Turku PET Centre, University of Turku, Turku, Finland.
Mol Imaging Biol. 2011 Dec;13(6):1241-9. doi: 10.1007/s11307-010-0449-z.
Small animal positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) facilitates the visualization and quantification of glucose uptake in rats and mice. The quantification of glucose uptake requires an input function, which is generally obtained by measuring radioactivity in arterial plasma withdrawn during PET imaging; however, this approach is not always feasible because abundant blood sampling may affect the physiological process being measured. The purpose of the present study was to develop a new model-based technique (K-Model) and compare it to the previous F-Model.
The study material consisted of two separate groups of rats having different physiological conditions. Each group was scanned by different PET cameras, i.e., HRRT and Inveon-PET/CT, and blood samples were drawn during imaging. Two kinds of model functions, i.e., F-Model and K-Model, were used for estimating input functions by an optimization procedure, applying restrictions on boundary conditions. To validate the method, glucose influx rate, Ki, was computed from the estimated and measured input functions for comparison.
The input functions were well reproduced when single-point blood count data were used for both models. The difference in Ki values between the model-based and blood sampling methods was 1.1±15.1% by K-Model which showed the most feasible in the study. The regression analysis showed a tight correlation between the image-based and blood sampling methods, and the slope was close to unity and the intercept close to zero.
It is possible to estimate the input function from rat [18F]FDG PET images, thus facilitating the assessment of glucose metabolism without affecting the physiological conditions of the animal as a result of abundant blood sampling.
小动物正电子发射断层扫描（PET）结合 2-脱氧-2-[18F]氟代-D-葡萄糖（[18F]FDG）可促进葡萄糖摄取在大鼠和小鼠中的可视化和量化。葡萄糖摄取的定量需要输入函数，通常通过在 PET 成像期间测量从动脉血浆中取出的放射性来获得；然而，这种方法并不总是可行的，因为大量采血可能会影响正在测量的生理过程。本研究的目的是开发一种新的基于模型的技术（K 模型），并将其与之前的 F 模型进行比较。
研究材料包括具有不同生理条件的两组大鼠。每组均由不同的 PET 相机（即 HRRT 和 Inveon-PET/CT）扫描，并在成像期间抽取血样。两种模型函数，即 F 模型和 K 模型，通过优化程序用于估计输入函数，同时对边界条件施加限制。为了验证该方法，通过计算估计和测量的输入函数的葡萄糖内流率 Ki 值来进行比较。
当使用单点血样计数数据时，两种模型都可以很好地再现输入函数。使用 K 模型时，模型法和采血法的 Ki 值差异为 1.1±15.1%，在研究中表现最为可行。回归分析显示，图像法和采血法之间存在紧密的相关性，斜率接近 1，截距接近 0。
可以从大鼠 [18F]FDG PET 图像中估计输入函数，从而在不影响动物生理状况的情况下，无需大量采血即可评估葡萄糖代谢。
