Lawson Health Research Institute, London, Ontario, Canada.
Department of Medical Biophysics, Western University, London, Ontario, Canada.
Phys Med Biol. 2021 Mar 4;66(6):065009. doi: 10.1088/1361-6560/abe737.
Positron emission tomography (PET) remains the gold standard for quantitative imaging of the cerebral metabolic rate of oxygen (CMRO); however, it is an invasive and complex procedure that requires accounting for recirculating [O]HO (RW) and the cerebral blood volume (CBV). This study presents a non-invasive reference-based technique for imaging CMRO that was developed for PET/magnetic resonance imaging (MRI) with the goal of simplifying the PET procedure while maintaining its ability to quantify metabolism. The approach is to use whole-brain (WB) measurements of oxygen extraction fraction (OEF) and cerebral blood flow (CBF) to calibrate [O]O-PET data, thereby avoiding the need for invasive arterial sampling. Here we present the theoretical framework, along with error analyses, sensitivity to PET noise and inaccuracies in input parameters, and initial assessment on PET data acquired from healthy participants. Simulations showed that neglecting RW and CBV corrections caused errors in CMRO of less than ±10% for changes in regional OEF of ±25%. These predictions were supported by applying the reference-based approach to PET data, which resulted in remarkably similar CMRO images to those generated by analyzing the same data using a modeling approach that incorporated the arterial input functions and corrected for CBV contributions. Significant correlations were observed between regional CMRO values from the two techniques (slope = 1.00 ± 0.04, R > 0.98) with no significant differences found for integration times of 3 and 5 min. In summary, results demonstrate the feasibility of producing quantitative CMRO images by PET/MRI without the need for invasive blood sampling.
正电子发射断层扫描（PET）仍然是氧代谢率（CMRO）脑代谢的定量成像的金标准；然而，它是一种侵入性和复杂的过程，需要考虑再循环的[O]HO（RW）和脑血容量（CBV）。本研究提出了一种用于 PET/磁共振成像（MRI）的非侵入性基于参考的 CMRO 成像技术，旨在简化 PET 程序，同时保持其代谢定量能力。该方法是使用全脑（WB）测量氧摄取分数（OEF）和脑血流（CBF）来校准[O]O-PET 数据，从而避免了侵入性动脉采样的需要。在这里，我们提出了理论框架，以及误差分析、对 PET 噪声和输入参数不准确的敏感性，以及对健康参与者采集的 PET 数据的初步评估。模拟表明，忽略 RW 和 CBV 校正会导致 CMRO 误差小于±10%，对于区域性 OEF 的±25%变化。通过将基于参考的方法应用于 PET 数据，证实了这些预测，这导致与使用包含动脉输入函数并校正 CBV 贡献的建模方法分析相同数据生成的 CMRO 图像非常相似。两种技术的区域 CMRO 值之间观察到显著的相关性（斜率=1.00±0.04，R>0.98），对于 3 和 5 分钟的积分时间，没有发现显著差异。总之，结果表明，在不需要侵入性血液采样的情况下，通过 PET/MRI 生成定量 CMRO 图像是可行的。
