首页 水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查中的应用

水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查中的应用

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水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查中的应用水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查 中的应用 论文译文: 水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查中的应用 方法与资料 本文研究了30例MRI膝关节扫描病例,临床检查均疑似膝关节内紊乱综合症。此后均做了膝关节关节镜检查。 检查图像来自0.35T永磁磁共振(Superstar, 东软医疗,中国)。 本研究使用的扫描参数如下:矢状T1加权(TR/TE=440/16)矩阵256x256,层厚4mm,视野17x17cm。矢状和轴位三点Dixon序列(TR/TE=1500...

水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查中的应用
水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查 中的应用 论文 政研论文下载论文大学下载论文大学下载关于长拳的论文浙大论文封面下载 译文: 水脂分离技术(Dixon)在低场磁共振膝关节软骨缺损检查中的应用 方法与资料 本文研究了30例MRI膝关节扫描病例,临床检查均疑似膝关节内紊乱综合症。此后均做了膝关节关节镜检查。 检查图像来自0.35T永磁磁共振(Superstar, 东软医疗,中国)。 本研究使用的扫描参数如下:矢状T1加权(TR/TE=440/16)矩阵256x256,层厚4mm,视野17x17cm。矢状和轴位三点Dixon序列(TR/TE=1500/20),扫描矩阵216x216,重建矩阵244x244,层厚5mm,视野17x17cm,冠状STIR (TR/TE=1900/20),TI 100ms,层厚5mm, 视野17x17cm,矩阵216x216。 两名骨科影像医生对30名患者的MR图像进行了诊断。诊断聚焦在四个关节表面:股骨的内侧髁和外侧髁,胫骨平台及股骨滑车沟。关节内镜检查于MRI检查后四周内进行。结果图1:矢状三点Dixon图像显示正常股骨滑车沟周边正常软骨(空心箭头)和外髁(实心箭头);图2:36岁男性, 膝关节髌骨下疼痛,矢状三点Dixon图像显示股骨外侧髁关节软骨不规则;图3:37岁男性,有前交叉韧带断裂病史,矢状三点Dixon显示股骨外侧髁内软骨下骨髓水肿并全层软骨缺损;图4:45岁女性,膝关节髌骨下疼痛,矢状三点Dixon显示股骨内上髁前方局部软骨缺损(箭头)并表面不规则改变。 多篇学术文章报道,关节镜下相关研究印证了三点Dixon序列在检测膝关节软骨损害{1,2,3}中的影像诊断表现。 本研究不可能将Dixon成像序列的敏感度和特异性价值与此前发表的研究进行比较,因为成像参数、MRI硬件和阅片人经验上都存在差异性。 本研究是针对30名有关节内窥镜相关检查的病人。2名骨科影像医生阅读了150个软骨表面。关节内窥镜显示的40个畸形中有32处畸形在之前的MRI扫描中前瞻性地检测出。总的来说三点Dixon的敏感度为80%,特异性为68%。 讨论 一种通过静磁场不均匀校正实现MRI单次扫描中水脂分离的方法研究出来了。图像序列使用夹在两个梯度回波中间的单独的射频回波。梯度回波用来确定B0分布,并在用场图进行相位校正后产生反相位图像。研究人员开发出一个算法来进行相位图像去折叠,以便量化B0的不均匀性。为了考虑由读梯度翻转引起的、位于射频回波图像和梯度回波图像 之间几何畸变的差异,研发人员开发了专门方法,在计算最后的水和脂肪图像前,对图像进行校正。 在低场情况下,水脂信号从同相传到反相的时间比高场情况下的要长。因此,同相和反相数据在单次激发以后就可以获得,这样就极大减少了该序列的成像时间。 在我们的研究中,Dixon技术对膝关节软骨形成良好的成像效果。矢状三点Dixon序列在检测膝关节软骨损害的总体的敏感度是80%。在永磁磁共振上,三点Dixon序列是获得膝关节脂肪抑制的有效技术。 参考文献 1.M.A. Bredella, C. Losasso, S. C. Moelleken, R. W. Huegli, H. K. Genant, P. F. J. Tirman.Three-Point Dixon Chemical-Shift Imaging for Evaluating Articular Cartilage Defects in the Knee Joint on a Low-Field-Strength Open Magnet.American Journal of Roentgenology.2.Skinner TE, Glover GH. An extended two-point Dixon algorithm for calculating separate water, fat, and B0 images. Magn Reson Med 1997; 37:628-630 [CrossRef] [Medline]3.Wang Y, Li D, Haacke EM, Brown JJ. A three-point Dixon method for water and fat separation using 2D and 3D gradient-echo techniques. J Magn Reson Imaging 1998; 8:703-710 [CrossRef] [Medline] 论文原文 The value of Dixon Imaging for Evaluating Articular Cartilage Defects in the Knee Joint on Open MRI We studied 30 patients who were referred for MR imaging of the knee joint for suspected internal derangement. All of the patients underwent arthroscopy of the knee joint. The images were obtained with an open permanent 0.35T MRI (Superstar,Neusoft Medical Systems,China ). Imaging parameters in our study were: Sagittal T1w(TR/TE 440/16) matrix 256x256, slice thickness 4mm, field of view 17x17cm . Sagittal and axial three- point Dixon sequence (TR/TE 1500/20) scan matrix 216x216 and reconstruction matrix 244x244 , slice thickness 5mm, field of view 17x17cm, Coronal STIR (TR/TE 1900/20),TI 100ms, slice thickness 5mm, field of view 17x17cm and matrix 216x216. Two muskuloskeletal radiologists reviewed the medical records of 30 patients who underwent knee MR examinations. Our evaluation focused on 5 articular surfaces:medial and lateral femoral condyles and tibial plateaus and trochlear groove. Arthroscopy was performed within 4 weeks of the MR examinations .Fig.1: Sagittal three-point Dixon image shows normal cartilage along trochlear groove (Hollow arrow ) and lateral condyle (solid arrow);Fig.2: 36 year old man with knee pain. Sagittal tree-point Dixon image shows irregularity of articular cartilage on lateral femoral condyle (arrow);Fig.3: 37 year old man with history of anterior cruciate ligament tear Sagittal tree-point Dixon image shows subchondral bone marrow edema within lateral femoral condyle.Also note full-thickness cartilage defect;Fig.4: 45 year old woman with knee pain. Sagittal three-point Dixon image shows partial -thickness cartilage defect on medial condyle (arrow ).Surface irregularity is noted. Multiple studies with arthroscopic correlation have evaluated the diagnostic performance of three - point Dixon sequence for detecting cartilage lesions on the knee joint{1,2,3}.It's impossible to compare the sensitivity and spesificity values of the Dixon imaging sequences used in previously published studies because of the differences in imaging parameters,MR hardware and reader experience. Our study performed on 30 patients with arthroscopical correlation.150 cartilage surfaces evaluated by 2 musculoskeletal radiologists. Arthroscopy showed 32 of 40 abnormalities were prospectively detected on MR imaging. The overall sensitivity of the three-point Dixon sequence in detecting cartilage lesions was 80% and specificity was 68%. Conclusion A method was developed for separation of water and fat MR images in a single scan with correction of static field inhomogeneity. The image sequence uses a single radiofrequency echo (RF) that is 'sandwiched ' between two gradient echoes.The gradient echoes are used to determine the B0 distribution and to produce out of phase images after phase correction using the field map.An algorithm was developed to unwrap the phase images for quantitating the B0 inhomogeneity.To account for difference in geometric distortion between the RF echo image and the gradient echo images due to the reversal of the read gradients, methods were developed to correct the images before the calculation of the final water and fat images. At a low field strenght,the time needed for the water and fat signals to transition from in phase to out of phase is longer than at a high field strenght. Therefore, both in phase and out of phase data can be ascuired after a single excitation witch leads to a considerable reduction in image time for this sequence. The Dixon technique resulted in good visualization of the knee cartilage in our study.The overall sensitivity of the sagittal three-point Dixon sequences indetecting knee cartilage lesions was 80%.The tree-point Dixon sequence is a useful technique for acheiving fat-suppression images in the knee joint on permanent open MRI.
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