Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Center for Biomedical Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
J Nucl Med. 2014 Aug;55(8):1380-8. doi: 10.2967/jnumed.113.127381. Epub 2014 Jun 9.
Measurement of arterial input function is a restrictive aspect for quantitative (18)F-FDG PET studies in rodents because of their small total blood volume and the related difficulties in withdrawing blood.
In the present study, we took advantage of the high spatial resolution of a recent dedicated small-animal scanner to extract the input function from the (18)F-FDG PET images in Sprague-Dawley rats (n = 4) and C57BL/6 mice (n = 5), using the vena cava. In the rat experiments, the validation of the image-derived input function (IDIF) method was made using an external microvolumetric blood counter as reference for the determination of the arterial input function, the measurement of which was confirmed by additional manually obtained blood samples. Correction for tracer bolus dispersion in blood between the vena cava and the arterial tree was applied. In addition, simulation studies were undertaken to probe the impact of the different IDIF extraction approaches on the determined cerebral metabolic rate of glucose (CMRGlc). In the mice measurements, the IDIF was used to compute the CMRGlc, which was compared with previously reported values, using the Patlak approach.
The presented IDIF from the vena cava showed a robust determination of CMRGlc using either the compartmental modeling or the Patlak approach, even without bolus dispersion correction or blood sampling, with an underestimation of CMRGlc of 7% ± 16% as compared with the reference data. Using this approach in the mice experiments, we measured a cerebral metabolic rate in the cortex of 0.22 ± 0.10 μmol/g/min (mean ± SD), in good agreement with previous (18)F-FDG studies in the mouse brain. In the rat experiments, dispersion correction of the IDIF and additional scaling of the IDIF using a single manual blood sample enabled an optimized determination of CMRGlc, with an underestimation of 6% ± 7%.
The vena cava time-activity curve is therefore a minimally invasive alternative for the measurement of the (18)F-FDG input function in rats and mice, without the complications associated with repetitive blood sampling.
在啮齿动物中，由于其总血容量较小，且采血相关难度较大，动脉输入函数的测量成为定量（18）F-FDG PET 研究的一个限制因素。
在本研究中，我们利用最近专用小动物扫描仪的高空间分辨率，从 Sprague-Dawley 大鼠（n=4）和 C57BL/6 小鼠（n=5）的（18）F-FDG PET 图像中提取输入函数，方法是利用腔静脉。在大鼠实验中，使用外部微量体积血液计数器作为动脉输入函数的参考，验证了图像衍生输入函数（IDIF）方法的准确性，通过额外手动获得的血液样本确认了动脉输入函数的测量。对腔静脉和动脉树之间的示踪剂团注扩散进行了校正。此外，还进行了模拟研究，以探究不同的 IDIF 提取方法对确定脑葡萄糖代谢率（CMRGlc）的影响。在小鼠测量中，使用 IDIF 计算 CMRGlc，并用 Patlak 方法与之前报道的值进行比较。
即使不进行示踪剂团注扩散校正或血液取样，使用房室模型或 Patlak 方法，从腔静脉获得的 IDIF 也可稳定地确定 CMRGlc，与参考数据相比，CMRGlc 的低估率为 7%±16%。在小鼠实验中，使用该方法测量皮层的脑代谢率为 0.22±0.10 μmol/g/min（平均值±标准差），与之前在小鼠大脑中进行的（18）F-FDG 研究结果一致。在大鼠实验中，对 IDIF 进行示踪剂团注扩散校正，并使用单个手动血液样本对 IDIF 进行额外缩放，可优化 CMRGlc 的确定，低估率为 6%±7%。
因此，腔静脉时间-活性曲线是一种微创替代方法，可用于测量大鼠和小鼠的（18）F-FDG 输入函数，无需重复采血相关并发症。
