SSFSE sequence functional MRI of the human cervical spinal cord with complex finger tapping

Purpose

Functional MR imaging of the human cervical spinal cord was carried out on volunteers during alternated rest and a complex finger tapping task, in order to detect image intensity changes arising from neuronal activity.

Methods

Functional MR imaging data using single-shot fast spin-echo sequence (SSFSE) with echo time 42.4 ms on a 1.5 T GE Clinical System were acquired in eight subjects performing a complex finger tapping task. Cervical spinal cord activation was measured both in the sagittal and transverse imaging planes. Postprocessing was performed by AFNI (Analysis of Functional Neuroimages) software system.

Results

Intensity changes (5.5–7.6%) were correlated with the time course of stimulation and were consistently detected in both sagittal and transverse imaging planes of the cervical spinal cord. The activated regions localized to the ipsilateral side of the spinal cord in agreement with the neural anatomy.

Conclusion

Functional MR imaging signals can be reliably detected with finger tapping activity in the human cervical spinal cord using a SSFSE sequence with 42.4 ms echo time. The anatomic location of neural activity correlates with the muscles used in the finger tapping task.     

Reliability of knee biomechanics during a vertical drop jump in elite female athletes

The purpose of the study was to assess the within-session and between-session reliability of knee kinematics and kinetics in a vertical drop jump task among elite female handball and football athletes. Specifically, we aimed to quantify the within-session waveform consistency and between-session consistency of the subject ranking for a variety of knee kinematics and kinetics.Forty-one elite female handball and football (soccer) athletes were tested in two sessions. The reliability of three-dimensional knee biomechanical measurements was quantified by the intra-class correlation, Spearman's rank correlation, and typical error. All the selected discrete variables achieved excellent within-session reliability (ICC > 0.87). The typical error of valgus angles, internal rotation angles, and internal rotation moment was constant throughout the whole stance phase. For between-session reliability, the selected discrete variables achieved good to excellent reliability (ICC > 0.69), except peak internal rotation moment (ICC = 0.40). All between-session rank correlation coefficients ranged from 0.56 to 0.90. Most of the discrete variables achieved good to excellent reliability in both within-session and between-session analysis. Moreover, moderate to strong between-session consistency of subject rankings was found, implying that the measurements assessed during the vertical drop jump demonstrate sufficient reliability to be used in both single-session and multiple-session studies.     

Functional MR imaging of cortical activation of the cerebral hemispheres during motor tasks.

PURPOSEWe used functional MR imaging to evaluate cortical activation in the precentral, central, and postcentral regions of the contralateral and ipsilateral cerebral hemispheres during left- and right-handed motor tasks.METHODSTen healthy right-handed volunteers were studied with echo-planner MR imaging (1.5 T) while performing alternating finger apposition tasks with both hands. During the hand tasks, the areas of activated pixels were compared between subregions (precentral, central, and postcentral) of the contralateral and ipsilateral sensorimotor cortex.RESULTSThe activated area of the contralateral sensorimotor cortex was significantly larger than that of the ipsilateral cortex during tasks with either hand, whereas the ipsilateral activated area was significantly larger during the left-handed task than during the right-handed task. Ipsilateral activation was greatest in the precentral region, less in the central region, and least prominent in the postcentral region.CONCLUSIONSOur results confirmed those of previous investigators that ipsilateral activation is more pronounced during left-sided movements than during right-sided movements. The variation in activation of the precentral, central, and postcentral subregions suggests different roles of the ipsilateral and contralateral hemispheres during motor tasks.     

Optimized activation of the primary sensorimotor cortex for clinical functional MR imaging

BACKGROUND AND PURPOSE: One application of functional MR imaging is to identify the primary sensorimotor cortex (M1 and S1) around the central sulcus before brain surgery. However, it has been shown that undesirable coactivation of nonprimary motor areas, such as the supplementary motor area and the premotor area, can interfere with the identification of the primary motor cortex, especially in patients with distorted anatomic landmarks. We therefore sought to design a simple functional MR imaging paradigm for selective activation of the primary sensorimotor cortex. METHODS: Different paradigms using finger tapping for motor activation were examined and compared with respect to the distribution of activated voxels in primary and nonprimary cortical areas. Studies were conducted in 14 healthy volunteers using a blood oxygen level-dependent multislice echo-planar imaging sequence. RESULTS: The most selective activation of the primary sensorimotor cortex was obtained with a paradigm combining right-sided finger tapping as the activation condition with left-sided finger tapping as the control condition. Analysis of the signal time course of primary and nonprimary areas revealed that the highly selective primary motor activation was due to it being restricted to contralateral finger movements, as opposed to the nonprimary motor areas, which were activated by ipsilateral, contralateral, and bilateral finger movements alike. CONCLUSION: When performing functional MR imaging to determine the location of the primary sensorimotor cortex, one should compare unilateral voluntary movements as the activation condition with contralateral movements as the control condition to accentuate activation of the primary motor area and to suppress undesirable coactivation of nonprimary motor areas.     

简单与复杂手指运动的fMRI对比分析

目的；研究简单和复杂手指运动激活脑皮层功能区的异同。资料与方法：选择一组正常志愿者（12例）按要求分别进行简单与复杂手指运动，同时进行BOLD功能性磁共振成像（fMRI)扫描，用t检验统计学方法分析获得运动状态与静息状态信号对比的脑功能图。对比观察脑皮层区的兴奋区的异同。结果：12例受试者中，复杂手指运动可激活对侧初级躯体感觉区（SM1),11例可观察到一侧或双侧辅助运动区（SMA）兴奋，9例运动前区（PMA）兴奋；简单手指运动则均表面为对侧SM1兴奋，而MA，PMA区被激活仅为2例和5例。激活区检测的可靠复性大于95％。结论：复杂手指运动需要更多的脑皮层功能区参与运动的协调，因而能更多地激活非初始运动皮层区。     

Ipsilateral hemisphere activation during motor and sensory tasks.

PURPOSETo compare activation of the ipsilateral cerebral hemisphere during tactile sensory and motor tasks involving the right and left hands.METHODSEight volunteers had functional MR imaging to measure the extent of cerebral hemisphere activation during a motor task and sensory task involving each hand. Hemispheric indexes (left hemisphere activation minus right hemisphere activation)/(left hemisphere activation plus right hemisphere activation) were computed for each hand and each task. The indexes for two tasks and the two hands were compared.RESULTSThe left-hand motor tasks activated the ipsilateral hemisphere in right handers significantly more than did the right-hand tasks. Motor tasks produced a greater activation of the ipsilateral hemisphere than did the sensory tasks. No significant differences were found between the hemispheric indexes for the right-hand and left-hand sensory tasks.CONCLUSIONThis study confirms findings of a previous study, showing that the left hemisphere is active in left-hand motor tasks. Activation of the ipsilateral hemisphere is significantly less pronounced during sensory tasks than during motor tasks.     

Functional MR imaging of the human sensorimotor cortex after toe-to-finger transplantation

BACKGROUND: A model of toe-to-finger transplantation has been used in studying peripheral nerve regeneration and central reorganization. It was found that recovery of sensory perception depends not only on peripheral reinnervation but also on central integrative mechanisms. OBJECTIVE: Our aim was to investigate functional changes of the brain and somatotopic representation of the transplanted toes after toe-to-finger transplantation. MATERIALS AND METHODS: Six patients who had toe-to-finger transplantation from 3 to 8 years earlier underwent motor and sensory functional MR imaging studies of transplanted toes and opposite corresponding normal fingers. The motor task was performed by repetitively tapping of the transplanted toe or finger against the thumb, whereas the sensory task was applied by tactilely stimulating the pulp of the transplanted toe or finger. RESULTS: The main activation areas from both types of stimulations were located in the expected location of the finger homunculus of the primary sensorimotor cortex. In addition, activated volumes from the transplanted toes were significantly greater than those from the opposite fingers (P = .017 for motor task and P = .005 for tactile sensory task, paired samples Student t test). CONCLUSIONS: Functional recruitment in the primary sensorimotor cortex seemed to have occurred following toe-to-finger transplantation. The transplanted toe was somatotopically represented in the hand area.     

Single- and multiple-event paradigms for identification of motor cortex activation

BACKGROUND AND PURPOSE: The "single-event" technique has been used as an alternative to the "block-trial" method to detect activation that may be accompanied by head motion. The purpose of this study was to compare the two methods for measuring activation in the sensorimotor cortex secondary to motor tasks. METHODS: Functional MR imaging data were acquired from six participants as they performed tasks with their fingers, tongues, and toes in a block-trial and a single-event paradigm. For the block trial, the participant was instructed to perform the task when cued at a rapid self-timed rate for 15 seconds, alternating with 15 seconds of rest. Five periods of task performance and six rest periods were included in one acquisition. For the single-event method, the participant performed the task a single time every 15 seconds when cued by the investigator, for a total of 21 times. Using conventional parcellation methods, activation was detected by a cross-correlation technique and was classified as occurring in the sensorimotor cortex, supplementary motor area (SMA), or as nonspecific. Differences between the two acquisition paradigms were tested using the standard t test at a significance level of P < .05. RESULTS: Activation was identified by both the block-trial and the single-event methods for the finger task, for the tongue task, and inconsistently for the toe task. More motion artifact occurred in conjunction with the toe and tongue tasks than with the finger tasks. On average, more activated pixels were identified by the single-event method than by the block-trial method. For these motor tasks, however, a larger percentage of pixels detected by the block-trial method than by the single-event method were specific for the sensorimotor cortex or SMA as sites of activation. CONCLUSION: For the tongue and the toe movement tasks, which may produce some head motion artifacts, the single-event paradigm provides a useful alternative to the block-trial method for identifying the sensorimotor cortex or SMA. It does not achieve a greater percentage of activation within primary motor areas. For the finger movement task, which does not usually produce head motion artifacts, the block-trial method generally produced a greater percentage of activated pixels in the sensorimotor cortex or SMA than did the single-event method.     

Repeatability of surface EMG during gait in children

Although mean amplitude and ON–OFF timing of muscle recruitment and electromyography (EMG) activation during gait is achieved by an age of six to eight years in normally developing children, recruitment dynamics illustrated by the shape of the EMG waveform may require continued developmental practice to achieve a stable pattern. Previous analyses have quantified the repeatability of the EMG waveform in adult subjects, but EMG variability for a pediatric population may be significantly different. The goal of this study was to quantify intra-session and inter-session variability in the phasic EMG waveform patterns from the lower limb muscles during self-selected speeds of walking in healthy-normal children for comparison with adult variability in gait EMG. The variance ratio quantifies the repeatability of the integrated EMG waveform shape in a group of normally-developing children. Results reveal that between-session EMG waveform variability were similar in adult and pediatric populations, but within-session variability for the children was approximately twice the published value for adults. Clinical implications of this pediatric EMG variability suggest cautious interpretation of data from limited trial samples or inter-session changes in performance of gait data.     

Repeatability of lower limb three-dimensional kinematics in patients with stroke

The within- and between-session repeatability of time-distance and sagittal plane kinematic gait parameters were evaluated in 20 hemiparetic patients with sub-acute stroke. A test-retest design was used in which the patients were tested during two sessions within a 2h period. Each session comprised three consecutive trials. The intraclass correlation coefficients (ICCs) for time-distance parameters ranged from 0.82 to 0.99. The within- and between-session repeatability of pelvis, hip, knee and ankle kinematic waveforms were high: the mean coefficient of multiple correlations (CMCs) ranged from 0.85 to 0.95. The within-session coefficient of variation (CV%) for time-distance parameters ranged from 3.9 to 14.1, whereas, between-session CV% ranged from 6.1 to 17.2, showing similar but higher variability. The within- and between-session CV% for sagittal plane kinematics of the paretic lower limb ranged from 3.6 to 32.4. The results indicate that time-distance parameters and sagittal plane gait kinematics of the paretic lower limb, measured by the Vicon 370 gait analysis system, are repeatable and can be used to assess treatment effects after stroke.     

Repeatability of surface EMG during gait in children

Although mean amplitude and ON–OFF timing of muscle recruitment and electromyography (EMG) activation during gait is achieved by an age of six to eight years in normally developing children, recruitment dynamics illustrated by the shape of the EMG waveform may require continued developmental practice to achieve a stable pattern. Previous analyses have quantified the repeatability of the EMG waveform in adult subjects, but EMG variability for a pediatric population may be significantly different. The goal of this study was to quantify intra-session and inter-session variability in the phasic EMG waveform patterns from the lower limb muscles during self-selected speeds of walking in healthy-normal children for comparison with adult variability in gait EMG. The variance ratio quantifies the repeatability of the integrated EMG waveform shape in a group of normally-developing children. Results reveal that between-session EMG waveform variability were similar in adult and pediatric populations, but within-session variability for the children was approximately twice the published value for adults. Clinical implications of this pediatric EMG variability suggest cautious interpretation of data from limited trial samples or inter-session changes in performance of gait data.     

Reliability of upper limb movement quality metrics during everyday tasks

BackgroundQuantitative assessments of an individual’s functional status commonly involve the use of movement quality metrics.Research questionThe purpose of this work was to quantify the reliability of movement quality metrics in healthy adults during a variety of unconstrained activities of daily living (ADLs).MethodsNineteen participants performed six ADLs (lifting a laundry basket, applying deodorant, turning a doorknob, placing a pill in a pillbox, placing a pushpin in a bulletin board, and drinking water from a glass) during two separate sessions. The ADLs were divided into reaching and object manipulation phases. Movement quality for each phase was assessed using three measures of smoothness (log dimensionless jerk, spectral arc length, and number of submovements) and one measure of straightness (index of curvature). Within- and between-session reliability was quantified using intraclass correlation coefficients (ICCs) and minimum detectable changes in measured units and as a percentage of their mean value (MDC%).ResultsReliability was generally lower within-session than between-session and for object manipulation tasks compared to reaching tasks. The ICCs exceeded 0.75 for 5% of the within-session metrics and 73% of the between-session metrics. The average MDC% was 35% for the within-session metrics and 20% for the between-session metrics. Reliability was similar for most metrics when averaged across the tasks, but the number of submovements consistently indicated much lower reliability.SignificanceUnconstrained ADLs can reliably be used to assess movement quality in functional settings that mimic real-world challenges. However, the specific movement quality metrics used in the assessment should be chosen carefully since some metrics perform dissimilarly when applied to the same data. In particular, it may be advisable to use the number of submovements in combination with other metrics, if it is to be used at all.     

Quantification and reproducibility of tracking cortical extent of activation by use of functional MR imaging and magnetoencephalography

BACKGROUND AND PURPOSE: Functional MR imaging and magnetoencephalography are commonly used to study normal cortical sensory and cognitive processing as well as a variety of disease states. The usefulness of these techniques is dependent on the reproducibility and sensitivity to change of derived measures of brain function. The purpose of this study was to compare the efficacy of functional MR imaging and magnetoencephalography as measures of the extent of cortical activity in response to a graded stimulus. METHODS: Five participants underwent functional MR imaging and magnetoencephalography involving stimulation of one, two, three, and four digits of the left hand. Measurements of activation were repeated three times per participant. The cortical extent of activation was assessed for functional MR imaging by observing the number of "activated" pixels and the "amount of activation": the product of the number of activated pixels and the mean signal change. Activation was quantified for magnetoencephalography as the magnitude of the evoked magnetic field peak and as the strength of the modeled current source, Q. RESULTS: For functional MR imaging, the number of activated pixels tended to increase with the increasing number of stimulated digits. High intra- and interparticipant variability (66% and 85% variation, respectively) did not, however, allow statistical resolution of this trend. The amount of activation was similarly variable (interparticipant, 89%). Magnetoencephalography was more robust regarding quantification. The evoked field amplitude varied linearly with the number of digits stimulated; intra- and interparticipant variability was 18% and 41%, respectively, permitting resolution of significant differences between any combination of stimulated digits, except two versus three (P < .05). CONCLUSION: Although functional MR imaging and magnetoencephalography show measurable evoked responses with somatosensory stimulation, in this study, functional MR imaging did not permit robust quantification of increasing cortical areas of activation.     

Location of language in the cortex: a comparison between functional MR imaging and electrocortical stimulation.

PURPOSETo determine the accuracy of functional MR imaging in locating language areas for planning surgical resection.METHODSIntraoperative photographs were digitized and overlaid on functional MR language maps. The sensitivity and specificity of functional MR imaging for identifying language areas were determined for five different language tasks by comparing functional MR areas of language activation with results of electrocortical stimulation. A match was considered to occur if an activated area contacted overlapped, or surrounded a language tag. The borders of the activation areas were extended by 1 and 2 cm to determine whether the number of matches changed. Language and nonlanguage tag matches were tabulated separately.RESULTSSensitivity/specificity for all patients and all language tasks ranged from 81%/53% for areas that touched to 92%/0% for areas separated by 2 cm. Individual language tasks were not as sensitive as a battery of language tasks combined. Location of language areas varied among subjects for a given task and among tasks for a given subject.CONCLUSIONFunctional MR imaging should be considered a useful presurgical planning tool for mapping cortical language areas, because it is sensitive, it provides increased time for planning before surgery, and it is noninvasive.     

Reproducibility of functional MR imaging: preliminary results of prospective multi-institutional study performed by Biomedical Informatics Research Network

PURPOSE: To prospectively investigate the factors--including subject, brain hemisphere, study site, field strength, imaging unit vendor, imaging run, and examination visit--affecting the reproducibility of functional magnetic resonance (MR) imaging activations based on a repeated sensory-motor (SM) task. MATERIALS AND METHODS: The institutional review boards of all participating sites approved this HIPAA-compliant study. All subjects gave informed consent. Functional MR imaging data were repeatedly acquired from five healthy men aged 20-29 years who performed the same SM task at 10 sites. Five 1.5-T MR imaging units, four 3.0-T units, and one 4.0-T unit were used. The subjects performed bilateral finger tapping on button boxes with a 3-Hz audio cue and a reversing checkerboard. In a block design, 15-second epochs of alternating baseline and tasks yielded 85 acquisitions per run. Functional MR images were acquired with block-design echo-planar or spiral gradient-echo sequences. Brain activation maps standardized in a unit-sphere for the left and right hemispheres of each subject were constructed. Areas under the receiver operating characteristic curve, intraclass correlation coefficients, multiple regression analysis, and paired Student t tests were used for statistical analyses. RESULTS: Significant factors were subject (P < .005), k-space (P < .005), and field strength (P = .02) for sensitivity and subject (P = .03) and k-space (P = .05) for specificity. At 1.5-T MR imaging, mean sensitivities ranged from 7% to 32% and mean specificities were higher than 99%. At 3.0 T, mean sensitivities and specificities ranged from 42% to 85% and from 96% to 99%, respectively. At 4.0 T, mean sensitivities and specificities ranged from 41% to 73% and from 95% to 99%, respectively. Mean areas under the receiver operating characteristic curve (+/- their standard errors) were 0.77 +/- 0.05 at 1.5 T, 0.90 +/- 0.09 at 3.0 T, and 0.95 +/- 0.02 at 4.0 T, with significant differences between the 1.5- and 3.0-T examinations and between the 1.5- and 4.0-T examinations (P < .01 for both comparisons). Intraclass correlation coefficients ranged from 0.49 to 0.71. CONCLUSION: MR imaging at 3.0- and 4.0-T yielded higher reproducibility across sites and significantly better results than 1.5-T imaging. The effects of subject, k-space, and field strength on examination reproducibility were significant.     

Reliability of functional MR imaging with word-generation tasks for mapping Broca's area.

BACKGROUND AND PURPOSE: Functional MR (fMR) imaging of word generation has been used to map Broca's area in some patients selected for craniotomy. The purpose of this study was to measure the reliability, precision, and accuracy of word-generation tasks to identify Broca's area. METHODS: The Brodmann areas activated during performance of word-generation tasks were tabulated in 34 consecutive patients referred for fMR imaging mapping of language areas. In patients performing two iterations of the letter word-generation tasks, test-retest reliability was quantified by using the concurrence ratio (CR), or the number of voxels activated by each iteration in proportion to the average number of voxels activated from both iterations of the task. Among patients who also underwent category or antonym word generation or both, the similarity of the activation from each task was assessed with the CR. In patients who underwent electrocortical stimulation (ECS) mapping of speech function during craniotomy while awake, the sites with speech function were compared with the locations of activation found during fMR imaging of word generation. RESULTS: In 31 of 34 patients, activation was identified in the inferior frontal gyri or middle frontal gyri or both in Brodmann areas 9, 44, 45, or 46, unilaterally or bilaterally, with one or more of the tasks. Activation was noted in the same gyri when the patient performed a second iteration of the letter word-generation task or second task. The CR for pixel precision in a single section averaged 49%. In patients who underwent craniotomy while awake, speech areas located with ECS coincided with areas of the brain activated during a word-generation task. CONCLUSION: fMR imaging with word-generation tasks produces technically satisfactory maps of Broca's area, which localize the area accurately and reliably.     

The effect of magnetization transfer on functional MRI signals

A magnetization transfer (MT)-prepared echo-planar imaging (EPI) pulse sequence was developed to study motor cortex activation, using a finger tapping paradigm. MT weighting resulted in a reduction of both the activated area and, in the majority of activated pixels, the functional MRI signal, regardless of the correlation coefficient threshold used in generating the activation map. The magnetization transfer ratio (MTR) was higher during task activation than during rest. Because the MT effect is strongly tissue-dependent, these results support the hypothesis that incorporation of MT into functional MRI will help to understand the origin of the functional MRI signal.     

Reliability of landing 3D motion analysis: implications for longitudinal analyses

PURPOSE: Biomechanical measures quantified during dynamic tasks with coupled epidemiological data in longitudinal experimental designs may be useful to determine which mechanisms underlie injury risk in young athletes. A key component is the ability to reliably measure biomechanical variables between testing sessions. The purpose was to determine the reliability of three-dimensional (3D) lower-extremity kinematic and kinetic variables during landing in young athletes measured within a session and between two sessions 7 wk apart. METHODS: Lower-extremity kinetics and kinematics were quantified during a drop vertical jump. Coefficient of multiple correlations (CMC), intraclass correlation coefficients (ICC (3, k), ICC (3, 1)), and typical error (TE) analyses were used to examine within- and between-session reliability. RESULTS: There were no differences in within-session reliability for peak angular rotations between planes with all discrete variables combined (sagittal ICC > or = 0.933, frontal ICC > or = 0.955, transverse ICC > or = 0.934). Similarly, the between-session reliability of kinematic measures were not different between the three planes of motion but were lower than the within-session ICC. The within- and between-session reliability of discrete joint moment variables were excellent for all sagittal (within ICC > or = 0.925, between ICC > or = 0.800) and frontal plane moment measures (within ICC > or = 0.778, between ICC > or = 0.748). CMC analysis revealed similar averaged within-session (CMC = 0.830 +/- 0.119) and between-session (CMC = 0.823 +/- 0.124) waveform comparisons. CONCLUSION: The majority of the kinematic and kinetic variables in young athletes during landing have excellent to good reliability. The ability to reliably quantify lower-extremity biomechanical variables of young athletes during dynamic tasks over extended intervals may aid in identifying potential mechanisms related to injury risk factors.     

国人汉字书写神经基础的脑功能成像

目的:利用功能磁共振成像技术(fMRI),研究正常国人汉字书写功能的神经基础.材料和方法:采用GE公司Signa1.5T磁共振成像系统,对10名健康右利手母语为汉语的志愿者进行默读、复杂对指运动、抄写三个任务期间的功能活动进行了全脑扫描.数据经过空间平滑、头动矫正、卷积分析等处理,获得抄写减去默读、抄写减去对指之后脑功能激活图,统计出两者间共同的激活区.结果:主要共同激活区位于额顶叶皮质,包括左侧额中回,双侧顶上小叶,双侧顶下小叶,两侧额内侧回,左侧中央前、后回.结论:汉字的书写是双脑协同的过程,右侧大脑半球对汉字的书写尤其重要;书写功能涉及较多的皮质及皮质下结构,利用功能磁共振成像可以揭示这些结构在书写过程中的作用.