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。     

3D-SPACE、3D-True FISP序列测量膝关节软骨缺损面积的比较研究

目的 :比较三维可变翻转角快速自旋回波序列(3-dimensional sampling perfection with application optimized contrast using different flip angle evolutions,3D-SPACE)、三维真稳态进动快速成像序列(3D-true fast imaging with steady-state precession,3D-True FISP)测量膝关节软骨缺损面积的准确性。方法:选取38例膝关节软骨缺损患者,在1.5 T MRI仪上对比3D-SPACE、3DTrue FISP序列对膝关节软骨的显示质量,并将2组序列测量的缺损软骨面积(52处)与关节镜测量结果进行比较。结果 :3DSPACE、3D-True FISP序列测量的膝软骨缺损面积平均每膝分别为(2.337±0.868)cm2、(1.423±0.560)cm2。3D-SPACE序列比3D-True FISP序列在对膝关节软骨显示质量上更优(P0.05),且对软骨缺损面积的显示更准确(P0.05)。结论 :3D-SPACE序列比3D-True FISP序列能更好地显示膝关节软骨,对膝关节缺损软骨面积测量的准确性更高。     

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.     

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.     

3D-DESS序列MRI成像参数优化及其在膝关节软骨损伤影像诊断中的应用

目的 优化三维双回波稳态(three-dimensional double-echo steady state,3D-DESS)序列磁共振成像( magnetic resonance imaging,MRI)参数,探讨3D-DESS序列MRI在膝关节软骨损伤中的诊断价值.方法 对20例健康成年人选择不同反转角(flip angle,FA)进行3D-DESS序列成像,观察不同FA条件下正常膝关节软骨的MRI表现,测量不同FA条件下膝关节关节液、软骨的信噪比(signal noise ratio,SNR)和对比信噪比(contrast to noise ratio,CNR);收集30例膝关节软骨损伤患者进行3D-DESS序列MRI检查,对比关节镜检查所见,探讨3D-DESS序列MRI对膝关节软骨损伤的临床诊断价值.结果 在FA为60°时无论是健康者抑或是膝关节软骨损伤患者,3D-DESS序列的膝关节液体SNR最高,液体与软骨CNR最高,显示软骨效果最好,FA为30°时膝关节软骨SNR最高,3D-DESS序列MRI诊断膝关节软骨损伤与关节镜检查之间具有较高的一致性(Kappa值= 0.752).结论 在FA为60°时膝关节3D-DESS序列MRI显示关节软骨效果最好,显示关节软骨损伤与关节镜检查结果之间具有较高的一致性,在膝关节软骨成像中具有较高的应用价值.     

比较双回波稳态序列30°与90°反转角对诊断膝关节软骨损伤的价值

目的：比较三维双回波稳态(3D-DESS)序列30°与90°反转角对2级及以上膝关节软骨损伤程度的诊断准确性。方法利用1.5T MR 3D-DESS 序列分别采用30°及90°反转角成像获得13例膝关节软骨损伤患者(男2例,女11例,年龄18~68岁)的MR 图像。由2名放射科医生阅片判断：软骨损伤≥2级为阳性(P),<2级为阴性(N)。以关节镜作为金标准,并与随后行关节镜检查诊断的一致率进行比较。评估软骨损伤诊断得分分3类：3分,肯定诊断;2分,可能诊断;1分,不能做出诊断。结果通过3D-DESS 图像和关节镜检查结果作一致性比较,6个膝关节面90°反转角一致率显著较高(Kappa 值=1.000,0.843,1.000,0.806,0.967,0.909;P <0.001,P <0.004,P <0.004,P <0.002,P <0.001,P <0.001),90°反转角的图像比30°反转角的图像更好地显示所有软骨面。结论3D-DESS 序列评价膝关节软骨表面损伤,90°反转角比30°的常规设置更有效。     

三维稳态自由进动成像序列与三维抑脂扰相梯度回波序列诊断膝关节软骨病变的对比研究

目的以关节镜检查结果为金标准,比较三维抑脂扰相梯度回波(3D-SPGR)序列和三维稳态自由进动成像(3D-SSFP)序列在膝关节软骨病变的诊断准确性。资料与方法对连续54例患者的58个膝关节行矢状位3D-SPGR和3D-SSFP序列扫描。按照改良的Noyes评分标准对膝关节软骨进行MRI和关节镜分级。计算上述MR序列对膝关节软骨病变的诊断敏感性、特异性和准确性。通过K统计评价不同阅片者间结果的一致性。结果3D-SSFP序列对诊断膝关节软骨病变的敏感性、特异性和准确性分别为80%、94%和92%(阅片者1);76%、94%和90%(阅片者2)。而3D-SPGR序列对诊断膝关节软骨病变的敏感性、特异性和准确性则分别为82%、92%和90%(阅片者1);82%、90%和88%(阅片者2)。两阅片者阅片结果一致性为良～优(Kappa值为0.43～0.83)。结论3D-SSFP序列在诊断膝关节软骨病变方面与3D-SPGR序列有同等的价值,其较短的图像采集时间更适合作为膝关节的MR扫描常规序列。     

MRI3D-DESS序列在膝关节病变诊断中的应用

目的 探讨磁共振三维各向同性分辨率双回波稳态序列(three dimensional dualecho steady state,3DDESS)进行膝关节软骨、半月板、韧带病变诊断的有效性.方法 31 例患者接受了术前3DDESS序列扫描和膝关节镜手术治疗,由2名骨骼肌肉专业的放射科医生分别对图像进行分析,并与关节镜结果相对照.分别计算3DDESS序列诊断2级以上软骨病变、3级以上软骨病变、半月板撕裂、韧带损伤的敏感性和特异性.观察者间的差异用Kappa值表示.结果 3DDESS序列对2级以上软骨病变诊断敏感性和特异性:观察者A为63.95%和98.77%;观察者B为55.81%和94.44%;观察者之间Kappa值=0.77.对3级以上软骨病变诊断敏感性和特异性:观察者A为77.08%和99.00%;观察者B为68.75%和97.00%;观察者之间Kappa值=0.83.3DDESS序列对半月板撕裂诊断敏感性和特异性:观察者A为87.27%和96.18%;观察者B为69.09%和93.89%;两者之间Kappa值=0.79.对韧带损伤诊断敏感性和特异性:观察者A为100.00%和97.35%;观察者B为100.00%和92.04%;观察者之间Kappa值=0.82.结论 3DDESS序列通过准确评价软骨病变、各向同性重建关节韧带,可作为膝关节损伤术前检查重要手段.     

MR 3D SPGR、3D FIESTA和2D SE/FSE序列对外伤性膝关节软骨损伤的分级诊断研究

目的 回顾性研究外伤性膝关节关节软骨的损伤发生率及程度,比较三维扰相梯度回波序列(3DSPGR)、三维稳态采集快速成像序列(3D FIESTA)和膝关节常规检查序列(2D SE/FSE)在诊断外伤性膝关节软骨损伤中的准确性.资料与方法 45例患者的46个外伤膝关节,行手术治疗前均进行了多序列的MRI,包括膝关节常规MRI(SE T1WI,FSE PD/T2WI),3D SPGR和3D FIESTA序列.运用改良的Noyes分类系统来评价膝关节软骨面的损伤等级,每个膝关节的关节面包括:股骨外侧髁(LFC)、股骨内侧髁(MFC)、胫骨外侧平台(LTP)、胫骨内侧平台(MTP)、股骨滑车(Trochlea)和髌骨(Patella).以手术结果为"金标准",比较各序列发现软骨损伤的敏感性、特异性、准确性、阳性及阴性预测值.用Wilson评分法计算敏感性和特异性的95%可信区间,用McNemar统计法的双尾精确表来比较不同MRI序列对软骨分级诊断的显著性差异.结果 根据手术结果,软骨形态改变的发生率为43%(118/276),软骨缺损的发生率为23%(63/276).各个关节面软骨损伤的发生率无明显差异.MR图像(3D SPGR、3D FIESTA、3D SPGR结合常规MRI)表现与手术结果的完全一致率分别为53%、60%和85%,之间差异无统计学意义.但是3D SPGR结合常规MRI序列评价软骨损伤的敏感性、特异性、阳性预测值和阴性预测值均为最高,分别为73%、98%、95%和90%.结论 3D SPGR和3D FIESTA序列在诊断膝关节软骨病变时无明显差异.3D SPGR结合常规MRI序列,不仅可以在合理的扫描时间内提高诊断软骨病变的准确性,而且还可对膝关节的其他组织结构做出全面的评价.     

半FOV匀场技术纠正FIESTA序列腹部磁敏感伪影的初步研究

目的:探讨快速稳态进动采集(fast imaging employing steady-state acquisition,FIESTA)序列腹部冠状位MRI成像时磁敏感伪影的形成机制,以及匀场技术对减少磁敏感伪影的应用价值。方法:在1.5T MRI,采用不同FOV匀场策略的FIESTA序列对患者行腹部冠状位扫描。以膈肌以下肝脏为ROI,对匀场后ROI部位伪影的改善效果进行评分,分析和比较不同匀场策略对于改善肝脏部位磁敏感伪影的差异。结果:1FIESTA序列腹部冠状位扫描时在膈肌附近易产生磁敏感伪影。2施加匀场之后可以改善伪影,半FOV匀场效果优于全FOV匀场效果(Z=-6.211,P0.05)。结论:FIESTA序列腹部扫描时正确施加适当范围的局部匀场可以减少磁敏感伪影,提高图像质量。     

Wrist and finger joint MR imaging in rheumatoid arthritis.

PURPOSE: To elaborate the best MR imaging protocol for studies in rheumatoid arthritis (RA) and to evaluate the sensitivity and interobserver agreement with respect to detection of bone erosions (MR and radiography) and grading of synovial membrane hypertrophy (MR imaging only). MATERIAL AND METHODS: MR imaging and conventional radiography of wrist and metacarpophalangeal (MCP) joints were performed in 41 RA patients and 3 healthy controls. The following pulse sequences were applied: T1-weighted spin-echo (T1-SE) with and without contrast enhancement, T2-SE, T2-turbo-SE, T1-2D-FLASH, T1-3D-FLASH, fat-saturated-T1-SE, STIR and 3D-DESS. RESULTS: Bone erosions were found by MR compared to radiography in 261 versus 85 bones of the wrist (ratio 3.1) and 59 versus 21 MCP joint quadrants (ratio 2.81). MR and radiography interobserver agreements were both approximately 90%. Likewise, MR scored synovial membrane hypertrophy in wrist and MCP joints with a high interobserver agreement. The most informative MR sequence appeared to be contrast-enhanced T1-SE MR, preferably with fat saturation. A STIR sequence or T2-weighted fat saturation sequence was useful in screening for joint disease. CONCLUSION: The sensitivity of MR is superior to conventional radiography with respect to detection of bone erosions in wrist and MCP joints. The interobserver agreement for MR and radiography was similar. Thus, MR of wrist and finger joints may become a useful supplement to conventional radiography in the evaluation of RA patients in clinical trials and clinical practice.     

Diagnosis of articular cartilage abnormalities of the knee: prospective clinical evaluation of a 3D water-excitation true FISP sequence

PURPOSE: To prospectively evaluate the accuracy of three-dimensional (3D) water-excitation true fast imaging with steady-state precession (FISP) in the assessment of cartilage abnormalities of the knee, by using surgery as the reference standard. MATERIALS AND METHODS: The study was approved by the hospital institutional review board. Written informed consent was obtained from all patients. Twenty-nine patients (30 knees) with a mean age of 56 years (range, 18-86 years) were prospectively evaluated with a sagittal 3D true FISP magnetic resonance (MR) sequence. The mean interval between MR imaging and surgery was 1 day (range, 0-9 days). During surgery, the articular surfaces of the knee were evaluated by using a modified Noyes score. The MR images were evaluated by two blinded readers on two separate occasions. Diagnostic performance was evaluated by setting the cutoff for abnormality between grade 1 (intact cartilage surface) and grade 2 (cartilage defects). Statistical methods used included calculation of sensitivity, specificity, and accuracy, with 95% confidence intervals (Wilson score method) and calculation of kappa values with standard errors. RESULTS: Overall sensitivity, specificity, and accuracy for the two readers and the two evaluations ranged from 56% to 66%, 78% to 93%, and 71% to 75%, respectively. Interobserver agreement was substantial for both the first (kappa = 0.73) and the second (kappa = 0.65) evaluation. Intraobserver agreement was almost perfect (kappa = 0.84) for reader 1 and moderate (kappa = 0.60) for reader 2. CONCLUSION: The 3D water-excitation true FISP MR sequence allows assessment of the articular cartilage of the knee with moderate-to-high specificity and low-to-moderate sensitivity.     

MR imaging of the wrist: comparison between 1.5- and 3-T MR imaging--preliminary experience

Institutional review board approval and informed consent were obtained from 25 healthy volunteers and 15 consecutive patients with chronic wrist pain or suspected carpal mass, and 1.5- and 3-T magnetic resonance (MR) imaging of the wrist was prospectively performed with comparable sequence parameters and surface coils of the same geometric design. Imaging protocols at both field strengths included a T1-weighted spin-echo sequence, two intermediate-weighted fast SE sequences with different echo times and with and without fat saturation, and a three-dimensional fast field-echo sequence. The contrast-to-noise ratio (CNR) between muscle and bone and between bone and cartilage was calculated for both field strengths. The visibility of various anatomic structures, including the triangular fibrocartilage complex, carpal ligaments, nerves, and cartilage, was analyzed with a four-point grading scale. CNRs were significantly higher on 3-T MR images than on 1.5-T MR images (P < .001; analysis of variance) for all sequences. Visibility of the triangular fibrocartilage complex and intercarpal ligaments and cartilage was significantly better on 3-T MR images than on 1.5-T MR images (paired sign test).     

Advanced morphological 3D magnetic resonance observation of cartilage repair tissue (MOCART) scoring using a new isotropic 3D proton-density, turbo spin echo sequence with variable flip angle distribution (PD-SPACE) compared to an isotropic 3D steady-state free precession sequence (True-FISP) and standard 2D sequences

Purpose

To evaluate a new isotropic 3D proton‐density, turbo‐spin‐echo sequence with variable flip‐angle distribution (PD‐SPACE) sequence compared to an isotropic 3D true‐fast‐imaging with steady‐state‐precession (True‐FISP) sequence and 2D standard MR sequences with regard to the new 3D magnetic resonance observation of cartilage repair tissue (MOCART) score.

Materials and Methods

Sixty consecutive MR scans on 37 patients (age: 32.8 ± 7.9 years) after matrix‐associated autologous chondrocyte transplantation (MACT) of the knee were prospectively included. The 3D MOCART score was assessed using the standard 2D sequences and the multiplanar‐reconstruction (MPR) of both isotropic sequences. Statistical, Bonferroni‐corrected correlation as well as subjective quality analysis were performed.

Results

The correlation of the different sequences was significant for the variables defect fill, cartilage interface, bone interface, surface, subchondral lamina, chondral osteophytes, and effusion (Pearson coefficients 0.514–0.865). Especially between the standard sequences and the 3D True‐FISP sequence, the variables structure, signal intensity, subchondral bone, and bone marrow edema revealed lower, not significant, correlation values (0.242–0.383). Subjective quality was good for all sequences (P ≥ 0.05). Artifacts were most often visible on the 3D True‐FISP sequence (P < 0.05).

Conclusion

Different isotropic sequences can be used for the 3D evaluation of cartilage repair with the benefits of isotropic 3D MRI, MPR, and a significantly reduced scan time, where the 3D PD‐SPACE sequence reveals the best results. J. Magn. Reson. Imaging 2011;33:180–188. © 2010 Wiley‐Liss, Inc.     

MR enteroclysis protocol optimization: comparison between 3D FLASH with fat saturation after intravenous gadolinium injection and true FISP sequences

The aim of this study was to introduce the true fast imaging with steady-state precession (FISP) sequence for MR enteroclysis and compare it with the already used T1-weighted fast low-angle shot (FLASH) sequence. Twenty-one patients underwent both MR and conventional enteroclysis. The MR enteroclysis examination was performed after administration of an iso-osmotic water solution through a nasojejunal catheter and the following sequences were included: (a) true FISP; and (b) 3D FLASH with fat saturation after intravenous injection of 20 mg Buscopan or 1 mg glucagon and 0.1 mmol/kg gadolinium chelates. The true FISP sequence provided images with significantly fewer motion artifacts, whereas 3D FLASH was less sensitive to susceptibility and chemical shift artifacts. The homogeneity of endoluminal opacification, wall conspicuity, and distention of the small bowel were very good to excellent and the two sequences presented no statistically significant differences here. True FISP provided significantly better overall image quality than did 3D FLASH. The true FISP sequence can provide good anatomic demonstration of the small bowel on T2-like images and could be combined with T1-weighted FLASH images for an integrated protocol of MR enteroclysis.     

Comparison of true FISP with turbo SE in ovarian imaging.

PURPOSE: To compare the signal pattern of True FISP (true fast imaging with steady state precession) with that of T2-weighted TSE (turbo spin echo) sequencing in several ovarian pathologies and to clarify the pathologies that may be misdiagnosed when True FISP is used as a fast T2-weighted MR (magnetic resonance) imaging technique. METHODS: A total of 56 patients with 58 ovarian lesions were prospectively studied. The histopathological diagnoses were surgically confirmed in all patients. All MR images were acquired with a 1.5T MR scanner. After routine MR examination (T2-weighted sagittal imaging with a turbo spin echo sequence and T1 and T2 transverse imaging with a spin echo and turbo spin echo sequence, respectively), True FISP was performed in the sagittal plane with a fat-saturation technique. The acquisition times for the True FISP and TSE techniques were 27 s and 4 min, 42 s, respectively. Three radiologists interpreted all images according to three grading scores and with particular reference to the difference in signal pattern between the two sequences (1=similar signal patterns in the ovarian lesions in both True FISP and TSE images; 2=partially different signal patterns in both True FISP and TSE images; and 3=conflicting signal patterns in both True FISP and TSE images). RESULTS: Those assigned a score of "1" included 30 patients with 30 ovarian lesions (12 malignant lesions and 18 benign lesions); those assigned a score of "2" included 10 patients with 10 lesions (two malignant and eight benign); and those assigned a score of "3" included 16 patients with 18 ovarian lesions (two malignant and 16 benign). With the influence of the fat-suppression technique excluded, eight ovarian lesions showed conflicting signal patterns between the two sequences and high signal intensity of hemorrhaging in the corresponding lesion in T1-weighted images. Lesions of both high and low signal intensity in TSE images appeared as lesions of high signal intensity in True FISP images. About 14% (8/56 lesions) of the True FISP and TSE signal patterns in ovarian pathology were conflicting in this study. CONCLUSION: The results indicate that the True FISP technique cannot replace the T2-weighted TSE technique in the evaluation of ovarian pathology. T1-weighted images with or without fat suppression are required for the evaluation of ovarian lesions with FISP images.     

MRI of patellar articular cartilage: Evaluation of an optimized gradient-echo sequence (3D-DESS)

Our purpose was to evaluate the diagnostic efficacy of a gradient-echo sequence optimized for cartilage imaging in patellar cartilage abnormalities and to compare it to a standard turbo-spin-echo sequence. Fifty-eight consecutive patients who underwent, within 3 months both MRI and arthroscopy or surgery, were included in the investigation. Two radiologists specializing in musculoskeletal imaging independently assessed axial three-dimensional double-echo steady state (3D-DESS) gradient-echo images and sagittal proton- and T2-weighted turbo-spin-echo images with regard to retropatellar cartilage abnormalities. Possible findings were: 0: normal, 1: cartilage softening, and 2: lesion of the articular surface. Inter- and intraobserver variability was assessed. For cartilage softening, the axial 3D-DESS sequence had a sensitivity of 73%, a specifity of 75%, and an accuracy of 70%. The corresponding results for the sagittal turbo-spin-echo sequence were 53%, 65%, and 62%. For surface lesions, the results for the 3D-DESS sequence were 43%, 92%, and 83% and for the turbo-spin-echo sequence were 60%, 92%, and 86%. Intra- and interobserver agreement was moderate (k = 0.59 and 0.45 [DESS], 0.6 and 0.46 [turbo -spin-echo]). We conclude that the 3D-DESS sequence is moderately accurate in detecting patellar cartilage abnormalities. Compared with the sagittal turbo-spin-echo sequence, the axial 3D-DESS sequence is superior in diagnosing cartilage softening but not surface lesions.     

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.     

Human articular cartilage: in vitro correlation of MRI and histologic findings

The aim of our study was to correlate MRI with histologic findings in normal and degenerative cartilage. Twenty-two human knees derived from patients undergoing amputation were examined with 1.0- and 1.5-T MR imaging units. Firstly, we optimized two fat-suppressed 3D gradient-echo sequences. In this pilot study two knees were examined with fast imaging with steady precession (FISP) sequences and fast low-angle shot (FLASH, SPGR) sequence by varying the flip angles (40, 60, 90 °) and combining each flip angle with different echo time (7, 10 or 11, 20 ms). We chose the sequences with the best visual contrast between the cartilage layers and the best measured contrast-to-noise ratio between cartilage and bone marrow. Therefore, we used a 3D FLASH fat-saturated sequence (TR/TE/flip angle = 50/11 ms/40 °) and a 3D FISP fat-saturated sequence (TR/TE/flip angle = 40/10 ms/40 °) for cartilage imaging in 22 human knees. The images were obtained at various angles of the patellar cartilage in relation to the main magnetic field (0, 55, 90 °). The MR appearances were classified into five categories: normal, intracartilaginous signal changes, diffuse thinning (cartilage thickness < 3 mm), superficial erosions, and cartilage ulcers. After imaging, the knees were examined macroscopically and photographed. In addition, we performed histologic studies using light microscopy with several different stainings, polarization, and dark field microscopy as well as electron microscopy. The structural characteristics with the cartilage lesions were correlated with the MR findings. We identified a hyperintense superficial zone in the MR image which did not correlate to the histologically identifiable superficial zone. The second lamina was hypointense on MRI and correlated to the bulk of the radial zone. The third (or deep) cartilage lamina in the MR image seemed to represent the combination of the lowest portion of the radial zone and the calcified cartilage. The width of the hypointense second zone correlated weakly to the accumulation of proteoglycans in the radial zone. The trilaminar MRI appearance of the cartilage was only visible when the cartilage was thicker than 2 mm. In cartilage degeneration, we found either a diffuse thinning of all layers or circumscribed lesions (“cartilage ulcer”) of these cartilage layers in the MR images. Early cartilage degeneration was indicated by a signal loss in the superficial zone, correlating to the histologically proven damage of proteoglycans in the transitional and radial zone along with destruction of the superficial zone. We found a strong effect of cartilage rotation in the main magnetic field, too. A rotation of the cartilage structures caused considerable variation in the signal intensity of the second lamina. Cartilage segments in a 55 °angle to the magnetic main field had a homogeneous appearance, not a trilaminar appearance. The signal behavior of hyaline articular cartilage does not reflect the laminar histologic structure. Osteoarthrosis and cartilage degeneration are visible on MR images as intracartilaginous signal changes, superficial erosions, diffuse cartilage thinning, and cartilage ulceration. Received 13 February 1997; Revision received 27 June 1997; Accepted 29 December 1997