Clinical functional MRI of sensorimotor cortex using passive motor and sensory stimulation at 3 Tesla

Purpose:

To establish a passive motor paradigm for clinical functional MRI (fMRI) that could be beneficial for patients with motor or attention deficits who are not able to perform active motor tasks.

Materials and Methods:

A novel standardized sensorimotor fMRI protocol was applied in 16 healthy volunteers at 3 Tesla (T) using active and passive motor tasks as well as sensory stimulation of hands and feet. Data analysis was carried out individually using a dynamic thresholding routine.

Results:

Active motor tasks yielded time efficient and robust blood‐oxygen‐level‐dependent (BOLD) signals in primary motor cortex. Noteworthy, it was possible to achieve equal activation levels within identical anatomical localization for passive and active motor tasks with these paradigms.

Conclusion:

Patients unable to perform active movements can benefit from paradigms with passive motor and sensory stimulation. Therefore, we recommend these paradigms for functional somatotopic mapping of the central region at 3T in clinical routine. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

脑肿瘤患者术前手运动区的功能MRI

目的：探讨应用功能ＭＲＩ（ｆＭＲＩ）研究脑肿瘤患者手运动区（ＨＲＡ）的结构和功能变化特征。材料和方法：２２例位于或邻近实级运动皮质肿瘤患者采用单次激发ＧＲＥ－ＥＰＩ序列采集Ｔ＾＊２Ｗ图像,共３个周期即６个时相,每个周期包括手指对掌运动激发的１０幅活动图像和１０幅静止图像。经离线工作站重建获取减影后的差别图像,设定ＲＯＩ,描绘动态时间－信号强度曲线,测量信号强度（ＳＩ）上升百分率。结果：８例ＨＲＡ呈局限分布,１４例呈弥漫分布。肿瘤实体的边缘与ＨＲＡ活动中心的最短距离为０．３￣２．８ｃｍ。有５例患者在肿瘤内见到高信号区。肿瘤侧ＳＩ上升百分率为１．５％￣３％,正常侧ＳＩ上升百分率为２．５％￣１０％,结论：对位于或邻近初级运动皮质脑肿瘤患者,功能ＭＲＩ为术前手术计划的制定提供了一种非侵袭性而有效的方法。如果肿瘤实体的边     

Blood oxygenation level-dependent (BOLD) MRI of human skeletal muscle at 1.5 and 3 T

Purpose:

To evaluate the dependence of skeletal muscle blood oxygenation level‐dependent (BOLD) effect and time course characteristics on magnetic field strength in healthy volunteers using an ischemia/reactive hyperemia paradigm.

Materials and Methods:

Two consecutive skeletal muscle BOLD magnetic resonance imaging (MRI) measurements in eight healthy volunteers were performed on 1.5 T and 3.0 T whole‐body MRI scanners. For both measurements a fat‐saturated multi‐shot multiecho gradient‐echo EPI sequence was applied. Temporary vascular occlusion was induced by suprasystolic cuff compression of the thigh. T2* time courses were obtained from two different calf muscles and characterized by typical curve parameters. Ischemia‐ and hyperemia‐induced changes in R2* (ΔR2*) were calculated for both muscles in each volunteer at the two field strengths.

Results:

Skeletal muscle BOLD changes are dependent on magnetic field strength as the ratio ΔR2*(3.0 T)/ΔR2*(1.5 T) was found to range between 1.6 and 2.2. Regarding time course characteristics, significantly higher relative T2* changes were found in both muscles at 3.0 T.

Conclusion:

The present study shows an approximately linear field strength dependence of ΔR2* in the skeletal muscle in response to ischemia and reactive hyperemia. Using higher magnetic fields is advisable for future BOLD imaging studies of peripheral limb pathologies. J. Magn. Reson. Imaging 2012;35:1227‐1232. © 2012 Wiley Periodicals, Inc.     

3T高场强功能MRI在脑功能区胶质瘤皮质电刺激手术中的应用

目的研究应用3T高场强功能MRI（fMRI）定位脑运动功能区，及在脑胶质瘤直接皮质电刺激手术中的指导作用。方法26例邻近或累及脑运动功能区的胶质瘤患者术前采用双手握拳刺激策略，根据血氧水平依赖（BOLD）原理进行功能成像。经工作站提供的BOLD功能图像分析软件包进行分析，获得脑运动功能区的激活图像，制定手术方案。所有患者均在唤醒麻醉下进行显微外科手术，在术前fMRI指导下利用直接皮质电刺激定位运动区。在保护脑功能不受损的前提下，最大程度地切除胶质瘤。术前、术后均行Karnofsky生活状态（KPS）评分，判断患者的状态。结果26例术前BOLD运动fMRI有23例获得良好的手运动脑功能区激活图像。患者在唤醒麻醉下，在术前fMRI指导下利用直接皮质电刺激快捷、准确定位初级运动皮质区，并且两者具有良好的一致性。同时术前fMRI提供术中未检测到的脑功能区的信息，相互补充。术前KPS评分80．0～90．0分患者21例（平均85．7分）术后恢复至平均95．2分，术前KPS评分40．0～70．0分患者5例（平均68．0分）术后恢复至平均90．0分。结论术前fMRI可活体和无创地描绘出脑运动功能区与肿瘤的功能解剖位置关系，优化手术方案，在唤醒麻醉下指导直接皮质电刺激定位运动区的手术，实现最大程度保护脑功能，并最大程度地切除肿瘤。     

New coil positioning method for interleaved transcranial magnetic stimulation (TMS)/functional MRI (fMRI) and its validation in a motor cortex study

Purpose

To develop and test a novel method for coil placement in interleaved transcranial magnetic stimulation (TMS)/functional MRI (fMRI) studies.

Materials and Methods

Initially, a desired TMS coil position at the subject's head is recorded using a neuronavigation system. Subsequently, a custom‐made holding device is used for coil placement inside the MR scanner. The parameters of the device corresponding to the prerecorded position are automatically determined from a fast structural image acquired directly before the experiment. The spatial accuracy of our method was verified on a phantom. Finally, in a study on five subjects, the coil was placed above the cortical representation of a hand muscle in M1 and the blood oxygenation level‐dependent (BOLD) responses to short repetitive TMS (rTMS) trains were assessed using echo‐planar imaging (EPI) recordings.

Results

The spatial accuracy of our method is in the range of 2.9 ± 1.3 (SD) mm. Motor cortex stimulation resulted in robust BOLD activations in motor‐ and auditoryrelated brain areas, with the activation in M1 being localized in the hand knob.

Conclusion

We present a user‐friendly method for TMS coil positioning in the MR scanner that exhibits good spatial accuracy and speeds up the setup of the experiment. The motor‐cortex study proves the viability of the approach and validates our interleaved TMS/fMRI setup. J. Magn. Reson. Imaging 2009;29:189–197. © 2008 Wiley‐Liss, Inc.     

Functional MRI activation of somatosensory and motor cortices in a hand-grafted patient with early clinical sensorimotor recovery

The aim of this study was to investigate somatosensory and motor cortical activity with functional MRI (fMRI) in a hand-grafted patient with early clinical recovery. The patient had motor fMRI examinations before transplantation, and motor and passive tactile stimulations after surgery. His normal hand and a normal group were studied for comparison. A patient with complete brachial plexus palsy was studied to assess the lack of a fMRI signal in somatosensory areas in the case of total axonal disconnection. Stimulating the grafted hand revealed significant activation in the contralateral somatosensory cortical areas in all fMRI examinations. The activation was seen as early as 10 days after surgery; this effect cannot be explained by the known physiological mechanisms of nerve regeneration. Although an imagination effect cannot be excluded, the objective clinical recovery of sensory function led us to formulate the hypothesis that a connection to the somatosensory cortex was rapidly established. Additional cases and fundamental studies are needed to assess this hypothesis, but several observations were compatible with this explanation. Before surgery, imaginary motion of the amputated hand produced less intense responses than executed movements of the intact hand, whereas the normal activation pattern for right-handed subjects was found after surgery, in agreement with the good clinical motor recovery.     

正常人及脑肿瘤患者听觉性中英文语言刺激的fMRI研究

目的应用BOLD-MfRI研究正常人及脑肿瘤患者听觉性中英文语言皮层定位并探讨其对脑肿瘤的临床应用价值。方法应用MarconiEclipse1.5T超导型磁共振机,30例受试者,行听觉性中、英文语言刺激的BOLD-MfRI,以定位正常人和脑肿瘤患者的语言皮层。结果正常人听觉性中英文语言任务激活区域均以左侧大脑半球为主,主要有双侧颞横回、Wernicke区、Broca区和SMA区。中文语言任务刺激时脑区激活面积和程度比英文语言任务大,但英文语言任务时可见更明显的Broca区和角回激活。累及功能皮层的脑肿瘤患者患侧半球可见残留部分功能激活区,但激活区移位,分布弥散,激活程度及范围较正常人略增高。未累及功能皮层者功能区定位与正常人大致相同。结论BOLD-MfRI是一种有效而无创的功能皮层定位方法,有利于脑肿瘤的精确定位诊断并指导临床治疗。     

Improvement in breast lesion characterization with dynamic contrast-enhanced MRI using pharmacokinetic modeling and bookend T(1) measurements.

Dynamic contrast-enhanced breast MR imaging was performed on 14 patients (five cancerous lesions, nine benign) with slice-selective spoiled gradient-recalled echo (2D SPGR) imaging. Adiabatic saturation recovery T(1) measurements were performed before (T(1pre)) and after (T(1post)) 2D SPGR imaging. These two "bookend" T(1) measurements were used to calibrate the equations which were employed to convert the time course of the 2D SPGR signal strength to T(1)-vs.-time, which in turn was used to compute the gadolinium concentration-vs.-time ([C](t)) in the lesion. The extraction-flow product (EF) was computed for each lesion by pharmacokinetic modeling of [C](t). For this study, EF provided a sensitivity and specificity for cancer of 100% and 78%, respectively. When only T(1pre) was used to estimate [C](t) (which assumes a priori knowledge of the shape and amplitude of the slice profile), the sensitivity and specificity fell to 80% and 56%, respectively. This is presumably due to unexpected variations in the shape and/or amplitude of the slice profile, which could be caused by factors such as patient-to-patient variations in breast geometry or inconsistently set transmit gains. Therefore, both T(1pre) and T(1post) measurements are necessary for optimum sensitivity and specificity using pharmacokinetic analysis.     

Preliminary observations and diagnostic value of lipid peak in ovarian thecomas/fibrothecomas using in vivo proton MR spectroscopy at 3T

Purpose:

To retrospectively evaluate the significance of lipid peak in in vivo proton magnetic resonance (MR) spectroscopy for the diagnosis of ovarian thecomas/fibrothecomas in patients with solid gynecologic tumors exhibiting totally or partially low signal intensity on T2‐weighted images.

Materials and Methods:

MR spectroscopy was performed in patients with pathologically diagnosed gynecologic tumors at 3T MRI. Single‐voxel MR spectroscopy data were collected from a single square volume of interest that encompassed the gynecologic masses. The lipid concentration level was classified into three classes (high; low; none).

Results:

A total of 20 gynecologic tumors in 20 patients were evaluated in this study. High lipid peak was observed in all seven thecomas/fibrothecomas, whereas low lipid peak was observed in only one fibroma in 13 nonthecomatous tumors (six benign ovarian tumors and seven subserosal uterine leiomyomas). The presence of lipid peak for the diagnosis of thecomas/fibrothecomas had a sensitivity of 100%, specificity of 92%, positive predictive value of 88%, and negative predictive value of 100%.

Conclusion:

The high lipid peak reflecting abundant intracellular lipid contents is considered a specific metabolite concentration for thecomas/fibrothecomas. Demonstration of high lipid peak may contribute to the diagnosis of thecomas/fibrothecomas in distinguishing from other benign ovarian fibrous tumors or subserosal uterine leiomyomas. J. Magn. Reson. Imaging 2012;36:907–911. © 2012 Wiley Periodicals, Inc.     

Real-time display of artifact-free electroencephalography during functional magnetic resonance imaging and magnetic resonance spectroscopy in an animal model of epilepsy.

Simultaneous recording of electroencephalogram (EEG) and functional MRI (fMRI) or MR spectroscopy (MRS) can provide further insight into our understanding of the underlying mechanisms of neurologic disorders. Current technology for simultaneous EEG and MRI recording is limited by extensive postacquisition processing of the data. Real-time display of artifact-free EEG recording during fMRI/MRS studies is essential in studies that involve epilepsy to ensure that they address specific EEG features such as epileptic spikes or seizures. By optimizing the EEG recording equipment to maximize the common mode rejection ratio of its amplifiers, a unique EEG system was designed and tested that allowed real-time display of the artifact-free EEG during fMRI/MRS in an animal model of epilepsy. Spike recordings were optimized by suppression of the background EEG activity using fast-acting and easily controlled inhalational anesthesia. Artifact suppression efficiency of 70-100% was achieved following direct subtraction of referentially recorded filtered EEG tracings from active electrodes, which were located in close proximity to each other (over homologous occipital cortices) and a reference electrode. Two independent postacquisition processing tools, independent component analysis and direct subtraction of unfiltered digital EEG data in MATLAB, were used to verify the accuracy of real-time EEG display.     

Discrimination of errors from neuronal activity in functional MRI of the human spinal cord by means of general linear model analysis.

Functional MRI (fMRI) of the spinal cord has been demonstrated to provide reliable and sensitive maps of neuronal activity, particularly when combined across several experiments. Individual experiments reveal neuronal activity as well as errors. The dominant source of errors is hypothesized to be physiological motion, including cardiac and respiratory motion, flow of blood and cerebrospinal fluid (CSF), and motion of the spinal cord within the spinal canal. All of the hypothesized sources of error are therefore related to cardiac and respiratory motion, which can be recorded during an fMRI experiment. Analyses were carried out with a general linear model (GLM) with peripheral pulse and respiration recordings used as models of errors. The results demonstrate that the sensitivity of spinal fMRI is improved and errors are reduced when peripheral pulse traces are used in the GLM, but no improvement was detected with the inclusion of respiratory traces.     

High-resolution MRI of the triangular fibrocartilage complex (TFCC) at 3T: comparison of surface coil and volume coil

PURPOSE: To evaluate high-resolution MRI of the triangular fibrocartilage complex (TFCC) at 3T using a surface coil (SC) or volume coil (VC). MATERIALS AND METHODS: MRI was obtained from nine volunteers in the supine position with a 3-inch SC and in prone position with a transmit-receiver wrist VC at 3 T. Coronal two-dimensional-gradient echo (2D-GRE) images (TR/TE/FA = 500 msec/15 msec/40 degrees , 1 mm slice-thickness, 60 mm field of view [FOV], 192 x 256 matrix) and coronal 3D-GRE images (TR/TE/FA = 33 msec/15 msec/10 degrees , 0.8 mm slice-thickness, 80 mm FOV, 256 x 256 matrix) were used. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the TFCC and surrounding structures were measured. For qualitative measurement, visualization of TFCC and intercarpal ligaments was graded. RESULTS: SNR of TFCC, cartilage, and bone marrow on 2D-GRE with SC/VC was as follows: 5.3/5.3 (TFCC), 16.5/14.4 (cartilage), and 3.61/3.96 (bone marrow). 3D-GRE showed similar SNR. Cartilage-TFCC/cartilage-bone marrow CNR were 11.1/12.8 (SC-2D-GRE), 8.8/10.5 (VC-2D-GRE), 14.1/15.5 (SC-3D-GRE), and 11.9/15.0 (VC-3D-GRE). Quantitative values were not significantly different between SC and VC. Visualization of TFCC and intercarpal ligament with SC was superior to that with VC. All structures show higher scores with 3D-GRE imaging compared to 2D-GRE imaging. CONCLUSION: SC may provide superior qualitative and quantitative results and can be an alternative in case of difficulty in prone position at 3T.     

Renal perfusion: comparison of saturation-recovery TurboFLASH measurements at 1.5T with saturation-recovery TurboFLASH and time-resolved echo-shared angiographic technique (TREAT) at 3.0T

PURPOSE: To investigate the dependence of semiquantitative renal perfusion parameters on the acquisition technique and field strength used. MATERIALS AND METHODS: After intravenous injection of 7-mL Gd-chelates, high-temporal-resolution turbo fast low-angle shot (TurboFLASH) renal perfusion measurements were performed on eight healthy volunteers at 1.5T and another eight healthy volunteers at 3.0T. Another eight healthy volunteers were examined at 3.0T using time-resolved echo-shared angiographic technique (TREAT) after bolus administration of 7-mL Gd-chelates with a temporal resolution of 1.4 seconds. Analysis of the first-pass perfusion data yielded the following semiquantitative renal perfusion indices: mean transit time (MTT), time to peak (TTP), maximal upslope (MUS), and maximal signal intensity (MSI). RESULTS: MTT and TTP did not show significant differences between the different techniques. MSI and MUS were significantly (P < or = 0.002) higher with TREAT (591.1 a.u./second and 103.5 a.u./second) than with TurboFLASH at both field strengths (1.5T: 400.5 a.u./second and 65.4 a.u./second; 3.0T: 362.2 a.u./second and 68.7 a.u./second). CONCLUSION: Semiquantitative renal perfusion measurements are feasible with time-resolved echo-shared sequences and TurboFLASH techniques. While MTT and TTP appear to be independent of the technique and field strength applied, MUS and MSI are higher with TREAT.     

DWI及PWI对川芎嗪治疗急性脑缺血疗效监测的实验研究

目的利用DW I及PW I动态观察缺血前预注川芎嗪(TMP)对大鼠缺血后脑实质的系列变化,探讨功能磁共振成像在脑缺血神经保护药物的作用机理、疗效监测方面的应用价值。方法建立大鼠急性脑缺血再灌注模型,30只雄性SD大鼠(280~320 g),随机分成2组(每组,n=15):实验组(A组)和对照组(B组),分别于缺血前30 m in腹腔注射TMP 100 mg/kg和生理盐水1 m l。A组、B组分别于阻闭2 h后抽出尼龙线,恢复再灌注。于再通前,再通后1、2、3、6、12 h及24 h行功能及常规磁共振扫描。对2组结果进行比较分析。结果(1)DW I显示在缺血前腹腔注射TMP 100 mg/kg可明显缩小缺血后各时间点脑缺血面积,与对照组相比,差异有统计学意义(Ρ<0.05)。(2)急性期病灶中心血流灌注减少程度2组间差异无统计学意义(P>0.05)。结论DW I及PW I可以很好地观察TMP对大鼠缺血后脑实质保护作用的动态变化,显示功能磁共振在脑缺血神经保护药物的作用机理、疗效监测等方面具有极大的应用潜力。     

Functional Neuroanatomy Associated with Natural and Urban Scenic Views in the Human Brain: 3.0T Functional MR Imaging

Objective

By using a functional magnetic resonance imaging (fMRI) technique we assessed brain activation patterns while subjects were viewing the living environments representing natural and urban scenery.

Materials and Methods

A total of 28 healthy right-handed subjects underwent an fMRI on a 3.0 Tesla MRI scanner. The stimulation paradigm consisted of three times the rest condition and two times the activation condition, each of which lasted for 30 and 120 seconds, respectively. During the activation period, each subject viewed natural and urban scenery, respectively.

Results

The predominant brain activation areas observed following exposure to natural scenic views in contrast with urban views included the superior and middle frontal gyri, superior parietal gyrus, precuneus, basal ganglia, superior occipital gyrus, anterior cingulate gyrus, superior temporal gyrus, and insula. On the other hand, the predominant brain activation areas following exposure to urban scenic views in contrast with natural scenes included the middle and inferior occipital gyri, parahippocampal gyrus, hippocampus, amygdala, anterior temporal pole, and inferior frontal gyrus.

Conclusion

Our findings support the idea that the differential functional neuroanatomies for each scenic view are presumably related with subjects'' emotional responses to the natural and urban environment, and thus the differential functional neuroanatomy can be utilized as a neural index for the evaluation of friendliness in ecological housing.     

T2 mapping of hip articular cartilage in healthy volunteers at 3T: a study of topographic variation

PURPOSE: To perform baseline T2 mapping of the hips of healthy volunteers, focusing on topographic variation, because no detailed study has involved hips. T2 mapping is a quantitative magnetic resonance imaging (MRI) technique that evaluates cartilage matrix components. MATERIALS AND METHODS: Hips of 12 healthy adults (six men and six women; mean age = 29.5 +/- 4.9 years) were studied with a 3.0-Tesla MRI system. T2 measurement in the oblique-coronal plane used a multi-spin-echo (MSE) sequence. Femoral cartilage was divided into 12 radial sections; acetabular cartilage was divided into six radial sections, and each section was divided into two layers representing the superficial and deep halves of the cartilage. T2 of these sections and layers were measured. RESULTS: Femoral cartilage T2 was the shortest (-20 degrees to 20 degrees and -10 degrees to 10 degrees, superficial and deep layers), with an increase near the magic angle (54.7 degrees ). Acetabular cartilage T2 in both layers was shorter in the periphery than the other parts, especially at 20 degrees to 30 degrees. There were no significant differences in T2 between right and left hips or between men and women. CONCLUSION: Topographic variation exists in hip cartilage T2 in young, healthy adults. These findings should be taken into account when T2 mapping is applied to patients with degenerative cartilage.