INTER-SITE QA DEVELOPMENT FOR THE FIRST BIRN

第一个诞生的站点间质量保证开发

• 批准号: 7601876
• 负责人: Gary H Glover
• 金额: $ 1.73万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7601876
• 关键词: Agar; All Sites; Biomedical Informatics Research Network; Caliber; Characteristics; Computer Retrieval of Information on Scientific Projects Database; Data; Dependence; Development; Figs - dietary; Floor; Frequencies; Functional Imaging; Functional Magnetic Resonance Imaging; Funding; Gel; Grant; Head; Image; Institution; Maps; Measures; Methods; Monitor; Morphologic artifacts; Noise; Numbers; Performance; Population Study; Protocols documentation; Research; Research Personnel; Resources; Scanning; Schizophrenia; Sepharose; Series; Signal Transduction; Site; Slice; Source; Standards of Weights and Measures; System; Testing; Time; United States National Institutes of Health; Water; Width; abstracting; data acquisition; programs; quality assurance; size; trend

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The FIRST (Functional Imaging Research Schizophrenia Testbed) Biomedical Informatics Research Network (fBIRN) program is the first-ever large scale, multi-center fMRI study of schizophrenia (http://www.nbirn.net). The fBIRN project will pool fMRI data from each of the 11 participating sites to enable the acquisition of a large and diverse study population in a modest time period. To maintain scanner stability, our Center developed methods in use at all the sites for periodic quality assurance (QA). Scans are performed regularly at each of the sites and data uploaded to the network servers. An abstract was prepared and accepted for ISMRM 2004. For longitudinal fMRI studies, it is important to periodically monitor scanner performance to assure that stability, geometric accuracy, signal to noise ratio (SNR) and other characteristics remain accurate and consistent. Constancy is even more important when data from multiple scanners are being compared or combined both initially and over extended periods of time, such as in the fBIRN project. QA methods developed at our Center were adapted for fBIRN. The most important of these examines scanner stability but also derives SNR and is described here. Data Acquisition The weekly stability test uses the fBIRN fMRI scan protocol with a 17 cm diameter agar phantom (35 axial, 4 mm contiguous slices, 22 cm FOV, 64x64 matrix, TE 30ms/40ms (3T-4T/1.5T), TR 3000ms, 200 time frames, 10 minute scan time, EPI or spiral). The agarose gel phantom was doped with NaCl to present RF loading typical of a head and was preferred over water to avoid swirling artifacts. Analysis Only timeseries data from the central slice (18) is used for analysis. Image intensities are measured for each time frame in the series using a 20x20 ROI centered in the image. The RMS fractional fluctuation is calculated after quadratic detrending, and drift is obtained from extrema of the trend line (Fig. 1, top). The Fourier spectrum is calculated (Fig. 1, middle). A 'Weisskoff analysis' is performed using ROIs with sizes varying from 1x1 to 20x20, as shown in Fig. 1, bottom. In this analysis, the standard deviation (STD) should decrease as ?(number of voxels in ROI) if the noise is uncorrelated. System instabilities from RF or gradient sources tend to cause low spatial-frequency image fluctuations, which are manifested as cross-correlation between voxels. This in turn causes STD to depart from linear dependence on 1/(ROI width) and hit a floor as the ROI size becomes larger, as shown in Fig. 1 (cf. with dashed line). Note that the top plot is performed with the largest ROI size, intentionally picked to represent the system limited (rather than SNR limited) noise. In addition, the signal to fluctuation noise ratio (SFNR) is measured by an ROI in a map made from (timeseries mean image)/(timeseries standard deviation image). Finally, the SNR is calculated from noise measured with an ROI in the noise image obtained by subtracting the average of the even time frames and average of the odd time frames and dividing into the mean signal.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 第一个（功能成像研究精神分裂症测试）生物医学信息学研究网络（FBIRN）程序是精神分裂症的首个大型大型，多中心的功能磁共振成像研究（http://www.nbirn.net）。 FBIRN项目将在11个参与站点中的每个站点中汇总fMRI数据，以便在适度的时间段内获得大量多样化的研究人群。为了保持扫描仪的稳定性，我们的中心开发了在所有地点使用定期质量保证（QA）的方法。扫描定期在每个站点上执行，并将数据上传到网络服务器。为ISMRM 2004准备并接受了摘要。 对于纵向FMRI研究，重要的是要定期监视扫描仪性能，以确保稳定性，几何准确性，信号与噪声比（SNR）和其他特征保持准确且一致。当比较多个扫描仪的数据最初和长时间（例如在FBIRN项目中）进行比较或组合时，恒定是更重要的。在我们中心开发的质量检查方法是针对FBIRN的。这些最重要的研究是扫描仪的稳定性，但也得出了SNR，并在此处进行了描述。 Data Acquisition The weekly stability test uses the fBIRN fMRI scan protocol with a 17 cm diameter agar phantom (35 axial, 4 mm contiguous slices, 22 cm FOV, 64x64 matrix, TE 30ms/40ms (3T-4T/1.5T), TR 3000ms, 200 time frames, 10 minute scan time, EPI or spiral).将琼脂糖凝胶幻影用NaCl掺杂，以呈现典型的头部rf载荷，并优先于水，以避免旋转伪影。 分析仅使用中央切片（18）的时间分析数据进行分析。使用以图像为中心的20x20 ROI来测量该系列中每个时间范围的图像强度。 RMS的分数波动是在二次下趋势后计算的，并且从趋势线的极端获得漂移（图1，顶部）。计算傅立叶光谱（图1，中间）。如图1，底部所示，使用尺寸从1x1到20x20的ROI进行“ Weisskoff分析”。在此分析中，如果噪声不相关，则标准偏差（STD）应减小为？（ROI中的体素数）。来自RF或梯度源的系统不稳定性倾向于引起较低的空间频率图像波动，这表现为体素之间的互相关。反过来，这导致STD脱离对1/（ROI宽度）的线性依赖性，并随着ROI尺寸变大而撞到地板，如图1所示（参见带有虚线）。请注意，顶部图是最大的ROI大小执行的，故意选择以表示系统限制（而不是SNR限制）噪声。此外，信号与波动噪声比（SFNR）是通过ROI在（时间均值均值）/（时间赛标准偏差图像）中测量的。最后，通过减去偶数时间帧的平均值和奇数时间帧的平均值并分为平均信号，从噪声图像中测得的噪声计算得出SNR。