磁共振SPACE序列在诊断极外侧椎间盘突出中的临床应用

目的:探讨磁共振不同序列在极外侧椎间盘突出上的表现及诊断价值.方法:对经手术证实的5例极外侧椎间盘突出患者的磁共振常规扫描图像、SPACE序列图像及临床资料进行回顾性分析.结果:本组5例均为男性,年龄32～53岁,平均34岁.椎间孔内侧型2例,椎间孔外侧型2例,混合型1例.极外侧椎间盘突出在平扫矢状位椎间孔层面上表现为椎间孔内和(或)外软组织肿块信号,形态多呈圆形、卵圆形或不规则形,T<,2>WI轴位呈等或混杂信号,边缘不清,T<,2>WI冠状位呈位于孔内和(或)外软组织肿块信号,硬膜囊受压,强化扫描呈中央不强化,周边环状强化信号;SPACE序列冠状位椎间孔周围出现异常低信号,呈圆形、卵圆形或不规则形并与线状马尾神经根相交;SPACE-STIR序列显示受压移位的神经根与突出的椎间盘呈"腋下网球"样征象.结论:在磁共振SPACE序列上能直观地显示神经根与椎间盘之间空间关系,具有一定的特征性,对临床的定性及定位诊断有重要参考价值.     

T2-weighted MR imaging of the liver: Qualitative and quantitative comparison of SPACE MR imaging with turbo spin-echo MR imaging

Objective

To qualitatively and quantitatively compare T2-weighted MR imaging of the liver using volumetric spin-echo with sampling perfection with application-optimized contrast using different flip angle evolutions (SPACE) with conventional turbo spin-echo (TSE) sequence for fat-suppressed T2-weighted MR imaging of the liver.

Materials and methods

Thirty-three patients with suspected focal liver lesions had SPACE MR imaging and conventional fat-suppressed TSE MR imaging. Images were analyzed quantitatively by measuring the lesion-to-liver contrast-to-noise ratio (CNR), and the signal-to-noise ratio (SNR) of main focal hepatic lesions, hepatic and splenic parenchyma and qualitatively by evaluating the presence of vascular, respiratory motion and cardiac artifacts. Wilcoxon signed rank test was used to search for differences between the two sequences.

Results

SPACE MR imaging showed significantly greater CNR for focal liver lesions (median = 22.82) than TSE MR imaging (median = 14.15) (P < .001). No differences were found for SNR of hepatic parenchyma (P = .097), main focal hepatic lesions (P = .35), and splenic parenchyma (P = .25). SPACE sequence showed less artifacts than TSE sequence (vascular, P < .001; respiratory motion, P < .001; cardiac, P < .001) but needed a longer acquisition time (228.4 vs. 162.1 s; P < .001).

Conclusion

SPACE MR imaging provides a significantly increased CNR for focal liver lesions and less artifacts by comparison with the conventional TSE sequence. These results should stimulate further clinical studies with a surgical standard of reference to compare the two techniques in terms of sensitivity for malignant lesions.     

High-resolution cartilage imaging of the knee at 3 T: Basic evaluation of modern isotropic 3D MR-sequences

Purpose

To evaluate qualitative and quantitative image quality parameters of isotropic three-dimensional (3D) cartilage-imaging magnetic resonance (MR)-sequences at 3 T.

Materials and methods

The knees of 10 healthy volunteers (mean age, 24.4 ± 5.6 years) were scanned at a 3 T MR scanner with water-excited 3D Fast-Low Angle Shot (FLASH), True Fast Imaging with Steady-state Precession (TrueFISP), Sampling Perfection with Application-optimized Contrast using different flip-angle Evolutions (SPACE) as well as conventional and two individually weighted Double-Echo Steady-State (DESS) sequences. The MR images were evaluated qualitatively and quantitatively (signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), SNR efficiency, CNR efficiency). Quantitative parameters were compared by means of a Tukey-test and sequences were ranked according to SNR/CNR, SNR/CNR efficiency and qualitative image grading.

Results

The highest SNR was measured for SPACE (34.0 ± 5.6), the highest CNR/CNR efficiency (cartilage/fluid) for the individually weighted DESS (46.9 ± 18.0/2.18 ± 0.84). SPACE, individually weighted and conventional DESS were ranked best with respect to SNR/CNR and SNR/CNR efficiency. The DESS sequences also performed best in the qualitative evaluation. TrueFISP performed worse, FLASH worst. The individually weighted DESS sequences were generally better than the conventional DESS with the significant increase of cartilage-fluid contrast (46.9 ± 18.0/31.9 ± 11.4 versus 22.0 ± 7.3) as main advantage.

Conclusion

Individually weighted DESS is the most promising candidate; all tested sequences performed better than FLASH.     

Benefits for bone from resistance exercise and nutrition in long-duration spaceflight: Evidence from biochemistry and densitometry

Exercise has shown little success in mitigating bone loss from long-duration spaceflight. The first crews of the International Space Station (ISS) used the “interim resistive exercise device” (iRED), which allowed loads of up to 297 lb_f (or 1337 N) but provided little protection of bone or no greater protection than aerobic exercise. In 2008, the Advanced Resistive Exercise Device (ARED), which allowed absolute loads of up to 600 lb_f (1675 N), was launched to the ISS. We report dietary intake, bone densitometry, and biochemical markers in 13 crewmembers on ISS missions from 2006 to 2009. Of these 13, 8 had access to the iRED and 5 had access to the ARED. In both groups, bone-specific alkaline phosphatase tended to increase during flight toward the end of the mission (p = 0.06) and increased 30 days after landing (p < 0.001). Most markers of bone resorption were also increased in both groups during flight and 30 days after landing (p < 0.05). Bone densitometry revealed significant interactions (time and exercise device) for pelvis bone mineral density (BMD) and bone mineral content (p < 0.01), hip femoral neck BMD (p < 0.05), trochanter BMD (p < 0.05), and total hip BMD (p < 0.05). These variables were unchanged from preflight only for ARED crewmembers, who also returned from flight with higher percent lean mass and lower percent fat mass. Body mass was unchanged after flight in both groups. All crewmembers had nominal vitamin D status (75 ± 17 nmol/L) before and during flight. These data document that resistance exercise, coupled with adequate energy intake (shown by maintenance of body mass determined by dual-energy X-ray absorptiometry [DXA]) and vitamin D, can maintain bone in most regions during 4- to 6-month missions in microgravity. This is the first evidence that improving nutrition and resistance exercise during spaceflight can attenuate the expected BMD deficits previously observed after prolonged missions. © 2012 American Society for Bone and Mineral Research.     

3D-imaging of the knee with an optimized 3D-FSE-sequence and a 15-channel knee-coil

Objectives

To evaluate the clinical usefulness of an optimized 3D-Fast-Spin-Echo-sequence (3D-SPACE) in combination with a 15-channel knee-coil for 3D-imaging of the knee at 3 T.

Methods

15 volunteers and 50 consecutive patients were examined at 3 T with fat-saturated moderately T2-weighted 3D-SPACE (Voxel-size (VS): 0.6 mm × 0.5 mm × 0.5 mm/acquisition-time (AT) 10:44 min) using a 15-channel knee-coil. Flip angle optimization and radial k-space reordering were applied. Signal- and contrast-to-noise-ratios (SNR, CNR) were compared to non-optimized 3D-SPACE (8-channel knee-coil) and conventional 2D-FSE (VS: 0.4 mm × 0.4 mm × 3 mm/total AT: 12 min). Two radiologists independently rated depiction of internal knee structures and assessed detection and depiction of cartilage and meniscus abnormalities compared to conventional 2D-FSE-sequences. Sensitivity and specificity were calculated for a subgroup with arthroscopy as reference standard. Statistical analysis was performed with paired t-tests, confidence intervals and weighted-κ-coefficients.

Results

SNR and CNR particularly of fluid/cartilage of optimized 3D-SPACE were significantly higher (p < 0.05) than of the non-optimized 3D-sequence and conventional 2D-sequence. Blurring and image inhomogeneity were reduced in the optimized sequence. The thin slice-thickness was beneficial for depiction of problematical anatomical structures such as meniscal roots. 3D-SPACE showed significantly higher diagnostic confidence (p < 0.05) for diagnosis of cartilage lesions of the femoral trochlea. Overall sensitivity and specificity of 3D-SPACE and 2D-FSE for cartilage lesions was 82.3%/80.2% and 79.4%/84.2% and 100%/86.4% and 92.3%/81.8% for meniscus lesions.

Conclusions

Optimized 3D-SPACE provides significantly higher signal and contrast compared to conventional 2D-FSE, particularly for fluid and cartilage, leading to improved diagnostic confidence, particularly in problematic areas, such as the femoral trochlea.     

固相致敏血球凝聚试验检测肉毒毒素的改进

为了克服ELISA和固相放射免疫(SPRIA)试验中存在的某些问题,Braolburne等1979年利用抗体致敏红血球作为显示剂,设计了固相血球凝聚(SPACE)系统,即先用抗体包被聚苯乙烯血凝滴定板,洗板后加检材(抗原)结合,然后加抗体致敏红血球作用,根据血球凝聚(固相吸附)     

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.