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。     

无创呼吸机在呼吸衰竭急诊患者中的应用效果分析

目的分析和研究无创呼吸机在呼吸衰竭急诊患者中的应用效果。方法选取2013-04—2015-03呼吸衰竭急诊患者105例,将其按投币法随机分为无创正压通气组与持续给氧组。持续给氧组患者治疗方式为常规对症支持+低流量持续吸氧;无创正压通气组患者治疗方式为常规对症支持+无创呼吸机通气,将两组患者救治后肺功能、血气分析结果进行对比。结果两组患者急诊救治前后肺功能检测指标组间对比:两组患者救治前FVC、FEV1、FEV1%等检测值差异均无统计学意义(P0.05);无创正压通气组患者救治后FVC、FEV1、FEV1%等检测值均高于持续给氧组(P0.05)。两组患者急诊救治前后血气分析指标组间对比:两组患者救治前Pa O2、Pa CO2、p H值差异无统计学意义(P0.05);无创正压通气组患者救治后Pa O2、p H值明显高于持续给氧组,Pa CO2明显低于持续给氧组(P0.05)。结论无创呼吸机在呼吸衰竭急诊患者中的应用效果确切,可有效改善患者血气分析情况和肺功能。     

七氟烷和丙泊酚对食管癌单肺通气患者术中和术后的影响

目的:分析七氟烷和丙泊酚对食管癌单肺通气患者术中、术后肺氧合功能的影响。方法:随机选取2016年5月～2018年4月收治的食管癌患者80例,依据麻醉方式不同分成研究组与对照组,各40例。研究组单肺通气手术时接受七氟烷麻醉,对照组接受丙泊酚麻醉,比较两组麻醉效果。结果:研究组单肺通气1 h与双肺恢复通气15 min时血氧分压、氧合指数均高于对照组,差异有统计学意义(P0.05);两组通气15 min时血二氧化碳分压、血氧分压、氧合指数及肺顺应性,单肺通气1 h与双肺恢复通气15 min时血氧分压、氧合指数比较,差异无统计学意义(P0.05)。研究组核因子κB表达低于对照组,研究组并发症总发生率为7.50%,低于对照组的35.00%,差异有统计学意义(P0.05)。结论:食管癌单肺通气手术时给予七氟烷麻醉,可对患者核因子κB表达产生抑制,显著改善患者肺氧合功能,安全性高。     

对比分析放射状与线性k空间采集技术在骨关节MRI的应用

磁共振成像作为一种高端的影像检查手段,它的技术日新月异,脉冲序列层出不穷。放射状K空间采集技术是一种以特殊k空间填充方式进行图像采集的新技术,其控制数据采集方式与传统线性k空间采集方式截然不同。     

磁共振零回波成像应用进展

零回波时间(zero echo time,ZTE)成像技术是一种3D容积成像技术,其独特的梯度开启顺序以及K空间径向填充方式,使得射频激励后即可进行梯度编码,从而实现较高的信号采集效率,临床相关研究主要集中在脑血管成像、肺实质结构的显示以及病变的检测、骨关节等结构的测量评估。本文重点针对ZTE在以上各方面的主要临床应用进展进行了系统的分析综述。     

肺复张及俯卧位通气治疗重症甲型H1N1流感致ARDS产妇

成人呼吸窘迫综合征(ARDS)的机械通气方式,目前提倡肺保护通气策略,用小潮气量以减少呼吸机相关性肺损伤[1].在此基础上的定期肺复张(RM)是恢复肺通气均一性最为有效的方法,定期的俯卧位通气可改善下肺区陷闭肺泡的通气[1].重症甲型H1N1流感致ARDS产妇,肺部渗出严重,氧合差.笔者用上述方法治疗1例患者,取得良好效果,现报道如下.     

肺复张及俯卧位通气治疗重症甲型H1N1流感致ARDS产妇

成人呼吸窘迫综合征(ARDS)的机械通气方式,目前提倡肺保护通气策略,用小潮气量以减少呼吸机相关性肺损伤[1].在此基础上的定期肺复张(RM)是恢复肺通气均一性最为有效的方法,定期的俯卧位通气可改善下肺区陷闭肺泡的通气[1].重症甲型H1N1流感致ARDS产妇,肺部渗出严重,氧合差.笔者用上述方法治疗1例患者,取得良好效果,现报道如下.     

俯卧位通气对ARDS患者呼吸力学和氧合参数及血流动力学指标的影响研究

目的:探讨俯卧位通气对急性呼吸窘迫综合征(acute respiratory distress syndrome, ARDS)患者呼吸力学、氧合参数及血流动力学指标的影响。方法:选择2018年1月—2022年12月我院收治的100例ARDS患者，回顾性收集患者临床资料，按照通气方式将其分为观察组(俯卧位通气，n=62)和对照组(仰卧位通气，n=38)。对比2组治疗前后呼吸力学指标(肺顺应性、气道平均压、气道平台压)、通气前(T0)及通气12 h(T1)时氧合参数[动脉血氧分压(PaO₂)、动脉氧合指数(PaO₂/FiO₂)]及血流动力学指标[心率(HR)、平均动脉压(MAP)、中心静脉压(CVP)];分析2组预后指标[APACHEⅡ评分、多器官功能障碍综合征(multiple organ dysfunction syndrome, MODS)评分、机械通气时间、ICU时间及28 d病死率]及并发症发生率差异。结果:观察组治疗后气道平均压和气道平台压较对照组更低，肺顺应性、PaO₂及PaO_2...     

对比分析螺旋桨与线性k空间填充方式在颅脑MRI中的应用

目的探讨螺旋桨式k空间填充方式在颅脑MRI中的应用价值。方法对同一患者同时行PROPT2WI和FRFSE T2 WI,PROP T2 FLAIR和FLAIR轴位扫描,对不能配合检查的23例患者,进行图像质量评分;对配合检查的40例脑梗死患者对比图像的信噪比（SNR）和对比噪声比（CNR）。结果不能配合检查的患者PROP T2 WI和PROP T2 FLAIR图像运动伪影显著减少,图像质量评分明显高于FRFSE T2 WI和FLAIR（P=0.000,P=0.000）。配合检查的脑梗死患者,其PROP T2 WI和PROP T2 FLAIR的SNR明显高于FRFSET2WI和FLAIR（P=0.000,P=0.002）,PROP T2 WI的CNR明显高于FRFSE T2 WI（P=0.000）,而PROP T2 FLAIR和FLAIR的CNR则没有显著性差异（P=0.150）。结论PROPELLER技术在减少运动伪影,提高图像SNR上优于线性k空间填充方式,而且并不降低病变的对比,甚至在T2WI上可以提高图像的对比度。所以在颅脑MRI中,螺旋桨式k空间填充方式可以作为常规序列。     

护理学研究

033168 ARI犯病人吸痰前后不同氧供方法对Slq的影响/韩淑贞…刀护理学杂志.佗002,17(9)一643一644 将提高吸人氧浓度法(A法)、过度通气法(B法)、单次控制性肺膨胀与提高吸氧浓度结合法(C法)及常规法用于8例ARD6病人吸痰前后,并对增加氧供前后的51又遥、吸痰后Sx义沁恢复时间及达稳定时间进行对比,各方法每例每天取值1次,各法每例均取值7次。结果:1.常规吸痰后51不毛下降0.15一0.25(平均0.19),5一15min(平均9.98min)方可恢复;2.与各自对应的基础值比较,3种不同氧供法均能使吸痰前、后的51众显著提高(P<0.01、尸<0.001),其中C法优于A、B…     

脂肪对比剂灌肠MR结肠成像在结直肠肿瘤中的应用

目的评估脂肪对比剂灌肠MR结肠成像检出结直肠肿瘤的可行性.方法26例患者常规肠道准备和肌注山莨菪碱后,经直肠导管注入脂肪对比剂,采用3D FSPGR with IR(LAVA)序列加脂肪抑制,行MR增强前后冠状位扫描,一次屏气(28 s)包括全部结直肠.观察MR结肠成像质量和患者对脂肪对比剂的耐受性,并与结肠镜和病理进行对照,计算病变检出的敏感性.结果所有患者均完成MR结肠成像检查.原始冠状位,多平面重建及MR仿真内镜成像质量良好.共有198个(95.2%)肠段扩张佳,增强后结直肠肿瘤的平均对比噪声比为16.2.大于10 mm病变的敏感性是95.8%.结论脂肪对比剂灌肠MR结肠成像是能够检出结直肠肿瘤的有前景的方法,并且能评估结直肠腔外的腹部器官.     

高分辨率磁共振扫描在颅内动脉狭窄中的应用

目的：探索高分辨率磁共振扫描技术在颅内动脉狭窄处管壁成像中的应用价值。方法采用3.0T 磁共振扫描仪,应用3D-TOF,TIRM,T2WI,T1WI(平扫+增强)序列对37例颅内动脉造影证实的颅内动脉狭窄患者进行扫描。结果3例患者因躁动及幽闭恐惧等原因无法完成扫描,其余34例患者正常完成扫描,可以有效的显示颅内动脉狭窄的程度及原因。结论应用3.0T 磁共振高分辨率扫描技术,可以明确显示颅内动脉狭窄的程度及原因,提供更有意义的诊断信息。     

An RF breast coil for 0.2T MRI

Breast cancer is the most frequently diagnosed cancer in women. High field studies have shown the diagnostic value of breast MRI, but the examination costs greatly exceed those of competing conventional mammography. Low field MRI offers typical MRI contrast at substantially lower cost, but has suffered from lower spatial resolution. Specificity of breast MRI can potentially be increased by acquiring MR imaging with higher spatial or temporal resolution, but the signal‐to‐noise ratio (SNR) achievable in a given imaging time becomes limiting. SNR for the particular pulse sequence and magnet field strength is strongly influenced by the characteristics of the radio‐frequency coil. An optimal breast coil should yield excellent SNR but also generate a homogeneous B₁ field, while allowing imaging of the both breasts simultaneously and maintaining patient comfort. RF receiver coil design is a key determinant of image quality, thus to address this we have designed and constructed a low field breast imaging coil. The coil was tested with a 4‐post 0.2T MRI providing high quality breast images. Designed and constructed saddle rf coil allows to obtain good quality image of the breast using low 0.2 T MRI system within 2 minutes. The coil provides patient comfort as breast compression is not required and minimizes artefacts caused by respiration or motion. A high contrast, low‐cost and pain‐free breast examination using optimized low field MRI system has the potential to serve a large patient population for whom current technologies have deficiencies. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 46B: 3–7, 2016     

磁共振仿真输尿管膀胱镜成像技术研究

目的 探讨磁共振仿真内窥镜尿路成像方法和技术。方法 采用磁共振水成像（MRH）和／或磁共振静脉尿路造影（MR－IVU）作为影像源,应用导航软件对150例患者进行了磁共振仿真尿路镜观察,其中107例同时行了X线静脉尿路造影（X－IVU）,33傲地了输尿管镜或膀胱镜检查。结果 单层块单激发FSE序列除外,几种MRH和MRIVU技术,均有效地采集了全尿路影像,并获得仿真内镜图像,无任何与检查相关的并发症,结论 磁共振仿真尿道镜的内腔和病变的内镜样显示,可由二维HT2－FSE或多薄层单激发FSE序列,和一次屏气下的二维或三维快速破坏梯度重聚FSPGR序列获取,是常规磁共振成像有效的补充方法。     

Image quality and myocardial scar size determined with magnetic resonance imaging in patients with permanent atrial fibrillation: a comparison of two imaging protocols

Background: Magnetic resonance imaging (MRI) of the heart generally requires breath holding and a regular rhythm. Single shot 2D steady‐state free precession (SS_SSFP) is a fast sequence insensitive to arrhythmia as well as breath holding. Our purpose was to determine image quality, signal‐to‐noise (SNR) and contrast‐to‐noise (CNR) ratios and infarct size with a fast single shot and a standard segmented MRI sequence in patients with permanent atrial fibrillation and chronic myocardial infarction. Methods: Twenty patients with chronic myocardial infarction and ongoing atrial fibrillation were examined with inversion recovery SS_SSFP and segmented inversion recovery 2D fast gradient echo (IR_FGRE). Image quality was assessed in four categories: delineation of infarcted and non‐infarcted myocardium, occurrence of artefacts and overall image quality. SNR and CNR were calculated. Myocardial volume (ml) and infarct size, expressed as volume (ml) and extent (%), were calculated, and the methodological error was assessed. Results: SS_SSFP had significantly better quality scores in all categories (P = 0·037, P = 0·014, P = 0·021, P = 0·03). SNR_infarct and SNR_blood were significantly better for IR_FGRE than for SS_SSFP (P = 0·048, P = 0·018). No significant difference was found in SNR_myocardium and CNR. The myocardial volume was significantly larger with SS_SSFP (170·7 versus 159·2 ml, P<0·001), but no significant difference was found in infarct volume and infarct extent. Conclusion: SS_SSFP displayed significantly better image quality than IR_FGRE. The infarct size and the error in its determination were equal for both sequences, and the examination time was shorter with SS_SSFP.     

ADC值鉴别甲状腺结节的良恶性

目的 探讨MR DWI的ADC值鉴别诊断甲状腺良恶性结节的价值。方法 回顾性分析27例(40个病灶)经病理证实的甲状腺结节患者资料,术前均接受常规MR、脂肪抑制增强扫描明确病变实性部分;单次激发自旋平面回波成像(SS SE-EPI)DWI扫描(b值取0、500 s/mm²),测量实性部分的平均ADC值。依据病理结果将结节分为良性组及恶性组,比较其ADC值差异,绘制ROC曲线,确定诊断阈值,评价筛检效能。结果 40个结节中,甲状腺恶性结节15个,平均ADC值为(1.22±0.27)×10^－3 mm²/s,95%可信区间(1.07~1.37)×10^－3 mm²/s;良性结节25个,平均ADC值为(2.20±0.40)×10^－3 mm²/s,95%可信区间(2.04~2.37)×10^－3 mm²/s。恶性组平均ADC值显著低于良性组(P＜0.05)。ROC曲线下面积为0.98、诊断阈值1.49×10^－3 mm²/s时,诊断敏感度为86.70%,特异度为100%,准确率为95.00%。结论 甲状腺良恶性结节的ADC值显著不同,MR DWI可鉴别甲状腺结节的良恶性。     

优选序列MRI测量胎儿股骨长度

目的 评价M RI测量胎儿股骨长度(FL)的价值,并选择最优序列.方法 回顾性分析205胎胎儿股骨M RI,包括弥散加权成像(DWI)、单次激发快速自旋回波(SSFSE)、快速稳态梯度回波(FIESTA)及快速反转恢复运动抑制(FIRM)序列图像及超声资料,对各序列图像质量进行评分,比较所测FL与超声测值的差异.结果 ...     

国产低场磁共振脂肪抑制技术在肝癌中的应用初探：附66例分析

目的:在国产低场磁共振设备上,研究脂肪抑制技术在肝癌诊断中应用价值。材料与方法:66例肝癌患者行SE序列和STIR脂肪抑制技术扫描,然后对所有图像进行阅片评分和统计学处理(t检验)。结果:在脂肪抑制序列的图像解剖分辨和为显示评分值均高于SE序列,并有极显著性差异(P<0.01)或显著性差异(P<0.05)。结论:脂肪抑制技术在获得比较高的图像质量前提下,能明显增加组织间的对比度及解剖清晰度,显示肝门及后腹膜淋巴结侵犯情况,从而提高检查的阳性率和敏感性。     

Assessment of myocardial infarction in mice by Late Gadolinium Enhancement MR imaging using an inversion recovery pulse sequence at 9.4T

Purpose

To demonstrate the feasibility of using an inversion recovery pulse sequence and to define the optimal inversion time (TI) to assess myocardial infarction in mice by late gadolinium enhancement (LGE) MRI at 9.4T, and to obtain the maximal contrast between the infarcted and the viable myocardium.

Methods

MRI was performed at 9.4T in mice, two days after induction of myocardial infarction (n = 4). For cardiovascular MR imaging, a segmented magnetization-prepared fast low angle shot (MP-FLASH) sequence was used with varied TIs ranging from 40 to 420 ms following administration of gadolinium-DTPA at 0.6 mmol/kg. Contrast-to-noise (CNR) and signal-to-noise ratio (SNR) were measured and compared for each myocardial region of interest (ROI).

Results

The optimal TI, which corresponded to a minimum SNR in the normal myocardium, was 268 ms ± 27.3. The SNR in the viable myocardium was significantly different from that found in the infarcted myocardium (17.2 ± 2.4 vs 82.1 ± 10.8; p = 0.006) leading to a maximal relative SI (Signal Intensity) between those two areas (344.9 ± 60.4).

Conclusion

Despite the rapid heart rate in mice, our study demonstrates that LGE MRI can be performed at 9.4T using a protocol similar to the one used for clinical MR diagnosis of myocardial infarction.     

Noise analysis and MR pulse sequence optimization in MREIT using an injected current nonlinear encoding (ICNE) method

Magnetic resonance current density imaging (MRCDI) and magnetic resonance electrical impedance tomography (MREIT) visualize an internal distribution of current density and/or conductivity by injecting current into an electrically conductive object such as the human body using an MRI scanner. MREIT measures the induced magnetic flux density which appears in the phase part of the acquired MR image data. Recently, the injected current nonlinear encoding (ICNE) method in MREIT extended the duration of the current injection until the end of a reading gradient to maximize the signal intensity of the magnetic flux density. In this paper, we investigate the signal-to-noise ratio (SNR) of the magnetic flux density measured by the ICNE method in the presence of a zero-mean Gaussian random noise in measured k-space MR data. Based on the analysis of the noise standard deviation s(B(z)) of the magnetic flux density, we determine an optimal combination between the current injection pulse width T(c) and data acquisition time T(s) which minimize the noise level of the measured magnetic flux density for a given echo time T(E). On one hand, theoretically, the proposed ICNE MR pulse sequence using the optimal data acquisition time T(s)* reduces the noise level of the measured magnetic flux density by about 42.3% compared with the optimal data acquisition time of the conventional MREIT pulse sequence. On the other hand, practically, the prolonged T(s)* may result in undesirable artifacts including blurring, chemical shift and phase error along the phase encoding direction. We observe that the noise level is a function of the data acquisition time T(s) and the rate of change in the noise level is slow near T(s)=T(s)*. Numerical phantom experiments show that a compromised T(s) between the ordinary data acquisition time and the optimal T(s)* reduces a relatively large amount of undesirable artifacts and almost maintains the optimized noise level of the measured magnetic flux density.