Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia.
Queensland Institute of Medical Research, Brisbane, Queensland, Australia.
J Cereb Blood Flow Metab. 2014 Feb;34(2):316-24. doi: 10.1038/jcbfm.2013.200. Epub 2013 Nov 20.
The hemodynamic response function (HRF) describes the local response of brain vasculature to functional activation. Accurate HRF modeling enables the investigation of cerebral blood flow regulation and improves our ability to interpret fMRI results. Block designs have been used extensively as fMRI paradigms because detection power is maximized; however, block designs are not optimal for HRF parameter estimation. Here we assessed the utility of block design fMRI data for HRF modeling. The trueness (relative deviation), precision (relative uncertainty), and identifiability (goodness-of-fit) of different HRF models were examined and test-retest reproducibility of HRF parameter estimates was assessed using computer simulations and fMRI data from 82 healthy young adult twins acquired on two occasions 3 to 4 months apart. The effects of systematically varying attributes of the block design paradigm were also examined. In our comparison of five HRF models, the model comprising the sum of two gamma functions with six free parameters had greatest parameter accuracy and identifiability. Hemodynamic response function height and time to peak were highly reproducible between studies and width was moderately reproducible but the reproducibility of onset time was low. This study established the feasibility and test-retest reliability of estimating HRF parameters using data from block design fMRI studies.
血流动力学响应函数（HRF）描述了脑脉管系统对功能激活的局部反应。准确的 HRF 建模能够研究脑血流调节，并提高我们解释 fMRI 结果的能力。由于检测能力最大化，块设计已被广泛用作 fMRI 范式；然而，块设计并不适合 HRF 参数估计。在这里，我们评估了块设计 fMRI 数据在 HRF 建模中的效用。使用计算机模拟和从 82 对健康年轻成年双胞胎在相隔 3 至 4 个月的两次采集的 fMRI 数据，评估了不同 HRF 模型的准确性（相对偏差）、精密度（相对不确定性）和可识别性（拟合优度），并评估了 HRF 参数估计的测试-重测可重复性。还检查了块设计范式的系统变化属性的影响。在对五个 HRF 模型的比较中，包含两个伽马函数的和六个自由参数的模型具有最高的参数准确性和可识别性。在研究之间，血流动力学响应函数的高度和峰值时间高度可重复，而宽度中度可重复，但起始时间的可重复性较低。这项研究确定了使用块设计 fMRI 研究的数据估计 HRF 参数的可行性和测试-重测可靠性。
