Accelerated 3D echo-planar spectroscopic imaging at 4 Tesla using modified blipped phase-encoding.

Whole-brain echo-planar spectroscopic imaging (EPSI) often substantially lengthens MRI/MRSI (magnetic resonance spectroscopic imaging) protocols. To halve acquisition time, application of a blipped phase-encoding (PE) gradient during the EPSI readout (RO) was previously suggested by PE of the even RO echoes in k-space at an interstitial location along k(PE), separated from the odd RO echoes, effectively reducing the number of PEs by a factor of 2. However, the approach is very susceptible to phase inconsistencies between even and odd RO echoes in the presence of B(0) inhomogeneities and gradient imbalance, leading to ghosting in the PE direction. In this work, the blipped PE gradient is placed in between pairs of even/odd RO gradient lobes to avoid these problems. This approach is demonstrated in a phantom and in normal human brain in vivo at 4T. While the proposed method allows substantial reduction in metabolite ghosting, it may be limited by the presence of a relatively large spurious signal at the Nyquist frequency.     

q-Space diffusion of myelin-deficient spinal cords.

The apparent water diffusion anisotropy in white matter (WM) of excised spinal cords of myelin-deficient (md) rats and their age-matched controls was studied by high-b-value q-space diffusion MRS and MRI at different diffusion times. Non-monoexponential signal decay was observed at long diffusion times. The mean displacements in the md spinal cords were found to be higher than those of the controls. The apparent anisotropy (AA) of the fast-diffusing component was found to decrease more dramatically with the increase in diffusion time for the md spinal cords as compared with controls, whereas the AA of the slow-diffusing component in the controls was found to increase with the increase in diffusion time while that of the md cords decreased with the increase in diffusion time. When diffusion MRI was performed, similar diffusion anisotropy was extracted for the md and control spinal cords at diffusion times of 22 and 50 ms. Only at a diffusion time of about 200 ms was a significant difference obtained in the AA of the two groups. This originates from the much smaller increase in the mean displacement perpendicular to the fiber direction in the control group vs. the md group when the diffusion time was increased.     

Functional outcome and general health status in patients after arthroscopic release in adhesive capsulitis

Frozen shoulder is said to be a self-limiting entity but full recovery often takes more than 2 years. For that, most patients are unwilling to tolerate painful restriction while awaiting resolution. We prospectively investigated 30 patients (16 women, 14 men) for the outcome of arthroscopic capsular release in idiopathic frozen shoulder. Results were determined by the assessment of subjective and objective parameters to estimate both shoulder function and general health status. Symptoms persisted without improvement for a minimum of 6 months of conservative treatment. Preoperative average American shoulder and elbow surgeons score (ASES) was 35, visual analog scale (VAS) to measure pain was 7, and simple shoulder test (SST) was 4. Mean scores of the physical component of SF-36 were considerably reduced. Mean forward elevation was 85°, average abduction was 70°, mean internal rotation was 15°, and mean external rotation was 10°. Patients were followed-up at 6 weeks, 3, 6, 12 months and by a mean of 36 months. Range of motion for all planes improved (P < 0.05). Median VAS reduced to 2, average ASES increased to 91, and SST enhanced to a mean of 10 (P < 0.05). We stated improvement of the physical components in the SF-36 questionnaire in particular bodily pain and the role-physical score. There were no significant differences between the measurements in the early postoperative phase compared to the mid-term follow-up (P > 0.05). Our results demonstrate that arthroscopic release of refractory idiopathic frozen shoulder combined with a gentle manipulation provides reliable expectations for improvement in both clinical and general health status for most patients. We recommend the use of a limb-specific and a general-health-status questionnaire to conclude the benefit of the surgical intervention and contribute the optimization of a therapy concept more effectively.     

Water- and fat-suppressed proton projection MRI (WASPI) of rat femur bone.

Investigators often study rats by microCT to investigate the pathogenesis and treatment of skeletal disorders in humans. However, microCT measurements provide information only on bone mineral content and not the solid matrix. CT scans are often carried out on cancellous bone, which contains a significant volume of marrow cells, stroma, water, and fat, and thus the apparent bone mineral density (BMD) does not reflect the mineral density within the matrix, where the mineral crystals are localized. Water- and fat-suppressed solid-state proton projection imaging (WASPI) was utilized in this study to image the solid matrix content (collagen, tightly bound water, and other immobile molecules) of rat femur specimens, and meet the challenges of small sample size and demanding submillimeter resolution. A method is introduced to recover the central region of k-space, which is always lost in the receiver dead time when free induction decays (FIDs) are acquired. With this approach, points near the k-space origin are sampled under a small number of radial projections at reduced gradient strength. The typical scan time for the current WASPI experiments was 2 hr. Proton solid-matrix images of rat femurs with 0.4-mm resolution and 12-mm field of view (FOV) were obtained. This method provides a noninvasive means of studying bone matrix in small animals.     

Adiabatic refocusing pulses for volume selection in magnetic resonance spectroscopic imaging.

Because of their excellent slice profiles and high immunity to RF inhomogeneity, adiabatic full passage (AFP) pulses are ideal for use in spatial localization. The nonlinear, position-dependent phase of a single AFP pulse generated during refocusing of transverse magnetization traditionally is eliminated by using identical pairs of AFP pulses, at the expense of increased RF power deposition and increased echo time (TE). Here it is shown that one can achieve significant phase refocusing by executing single AFP pulses along non-equivalent spatial axes. When used for volume selection in MR spectroscopic imaging (MRSI) the remaining nonlinear phase becomes inconsequential when the phase across a spectroscopic volume is small. Selection of rectangular and octagonal volumes is demonstrated with half the number of AFP pulses used in the traditional approach. It is shown that octagonal volume selection in the human brain provides excellent suppression of extracranial lipids, and thus allows multislice (1)H MRSI at 4 Tesla to be performed within the guidelines for RF power deposition.     

Fact or Fiction? MRI of Alar Ligaments and Craniocervical Junction Joints in Whiplash Syndrome

Abstract Whiplash injury of the cervical spine is a frequent issue in medical expertises and causes enormous consequential costs for motor insurance companies. Some authors accuse posttraumatic changes of alar ligaments to be causative of consequential disturbances, although biomechanical experiments achieve contradictory results and neuropsychiatric studies do not support this thesis. MRI provides excellent visualization of alar ligaments. However, signal alterations of alar ligaments must be differentiated from common normal variants. Functional MRI provides no diagnostic yield.      

关节镜下松解术治疗冻结肩25例报告

目的探讨关节镜下松解术治疗冻结肩的疗效.方法2001年10月～2003年10月,我院对25例冻结肩在关节镜下行松解术.全麻下肩关节后路进镜,前路进射频电刀烧灼肱二头肌长头肌腱及肩袖间隙部位的滑膜充血炎症区,切割盂肱上韧带、盂肱中韧带、肩胛下肌肌腱关节囊内部分,手法松解剩余挛缩.25例术后3、6个月随访肩关节活动范围及美国肩肘协会评分(ASES).结果手术时间75～98 min,平均85 min.无术中并发症.25例除术后1周肩关节内旋与术前无明显改善外(x2=8.558,P=0.073),术后各个时期肩关节其它活动范围比术前均有明显改善(P＜0.05).术后3个月和6个月比术后1周改善更明显(P＜0.05).25例术后3个月和6个月ASES评分(87.4±4.6,88.1±6.0)均比术前(45.8±10.0)明显改善(q=28.738,29.221;P＜0.05),但3个月与6个月评分相比较无显著性差异(q=0.484,P＞0.05).结论肩关节镜下手术松解冻结肩可以明显缩短病程,取得稳定满意的效果.     

Wernicke脑病的MRI诊断价值

目的探讨Wernicke脑病的MRI表现,以提高诊断水平。方法搜集7例经临床证实的Wernicke脑病的MRI资料进行回顾性分析。结果双侧丘脑、第三脑室周围广泛对称性异常信号(6例),导水管周围、桥脑被盖异常信号(7例),乳头体、丘脑下部、穹隆及四脑室周围异常信号(2例),上述病变呈长T1长T2信号,FLAIR序列呈高信号,2例DWI序列呈高信号,脑室壁模糊,2例静注Gd-DTPA增强后病变区域对比增强,1例可见侧脑室周围小血管放射状强化。结论Wernicke脑病具有典型的MRI表现,对临床诊断及治疗有重要意义。     

MR流量测定的实验研究

目的探讨MR流量测量与不同感兴趣区(ROI)直径的关系。方法使用Philips 1.5T双梯磁共振机流量测定程序,测量2mm内径塑胶管中不同流量的水(0.5、1.0、1.5、2.0、2.5ml/s),不同流向(流入及流出方向)、不同ROI位置(测量图中心区和偏中心区)与不同的ROI直径(直径0.5、1.0、1.5、2.0mm)流量变化关系,统计计算标准的ROI直径。结果在不同流量、流向和测量位置中,流量与ROI直径大小存在明显的直线相关(r>0.95,P<0.05),ROI直径大小显著地影响测量结果,当ROI直径取值等于测量图直径的0.6040±0.0480时,所测结果与实际流量一致。在不同流量下的不同流向及ROI位置对流量测定无影响(P>0.05)。结论对直径2mm流量测定,应选取测量图上直径的0.6040±0.0480 ROI进行。     

Serial in vivo MR tracking of magnetically labeled neural spheres transplanted in chronic EAE mice.

Neural stem cell (NSC) transplantation has been shown to attenuate the severity of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Central to the future success of NSC transplantation in MS is the ability of transplanted cells to migrate from the site of transplantation to relevant foci of disease. Using magnetically labeled mouse neurospheres and human embryonic stem cell (hESC)-derived neurospheres, we applied serial magnetic resonance imaging (MRI) to assess the biodynamics of transplanted cell migration in a chronic mouse EAE model. Magnetic labeling did not affect the in vitro and in vivo characteristics of cells as multipotential precursors. Cell migration occurred along white matter (WM) tracts (especially the corpus callosum (CC), fimbria, and internal capsule), predominantly early in the acute phase of disease, and in an asymmetric manner. The distance of cell migration correlated well with clinical severity of disease and the number of microglia in the WM tracts, supporting the notion that inflammatory signals promote transplanted cell migration. This study shows for the first time that hESC-derived neural precursors also respond to tissue signals in an MS model, similarly to rodent cells. The results are directly relevant for designing and optimizing cell therapies for MS, and achieving a better understanding of in vivo cell dynamics and cell-tissue interactions.