Combined spin- and gradient-echo perfusion-weighted imaging

In this study, a spin- and gradient-echo echo-planar imaging (SAGE EPI) MRI pulse sequence is presented that allows simultaneous measurements of gradient-echo and spin-echo dynamic susceptibility-contrast perfusion-weighted imaging data. Following signal excitation, five readout trains were acquired using spin- and gradient-echo echo-planar imaging, all of them with echo times of less than 100 ms. Contrast agent concentrations in brain tissue were determined based on absolute R2* and R(2) estimates rather than relative changes in the signals of individual echo trains, producing T(1)-independent dynamic susceptibility-contrast perfusion-weighted imaging data. Moreover, this acquisition technique enabled vessel size imaging through the simultaneous quantification of R2* and R(2), without an increase in acquisition time. In this work, the concepts of SAGE EPI pulse sequence and results in stroke and tumor imaging are presented. Overall, SAGE EPI combined the advantages of higher sensitivity to contrast agent passage of gradient-echo perfusion-weighted imaging with better microvascular selectivity of spin-echo perfusion-weighted imaging.     

Compensation of slice profile mismatch in combined spin‐ and gradient‐echo echo‐planar imaging pulse sequences

Combined acquisition of gradient‐echo and spin‐echo signals in MRI time series reveals additional information for perfusion‐weighted imaging and functional MRI because of differences in the sensitivity of gradient‐echo and spin‐echo measurements to the properties of the underlying vascular architecture. The acquisition of multiple echo trains within one time frame facilitates the simultaneous estimation of the transversal relaxation parameters R₂ and R. However, the simultaneous estimation of these parameters tends to be incorrect in the presence of slice profile mismatches between signal excitation and subsequent refocusing pulses. It is shown here that improvements in pulse design reduced R₂ and R estimation errors. Further improvements were achieved by augmented parameter estimation through the introduction of an additional parameter δ to correct for discordances in slice profiles to facilitate more quantitative measurements. Moreover, the analysis of time‐resolved acquisitions revealed that the temporal stability of R₂ estimates could be increased with improved pulse design, counteracting low contrast‐to‐noise ratios in spin‐echo‐based perfusion and functional MRI. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

中国城市居民主观幸福感量表在基督教徒群体中的试用

目的对中国城市居民主观幸福感量表应用于基督徒群体的测量特性进行检验,对基督教徒主观幸福感进行初步研究。方法在广东省广州市范围内随机取样（n=304）,采用单因素分析方法对基督徒主观幸福感进行了组群分析。结果中国城市居民主观幸福感量表运用于基督徒群体时有良好的信度和效度;基督徒主观幸福感在主观幸福感总量表以及10个分量表的得分都显著高于居民平均水平;性别和年龄状况分别不同程度的影响基督徒的主观幸福感,收入程度对基督徒主观幸福感的影响则不明显。结论中国城市居民主观幸福感量表可以作为研究我国城市基督徒主观幸福感的一种可供选择的工具。     

Fast high-resolution brain imaging with balanced SSFP: Interpretation of quantitative magnetization transfer towards simple MTR

Magnetization transfer (MT) reflects the exchange of magnetization between protons bound to macromolecules, such as lipids and proteins, and protons in free liquid, and thus might be an early marker for subtle and undetermined pathologic changes in tissue. Detailed analysis of the entire MT phenomenon, however, commonly requires extensive data acquisition and scanning time, and hence is only of limited clinical interest. Therefore, in practice, magnetization transfer effects are commonly confined into a simple ratio measure, the so-called magnetization transfer ratio (MTR), calculated from a MT-weighted and a non-MT-weighted image. However, subtle physiologic and pathologic changes in tissue, invaluable for specific diagnostic imaging, may be lost since MTR-values depend not only on quantitative magnetization transfer (qMT) parameters but also on sequence parameters and relaxation properties.In order to evaluate and assess the diagnostic specificity of MTR versus qMT, high-resolution whole brain MT data was collected from twelve healthy volunteers using balanced steady-state free precession (bSSFP). In contrast to common MT imaging based on spoiled gradient echo (SPGR) sequences, whole brain qMT imaging can be performed with MT-sensitized bSSFP within a clinically feasible acquisition time. Hence, MT-sensitized bSSFP provides access to both MTR and qMT parameters within a clinical setting. The reliability and possible diagnostic value of MTR are analyzed for twelve white matter (WM) and eleven gray matter (GM) structures of the normal appearing brain.Strong correlations were found within and between longitudinal and transverse relaxation times (T1, T2) and MT parameters (ratio between macromolecular and water protons, F, and magnetization exchange rate, kf), whereas weaker correlations were observed between MTR-values and relaxation times or MT parameters. Structures with highly similar MTR-values, such as the crus cerebri and the anterior commissure in the WM, or the pallidum and the amygdala in the GM, however, were also found that showed significant differences in most quantitative parameters. This observation was confirmed from simulations revealing that the overall effect on MTR from an increase (decrease) in relaxation times may be counterbalanced with a decrease (increase) in MT parameters. These findings corroborate the expectation that qMT is superior to MTR imaging, especially for the evaluation and assessment of pathologic or physiological changes in healthy and pathologic brain tissue.     

短暂性脑缺血发作的脑电地形图与功能磁共振及血管病变的相关研究

目的观察短暂性脑缺血发作（TIA）患者间期脑电地形图（BEAM）变化情况,并与磁共振、血管病变对比,深入探讨TIA的病变机制。方法 18例颈内动脉系统TIA患者均行常规头MRI（T1WI、T2WI）、功能磁共振（DWI、PWI）,BEAM检查,综合磁共振血管成像（MRA）、数字减影脑血管造影（DSA）及颈动脉超声联合经颅多普勒超声（TCD,简称超声）检测判定血管病变并对上述结果进行分析。结果 BEAM病灶检出率94.4%,灌注加权成像（PWI）异常率70.6%,TCD异常率50%,DWI异常率16.7%。TIA间期BEAM广泛异常77.8%,责任病变部位集中于中央、顶部、前颞,主要表现为α频段较对侧功率降低,δ和θ频段较对侧功率增高。结论将BEAM和TCD/PWI相结合,可为TIA提供可靠的辅助检查。临床医生应重视TIA患者的神经保护治疗。     

The Utility of the Personal Wellbeing Index Intellectual Disability Scale in an Australian Sample

Background Subjective wellbeing (SWB) in people with intellectual disabilities has been the focus of increased interest in the identification of support needs and as an outcome measure for interventions and service delivery evaluations. It is therefore important to conduct further research in this area, and to develop appropriate scales to measure SWB. Methods A new scale, the Personal Wellbeing Index‐Intellectual Disability (PWI‐ID) was administered to 114 adults with mild (n = 82) or moderate (n = 32) level ID in Victoria, Australia. Results The PWI‐ID demonstrated good reliability and validity. A comparison of the findings with previous research indicates that participants’ SWB levels are within the normative range, and are similar to those reported by the general population. Conclusions The results support the notion that individuals with ID do not experience life quality lower than normal, which can be explained theoretically by the Theory of Subjective Wellbeing Homeostasis. The use of the PWI‐ID may ultimately assist in ensuring that the needs of people with ID are being met and inform the planning and delivery of congruent resources and services.     

Support vector machine multiparametric MRI identification of pseudoprogression from tumor recurrence in patients with resected glioblastoma

Purpose

To automatically differentiate radiation necrosis from recurrent tumor at high spatial resolution using multiparametric MRI features.

Materials and Methods

MRI data retrieved from 31 patients (15 recurrent tumor and 16 radiation necrosis) who underwent chemoradiation therapy after surgical resection included post‐gadolinium T1, T2, fluid‐attenuated inversion recovery, proton density, apparent diffusion coefficient (ADC), and perfusion‐weighted imaging (PWI) ‐derived relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and mean transit time maps. After alignment to post contrast T1WI, an eight‐dimensional feature vector was constructed. An one‐class‐support vector machine classifier was trained using a radiation necrosis training set. Classifier parameters were optimized based on the area under receiver operating characteristic (ROC) curve. The classifier was then tested on the full dataset.

Results

The sensitivity and specificity of optimized classifier for pseudoprogression was 89.91% and 93.72%, respectively. The area under ROC curve was 0.9439. The distribution of voxels classified as radiation necrosis was supported by the clinical interpretation of follow‐up scans for both nonprogressing and progressing test cases. The ADC map derived from diffusion‐weighted imaging and rCBV, rCBF derived from PWI were found to make a greater contribution to the discrimination than the conventional images.

Conclusion

Machine learning using multiparametric MRI features may be a promising approach to identify the distribution of radiation necrosis tissue in resected glioblastoma multiforme patients undergoing chemoradiation. J. Magn. Reson. Imaging 2011;33:296–305. © 2011 Wiley‐Liss, Inc.     

PWI联合MRS在鞍旁海绵状血管瘤与脑膜瘤鉴别诊断中的价值

目的探讨灌注加权成像(perfusion weighted imaging,PWI)、磁共振波谱成像(magnetic resonance spectroscopy,MRS)对鞍旁海绵状血管瘤和鞍旁脑膜瘤的鉴别诊断价值。方法回顾性分析经证实的6例鞍旁海绵状血管瘤和10例鞍旁脑膜瘤患者磁共振常规扫描、MRS、PWI及增强扫描影像资料,测量肿瘤内最大局部血容量(region cerebral blood volume,rCBV)值与正常白质区局部血容量值并求两者的比值(nCBV),对两组间nCBV值进行统计学分析。结果常规和增强扫描在二者鉴别上困难,但鞍旁脑膜瘤组nCBV(6.119±2.564)值明显高于鞍旁海绵状血管瘤组nCBV(1.367±1.132),差异有显著性;鞍旁海绵状血管瘤波谱特点为无N-乙酰天门冬氨酸、胆碱和肌酸等峰,只见明显脂质峰;鞍旁脑膜瘤无N-乙酰天门冬氨酸、肌酸等峰,均见明显胆碱峰,3例可见丙氨酸峰,两者MRS表现具有明显差异性。结论 PWI联合MRS在鞍旁海绵状血管瘤与鞍旁脑膜瘤的鉴别诊断中具有较高的价值。     

磁共振灌注成像技术在运动性失语中的价值探讨

目的研究磁共振灌注成像对运动性失语脑激活图中肿瘤内及肿瘤周边激活区阳性率显示的价值。方法 17例肿瘤患者,语言磁共振任务完成后,加做PWI检查,并在Linux系统下做Bold激活区与PWI图像的融合。PWI图中白色血管若与红色的脑激活区重叠,则认为是假阳性结果;反之,则认为是与语言相关的激活区。结果17例病人中,Ⅱ级星形胶质细胞瘤7例,Ⅲ级星形胶质细胞瘤5例,胶母细胞瘤5例。在7例Ⅱ级星形胶质细胞瘤患者的图片命名任务激活图中,位于肿瘤内及肿瘤周边的激活区共计11处,其中BOLD激活信号与CBV图中的血管影重叠的共计3处,两者不重叠的共计8处,即假阳性率26%,阳性率74%;在5例Ⅲ级星形胶质细胞瘤患者中,位于肿瘤内及肿瘤周边的激活区共计14处,其中BOLD激活信号与CBV图中的血管影重叠的共计4处,两者不重叠的共计10处,即假阳性率31%,阳性率69%;在5例胶母细胞瘤的图片命名任务激活图中,位于肿瘤内及肿瘤周边的激活区共计18处,其中BOLD激活信号与CBV图中的血管影重叠的共计7处,两者不重叠的共计11处,即假阳性率39%,阳性率61%。结论 BOLD激活信号阳性率与肿瘤级别呈负相关,结合PWI图像是判断Bold信号真实性的较特异方法。