Multiple reproducibility indices for evaluation of cognitive functional MR imaging paradigms

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate a variety of reproducibility indices for cognitive functional MR imaging (fMRI) paradigms that account for both overlapping and extraneous regions of activation. METHODS: Eight right-handed volunteers were imaged with fMRI by using a word-generation paradigm and a forward-backward text-listening paradigm. The paradigms were performed twice in the session and repeated 1 week later. Reproducibility indices for the four repeated studies were determined on the basis of pair-wise computation of the ratio of the probability-weighted intersection volume divided by the union volume of surviving activation clusters. The intersection volume was determined by using several iterations of the morphologic dilatation operator with additional voxels accrued in the intersection weighted by an exponential function. Computed indices included global reproducibility, language area reproducibility, extraneous activation reproducibility, and laterality. RESULTS: The word-generation paradigm had reproducibility values that were significantly greater than those of the forward-backward text-listening paradigm (global reproducibility, 0.75 vs 0.5, P <.005; language area reproducibility, 0.85 vs 0.6, P <.008; mean extraneous activation reproducibility, 0.68 vs 0.41, P <.002). The forward-backward text-listening paradigm demonstrated more focal activations, whereas the word-generation demonstrated larger activations outside the dominant language areas that were highly reproducible. CONCLUSION: For clinically relevant language paradigms, multiple reproducibility indices should be taken into account in selecting an appropriate paradigm. Compared with a forward-backward text-listening task, a word-generation task has higher reproducibility indices at the expense of localizing ability. The forward-backward paradigm demonstrates more focal activations with less extraneous activation.     

Test-retest reliability of a functional MRI anticipatory anxiety paradigm in healthy volunteers

PURPOSE: To evaluate the reproducibility of neural activations induced by an anticipatory anxiety provocation challenge in healthy volunteers. MATERIALS AND METHODS: Fourteen healthy male volunteers participated in two separate functional MRI (fMRI) sessions in which they underwent a paradigm based on anticipation of aversive transcutaneous electrical nerve stimulations. This paradigm consisted of alternating presentation of red circles associated with the likelihood that aversive stimuli may be given and blue circles during which the subjects knew that no shock could be given. Anxiety state was compared before the fMRI sessions and during the threat periods using clinical scales (Hamilton, STAI-Y1), the Bond and Lader Visual Analogue Scale, and self-rating scales of apprehension and stimulus aversivity. RESULTS: The selected paradigm induced anticipatory anxiety of moderate intensity as suggested by clinical scales and apprehension rating, without any habituation to the somatosensory stimulus across sessions. Compared to rest periods, threat of the aversive stimulus induced clear brain activation in anticipatory anxiety-related areas: frontal/prefrontal cortex, insula, lentiform nucleus, temporal pole, and cingulate cortex. Anxiety symptoms and cerebral activity were reproducible across sessions. CONCLUSION: The fMRI paradigm and its assessment method include all criteria to speed up the evaluation and the development of new anxiolytics.     

Intrasubject reproducibility of functional MR imaging activation in language tasks

BACKGROUND AND PURPOSE: The purpose of this study was to examine the reproducibility of functional MR imaging (fMRI) activation (volume and laterality) within both inferior frontal and temporoparietal regions of interest for both receptive and expressive language tasks. METHODS: Ten healthy volunteers participated in fMRI experiments for 6 language tasks: verb generation, confrontation naming, semantic decision making, visual sentence comprehension, auditory sentence comprehension, and story listening. Each subject was scanned during 2 separate sessions separated by a minimum of 4 weeks. Laterality of activation was defined by laterality indices (LIs), which were calculated by 2 methods: one method based on the measured volume of activation and the other method based on the F statistic of the activation. Reproducibility was calculated by using concurrence ratios for the volume of activation (R(overlap), R(volume)) and test-retest correlation for LIs. RESULTS: All tasks generated reproducible LIs within at least one of the regions of interest, but verb generation produced the highest test-retest correlations (r = 0.99) within both regions of interest. Verb generation was associated with the highest average concurrence ratios within the inferior frontal region of interest (R(overlap) = 45.2; R(volume) = 70.9). In general, the concurrence ratios were lower within the temporoparietal region of interest compared with the inferior frontal region of interest. LIs calculated with F statistics were more reproducible than the LIs calculated by activation volume. CONCLUSION: fMRI is able to provide reproducible LIs in both inferior frontal and temporoparietal regions for assessing hemispheric dominance in language processing. The volume of activation, especially within the temporoparietal regions, is less reproducible than the laterality of activation, so the former should be used with caution.     

Lack of sex effect on brain activity during a visuomotor response task: functional MR imaging study

BACKGROUND AND PURPOSE: As more individuals are enrolled in clinical functional MR imaging (fMRI) studies, an understanding of how sex may influence fMRI-measured brain activation is critical. METHODS: We used fixed- and random-effects models to study the influence of sex on fMRI patterns of brain activation during a simple visuomotor reaction time task in the group of 26 age-matched men and women. We evaluated the right visual, left visual, left primary motor, left supplementary motor, and left anterior cingulate areas. RESULTS: Volumes of activations did not significantly differ between the groups in any defined regions. Analysis of variance failed to show any significant correlations between sex and volumes of brain activation in any location studied. Mean percentage signal-intensity changes for all locations were similar between men and women. A two-way t test of brain activation in men and women, performed as a part of random-effects modeling, showed no significant difference at any site. CONCLUSION: Our results suggest that sex seems to have little influence on fMRI brain activation when we compared performance on the simple reaction-time task. The need to control for sex effects is not critical in the analysis of this task with fMRI.     

Functional arterial spin labeling: Optimal sequence duration for motor activation mapping in clinical practice

Purpose:

To determine the minimal optimal functional arterial spin labeling (fASL) sequence duration allowing steady and reproducible motor activation mapping.

Materials and Methods:

Three magnetic resonance imaging (MRI) sessions including fASL and blood oxygenation level‐dependent (BOLD) functional MRI (fMRI) sequences were performed on 12 healthy subjects at 3T with a 32‐channel coil. The raw 7‐minute fASL sequence was truncated to obtain six fASL sequences with durations ranging from 1–6 minutes. All the resulting fASL activations were compared between themselves and with both the 7‐minute fASL and BOLD activations. Quantitative parameters assessed activation location (activated volume, barycenter, and distance between barycenters), activation quantification (activation‐related cerebral blood flow), and intraindividual reproducibility across fMRI sessions. The statistical analysis was based on analysis of variance (ANOVA) and Tukey's multiple comparisons.

Results:

Four‐minute fASL achieved steady location and quantification of activation with the activated volume corresponding to 81% of the 7‐minute fASL volume and a barycenter located 1.2 mm from the 7‐minute fASL barycenter and 3.0 mm from the BOLD fMRI barycenter. Four‐minute fASL reproducibility was high and statistically equivalent to 7‐minute values.

Conclusion:

A 4‐minute fASL sequence is thus a reliable tool for motor activation mapping and suitable for use in clinical practice. J. Magn. Reson. Imaging 2012; 36:1435–1444. © 2012 Wiley Periodicals, Inc.     

中英文双语者语义加工的词频相关性磁共振脑功能成像

目的通过对高度流利的中英文晚双语者词频相关性语义判断任务的fMRI研究,探讨语言加工相关脑功能区、词频效应及中英文加工脑功能区可能存在的差异。资料与方法对10名健康志愿者行中文高频、中文低频、英文高频、英文低频语义判断任务,比较不同任务各脑区激活强度及范围的差异。结求语义相关判断任务激活双侧Broca区（BA44、45）、前额叶背外侧（BA9、46）、额叶内侧面（BA6、32、24）,颞中回后部（BA21）,左侧角回（BA39）和右侧缘上回（BA40）。中文任务词频效应出现在左侧Broca区：英文任务在双侧Broca区。英文高频大于中文高频任务的脑区为双侧Broca区和右侧颞中回后部;中文高频大于英文高频任务的脑区为双侧扣带回前部。结沦词频效应即熟练程度差异影响语言加工相关脑区的激活强度及范围;中英文两种语言激活脑区大部分相互重叠．但仍有差异。     

Functional MR study of a motor task and the Tower of London task at 1.0 T

Introduction The use of functional magnetic resonance imaging (fMRI) for clinical applications and basic neuroscience is constantly increasing. The discussion about minimum performance requirement for a correct implementation of fMRI is still open, and one of the critical points is the magnetic field strength. We tested the feasibility of fMRI at 1.0 T during motor and cognitive tasks.Methods Fourteen healthy subjects were scanned during a motor task and 12 while performing the Tower of London task. In the activated areas, the percentage signal change due to BOLD (blood oxygenation level dependent) contrast was analysed. To check basic image quality of the acquisition system we measured quality indices in a temporal series of images of a phantom.Results Motor and cognitive brain activations matched previous results obtained at higher field strengths. The mean percentage change over subjects in the motor task was in the range 1.3–2.6% for the primary motor area and 0.8–6.7% for the cerebellum. In the cognitive task, the mean percentage change over subjects was 0.7–1.2% for a frontal area and 0.6–2.8% for a parietal area. The percentage noise of the phantom temporal series was less than 0.4%. Percentage changes and signal to noise ratio, although lower than that obtained with high-field systems, allowed activation maps to be obtained in all subjects.Conclusion Our results replicate previous fMRI results demonstrating reproducible motor-related brain activations and extend the field to a complex cognitive task, thus providing evidence of the safety for routine clinical use of 1-T equipment.A.B. and O.R. contributed equally to the realization of the study and to the drafting of the paper.     

Cortical intraoperative stimulation in brain tumors as a tool to evaluate spatial data from motor functional MRI

RATIONALE AND OBJECTIVE: The purpose of this prospective, double-blind study was to correlate motor functional MRI (fMRI) with cortical brain mapping by intraoperative stimulation using 3D reconstructed images of the surface of the brain, and to validate the spatial data of fMRI in patients with brain tumors. METHODS: Fourteen patients with tumors of the rolandic region underwent functional MR mapping of the hand region and subsequently cortical mapping before tumor resection. Data obtained with fMRI and brain mapping were not known previously by the neurosurgeon and by the neuroradiologist, respectively (double-blind study). RESULTS: In each case, the results of direct cortical mapping matched those obtained with fMRI, both positively and negatively, although the extent of the functional activations was larger than the area required to elicit the corresponding movement during intraoperative brain mapping. CONCLUSION: fMRI can be used before surgery to assess motor functional area in patients with rolandic tumors. More studies are needed to validate during surgery the real extent of fMRI activations.     

蒙汉双语者的汉语词汇命名加工脑机制的功能磁共振成像

目的:利用功能磁共振成像技术探讨蒙汉双语者及单汉语志愿者在汉语词汇信息加工差异的脑机制。方法:采用汉语词汇命名任务,15例蒙汉双语健康志愿者(男8例,女7例)和15例汉语健康志愿者(男7例,女8例)进行fMRI研究。应用软件包AFNI分析其脑功能激活情况及差异。结果:熟练蒙汉双语者及单汉语志愿者在汉语信息加工过程中,均激活词汇信息加工的经典脑区,包括左侧颞上回后部、左侧顶下小叶、左侧额下回盖部、双侧辅助运动区等区域。在加工汉语词汇命名信息过程中蒙汉双语者双侧枕叶、双侧顶叶、扣带回后部、右侧颞上回和颞中回后部及左丘脑的激活显著比单汉语者增加。结论:蒙汉双语者的汉语加工特异脑区主要为右侧颞中回,功能磁共振成像研究能够为研究蒙汉双语者的脑加工神经机制提供影像学依据。     

Differences in functional MR imaging activation patterns associated with confrontation naming and responsive naming

BACKGROUND AND PURPOSE: Direct cortical stimulation studies suggest that responsive naming is more widely distributed within the temporal lobe than confrontation naming and involves anterior temporal regions typically resected in a standard temporal lobectomy. The aim of the current study was to further demonstrate the anatomic dissociation between confrontation and responsive naming by using functional MR imaging (fMRI). METHODS: Twenty participants underwent fMRI while performing either a confrontation or responsive naming task. Regions of interest were identified within the anterior and posterior temporal lobe. RESULTS: Responsive naming produced more activation than confrontation naming within the dominant temporal lobe, with activation extending into the temporal pole. Activation in the dominant temporal lobe associated with responsive naming was observed in the superior, middle, and inferior temporal gyri but was limited to the middle temporal gyrus for confrontation naming. Although both naming tasks produced activation within the posterior temporal region of interest in all participants, responsive and confrontation naming produced activation within the anterior temporal region of interest in 90% versus 60% of the sample, respectively. Areas of the dominant hemisphere activated by both tasks included parts of the middle occipital and middle temporal gyri, inferior frontal lobe, and hippocampus, among others. CONCLUSION: Findings are consistent with cortical stimulation studies and suggest that responsive naming produces more widespread activation within the temporal lobe compared with confrontation naming. The activation more often included anterior temporal regions during responsive naming as compared with confrontation naming. In clinical cases where the functional assessment of the temporal lobe-particularly the anterior regions-is important, the current results suggest responsive naming should be a useful fMRI paradigm and may ultimately help predict the risk of postsurgical language changes.     

利用fMRI研究衰老对听觉数字工作记忆的影响

目的:利用功能磁共振研究衰老对数字工作记忆的影响.材料和方法:6个青年和3个老年被试者参加了有关正序和反序记忆阿拉伯数字的工作记忆实验,同时,fMRI被用来记录大脑的反应.结果:①在青年组中,编码阶段,反序记忆左侧BA9-46区激活高于正序记忆;提取阶段,反序记忆在双侧BA7区激活点体积高于正序记忆.②老年组与青年组比较,在编码阶段反序记忆中青年组左侧BA 9-46区激活高于老年组.结论:功能磁共振有助于加深对衰老的理解.     

Assessment of airways with three-dimensional quantitative thin-section CT: in vitro and in vivo validation

PURPOSE: To prospectively validate the ability of customized three-dimensional (3D) software to enable bronchial tree skeletonization, orthogonal reconstruction of the main bronchial axis, and measurement of cross-sectional wall area (WA) and lumen area (LA) of any visible bronchus on thin-section computed tomographic (CT) images. MATERIALS AND METHODS: Institutional review board approval and patient agreement and informed consent were obtained. Software was validated in a phantom that consisted of seven tubes and an excised human lung obtained and used according to institutional guidelines. In vivo validation was performed with multi-detector row CT in six healthy subjects (mean age, 47 years; range, 20-55 years). Intra- and interobserver agreement and reproducibility over time for bronchial tree skeletonization were evaluated with Bland-Altman analysis. Concordance in identifying bronchial generation was assessed with the kappa statistic. WA and LA obtained with the manual method were compared with WA and LA obtained with validated software by means of the Wilcoxon test and Bland-Altman analysis. RESULTS: WA and LA measurements in the phantom were reproducible over multiple sessions (P > .90) and were not significantly different from WA and LA assessed with the manual method (P > .62). WA and LA measurements in the excised lung and the subjects were not different from measurements obtained with the manual method (intraclass correlation coefficient > 0.99). All lobar bronchi and 80.8% of third generation bronchi, 72.5% of fourth generation bronchi, and 37.7% of fifth generation bronchi were identified in vivo. Intra- and interobserver agreement and reproducibility over time for airway skeletonization and concordance in identifying bronchial generation were good to excellent (intraclass correlation coefficient > 0.98, kappa > 0.54, respectively). CONCLUSION: This method enables accurate and reproducible measurement of WA and LA on reformatted CT sections perpendicular to the main axis of bronchi visible on thin-section CT scans.     

儿童注意缺陷多动障碍的功能磁共振成像研究

目的使用功能磁共振成像(functional magnetic resonance imaging，fMRI)方法研究正常儿童及注意缺陷多动障碍儿童在执行高级抑制功能执行-不执行(Go-NoGo)操作任务时脑功能状态及激活模式。方法注意缺陷多动障碍患儿10例与年龄、性别、利手匹配的正常儿童11例执行组块设计的Go-NoGo任务，采集全脑血氧水平依赖对比的fMRI扫描数据，用SPM99软件包进行￡检验统计分析，以获取执行不同任务与静息状态对比的脑功能图像。结果(1)在执行刺激匹配的Go任务时，正常儿童脑激活区主要在左侧丘脑及右侧扣带回，右侧额中回(BA9／10)有小范围激活。注意缺陷多动障碍儿童左侧丘脑激活范围显著减小，右侧基底节区及中脑出现了激活。(2)在执行反应匹配的Go任务时，正常儿童右侧岛叶、扣带回及左侧额叶可见激活。多动症儿童在右侧额中回(BA6／9)可见少量激活。(3)在执行NoGo任务时正常儿童右侧额中回(BA46)为主要激活区，左侧前扣带回、左侧额中回及右侧丘脑可见激活。多动症儿童右侧额叶激活区增多，但主要在BA8区，而前额叶(BA9、10)的激活并不显著，丘脑激活范围及强度较正常儿童均有增加。结论注意缺陷多动障碍儿童存在以前额叶及扣带回前部为主的功能低下脑区，同时有丘脑功能的异常。     

利用fMRI研究正常人执行Stroop任务的脑功能网络

目的:利用功能磁共振成像(fMRI)探讨正常人执行汉字Stroop任务时任务相关的激活与去激活脑功能网络。方法:14例正常志愿者接受了Stroop任务的组块式fMRI,扫描序列为平面回波血氧水平依赖(BOLD)序列,利用统计参数图(SPM99)软件进行图像分析。所有检查完毕后,对受试者进行Stroop的行为学测试,记录反应时间及错误数。结果:正常对照组认字试验的反应时间与颜色命名试验之间差异有显著性意义(t=-8.188,P=0.000)。对照状态下,正常人出现后扣带回皮层、中线前额叶皮层、背侧前扣带回的去激活。正常人执行颜色命名任务较认字任务时出现更多脑区的激活,且其激活强度较第1个任务的脑区激活强度增加。执行颜色命名任务时动用了双侧额中回、左侧额上回、左侧额下回及双侧顶叶。结论:本研究进一步证实静息状态下存在大量的神经元活动,其与任务相关的脑功能网络共同维持正常的认知活动。     

Localizing and lateralizing language in patients with brain tumors: feasibility of routine preoperative functional MR imaging in 81 consecutive patients

PURPOSE: To prospectively assess the feasibility of standardized presurgical functional magnetic resonance (MR) imaging for localizing the Broca and Wernicke areas and for lateralizing language function. MATERIALS AND METHODS: The study was approved by the responsible ethics commission, and patients gave written informed consent. Eighty-one patients (36 female and 45 male patients; age range, 7-75 years) with different brain tumors underwent blood oxygen level-dependent functional MR imaging at 1.5 T with two paradigms: sentence generation (SG) and word generation (WG). Functional MR imaging measurements, data processing, and evaluation were fully standardized by using dedicated software. Four regions of interest were evaluated in each patient: the Broca and Wernicke areas and their anatomic homologues in the right hemisphere. Statistics were calculated. RESULTS: The SG and WG paradigms were successfully completed by all (100%) and 70 (86%) patients, respectively. Success rates in localizing and lateralizing language were 96% for the Broca and Wernicke areas with the SG paradigm, 81% for the Broca area and 80% for the Wernicke area with the WG paradigm, and 98% for both areas when the SG and WG paradigms were used in combination. Functional localizations were consistent for SG and WG paradigms in the inferior frontal gyrus (Broca area) and the superior temporal, supramarginal, and angular gyri (Wernicke area). Surgery was not performed in seven patients (9%) and was modified in two patients (2%) because of functional MR imaging findings. CONCLUSION: Functional MR imaging proved to be feasible during routine diagnostic neuroimaging for localizing and lateralizing language function preoperatively.     

急性期脑梗死引起的运动性失语的功能磁共振研究

目的:探讨急性脑梗死引起的运动性失语脑内代偿情况。方法:急性脑梗死患者8例,男女比例1.3:1,平均44.5岁;正常健康志愿者20人,男10例,女10例,平均38.5岁,均为右利手。检查者均完成图片命名任务。AFNI软件处理实验数据。统计分析采用SPSS12.0分析软件。同一感兴奋区(ROI)比较采用两样本t检验或非参数统计:Mann-Whitney test。结果:患者组因病灶位置不同分为两组:①病灶位于左侧岛叶及左侧脑室旁白质5例。激活脑区如下:右侧Broca区,右侧BA10区,左侧角回,左侧顶上小叶,辅助运动区等。其中右侧Broca区激活强度和体素具有统计学意义,P0.05;②病灶位于左侧额下回(Broca区)3例。激活脑区如下:左侧BA46区,右侧顶上小叶,右侧额中回,左侧角回,辅助运动区等。正常对照组激活脑区:双侧岛叶,双侧额下回(Broca区,以左侧为著);双侧额中回,双侧额叶背外侧区,双侧顶上小叶,双侧颞上回,辅助运动区,双侧梭状回等激活。结论:急性脑梗死所致运动性失语,脑内代偿方式因位置不同而有差异。     

失语症病人皮层语言活动的功能MRI初步研究

目的用功能磁共振成像(fMRI)技术研究失语症患者皮层语言功能状态，并探讨该技术临床应用的可行性。方法在6位健康志愿者和3位处于恢复阶段的失语症患者完成词汇联想任务的同时，用fMRI技术测量局部神经元活动引起的脑区信号改变，分析处理成代表语言功能区的统计激活图。结果6例正常志愿者的语言加工活动激活了1个由额叶、顶叶、颞叶和枕叶等许多脑区组成的神经网络。而失语症患者无论左侧额叶有无病变，均无左侧额叶下部的激活。此外，2位患者显示了右侧大脑半球某些区域的激活，而这些区域没有参与正常志愿者的语言加工。结论失语症患者皮层语言功能存在脑内局部病灶的远隔效应和皮层语言功能区的重新分布或重组现象。fMRI技术是评价失语症患者语言功能的有效方法。     

Neural mechanism of cognitive control impairment in patients with hepatic cirrhosis: a functional magnetic resonance imaging study

BACKGROUND: Many studies have claimed the existence of attention alterations in cirrhotic patients without overt hepatic encephalopathy (HE). No functional magnetic resonance imaging (fMRI) study in this respect has been published. PURPOSE: To investigate the neural basis of cognitive control deficiency in cirrhotic patients using fMRI. MATERIAL AND METHODS: 14 patients with hepatic cirrhosis and 14 healthy volunteers were included in the study. A modified Stroop task with Chinese characters was used as the target stimulus, and block-design fMRI was used to acquire resource data, including four stimulus blocks and five control blocks, each presented alternatively. Image analysis was performed using statistical parametric mapping 99. After fMRI examinations were complete, behavior tests of Stroop interference were performed for all subjects. Overall reaction time and error numbers were recorded. RESULTS: Both healthy volunteers and patients with hepatic cirrhosis had Stroop interference effects. Patients with hepatic cirrhosis had more errors and longer reaction time in performing an incongruous color-naming task than healthy volunteers (P<0.001); there was no significant difference in performing an incongruous word-reading task (P = 0.066). Compared with controls, patients with hepatic cirrhosis had greater activation of the bilateral prefrontal cortex and parietal cortex when performing the incongruous word-reading task. With increased conflict, activation of the anterior cingulate cortex (ACC), bilateral prefrontal cortex (PFC), parietal lobe, and temporal fusiform gyrus (TFG) was decreased when patients with hepatic cirrhosis performed the incongruous color-naming task. CONCLUSION: This study demonstrates that patients with hepatic cirrhostic have cognitive control deficiency. The abnormal brain network of the ACC-PFC-parietal lobe-TFG is the neural basis of cognitive control impairment in cirrhotic patients.     

Reproducibility of single-subject fMRI language mapping with AMPLE normalization

Purpose:

To evaluate the reproducibility of presurgical functional MRI (fMRI) language mapping based on test–retest scans, comparing traditional activation t‐maps to relative activation maps normalized by activation mapping as percentage of local excitation (AMPLE).

Materials and Methods:

Language fMRI scans were performed by 12 healthy volunteer subjects undergoing a standard clinical presurgical mapping protocol in multiple independent scan sessions. Objective relative AMPLE activation maps were generated automatically by normalizing statistical t‐value maps to the local peak activation amplitude within each functional brain region. The spatial distribution of activation was quantified and compared across mapping algorithms, subjects, scanners, and pulse sequences.

Results:

The spatial distribution of traditional blood oxygen level‐dependent (BOLD) t‐value statistical activation maps was highly variable in test–retest scans of single subjects, whereas AMPLE normalized maps were highly reproducible in terms of the location, hemispheric laterality, and spatial extent of relative activation. AMPLE map reproducibility was good regardless of scanner, field strength, or pulse sequence used, but reproducibility was best for scans acquired on the same scanner using the same pulse sequence.

Conclusion:

Reproducibility of the spatial pattern of BOLD activation makes relative amplitude fMRI mapping a useful normalization tool for clinical imaging of language function, where reproducibility and quantitative measurements are critical concerns. J. Magn. Reson. Imaging 2012;36:569–580. © 2012 Wiley Periodicals, Inc.     

A parallel approach to STAP implementation for fMRI data

PURPOSE: To exploit the capabilities of parallel processing in applying the space-time adaptive processing (STAP) algorithm, previously explored on a small scale for functional magnetic resonance imaging (fMRI) applications, to conventional size fMRI data sets. MATERIALS AND METHODS: STAP is a two-dimensional filter that is able to locate fMRI activations in both space and frequency. It is applied here for the construction of brain activation maps in fMRI using Visual Age C, incorporating Engineering and Scientific Subroutine Library (ESSL) functions, compiled in 64-bit, and executed on an IBM SP supercomputer. RESULTS: Computer simulations incorporating actual MRI noise indicate that STAP, incorporated using the method of steepest descent, is feasible on conventional size data sets and exhibits an improvement in detecting activations over the more traditional cross correlation method of fMRI analysis when the response is unknown. CONCLUSION: STAP is feasible on traditional size fMRI data sets and useful in elucidating spatial and temporal connectivity.