Kobayashi Masato, Okazawa Hidehiko, Tsuchida Tatsuro, Kawai Keiichi, Fujibayashi Yasuhisa, Yonekura Yoshiharu
Biomedical Imaging Research Center, University of Fukui, Fukui, Japan.
J Nucl Med. 2006 Oct;47(10):1581-6.
To avoid arterial blood sampling and complicated analyses in 15O-gas PET studies, we evaluated a noninvasive technique using the count-based method for measuring asymmetric increases in oxygen extraction fraction (OEF) in cerebrovascular disease.
Eighteen patients (mean age +/- SD, 61 +/- 16 y) with atherothrombotic large-cerebral-artery disease were studied for the measurement of hemodynamic parameters using the 15O-gas steady-state method with inhalation of 15O2, C15O2, and C15O. All patients also underwent H2(15)O PET with the bolus injection method. Count-based ratio images of 15O2/C15O2 and (15)O2/H2(15)O were calculated, and asymmetry indices (AIs) were obtained (cbOEF(SS)-AI and cbOEF(BO)-AI, respectively) using regions of interest drawn bilaterally on the cerebral cortices. These AIs were compared with the AIs of absolute OEF (qOEF-AI) and with those after cerebral blood volume (CBV) correction. A contribution factor for this correction was defined as a variable alpha, and the effect of the correction was evaluated.
cbOEF(SS)-AI underestimated qOEF-AI significantly, especially with a greater AI (P < 0.05). cbOEF(BO)-AI linearly correlated well with qOEF-AI. CBV correction improved the slopes of regression lines between qOEF-AI and cbOEF(SS)-AI, and the optimal alpha was defined as 0.5. On the other hand, cbOEF(BO)-AI fairly estimated qOEF-AI without CBV correction. Correlation between qOEF-AI and cbOEF(BO)-AI was adversely affected, and the mean bias was increased, with a greater alpha.
cbOEF(BO)-AI can fairly estimate the AI of OEF without CBV correction, whereas cbOEF(SS)-AI might require CBV correction for better estimation. The examination time and stress to patients would be reduced with the count-based method because it is noninvasive.
为避免在15O气体PET研究中进行动脉血采样和复杂分析，我们评估了一种使用基于计数法的无创技术，用于测量脑血管疾病中氧摄取分数（OEF）的不对称增加。
对18例（平均年龄±标准差，61±16岁）患有动脉粥样硬化性大脑大动脉疾病的患者进行研究，采用吸入15O2、C15O2和C15O的15O气体稳态法测量血流动力学参数。所有患者还采用团注注射法进行了H2(15)O PET检查。计算15O2/C15O2和(15)O2/H2(15)O的基于计数的比率图像，并使用在双侧大脑皮质上绘制的感兴趣区域获得不对称指数（AI）（分别为cbOEF(SS)-AI和cbOEF(BO)-AI）。将这些AI与绝对OEF的AI（qOEF-AI）以及脑血容量（CBV）校正后的AI进行比较。将该校正的贡献因子定义为变量α，并评估校正的效果。
cbOEF(SS)-AI显著低估了qOEF-AI，尤其是在AI较大时（P<0.05）。cbOEF(BO)-AI与qOEF-AI线性相关性良好。CBV校正改善了qOEF-AI与cbOEF(SS)-AI之间回归线的斜率，最佳α定义为0.5。另一方面，cbOEF(BO)-AI在不进行CBV校正的情况下能较好地估计qOEF-AI。随着α增大，qOEF-AI与cbOEF(BO)-AI之间的相关性受到不利影响，平均偏差增加。
cbOEF(BO)-AI在不进行CBV校正的情况下可以较好地估计OEF的AI，而cbOEF(SS)-AI可能需要进行CBV校正以获得更好的估计。基于计数的方法是无创的，因此可以减少检查时间和患者的压力。
