Calibrating the BOLD response without administering gases: comparison of hypercapnia calibration with calibration using an asymmetric spin echo.
Calibrating the BOLD response without administering gases: comparison of hypercapnia calibration with calibration using an asymmetric spin echo.
复制标题
DOI：
10.1016/j.neuroimage.2014.09.061
复制
发表时间：
2015-01-01
期刊：
影响因子：
5.7
通讯作者：
Buxton RB
中科院分区：
文献类型：
--
作者：
Blockley NP;Griffeth VE;Simon AB;Dubowitz DJ;Buxton RB
校准的BOLD（血氧水平依赖）技术的开发，以量化的BOLD信号在氧代谢的变化。为了实现这一点，必须进行校准实验，这通常需要向参与者施用高碳酸气体混合物。然而，一种新兴的技术试图使用基于重新聚焦的校准来执行这种校准而不管理气体。虽然高碳酸血症校准试图模拟从血液中物理去除脱氧血红蛋白，但基于重新聚焦的校准的目的是使用自旋回波重新聚焦脱氧血红蛋白对MR信号的失相效应。然而，不可能重新聚焦对BOLD信号有贡献的所有效应，并且需要比例因子来估计BOLD缩放参数M。在这项研究中，基于重新聚焦的校准的可行性进行了研究。通过模拟预测，将重新聚焦校准与M相关的比例因子近似为线性，并且经验测量为视觉皮层为0.88 ± 0.36，感兴趣的灰质区域为0.93 ± 0.32（平均值±标准差）。基于重新聚焦的校准是一种很有前途的方法，通过消除对受试者呼吸特殊气体混合物的需要，大大简化了校准的BOLD方法，并可能为更广泛地实施定量功能MRI提供基础。
The calibrated BOLD (blood oxygen level dependent) technique was developed to quantify the BOLD signal in terms of changes in oxygen metabolism. In order to achieve this a calibration experiment must be performed, which typically requires a hypercapnic gas mixture to be administered to the participant. However, an emerging technique seeks to perform this calibration without administering gases using a refocussing based calibration. Whilst hypercapnia calibration seeks to emulate the physical removal of deoxyhaemoglobin from the blood, the aim of refocussing based calibration is to refocus the dephasing effect of deoxyhaemoglobin on the MR signal using a spin echo. However, it is not possible to refocus all of the effects that contribute to the BOLD signal and a scale factor is required to estimate the BOLD scaling parameter M. In this study the feasibility of a refocussing based calibration was investigated. The scale factor relating the refocussing calibration to M was predicted by simulations to be approximately linear and empirically measured to be 0.88±0.36 for the visual cortex and 0.93±0.32 for a grey matter region of interest (mean±standard deviation). Refocussing based calibration is a promising approach for greatly simplifying the calibrated BOLD methodology by eliminating the need for the subject to breathe special gas mixtures, and potentially provides the basis for a wider implementation of quantitative functional MRI.