Evaluation of chondral injuriesby magnetic resonance imaging: Repair assessments

Magnetic resonance (MR) is a versatile imaging modality that can be tailored to address many of the clinical andresearch questions encountered in musculoskeletal diseases. Developments in MR techniques for cartilage imaging have paralleled the advances in clinical approaches to cartilage injury assessment and repair. This article reviews the current state-of-the-art clinical MR imaging methods designed for noninvasive evaluation of cartilage. Basic technical considerations are discussed, including selection of an imaging site for patient referral, interpretation of MR images, and the limitations of each acquisition technique. Clinical examples are used to illustrate the appearance of chondral lesions. Finally, the unique issues arising from cartilage assessment after surgical repair are examined.     

Nondestructive imaging of human cartilage glycosaminoglycan concentration by MRI.

Despite the compelling need mandated by the prevalence and morbidity of degenerative cartilage diseases, it is extremely difficult to study disease progression and therapeutic efficacy, either in vitro or in vivo (clinically). This is partly because no techniques have been available for nondestructively visualizing the distribution of functionally important macromolecules in living cartilage. Here we describe and validate a technique to image the glycosaminoglycan concentration ([GAG]) of human cartilage nondestructively by magnetic resonance imaging (MRI). The technique is based on the premise that the negatively charged contrast agent gadolinium diethylene triamine pentaacetic acid (Gd(DTPA)2-) will distribute in cartilage in inverse relation to the negatively charged GAG concentration. Nuclear magnetic resonance spectroscopy studies of cartilage explants demonstrated that there was an approximately linear relationship between T1 (in the presence of Gd(DTPA)2-) and [GAG] over a large range of [GAG]. Furthermore, there was a strong agreement between the [GAG] calculated from [Gd(DTPA)2-] and the actual [GAG] determined from the validated methods of calculations from [Na+] and the biochemical DMMB assay. Spatial distributions of GAG were easily observed in T1-weighted and T1-calculated MRI studies of intact human joints, with good histological correlation. Furthermore, in vivo clinical images of T1 in the presence of Gd(DTPA)2- (i.e., GAG distribution) correlated well with the validated ex vivo results after total knee replacement surgery, showing that it is feasible to monitor GAG distribution in vivo. This approach gives us the opportunity to image directly the concentration of GAG, a major and critically important macromolecule in human cartilage.     

定量MRI技术在跑步人群膝关节软骨中的应用进展

膝关节软骨作为膝关节最重要的结构之一,在维持膝关节正常运动中具有非常关键的作用。适度合理的跑步对关节软骨有着积极健康的作用,可以有效减少关节疾病,而不合理的跑步会增加膝关节软骨损伤和退变风险。在常规MRI基础上发展起来的T_1ρ、T₂ mapping、T₂* mapping、T₁ mapping、扩散张量成像及软骨延迟动态增强MRI等定量MRI新技术,不仅可以优化显示膝关节软骨的形态改变、组织构成及超微结构的改变,还可为损伤的诊断提供丰富的定量信息,对指导跑步人群的运动具有重要意义。就不同定量MRI技术对跑步相关的膝关节软骨变化的研究进展予以综述。     

MRI与关节镜测量膝关节软骨缺损面积的对比

目的：探讨磁共振成像(MRI)与关节镜测量膝关节软骨缺损面积的一致性。方法选取36例(36膝)因膝关节软骨缺损的入院患者,对照分析其关节镜及术前 MRI 资料。比较 MRI 与关节镜术中测量软骨缺损区面积的一致性。结果MRI 与关节镜均发现膝关节软骨缺损92处,平均每例2.6处。经 MRI 测量,平均每膝的软骨缺损面积为(1.9±1.5)cm2;经关节镜测量,平均每膝的软骨缺损面积为(2.9±2.6)cm2;MRI 与关节镜测量结果之间差异有统计学意义(P <0.001)。MRI 的评估结果低于关节镜测量结果,平均差值为(1.7±1.1)cm2。MRI 测量的面积为关节镜测量结果的70.1%。结论MRI 诊断关节软骨缺损病灶数目上与关节镜具有良好的一致性;可直接或间接反映膝关节软骨缺损面积,定位、定性诊断较为准确。     

运动训练对血清及关节液内软骨生物标记物水平的影响

目的了解软骨寡聚基质蛋白(COMP)、金属基质蛋白酶-1(MMP-1)、MMP-3、金属基质蛋白酶抑制因子-1(TIMP-1)作为生物标记物对不同运动训练模式下膝关节软骨早期运动性损伤及修复进行评估的意义。方法20只实验用狗随机分为一般训练组(训练组,n=8)、强化训练组(强化组,n=8)、对照组(n=4),训练组跑步路线坡度为10°,速度为200m/min;强化组跑步路线坡度为10°,速度为300m/min;对照组自由活动。于0、2、4、6、8、10周抽取3组动物血液及关节液,应用ELISA方法检测COMP、MMP-1、MMP-3、TIMP-1水平,并以MRI检查训练组及强化组动物膝关节软骨损伤情况。结果MRI检查显示训练组与强化组动物2周后均出现膝关节软骨运动性损伤改变,4~6周时最严重,6周后开始缓解。血清及关节液内COMP、MMP-1、MMP-3、TIMP-1浓度在训练开始后均有不同程度升高,并随时间改变而发生改变。血清COMP水平训练组与强化组分别于第4周和第6周达到最高,分别为5.7和6.8ng/ml;血清MMP-1水平训练组与强化组分别于第8周和第10周达到最高,分别为14.7和11.3ng/ml;血清MMP-3水平训练组与强化组都于第10周达到最高,分别为116.4和109.3ng/ml;血清MMP-3/TIMP-1水平训练组与强化组都于第10周达到最高,分别为0.365和0.410;关节液COMP水平训练组与强化组都于第4周达到最高,分别为14.2和17.9ng/ml;关节液MMP-1水平训练组与强化组都于第10周达到最高,分别为89.9和82.7ng/ml;关节液MMP-3水平训练组与强化组都于第6周达到最高,分别为6961.4和5832.1ng/ml;关节液MMP-3/TIMP-1水平训练组与强化组都于第6周达到最高,分别为8.434和7.243;血清及关节液内TIMP-1水平变化无明显规律。强化组MMP-1、MMP-3、MMP-3/TIMP-1总体水平低于训练组,COMP总体水平高于训练组,提示强化组关节损伤趋势低于训练组,修复程度高于训练组。血清与关节液中标记物浓度变化显著相关(P<0.01)。结论强化训练较一般训练能更好地促进关节软骨的塑形改建;联合应用数种生物标志物预测早期关节软骨损伤、修复情况及监测病程变化较影像学检查更为灵敏。     

动态增强MR量化参数无创评估肝细胞癌生物学行为

目的:探讨动态对比剂增强MR技术量化参数在评估肝细胞癌(HCC)生物学行为中的价值.方法:选取行手术切除并经病理证实的肝细胞癌46例,术前行MR动态对比剂增强扫描,然后分析测量病灶和周围肝实质的动态增强曲线类型、最大上升斜率(MSI)、信号增强率(SER)、正性增强积分(PEI)、最大下降斜率(MSD)和峰值(PV).根据患者手术和病理结果测量病灶最大直径,病理分级采用Edmondson法分为4级.根据病灶有无包膜及肝硬化进行分组;凡出现门静脉癌栓、周围淋巴结转移或周围子灶等之一者定为侵袭转移组,否则为阴性组.分析动态增强MR各测量参数与HCC手术和病理资料之间的关系.结果:HCC的MSI、PEI、MSD和PV均大于肝实质,差异具有统计学意义(P＜0.05),但SER在两者之间的差异无统计学意义(P＞0.05).MSI和PV在阴、阳性侵袭转移组,MSI和PEI在有、无包膜组,MSI、PEI和PV在有、无肝硬化组之间差异均具有统计学意义(P＜0.05).病灶直径也与MSI、PEI呈正相关关系(r值分别为0.369和0.325,P值分别为0.011和0.026).另外,在侵袭转移组,Ⅰ、Ⅱ和Ⅲ型曲线分别占85.7%(6/7)、75.0%(15/20)、31.6%(6/19),与无侵袭转移组之间差异具有统计学意义(χ2=10.63, P=0.007).本研究中其他动态增强指标在以上各组之间及Edmondson分级及有、无腹水组之间的差异均无统计学意义(P＞0.05).结论:利用动态对比剂增强MR扫描技术可在一定程度上对HCC的生物学行为进行无创性量化评估.     

定量MRI在乳腺癌诊断中的研究进展

MRI已经成为诊断乳腺癌较为敏感的无创性检查技术,定量MRI包括动态增强MRI(DCE-MRI)、扩散加权成像(DWI)、体素内不相干运动DWI(IVIM-DWI)、合成MRI(SyMRI)、氢质子MR波谱成像(¹H-MRS)、MR弹性成像(MRE)、血氧水平依赖MRI(BOLD-MRI)等,可以对乳腺癌进行定量分析,从而有助于诊疗策略制定、预后判断及疗效评价。就定量MRI在乳腺癌诊断中的研究进展予以综述。     

Characterization of the dynamic shear properties of hyaline cartilage using high-frequency dynamic MR elastography.

This work evaluated the feasibility of dynamic MR Elastography (MRE) to quantify structural changes in bovine hyaline cartilage induced by selective enzymatic degradation. The ability of the technique to quantify the frequency-dependent response of normal cartilage to shear in the kilohertz range was also explored. Bovine cartilage plugs of 8 mm in diameter were used for this study. The shear stiffness (mu(s)) of each cartilage plug was measured before and after 16 hr of enzymatic treatments by dynamic MRE at 5000 Hz of shear excitation. Collagenase and trypsin were used to selectively affect the collagen and proteoglycans contents of the matrix. Additionally, normal cartilage plugs were tested by dynamic MRE at shear-excitations of 3000-7000 Hz. Measured micro(s) of cartilage plugs showed a significant decrease (-37%, P < 0.05) after collagenase treatment and a significant decrease (-28%, P < 0.05) after trypsin treatment. Furthermore, a near-linear increase (R(2) = 0.9141) in the speed of shear wave propagation with shear-excitation frequency was observed in cartilage, indicating that wave speed is dominated by viscoelastic effects. These experiments suggest that dynamic MRE can provide a sensitive quantitative tool to characterize the degradation process and viscoelastic behavior of cartilage.     

主动脉缩窄术后磁共振脉搏波传导速度法评估主动脉顺应性

目的 使用磁共振脉搏波传导速度法(PWV)评估主动脉缩窄(CoA)术后主动脉顺应性.方法 回顾性分析22例CoA术后患儿心脏磁共振,使用MRI相位对比序列测量并计算主动脉PWV,同时期行超声心动图测量双侧心室功能及心肌厚度.另选取年龄、性别匹配的22例健康儿童组成对照组测量主动脉PWV.结果 研究组平均PWV明显高于对照组[(4.42±3.02)m/s vs(2.73±0.76)m/s,P=0.02].在研究组中,吻合口中度狭窄患儿PWV值最高,受试者工作特征(ROC)曲线分析发现,取PWV为3.37 m/s时,区分轻、中度吻合口狭窄的敏感性、特异性最高.左侧心室舒张末期容积、收缩末期容积、射血分数及左室壁厚度与PWV无明显相关性.结论 CoA术后患儿PWV升高,中度吻合口狭窄患儿存在较显著主动脉重构.     

T2 relaxation reveals spatial collagen architecture in articular cartilage: a comparative quantitative MRI and polarized light microscopic study.

It has been suggested that orientational changes in the collagen network of articular cartilage account for the depthwise T2 anisotropy of MRI through the magic angle effect. To investigate the relationship between laminar T2 appearance and collagen organization (anisotropy), bovine osteochondral plugs (N = 9) were T2 mapped at 9.4T with cartilage surface normal to the static magnetic field. Collagen fibril arrangement of the same samples was studied with polarized light microscopy, a quantitative technique for probing collagen organization by analyzing its ability to rotate plane polarized light, i.e., birefringence (BF). Depthwise variation of safranin O-stained proteoglycans was monitored with digital densitometry. The spatially varying cartilage T2 followed the architectural arrangement of the collagen fibril network: a linear positive correlation between T2 and the reciprocal of BF was established in each sample, with r = 0.91 +/- 0.02 (mean +/- SEM, N = 9). The current results reveal the close connection between the laminar T2 structure and the collagen architecture in histologic zones.     

超声评价蛋白多糖对关节软骨水合作用的影响

目的 应用高频超声测量技术监测蛋白多糖降解导致的关节软骨水合膨胀行为的改变,探讨蛋白多糖对关节软骨水合作用的影响.方法 将12块表面光滑无损伤的猪髌骨关节软骨样本随机均分为2组,每组6块:正常组不做任何处理;胰蛋白酶消化组在0.25％的胰蛋白酶溶液中浸泡8h,以消化软骨组织内的蛋白多糖成分,从而建立经蛋白多糖降解软骨的离体退化模型,以模拟自然骨性关节炎关节软骨的退化.利用中心频率为25MHz的A型超声系统扫描两组样本,计算软骨的水合应变及软骨厚度.光镜观察关节软骨的病理组织学变化.结果 正常组软骨大约20min时达到水合平衡状态,而胰蛋白酶消化组在大约5min时即达到平衡.正常组软骨的平衡应变值为3.5％±0.5％,明显高于胰蛋白酶消化组(1.8％±0.2％,P＜0.05).胰蛋白酶消化组的软骨厚度(1.34±0.04mm)与正常组(1.34±0.07mm)比较差异无统计学意义(P＞0.05).光镜观察结果显示,正常组软骨表面光滑,软骨细胞排列规则,无裂隙,组织呈均匀红色;胰蛋白酶消化组软骨表面较光滑,可见软骨细胞破坏,番红染色中度减少,提示蛋白多糖减少.结论 正常关节软骨具有膨胀特性,蛋白多糖成分缺失可导致软骨结构、水合作用及脱水后恢复能力降低.     

运动训练及中医疗法对关节软骨GAG和软骨细胞形态影响的研究

采用计算机图形处理技术对非周期大强度训练后兔膝关节软骨糖胺多糖 (GAG)含量和软骨细胞形态做半定量和定量分析。结果表明 ,训练对软骨GAG和细胞形态有明显影响 ,而中医恢复疗法对这些影响有一定的的恢复作用     

膝关节半月板撕裂的MRI诊断

目的探讨膝关节半月板撕裂的MR I表现及MR I诊断价值。方法行MR I检查并行关节镜检查或手术的患者98例,对其结果进行对照分析。结果在98例196个半月板中,与关节镜检查及手术结果比较,MR I诊断半月板撕裂的准确性为95.9%。结论MR I是诊断膝关节半月板撕裂理想的非创伤性的检查方法。     

Signal‐to‐noise optimization for sodium MRI of the human knee at 4.7 Tesla using steady state

Sodium magnetic resonance imaging of knee cartilage is a possible diagnostic method for osteoarthritis, but low signal‐to‐noise ratio yields low spatial resolution images and long scan times. For a given scan time, a steady‐state approach with reduced repetition time and increased averaging may improve signal‐to‐noise ratio and hence attainable resolution. However, repetition time reduction results in increased power deposition, which must be offset with increased radiofrequency pulse length and/or reduced flip angle to maintain an acceptable specific absorption rate. Simulations varying flip angle, repetition time, and radiofrequency pulse length were performed for constant power deposition corresponding to ～6 W/kg over the human knee at 4.7T. For 10% agar, simulation closely matched experiment. For healthy human knee cartilage, a 37% increase in signal‐to‐noise ratio was predicted for steady‐state over “fully relaxed” parameters while a 29% ± 4% increase was determined experimentally (n = 10). Partial volume of cartilage with synovial fluid, inaccurate relaxation parameters used in simulation, and/or quadrupolar splitting may be responsible for this disagreement. Excellent quality sodium images of the human knee were produced in 9 mins at 4.7T using the signal‐to‐noise ratio enhancing steady‐state technique. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Imaging articular cartilage under compression--cartilage elastography.

We constructed a device to compress small samples of articular cartilage while the samples were imaged in a 1.5 T imager. With the use of a piezoelectric piston, the device compressed 1-cm-diameter cylindrical samples of articular cartilage (200 microm) at a rate of 2 Hz. Simultaneously, we imaged the samples with a displacement-sensitive stimulated-echo acquisition mode (STEAM) sequence. We validated the technique using tissue that mimicked silicone samples. We compared the results from the same cartilage samples before and after they were degraded by digestion in trypsin. The extent of degradation was visualized from T(1)-weighted images of the samples after they were soaked in 0.5 mmolar of GdDTPA. The resulting elastographic images show compression and differential strain in directions both parallel and perpendicular to the surface of the cartilage. The static elastographic images that depict compression made before digestion and after 5 and 15 hr of trypsin digestion show that the elastic modulus of the samples decreased with a spatial variation consistent with the enzymatic digestion as revealed by the T(1) images. We believe this technique will be useful in studies of the mechanical properties of articular cartilage and other tissues, and may in the future be extended to the clinical setting.