Steger Theodore R, White R Allen, Jackson Edward F
Department of Imaging Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Magn Reson Med. 2005 Apr;53(4):895-903. doi: 10.1002/mrm.20440.
The regional cerebral blood flow (rCBF) values determined using continuous arterial spin labeling (CASL) are subject to several sources of variability, including natural physiologic variations, sensitivity to the input parameters, and the use of different quantification models. To date, a thorough analysis of the impact of input parameters and the choice of quantification model has not been performed. These sources of variability were investigated through computer simulations using bootstrap techniques on actual CASL data. Coefficients of variation for representative single voxels were 6.7% for gray matter and 29% for white matter, and for eight-voxel regions of interest they were 4.5% for gray matter and 23% for white matter. Comparison of nine CASL quantification models showed differences in gray matter rCBF values of up to 42%. An analysis of the sensitivity of the rCBF to input parameters for each of the nine quantification models demonstrated that accurate quantification of the inversion efficiency, tissue and arterial blood longitudinal relaxation times, and transit times were critical in calculating precise rCBF values. The large potential variations in rCBF and the effect of the choice of quantification model suggest that interpreting absolute rCBF values in CASL studies can be challenging and requires great care.
使用连续动脉自旋标记（CASL）测定的局部脑血流量（rCBF）值存在多种变异来源，包括自然生理变异、对输入参数的敏感性以及不同定量模型的使用。迄今为止，尚未对输入参数的影响和定量模型的选择进行全面分析。通过对实际CASL数据采用自抽样技术进行计算机模拟，研究了这些变异来源。代表性单像素的变异系数，灰质为6.7%，白质为29%；对于八像素感兴趣区域，灰质为4.5%，白质为23%。对九种CASL定量模型的比较表明，灰质rCBF值差异高达42%。对九种定量模型中每种模型的rCBF对输入参数的敏感性分析表明，准确量化反转效率、组织和动脉血纵向弛豫时间以及通过时间对于计算精确的rCBF值至关重要。rCBF的巨大潜在变异以及定量模型选择的影响表明，在CASL研究中解释绝对rCBF值可能具有挑战性，需要格外谨慎。
