行合理的扫描,可清晰显示乳腺结构,观察到乳腺肿瘤周边、内部情况及其与邻近组织的关系;动态增强扫描可清晰显示肿瘤形态及较小病灶,对乳腺肿瘤定性诊断极具价值。     

MRI常规及3D-SPACE序列在先天性子宫畸形诊断中的应用价值

目的探讨磁共振成像（MRI）常规及3D-SPACE序列扫描在先天性子宫畸形诊断中的应用价值。方法回顾性分析62例行MRI常规和3D-SPACE序列扫描,并经宫、腹腔镜证实的先天性子宫畸形的MRI资料。结果单角子宫7例,双角子宫8例,双子宫7例,纵隔子宫28例,弓形子宫12例。MRI尤其用3D-SPACE序列扫描可从不同角度观察子宫外形、宫腔结构,尤其对宫底、宫颈及内膜形态。MRI对先天性子宫畸形的诊断准确率为100%。结论 MRI可清晰显示先天性子宫畸形的解剖结构,是诊断先天性子宫畸形的可靠方法,值得临床推广。     

磁共振磁敏感加权成像在出血性脑梗死诊断中的应用价值

目的:观察磁共振磁敏感加权成像(Susceptibility Weighted Imaging,SWI)在出血性脑梗死诊断中的应用价值。方法:选择2015年2月-2017年1月在我院检查的36例出血性脑梗死患者,为患者分别进行磁敏感加权成像(SWI)、弥散加权成像(DWI)及常规MRI扫描,对比三种不同诊断方法对出血性脑梗死患者检出率及出血灶数量的显示情况。观察SWI序列显示脑梗死区域及周围微出血灶数量情况,以及脑梗死灶内静脉血管变化情况。结果:磁共振磁敏感加权成像对出血性脑梗死的检出率和出血灶数量的显示明显优于弥散加权成像及常规MRI扫描的序列,数据差异具有统计学意义(p0.05);在所有患者中,发现12例患者脑梗死灶区域之外存在微出血灶,有19例患者脑梗死灶内的小静脉血管分支明显减少,6例患者其血管发生增多、增粗或扭曲的情况。结论:磁共振磁敏感加权成像在出血性脑梗死诊断中具有良好的应用价值,其诊断阳性率明显优于弥散加权成像及常规MRI序列,可早期发现脑梗死中的出血灶,值得临床应用及推广。     

磁共振成像在冠心病诊断中的应用

文章着重介绍了磁共振成像（MRI）“一站式”扫描在冠心病诊断中的应用。详细地论述了MRI在评估心脏结构功能、心肌灌注和心肌活力以及冠状动脉中的应用价值,旨在提高临床医师对心脏MRI的认识。     

骨关节金属植入物MRI伪影抑制技术的临床应用

目的:探讨不同扫描序列在骨关节金属植入物磁共振成像(MRI)的临床伪影抑制价值;方法:收集我院于2019年1月-2019年10月进行MRI成像的30例患者的影像学资料,上述患者均行骨关节金属植入术。依据扫描方法的不同分为STIR组(n=16例)和IDEAL组(n=14例)。两组患者先进行T1WI和T2W2加权处理,后进行短时间反转恢复(STIR)序列和三点非对称回波(IDEAL)序列伪影抑制术,并比较两组图像质量、伪影宽度、金属植入物与组织对比度;结果:两组MRI成像时间无显著差异,无统计学意义(P>0.05),IDEAL组金属植入物与组织和成像合格率均高于STIR组,而伪影宽度低于STIR组,存在显著差异(P<0.05)。结论:在MRI成像质量一致的情况下,IDEAL序列扫描的伪影抑制效果优于STIR序列扫描,可以有效降低进金属植入物对观察组织的影响,所以IDEAL序列具有临床伪影抑制的应用价值。     

磁共振神经成像在外周神经鞘膜瘤的应用研究

目的探讨磁共振神经成像对外周神经鞘膜瘤诊断的临床价值。材料与方法回顾性分析27例经手术和病理证实的外周神经鞘膜瘤资料,所有病例均行MRI常规成像和结合短TI反转恢复时间成像(3D-STIR)增强序列扫描。分析和评价3D-STIR增强扫描序列对外周神经鞘膜瘤诊断的可行性和准确性,比较常规MRI成像及3D-STIR序列增强扫描对外周神经鞘膜瘤诊断的征象和价值。结果27例外周神经鞘膜瘤患者,磁共振常规成像可以显示病灶的部位、数目、形态、体积、信号特征。3D-STIR增强扫描序列上均可清晰显示周围神经走行及病变同周围神经关系。结论磁共振常规序列及3D-STIR增强扫描序列对外周神经鞘膜瘤的定位定性诊断有重要的临床应用价值。     

眼眶疾病的MRI扫描方法研究

目的　探讨眼眶疾病的MRI扫描方法。方法　应用两次定位技术 ,脂肪抑制技术 ,磁共振水成像与磁共振血管成像技术 ,Gd DTPA对比增强 ,多方位成像技术 ,多序列参数成像的扫描方法对 183例眼眶病变进行MRI扫描。结果　两次定位技术可明显缩短扫描时间 ;脂肪抑制技术既能鉴别含脂类病变、抑制化学位移伪影 ,又能准确显示较小病变和更清晰地显示病变轮廓 ;磁共振水成像与血管成像技术可以辅助诊断囊性病变与血管类病变 ;对比增强和多方位多序列成像可以提供更多定位定性的诊断依据。结论　应用正确的MRI扫描方法 ,可以快速高效、清楚准确地显示眼眶病变。     

Application of SENSE in clinical pediatric body MR imaging

Pediatric body magnetic resonance imaging can be challenging because of the intrinsic physiologic motions from high respiratory and heart rates. Unlike in adults, in preadolescent children, breath holding is often not an available option. In this paper, the authors describe their clinical experience using the recently available parallel imaging technique, sensitivity encoding (SENSE), to improve on the image quality of pediatric body MR examinations. The three major areas described include rapid imaging using SENSE to achieve time-resolved contrast-enhanced MRA, improvement in single-shot turbo spin echo imaging with SENSE, and decreasing respiratory motion artifact with combination of SENSE and multiple signal averages in various pulse sequences. Some practical suggestions of using SENSE in clinical pediatric body MR examinations are highlighted. The addition of SENSE has allowed for improved image quality and more efficient overall MR examinations for pediatric body imaging.     

Acceleration of tissue phase mapping with sensitivity encoding at 3T

Background

The objective of this study was to investigate the impact of sensitivity encoding on the quantitative assessment of cardiac motion in black blood cine tissue phase mapping (TPM) sequences. Up to now whole volume coverage of the heart is still limited by the long acquisition times. Therefore, a significant increase in imaging speed without deterioration of quantitative motion information is indispensable.

Methods

20 volunteers were enrolled in this study. Each volunteer underwent myocardial short-axis TPM scans with different SENSE acceleration factors. The influence of SENSE acceleration on the measured motion curves was investigated.

Results

It is demonstrated that all TPM sequences with SENSE acceleration have only minimum influence on the motion curves. Even with a SENSE factor of four, the decrease in the amplitude of the motion curve was less than 3%. No significant difference was observed for the global correlation coefficient and deviation between the motion curves obtained by the reproducibility and the SENSE accelerated measurements.

Conclusions

It is feasible to accelerate myocardial TPM measurements with SENSE factors up to 4 without losing substantial information of the motion pattern.     

联合压缩感知技术优化脑神经一站式三维可调制翻转角超长回波链回聚脉冲(3D-MATRIX)成像

目的 采用联合压缩感知（uCS）技术优化脑神经一站式三维可调制翻转角超长回波链回聚脉冲（3D-MATRIX）成像，并筛选最佳加速因子（AF）。方法 前瞻性对11例三叉神经痛患者及28名健康志愿者以敏感度编码（SENSE）并行采样技术（SENSE=3）及AF为3~6的3D-MATRIX序列行脑神经成像，比较不同序列间脑神经图像质量，以及嗅神经、视神经、三叉神经信噪比（SNR）和对比度噪声比（CNR）的差异；测量脑池内与听神经相近处小血管信号强度，计算其与脑脊液的对比度（CR），比较不同序列间差异。结果 各序列图像间，嗅神经、视神经及三叉神经SNR、CNR，以及血管与脑脊液CR差异均有统计学意义（P均<0.01）。随AF增加，扫描时间缩短，uCS5序列图像质量呈降低趋势；AF为5时，uCS5序列图像中各神经主观评分、SNR及CNR均与SENSE3序列无明显差异（P均>0.05），而血管与脑脊液CR大于SENSE3序列（P<0.05）；AF为6时，uCS6序列图像中副神经及舌下神经主观评分低于其他序列（P均<0.01）。结论 利用3D-MATRIX序列结合uCS技术可对脑神经进行一站式成像，以AF为5最佳。     

Highly accelerated cardiac MRI using iterative SENSE reconstruction: initial clinical experience

To evaluate the qualitative and quantitative performance of an accelerated cardiovascular MRI (CMR) protocol that features iterative SENSE reconstruction and spatio-temporal L₁-regularization (IS SENSE). Twenty consecutively recruited patients and 9 healthy volunteers were included. 2D steady state free precession cine images including 3-chamber, 4-chamber, and short axis slices were acquired using standard parallel imaging (GRAPPA, acceleration factor = 2), spatio-temporal undersampled TSENSE (acceleration factor = 4), and IS SENSE techniques (acceleration factor = 4). Acquisition times, quantitative cardiac functional parameters, wall motion abnormalities (WMA), and qualitative performance (scale: 1-poor to 5-excellent for overall image quality, noise, and artifact) were compared. Breath-hold times for IS SENSE (3.0 ± 0.6 s) and TSENSE (3.3 ± 0.6) were both reduced relative to GRAPPA (8.4 ± 1.7 s, p < 0.001). No difference in quantitative cardiac function was present between the three techniques (p = 0.89 for ejection fraction). GRAPPA and IS SENSE had similar image quality (4.7 ± 0.4 vs. 4.5 ± 0.6, p = 0.09) while, both techniques were superior to TSENSE (quality: 4.1 ± 0.7, p < 0.001). GRAPPA WMA agreement with IS SENSE was good (κ > 0.60, p < 0.001), while agreement with TSENSE was poor (κ < 0.40, p < 0.001). IS SENSE is a viable clinical CMR acceleration approach to reduce acquisition times while maintaining satisfactory qualitative and quantitative performance.     

Reduced data acquisition methods in cardiac imaging

In cardiac imaging, acquisition speed is of primary importance. While improved performance has mainly been achieved through improvements in gradient hardware in the past, further developments along this direction are limited due to physiological constraints such as the risk of peripheral nerve stimulation. With the introduction of parallel imaging, alternative means for increasing acquisition speed have become available. Using information from multiple receiver coils, images can be reconstructed from a sparsely sampled set of data. In practice, parallel imaging allows for 2- to 3-fold acceleration of the imaging process in typical cardiac applications. Further increases in acquisition speed are, however, difficult to achieve for current clinical field strengths and typical field of views. To address the limited gain in acquisition speed achievable with parallel imaging, a new set of methods has been proposed to take into account the similarity of image information at different time points during a dynamic series. Using these methods, 5- to 8-fold acceleration can be achieved in cardiac imaging. It is the purpose of this paper to review cardiac applications of reduced data acquisition methods with focus on parallel imaging and the recently developed k-t BLAST and k-t SENSE techniques.     

动脉造影CT在腹部疾病诊断的应用

目的：提高腹部疾病影像诊断水平,探索动脉造影ＣＴ在腹部疾病诊断中的应用价值。对象与方法：２２例腹部疾病患者与行动脉造影ＣＴ检查,检查后均经手术或活检明确诊断。常规血管造影操作将导管抽入的病变供血动脉后,注入造影剂同时行ＣＴ扫描。观察影像学改变,做出诊断;同时观察离子造影剂和非离子型造影剂的差别。结果：诊断符合率９５．５％,离子型造影剂和非离子型造影剂之间的检查中未见差别。结论：动脉造影ＣＴ对于腹部     

Breathhold cardiac MRI and MRA

Recent developments in MRI software and hardware have increased the speed and versatility of cardiac MRI by allowing image acquisition in a single breathhold. Many studies have shown that conventional cardiac MRI is as accurate as echocardiography or cardiac catheterization for diagnosing numerous cardiac conditions. In many cases cardiac MRI is the most accurate diagnostic technique but has not been widely adopted for routine cardiac imaging. One reason why the use of cardiac MRI has been limited is the long examination times required for conventional cardiac MRI. The development of better hardware, such as faster gradient amplifiers and dedicated surface coils, has allowed the implementation of much faster EKG-gated imaging sequences. These can be used in a single breathhold period, with a significant improvement in image quality compared with conventional sequences. Breathhold sequences can provide all the information provided by conventional cardiac MRI in a shorter time and with equal or better accuracy. Breathhold imaging will allow much wider application of MRI to routine cardiac diagnosis.     

Accelerated cardiovascular magnetic resonance of the mouse heart using self-gated parallel imaging strategies does not compromise accuracy of structural and functional measures

Background

Self-gated dynamic cardiovascular magnetic resonance (CMR) enables non-invasive visualization of the heart and accurate assessment of cardiac function in mouse models of human disease. However, self-gated CMR requires the acquisition of large datasets to ensure accurate and artifact-free reconstruction of cardiac cines and is therefore hampered by long acquisition times putting high demands on the physiological stability of the animal. For this reason, we evaluated the feasibility of accelerating the data collection using the parallel imaging technique SENSE with respect to both anatomical definition and cardiac function quantification.

Results

Findings obtained from accelerated data sets were compared to fully sampled reference data. Our results revealed only minor differences in image quality of short- and long-axis cardiac cines: small anatomical structures (papillary muscles and the aortic valve) and left-ventricular (LV) remodeling after myocardial infarction (MI) were accurately detected even for 3-fold accelerated data acquisition using a four-element phased array coil. Quantitative analysis of LV cardiac function (end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF) and LV mass) in healthy and infarcted animals revealed no substantial deviations from reference (fully sampled) data for all investigated acceleration factors with deviations ranging from 2% to 6% in healthy animals and from 2% to 8% in infarcted mice for the highest acceleration factor of 3.0. CNR calculations performed between LV myocardial wall and LV cavity revealed a maximum CNR decrease of 50% for the 3-fold accelerated data acquisition when compared to the fully-sampled acquisition.

Conclusions

We have demonstrated the feasibility of accelerated self-gated retrospective CMR in mice using the parallel imaging technique SENSE. The proposed method led to considerably reduced acquisition times, while preserving high spatial resolution at sufficiently high CNR. The accuracy of measurements of both structural and functional parameters of the mouse heart was not compromised by the application of the proposed accelerated data acquisition method.     

SENSE factors for reliable cortical thickness measurement

The purposes of this study were to examine the effect of sensitivity encoding (SENSE) factors on cortical thickness measurements and to determine which SENSE factor to use to reliably measure cortical thickness in 3.0 T and 1.5 T T1-weighted MRI images. The 3D T1-TFE images were acquired from 11 healthy volunteers with 6 different SENSE acceleration factors from 1.0 (without SENSE acceleration) to 4.0 on a 1.5 T scanner, and 9 different SENSE factors from 1.0 to 6.0, plus a second-day 1.0 acquisition on a 3.0 T scanner. Cortical thickness was calculated for the entire cortical surface that was further subdivided into 33 regions. Repeated measures multivariate analysis of variance revealed that the main effect of SENSE factors (F=12.485, df=7, p=0.006) was a significant underestimation of cortical thickness at SENSE 5.0 (p=0.022) and 6.0 (p=0.011) at 3.0 T and at SENSE 4.0 (p<0.000) at 1.5 T. Repeated measures ANOVA showed that thickness measurements at the insula, superior temporal sulcus, the medial part of the superior frontal lobe, and cingulate cortex are highly affected by SENSE factors. SENSE factors affect thickness estimation more significantly at 1.5 T and thus 1.5 T imaging provides less reliable estimates using SENSE techniques. Faster imaging can be done without too much loss of reliability using a high SENSE factor, such as 3.0, at 3.0 T with acquisition time being inversely proportional to the SENSE factor.