真实稳态进动快速成像T_2加权序列在肝脏的应用价值

目的　评价true FISP(真实稳态进动快速成像 )T2 WI序列在肝脏病变中的应用。方法45 2例临床拟诊肝胆疾患病人行横断面、冠状面或 (和 )矢状面true FISPT2 WI,对其中临床证实的 6 8例 (16 3个病灶 )进行评价 ,包括肝脏局灶病变的检出率、对比信噪比、肝内静脉的显示、周围脏器的显示及伪影等 ,并与TSE(快速自旋回波 )T2 WI进行比较。结果　对肝海绵状血管瘤和肝囊肿的检出率 ,true FISP与TSE相近 ;true FISP对肝脏恶性结节的检出率略低于TSE(P >0 0 5 ) ;true FISP的病灶对比信噪比低于TSE(P <0 0 5 ) ;对肝内静脉的显示 ,true FISP明显优于TSE(P <0 0 1) ;对解剖结构的显示 ,true FISP优于TSE(P <0 0 1)。结论　true FISPT2 WI用于肝胆病变的优点 :(1)有较高的空间分辨率和信噪比 ;(2 )肝内静脉显示清晰 ;(3)解剖结构的显示优于常规TSE序列。缺点 :(1)T2 对比较差 ,易遗漏肝脏实性结节 ;(2 )近膈面及胆囊区易出现磁敏感伪影 ,可能造成误诊或漏诊     

利用自旋回波平面成像T_2加权序列提高肝脏实性病变的检出率

目的　评价自旋回波平面成像 (SE EPI)T2 W序列对肝脏实性病变的检出能力。方法74例病人 (2 0 2个病灶 )接受肝脏 3种SE EPIT2 W序列磁共振扫描 ,评价其图像信噪比 (SNR)、肝脾对比噪声比 (L SCNR)、病灶对比噪声比 (CNR)及病变检出率 ,并与真实稳态进动快速成像 (true FISP)、快速自旋回波 (TSE)及半傅立叶采集单次激发快速自旋回波 (HASTE)等屏气T2 W序列相比较。结果SE EPI的SNR高于TSE (P <0 0 5 ) ,与true FISP相近 (P >0 0 5 ) ,但低于HASTE(P <0 0 1)。SE EPI序列的L SCNR及实性病变的CNR均显著高于true FISP、HASTE及TSE(P <0 0 1)。对于囊性病变 ,各序列间的检出率无明显差异 (P >0 0 5 )。各序列均检出所有直径大于 5cm的实性病变。直径 2～ 5cm的实性病变 ,SE EPI序列的检出率略高于true FISP、HASTE及TSE ,但无显著性差异 (P >0 0 5 )。直径小于 2cm的实性病灶 ,SE EPI序列的检出率 (93 9% )明显高于true FISP(5 7 6 % )、HASTE(71 2 % )及TSE(6 8 2 % ) (P <0 0 1)。结论　与其他屏气T2 W序列相比 ,SE EPIT2 WI有较高的病灶对比 ,能提高肝脏实性病变的检出率     

磁共振True FISP序列在肝脏疾病影像学评价中的应用

MR T2WI对肝脏局灶性病变的检出和定性诊断起着非常重要的作用[1-2],随着近年来MRI技术的进步,1次屏气即可完成全肝T2WI的图像采集[1-3].真实稳态进动快速成像(true fast imaging with steady precession,True FISP)序列在肝脏疾病的临床诊断及治疗中发挥着越来越重要的作用.True FISP序列成像速度极快,单层采集时间短,对呼吸运动不敏感,即使不能自主屏气的病人也能获得较清晰图像.SIEMENS公司称之为真实稳态进动快速成像True FISP(true fast imaging with steady precession)序列;GE公司称之为快速平衡稳态进动成像FIESTA(fast imaging employing steady state acquisition)序列;PHLIPS公司称之为B FFE(balance fast field echo)技术[4-5].现就MR True FISP的成像原理、成像方法及其在肝脏疾病的诊断和治疗中的研究现况及发展前景予以综述.     

磁共振3D-SPACE、3D-Ture FISP序列对踝关节韧带成像的比较研究

目的 比较三维可变反转角快速自旋回波(3D-SPACE)序列、三维真稳态进动快速成像序列(3D-Ture FISP)在踝关节韧带的成像质量.方法 20例健康志愿者和15例患者在1.5T磁共振上行3D-SPACE、3D-True FISP序列成像.在正常组中比较韧带影像质量、信噪比(SNR)、对比信噪比(CNR);在患者组中比较对损伤韧带的显示能力.结果 3D-SPACE序列比3D-True FISP序列的韧带SNR、CNR更高.3D-SPACE序列比3D-True FISP序列有更好地显示踝关节正常韧带及损伤韧带的能力,但在发现损伤韧带的数量上未见明显差异.结论 相比3D-True FISP序列,3D-SPACE序列能更好地显示踝关节正常和损伤韧带的解剖结构.     

磁共振3D-SPACE、3D-TrueFISP、2D-FSE-PD序列膝关节软骨成像的比较研究

目的：比较三维可变反转角快速自旋回波序列(3D-SPACE)、三维真稳态进动快速成像序列(3D-Ture FISP)以及二维快速自旋回波质子像序列(2D-FSE-PD)膝关节软骨的成像质量。方法40例健康志愿者和20例患者在1.5T MR 上行3D-SPACE、3D-True FISP 和2D-FSE-PD 序列成像。比较各序列软骨信噪比(SNR)、对比信噪比(CNR)、损伤显示能力。结果3种序列中,3D-SPACE 序列的软骨信噪比、滑液与软骨的对比信噪比最高。3D-SPACE 比3D-True FISP 能更好地显示膝关节软骨的Ⅰ、Ⅱ级损伤,在软骨的Ⅲ、Ⅳ级损伤中,3D-SPACE 与3D-True FISP 无明显差异,对于各级软骨损伤,3D 序列均好于2D 序列。结论相比3D-True FISP、2D-FSE-PD 序列,3D-SPACE 序列能更好地显示膝关节软骨结构和损伤。     

3.0 T MR SPACE序列与传统关节软骨三维成像序列比较研究

目的通过比较软骨信号噪声比(SNR)和对比噪声比(CNR),分析临床三维MR序列显示软骨的效果。资料与方法选取25名健康志愿者进行软骨MRI(年龄21～29岁,平均24岁),使用Siemens Magnetom Trio Tim3.0T超导型磁共振成像仪和膝关节专用线圈。应用:(1)脂肪抑制快速小角度激发(fast low angle shot,FLASH)序列;(2)FLASH序列+水激发(water-excitation,WE);(3)双回波稳态进动(dualecho steady state,DESS)序列;(4)真稳态进动快速成像(true fast imaging with steady-state precession,True-FISP)序列;(5)三维质子加权快速自旋回波(sampling perfection with application-optimized contrast using different flip angle evolutions,SPACE)序列;(6)二维脂肪抑制快速自旋回波质子密度加权成像(fat-suppressed-2D-fast spine cho-pro...     

3T MRI关节软骨成像序列的比较和探讨

目的:通过分析比较各3T MRI关节软骨成像序列对关节软骨显示的能力与限度,探讨理想的3T MRI关节软骨成像序列组合.方法:收集因临床需要而检查的36例膝关节MRI,成像设备为SIEMENS3.0T VERIO高场MRI,关节软骨成像序列包括:自旋回波序列(SE),二维脂肪抑制质子密度加权像(FS-PD),二维短T1翻转恢复序列(2D-STIR),三维双重回波稳态(3D-DESS),三维平衡稳态序列(3D-True FISP)和关节软骨生理成像T2mapping.在股骨髁间凹中央层面上分别测量股骨髁软骨信号噪声比(SNR)、软骨-关节液对比度噪声比(CNR),比较各序列对于软骨和周围关节液的显示能力.结果:3D-DESS,3D-True FISP和FS-PD序列软骨SNR最高(P<0.001);同时3D-DESS,3D-True FISP和FS-PD序列软骨-关节液对比度噪声比(CNR)高于2D-STIR,但软骨-关节液边界对比以3D-DESS序列最好,能显示关节软骨水含量变化的只有T2mapping成像.结论:二维脂肪抑制质子密度加权像(FS-PD)加上三维双重回波稳态(3D-DESS)是进行软骨MRI的理想序列组合,T2mapping可以显示关节软骨含水量的变化.     

不同MR扫描序列在SPIO增强大鼠肝癌模型的对比研究

目的：比较多种扫描序列超顺磁氧化铁（SPIO）增强扫描对显示大鼠肝癌病灶的能力，找出最佳扫描方案。TSE T2WI、SE双回波的T2WI＋PDWI、GRE T1WI、T2^＊WI，分析增强前后大鼠肝癌病灶的强化特征，并进行病理学检查对照分析。结果：注射SPIO对比剂后，所有扫描序列均显示肝脏的信号强度较增强前有不同程度的下降，肝癌病灶CNR均分别高于平扫。增强后GRE T2^＊WI中病灶的CNR明显高于其它序列，但增强后TSE T2WI和常规SE T2WI在显示病变的SNR、CNR方面没有显著性差异。结论：SPIO增强后检测肝癌病灶的各种序列中，以GRE T2^*WI最为敏感，其次是双回波的T2WI＋PDWI序列。     

MR 快速扫描技术在胎儿先天性膈疝中的应用

目的：探讨 MR 快速扫描技术在胎儿先天性膈疝(CDH)中的影像诊断价值。方法对12例孕20周以上超声诊断或怀疑 CDH 的胎儿行 MR 检查。采用快速扫描序列：半傅里叶采集单次激发快速自旋回波序列(HASTE)、真稳态进动快速成像序列(True FISP)、超快速 FLASH(Turbo FLASH)T1 WI 序列。重点对胎儿的头颅和躯干行横断位、冠状位、矢状位扫描,将产前 MRI表现与新生儿手术病例或引产后尸体解剖结果对照分析。结果12例胎儿 CDH 中9例为左侧膈疝,2例为右侧膈疝,1例食管裂孔疝;其中2例合并其他先天性畸形。MRI 主要表现：HASTE 及 True FISP 序列可见部分或大量肠管及胎胃跨过膈肌疝入胸腔,疝入的胎胃为高信号,肠管呈散在的高信号,并可见肠型,仅肺尖处见肺组织,心脏向对侧移位;Turbo FLASH T1 WI 序列获得 T1图像,该序列肠管中胎粪为特征性高信号,可清晰显示结肠和部分小肠轮廓。全部病例的 MRI 产前诊断结果与手术(10例)或尸检(2例)结果一致。结论MR 快速扫描技术能清晰显示胎儿 CDH,多序列扫描图像清晰、全方位显示疝入胸腔的组织结构及周围的解剖关系,具有一定的临床诊断价值。     

磁共振稳态采集快速成像序列评价膝关节透明软骨实验研究

目的 探讨磁共振稳态采集快速成像序列(FIESTA)在软骨成像中的应用价值.方法 以新鲜的正常巴马香猪后膝关节为研究对象,进行扫描角度相同的不同序列MR扫描,扫描序列包括T1加权自旋回波序列(SET1WI)、T2加权快速自旋回波序列(FSET2WI),附加脂肪抑制的三维快速扰相梯度回波序列(FS3DSPGR)及稳态采集快速成像序列(FIESTA).在股骨髁间凹中央层面分别测量股骨远端软骨、股骨干骺端骨髓、半月板、韧带、关节腔滑液和背景噪声信号强度(SI),计算软骨信噪比(SNR)和软骨-骨髓、软骨-滑液、软骨-半月板、软骨-韧带对比噪声比(CNR),通过对SNR以及CNR的分析比较,评价各个序列对软骨显示的效果.结果 FIESTA序列在关节软骨显示中,无论SNR,还是CNR均显著优于常 规SET1WI、FSET2WI序列(P＜0.05).FIESTA序列中软骨与滑液、软骨与半月板、软骨与韧带间CNR较高(P＜0.05).结论 FIESTA序列能有效地显示关节透明软骨,在关节软骨形态学的评价中具有潜在的应用价值.     

Fast breath-hold T2-weighted MR imaging reduces interobserver variability in the diagnosis of adenomyosis

OBJECTIVE: We compared two rapid MR imaging T2-weighted pulse sequences with high-resolution turbo spin-echo for the diagnosis of adenomyosis, and we evaluated interobserver variability. SUBJECTS AND METHODS: Fifty-six consecutive patients referred for hysterectomy prospectively underwent MR imaging. Two fast pulse sequences using a breath-hold technique-true fast imaging with steady-state free precession (FISP) and turbo inversion recovery-and turbo spin-echo T2-weighted images of the pelvis were obtained in each patient. The images were analyzed in a blinded manner and independently by three reviewers with different levels of experience for the accuracy of adenomyosis diagnosis, image quality, anatomic visualization, and image artifacts. The accuracy for the diagnosis of adenomyosis on turbo spin-echo T2-weighted imaging combined with one or two fast pulse sequences was evaluated for each reviewer. RESULTS: Twenty-four patients (42.9%) had a histologic diagnosis of adenomyosis. The accuracy for the diagnosis of adenomyosis for reviewers 1, 2, and 3 using turbo spin-echo T2-weighted, true FISP, and turbo inversion recovery sequences was 83.9%, 67.8%, 75%; 83.9%, 67.8, 78.5%; and 87.5%, 73.2%, and 75%, respectively. A difference in the accuracy rate was found among the observers for the three sequences (p < 0.001). Whatever the pulse sequence, the accuracy rate was higher for the reviewer with more experience in gynecologic imaging. The combination of turbo spin-echo T2-weighted imaging with at least one rapid sequence increased the accuracy of observers with little experience in gynecology. With turbo inversion recovery sequences, the image quality score was low for the three reviewers compared with turbo spin-echo T2-weighted and true FISP sequences. The combination of turbo spin-echo T2-weighted and true FISP sequences gave the highest image quality scores. CONCLUSION: Breath-hold T2-weighted sequences optimize the accuracy of MR imaging for the diagnosis of adenomyosis and reduce interobserver variability.     

T2-Weighted fast MR imaging with true FISP versus HASTE: comparative efficacy in the evaluation of normal fetal brain maturation

OBJECTIVE: This study compares the relative efficacy of two fast T2-weighted MR imaging techniques-fast imaging with steady-state free precession (true FISP) and half-Fourier acquisition single-shot turbo spin-echo (HASTE)-in the evaluation of the normal fetal brain maturation during the second and third trimesters of gestation. SUBJECTS AND METHODS: The brain maturation of 10 normal nonsedated fetuses (5 during the second trimester and 6 during the third trimester of gestation [1 fetus underwent 2 examinations]) was examined by both techniques using a Vision+ 1.5-T MR system. We specifically looked for developing events, including white matter myelination, neuronal migration, and cortical sulcation. Image quality was graded according to the presence or absence of undesirable blurring. RESULTS: The specific absorption rate was lower for true FISP than for HASTE by a factor of 3 at equivalent imaging conditions. HASTE and true FISP provide comparable image quality in the second trimester when myelination of the cerebrum has not begun. Neuronal migration could be recognized as hypodense bands on both sequences during the second trimester. Myelination beginning at the third trimester was better delineated with true FISP than with HASTE because of point spread function-related blurring effects inherent in HASTE that hampered visualization of short-T2 structures. Cortical sulcation was well delineated by both sequences. CONCLUSION: With relatively superior image quality and significantly lower radiofrequency absorption than HASTE, true FISP is a safer and more effective alternative in the prenatal evaluation of normal fetal brain.     

Comparison of MR imaging sequences for liver and head and neck interventions: is there a single optimal sequence for all purposes?

RATIONALE AND OBJECTIVES: To compare the appropriate pulse sequences for interventional device guidance during magnetic resonance (MR) imaging at 0.2 T and to evaluate the dependence of sequence selection on the anatomic region of the procedure. MATERIALS AND METHODS: Using a C-arm 0.2 T system, four interventional MR sequences were applied in 23 liver cases and during MR-guided neck interventions in 13 patients. The imaging protocol consisted of: multislice turbo spin echo (TSE) T2w, sequential-slice fast imaging with steady precession (FISP), a time-reversed version of FISP (PSIF), and FISP with balanced gradients in all spatial directions (True-FISP) sequences. Vessel conspicuity was rated and contrast-to-noise ratio (CNR) was calculated for each sequence and a differential receiver operating characteristic was performed. RESULTS: Liver findings were detected in 96% using the TSE sequence. PSIF, FISP, and True-FISP imaging showed lesions in 91%, 61%, and 65%, respectively. The TSE sequence offered the best CNR, followed by PSIF imaging. Differential receiver operating characteristic analysis also rated TSE and PSIF to be the superior sequences. Lesions in the head and neck were detected in all cases by TSE and FISP, in 92% using True-FISP, and in 84% using PSIF. True-FISP offered the best CNR, followed by TSE imaging. Vessels appeared bright on FISP and True-FISP imaging and dark on the other sequences. CONCLUSION: In interventional MR imaging, no single sequence fits all purposes. Image guidance for interventional MR during liver procedures is best achieved by PSIF or TSE, whereas biopsies in the head and neck are best performed using FISP or True-FISP sequences.     

Comparison of echo planar imaging, gradient echo and fast spin echo MR scans of knee menisci.

In order to reduce the acquisition time, we compared a three-dimensional multi-shot echo-planar imaging (EPI) sequence with fat-suppression with two widely used sequences, the fat-suppressed gradient echo (GRE) and the proton-density weighted turbo spin-echo (FSE) in imaging the menisci of the knee. Sixty patients with various indications were studied prospectively with MRI. The menisci were imaged in the sagittal plane with all three sequences using a 1T MR scanner with 15mT/m gradients. The signal-to-noise ratio (SNR) of bone (b), cartilage (c), and meniscus (m) as well as contrast-to-noise ratio (CNR) and relative contrast (ReCon) between menisci and cartilage and between bone and cartilage were measured. A qualitative analysis was performed on grading of meniscal pathology (0-IV). The imaging accuracy of meniscal pathology was assessed compared to arthroscopy in 13 patients. The EPI provided the highest SNR in cartilage and meniscus (p<0.001), the highest CNR and the highest ReCon between bone and cartilage (p< or =0.001). MR grading of meniscal abnormalities showed overestimation compared to GRE and FSE. The EPI sequence could not be included in the routine protocol in imaging the menisci since the overestimation of meniscal abnormalities could lead to unnecessary arthroscopy.     

Fetal magnetic resonance imaging: indications,technique, anatomical considerations and a review of fetal abnormalities

Fetal MR imaging often poses a diagnostic challenge for the radiologist. Both fetal anatomy and pathology differ decidedly from pediatric and adult MR imaging. While ultrasound remains the method of choice for screening examinations of the fetus, MR imaging is playing an increasingly important role in the detection and classification of malformations not diagnosable by ultrasonography alone. Recently, advances in fast single-shot MR sequences have allowed high-resolution, high-quality imaging of the moving fetus. Preferable sequences to be applied are a true fast imaging steady precession (true-FISP) or a half-Fourier acquired single-shot turbo spin-echo (HASTE) sequence. Premedication is generally no longer required. In all fetal MR imaging, every aspect of fetal anatomy has to be scrutinized. Subsequently, any abnormalities need to be described and classified. A close collaboration with the referring obstetrician is of paramount importance.     

Familial form of cerebral cavernous malformations: evaluation of gradient-spin-echo (GRASE) imaging in lesion detection and characterization at 1.5 T

The purpose of this study was to evaluate the turbo gradient-spin-echo sequence (GRASE) in the MR assessment of the familial form of cerebral cavernous malformations (CCM). Twenty-one patients (15 male, six female) aged from 21 to 68 years (mean = 42.2 years) were prospectively examined with cerebral MR imaging, including T2-weighted turbo gradient-spin-echo (TGSE), turbo spin-echo (TSE) and gradient-echo (GRE) sequences. All sequences were performed in the same plane, the same matrix and the same field of view and were analyzed for signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), susceptibility effects, number of CCM, size of CCM and signal of CCM. It was found that SNR and CNR in the TGSE sequence were significantly inferior to those in both TSE and GRE sequences. TGSE and TSE sequences were significantly less prone to susceptibility effects than the GRE sequence. The sensitivity of TGSE and TSE sequences in detecting CCM was significantly lower than that of the GRE sequence. TGSE and TSE sequences provided comparable information about CCM size and signal. It was concluded that GRASE imaging was less sensitive than the GRE sequence in the detection of CCM and provided information similar to that yielded by the TSE sequence in the characterization of lesions, but with a higher number of artifacts. GRASE imaging cannot therefore replace TSE or GRE sequences in the MR evaluation of the familial form of CCM.     

Uterine peristalsis: comparison of transvaginal ultrasound and two different sequences of cine MR imaging

PURPOSE: To compare uterine peristalsis as seen on two different magnetic resonance (MR) imaging sequences and transvaginal ultrasound (TVUS), so as to better determine the best method for evaluating uterine peristalsis. MATERIALS AND METHODS: Eleven women in the periovulatory phase of the menstrual cycle underwent TVUS and cine MR imaging within a time period of three hours. Findings on cine MR images obtained with a serial 60 half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence and a 300 true fast imaging with steady-state precession (FISP) sequence were compared with TVUS. RESULTS: The image quality of the HASTE technique was the best among the three methods, followed by TVUS, and then true FISP technique (P < 0.001). Uterine peristalsis was detected in 100% of subjects using HASTE, 82% with True FISP, and 100% with TVUS. With HASTE technique, true FISP, and TVUS, respectively, endometrial stripping movement was identified in 100%, 82%, and 100%; direction was identified in 100%, 45% (P = 0.014), and 73%; and wave conduction toward the outer myometrium was identified in 55%, 9% (P = 0.025), and 0% (P = 0.014). CONCLUSION: Cine MR imaging by HASTE technique with a time resolution of two seconds best delineated uterine peristalsis compared to that by true FISP technique or with TVUS.     

Phase-sensitive inversion-recovery MR imaging in the detection of myocardial infarction

PURPOSE: To prospectively determine if phase-sensitive inversion-recovery (IR) magnetic resonance (MR) imaging eliminates the need to find the precise inversion time (TI) to null the signal of normal myocardium to achieve high contrast between infarcted and normal myocardium. MATERIALS AND METHODS: Informed consent was obtained from each patient for this prospective MR imaging research study, which was approved by the institutional review board. Twenty patients (16 men; four women; mean age, 56 years +/- 12.3) who experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 1.5-T MR system 10 minutes after administration of 0.1 mmol per kilogram of body weight gadobenate dimeglumine. To determine the optimal TI, a TI scout sequence was used. A segmented two-dimensional IR turbo fast low-angle shot (FLASH) sequence and a segmented two-dimensional IR true fast imaging with steady-state precession (FISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec (TI values were varied in 100-msec steps) and at optimal TI (mean value, 330 msec). Contrast-to-noise ratios (CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined. Magnitude-reconstructed IR turbo FLASH images were compared with magnitude-reconstructed and phase-sensitive IR true FISP images. Two-tailed unpaired sample Student t test was used to compare CNRs, and two-tailed paired-sample Student t test was used to compare area of infarction. RESULTS: Mean CNR of images acquired with IR turbo FLASH and IR true FISP (phase-sensitive and magnitude-reconstructed images) at optimal TI (mean value, 330 msec) were 6.6, 6.2, and 6.1, respectively. For a TI of 200 msec, CNR values were -4.3, -4.0, and 7.2, respectively; for TI of 600 msec, CNR values were 3.1, 3.3, and 4.3, respectively. Area of infarcted myocardium was underestimated on magnitude-reconstruction images (P = .002-.03) for short TI values (ie, 200 msec) for both sequences and for a TI of 300 msec for IR true FISP but not on phase-sensitive reconstructed IR true FISP images when compared with IR turbo FLASH images obtained at optimal TI. CONCLUSION: Phase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.