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     

化学位移成像和反转恢复快速自旋回波成像在肝脏的应用价值

目的 评价化学位移成像和反转恢复快速自旋回波对肝脏病变的检出能力。材料与方法 45例肝脏病变患者在进行常规SE T1WI和半傅立叶采集单次激发快速自旋回波（half-fFourier acquistition single-shot turbo spin-echo,HASTE)T2WI的同时,加用化学位移成像T1WI和反转恢复HASTE（IR－HASTE）T2WI。比较图像的信噪比（SNR）、肝脾对比噪声比（L－S CNR）、病灶对比噪声比（CNR）及病灶检出率。结果 化学位移成像T1WI的SNR、L－S CNR及SE T1WI均无显著性差异（P＞0．05）,但却能检出SET1WI无法显示的局灶性脂肪浸润和脂肪肝。IR－HASTE的SNR与HASTE相近（P＞0．05）,前者的L－S CNR及实性病灶的CNR均显著高于后者（P＜0．05）,特别是对较小的实质性病灶。结论 化学位移成像T1WI能提高肝脂肪成分的检出率,IR－HASTE的SNR与HASTE相近（P＞0．05）,前者的L－S CNR及实性病灶的CNR均显著高于后者（P＜0．05）,特别是对较小的实质性病灶。结论 化学位移成像T1WI能提高肝脂肪成分的检出率,IR－HASTE能提高肝实性病变的检出率,两种成像方法可作为常规肝脏检查方法的有力补充。     

HASTE及反转恢复HASTE序列在肝脏局灶病变定性诊断中的作用

目的　评价半傅立叶采集单次激发快速自旋回波 (HASTE)T2 加权 (T2 WI)序列和反转恢复HASTE(IR -HASTE)在肝脏局灶病变定性诊断中的作用。方法　对 5 4例 (10 6个病灶 )肝脏局灶病变病人行快速自旋回波 (TSE)T2 WI、HASTET2 WI以及回波平面成像 (EPI)T2 WI。评价各序列的病灶 -肝脏对比噪声比 (CNR)、病变的定性能力 (判断为囊性或实性 )。对出现病变的层面行一系列不同反转时间 (TI)的IR -HASTE ,观察病灶的最佳抑制TI值 (BS -TI)。结果　HASTET2 WI的病灶定性准确率为 97.2 % ,略高于TSET2 WI(91.5 % ) (Ρ >0 .0 5 ) ,明显高于EPIT2 WI(72 .6% ) (Ρ <0 .0 5 )。肝囊肿、海绵状血管瘤、肝细胞癌及转移瘤的BS -TI分别为(2 0 0 0± 2 5 0 )ms(14 0 0～ 2 3 0 0ms)、(90 0± 15 0 )ms(70 0～ 12 0 0ms)、(60 0± 10 0 )ms(4 0 0～ 80 0ms)及 (75 0± 10 0 )ms(60 0～ 10 0 0ms) ,肝囊肿与其他病灶无重叠 ,5个血管瘤和 9个实性病变的BS -TI在对方的BS -TI值范围内。结论　HASTET2 WI与IR -HASTE相结合能准确区分大多数肝囊肿、海绵状血管瘤及肝实性病变 ,可大大减少不必要的CT或MRI增强扫描     

真实稳态进动快速成像T2^＊加权序列在胎儿MRI中的应用

目的:探讨真实稳态进动快速成像T2*加权序列在胎儿MRI中的临床应用价值.材料和方法:6例中、晚期孕程的孕妇行真实稳态进动快速成像(true FISP)T2*加权序列扫描,评价图像质量、模糊程度、正常胎儿器官显示、胎儿和母体异常的显示以及胎儿信噪比(SNR)及胎儿-孕妇腰椎椎体对比噪声比(F-L CNR)等,并与TSE序列T2WI进行比较.结果:与TSE序列T2WI相比,true FISP序列T2*WI可清楚显示胎头、胎儿肢体、胎儿脊柱、胎儿的脏器解剖结构以及母体子宫、胎盘、脐带等附属结构,胎儿和母体异常显示也较清晰,并能清晰显示灰、白质分界、脑回、脑髓鞘等结构.true FISP序列获得的图像其SNR以及F-L CNR均优于TSE序列.结论:真实稳态进动快速成像T2*加权序列能够清晰显示胎儿及母体的解剖结构,获得的图像具有较高的T2对比,可作为胎儿MR成像的常用序列.     

不同场强和序列的超顺磁性氧化铁磁共振增强扫描在肝癌检出中的比较

比较不同的场强和扫描序列对超顺磁性氧化铁增强前后肝癌检出的影响。材料和方法：46例104个肝癌病灶在1．0T或1．5T场强下行磁共振T1加权及四个T2加权的平扫及SPIO增强扫描，比较不同场强下各扫描序列的信噪比、对比噪声比以及肝癌病灶的检出率。结果：SPIO增强扫描后，所有序列的信噪比均下降，但对比噪声比和肝癌检出率均增加。1．0T场强下，最佳的SPIO增强序列为SE和TSE的T2加权；1．5T场强下最佳的SPIO增强序列为HASTE和FS－HASTE的T2加权。结论：不同场强下最合适SPIO增强扫描的都是信噪比较好的、中等权重的T2加权序列，1．5T更适合屏气的快速序列，1．0T更适合非屏气的SE序列。     

八次激发SE-EPI在肝脏MRI的应用

目的；比较八次激发SE－EPI与呼吸门控FSE及SSFSE T2WI在肝脏的应用。方法：对14例志愿者及21例肝病患者行上腹部呼吸门控FSE及SSFSE和屏气八次激发SE－EPI扫描。所有T2WI序列均运用脂肪抑制技术。定量分析肝脏、病灶的信噪比及肝脏－病灶的对比噪声比，评价各序列的图像质量及伪影。结果：八次激发SE－EPI与SSFSE及FSE在肝脏及病灶信噪比，肝脏－病灶对比度噪声比和图像质量方面无明显差异（P＞0．05）。其磁敏感伪影较FSE及SSFSE重（P＜0．01），SE－EPI化学位移伪影与SSFSE及FSE相比无明显差别（P＞0．05）。SE－EPI及FSE运动伪影明显比SSFSE重（P＜0．01），但SE－EPI运动伪影与FSE相比无明显差别（P＞0．05）。SE－EPI与FSE及SSFSE的图像质量无明显差别（P＞0．05）。结论：八次激发SE－EPI能够在较短时间里提供较高质量的上腹部T2WI。被检查者在扫描时可自由平静呼吸或屏气，可作为肝脏T2WI的补充序列。     

FLASH序列T1加权成像在脊柱转移性肿瘤的应用价值

目的　评价FLASH序列T1 WI对脊柱转移性肿瘤的检出能力及其限度。方法　 5 9例病人 (2 79个病灶 )接受脊柱FLASH-T1 WI序列磁共振扫描 ,评价其图像信噪比 (SNR) ,脊椎—肌肉对比噪声比 (S -MCNR) ,病灶对比噪声比 (CNR)及病变检出率 ,并与SE -T1 WI ,TSE -T2 WI作比较。结果　FLASH -T1 WI的SNR低于SE -T1 WI、TSE -T2 WI ,两者Ρ <0 .0 0 1;其病灶CNR明显高于后两者 ,两者Ρ <0 .0 0 1;其S -MCNR高于SE -T1 WI ,Ρ <0 .0 0 1,近似于TSE -T2 WI,Ρ值 >0 .5。FLASH -T1 WI病变检出率 (98.6% )略高于SE -T1 WI(95 .3 % ) ,0 .0 2 5 <Ρ <0 .0 5 ;明显高于TSE -T2 WI(63 .4% ) ,Ρ <0 .0 0 5。椎体内局灶性黄骨髓 ,良性椎体压缩性骨折 ,脊柱结核在FLASH -T1 WI像上均表现为高信号。结论　与SE -T1 WI、TSE -T2 WI作比较 ,FLASH -T1 WI对脊柱转移性肿瘤有较高的病灶对比 ,能提高其检出率。其具有较高的敏感性 ,但特异性差。     

菲立磁增强MRI在肝脏局灶性病变诊断中的价值

目的 评价菲立磁增强MRI在肝脏实性占位性病变诊断中的应用价值。材料与方法 对21例怀疑有肝脏局灶性占位病变患者行MR平行及菲立磁增强MRI检查。扫描序列包括频率选择脂肪抑制及非脂肪抑制ASTE T2WI、True FISP T2WI、频率选择脂肪抑制FLASH T1WI。比较增强前后T2WI及T2WI病灶及肝脏的信噪比（SNR）及对比噪声比（CNR）;观察增强前后病灶数量及形态;结合MR平扫及增强MRI表现进行定性诊断。结果 菲立磁增强T2WI及T2WI肝脏信号强度较平扫明显下降,病灶与肝脏的CNR较平扫明显提高,差异具有统计学意义。结论 菲立磁增强T2WI及T2WI可明显提高肝脏实性占位性病灶的检出率。菲立磁增强T1WI在脏局灶性病变的定性诊断中具有潜在价值,有待于进一步开发与研究。     

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。     

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.     

Fast breath-hold T2-weighted MRI of the kidney by means of half-Fourier single-shot turbo spin echo: comparison with high resolution turbo spin echo sequence

PURPOSE: The value of the fast half-Fourier single-shot turbo spin echo (HASTE) sequence in T2-weighted MRI of the kidney was evaluated as a substitute for the conventional turbo spin echo (TSE) sequence. METHOD: Forty-five patients with suspected abnormalities of the kidney underwent MRI with a 1.5 T system. Breath-hold HASTE and respiratory-triggered TSE sequences were performed. Qualitative and quantitative analyses were performed for comparison of these sequences. RESULTS: The signal-to-noise ratio (SNR) with HASTE was higher than that with TSE. The lesion-to-kidney contrast-to-noise ratio for solid masses with HASTE was almost equal to that with TSE. For cystic masses, the CNR with HASTE was significantly higher than that with TSE (p < 0.05). Respiratory and chemical shift artifacts were significantly smaller on HASTE than on TSE (p < 0.01). However, the blurring artifact was higher on HASTE than on TSE (p = 0.01). CONCLUSION: The HASTE sequence generates high contrast images and is free of motion and chemical shift artifacts, with much better time efficacy. The sequence provides comparable diagnostic information to TSE sequences.     

Breath-hold MR imaging of focal liver lesions: comparison of fast and ultrafast techniques

The performance of breath-hold MR imaging using two T2-weighted hybrid sequences (TSE, TGSE), two T2-weighted single-shot sequences (HASTE, EPI-SE), and one T1-weighted gradientecho sequence (FLASH) was compared with a standard conventional T2-weighted SE sequence in 20 patients with focal liver lesions. Liver signal-to-noise ratio was highest spleen-liver contrast-to-noise ratio (54.3 ± 8.3) and thee HASTE (41.1 ± 12.5) sequence, whereas the highest spleen-liver contrast-noise-ratio was obtained by the TSE sequence (38.9 ± 20.7). Lesion-liver CNR was highest with the TSE sequence (63.9 ± 21.4). With both TSE and HASTE significantly (p < 0.01) more lesions were detected as compared with SE and EPE-SE sequences. Our results indicate that breath-hold TSE and HASTE sequences will eventually replace conventional T2-weighted SE techniques due to their insensitivity to motion artifacts, superior lesion detectability and inherently short acquisitions times.Correspondence to: J. Gaa     

Comparison of multishot turbo spin echo and HASTE sequences for T2-weighted MRI of liver lesions

The purpose of this study was to compare the relative usefulness of multishot turbo spin echo (TSE) and half-Fourier single-shot turbo spin echo (HASTE) for determination of optimal breath-hold fast T2-weighted technique in terms of lesion detection, lesion-to-liver contrast-to-noise ratio (CNR), and image quality. The images of TSE with and without fat suppression (FS) and of HASTE with and without FS were retrospectively reviewed for 49 patients with 128 lesions. Without FS, TSE and HASTE images allowed depiction of focal hepatic masses (112 of 128, sensitivity = 87.5%) at the same rate. TSE with FS depicted more focal lesions (115 of 128, 89.8%) than HASTE with FS (109 of 128, 85.2%), but the difference was not statistically significant (P > .05). The CNR of each lesion on HASTE sequences was greater (P < .01) than that on TSE sequences. The CNR of hemangioma was distinct from that of solid tumors and cystic lesions in all sequences, and the range of CNR in each group of pathologies overlapped less and were well separated in the HASTE sequences. HASTE sequences produced better image quality with fewer artifacts (P < .0001). The results of this study suggest that HASTE sequences allow differentiation between solid tumors, hemangiomas, and cystic lesions in terms of CNR, producing fewer image artifacts, with acceptable sensitivity in lesion detection.     

Hepatic T2-weighted MRI: A prospective comparison of sequences,including breath-hold,half-Fourier turbo spin echo (HASTE)

The purpose of this study was to quantitatively compare the hepatic contrast characteristics of conventional spin-echo (CSE) and fast spin-echo (FSE) sequences with breath-hold T2-weighted images acquired with half-Fourier turbo spin echo (HASTE). Forty-five patients were examined with a phased-array surface coil. Nineteen patients had focal hepatic lesions, including eight malignant tumors, 10 cavernous hemangiomas, and one hepatic adenoma. Twenty-six patients had no focal hepatic lesions. T2-weighted images with comparable TE were acquired with CSE, FSE, and HASTE pulse sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for liver, spleen, and lesions were measured. FSE demonstrated significantly better quantitative performance than CSE for liver-spleen CNR (P = .0084). No statistically significant difference was demonstrated between FSE and CSE for liver or spleen SNR. FSE demonstrated clear scan time and resolution advantages over CSE. HASTE performed significantly poorer than CSE and FSE for liver-spleen CNR (P < .0001), liver SNR (P = .0002 for CSE and P < .0001 for FSE), and spleen SNR (P < .0001). Optimized FSE images with a short echo train length performed comparably to CSE images of equivalent TE. Liver-lesion CNR was suppressed on HASTE images, suggesting that long echo train length FSE sequences could diminish solid lesion detection compared to CSE and short echo train length FSE.     

Image quality and focal lesion detection on T2-weighted MR imaging of the liver: comparison of two high-resolution free-breathing imaging techniques with two breath-hold imaging techniques

PURPOSE: To evaluate image quality and accuracy for the detection of focal hepatic lesions depicted on T2-weighted images obtained with two high-resolution free-breathing techniques (navigator-triggered turbo spin-echo [TSE] and respiratory-triggered TSE) and two standard-resolution breath-hold techniques (breath-hold TSE with restore pulse and half-Fourier acquisition single-shot TSE [HASTE]). MATERIALS AND METHODS: Our institutional review board approved this study, and written informed consent was obtained from all patients. Two readers independently reviewed 200 T2-weighted imaging sets obtained with four sequences in 50 patients. Both readers identified all focal lesions in session 1 and only solid lesions in session 2. The readers' confidence was graded using a scale of 1-4 (1 or= 95%). The diagnostic accuracies of the four MR sequences were evaluated using the free-response receiver operating characteristic (ROC) method. Region-of-interest (ROI) measurements were performed for the mean signal intensity (SI) in the liver, spleen, hepatic lesions, and background noise. RESULTS: The accuracy of navigator-triggered TSE and respiratory-triggered TSE was superior to that of breath-hold TSE with restore pulse and HASTE for the detection of all focal or solid hepatic lesions. The mean lesion-to-liver contrast-to-noise ratio (CNR) of solid lesions in navigator-triggered (P < 0.001) and respiratory-triggered TSE (P < 0.005) was significantly higher than that in HASTE. CONCLUSION: High-resolution, free-breathing, T2-weighted MRI techniques can significantly improve the detectability of focal hepatic lesions and provide higher lesion-to-liver contrast of solid lesions compared to breath-hold techniques.     

Evaluation of turbo spin echo sequences for MRI of focal liver lesions at 0.5 T

To determine whether turbo spin echo (TSE) sequences can replace conventional T2-weighted spin echo (SE) sequences in MRI of the liver, 40 patients with focal liver lesions were imaged at 0.5 T. A T2-weighted SE sequences (TR/TE 1800/90 ms, number of signals averaged [NEX]=2, scan time=7:16 min), a TSE sequence (TR/TE 1800/90 ms, NEX=4, number of echos per excitation=13, echo spacing=12.9 ms, scan time=4:16 min) and a T1-weighted SE sequence (TR/TE 350/15 ms, NEX=2, scan time=4:21 min) were obtained and image quality, lesion detectability and lesion differentiation were evaluated qualitatively by subjective assessment using scores and quantitatively by lesion-liver contrast-to-noise (CNR) and tumour/liver signal intensity (SI) ratios. The image quality of the TSE sequence was substantially better compared with the T2-weighted SE sequence due to a reduction in motion artefacts and better delineation of anatomical details. Of a total of 158 visible lesions the T1-weighted SE, TSE, and T2-weighted SE sequences showed 91%, 81% and 65% of the lesions, respectively. Thus the TSE sequence depicted 24% (P< 0.001) more lesions than the T2-weighted SE sequence. In all types of pathology the lesion-liver CNR of the TSE sequence was significantly (P< 0.001) higher compared to the CNR of the T2-weighted SE sequence (+ 55–65%), indicating superior lesion conspicuity. Lesion characterization was equally good on the two T2-weighted sequences with no difference in the tumour/liver SI ratio. Using a criterion of tumour/liver SI ratio equal to or higher than 2, haemangiomas larger than 1 cm in diameter could be differentiated from other lesions with a sensitivity and specificity of 95% and 96%, respectively. Our results indicate that the TSE sequence is suitable for replacing the conventional T2-weighted SE sequence in MRI of focal liver lesions.This paper was presented at ECR 1993 Correspondence to: B. Kreft