MR Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, UK.
Magn Reson Med. 2022 Sep;88(3):1170-1179. doi: 10.1002/mrm.29290. Epub 2022 May 9.
To investigate the potential effects of [1- C]lactate RF saturation pulses on [ C]bicarbonate detection in hyperpolarized [1- C]pyruvate MRI of the brain.
Thirteen healthy rats underwent MRI with hyperpolarized [1- C]pyruvate of either the brain (n = 8) or the kidneys, heart, and liver (n = 5). Dynamic, metabolite-selective imaging was used in a cross-over experiment in which [1- C]lactate was excited with either 0° or 90° flip angles. The [ C]bicarbonate SNR and apparent [1- C]pyruvate-to-[ C]bicarbonate conversion (k ) were determined. Furthermore, simulations were performed to identify the SNR optimal flip-angle scheme for detection of [1- C]lactate and [ C]bicarbonate.
In the brain, the [ C]bicarbonate SNR was 64% higher when [1- C]lactate was not excited (5.8 ± 1.5 vs 3.6 ± 1.3; 1.2 to 3.3-point increase; p = 0.0027). The apparent k decreased 25% with [1- C]lactate saturation (0.0047 ± 0.0008 s vs 0.0034 ± 0.0006 s ; 95% confidence interval, 0.0006-0.0019 s increase; p = 0.0049). These effects were not present in the kidneys, heart, or liver. Simulations suggest that the optimal [ C]bicarbonate SNR with a TR of 1 s in the brain is obtained with [ C]bicarbonate, [1- C]lactate, and [1- C]pyruvate flip angles of 60°, 15°, and 10°, respectively.
Radiofrequency saturation pulses on [1- C]lactate limit [ C]bicarbonate detection in the brain specifically, which could be due to shuttling of lactate from astrocytes to neurons. Our results have important implications for experimental design in studies in which [ C]bicarbonate detection is warranted.
研究[1-¹³C]乳酸 RF 饱和脉冲对脑内高极化[1-¹³C]丙酮酸 MRI 中[1-¹³C]碳酸氢盐检测的潜在影响。
13 只健康大鼠行脑部（n=8）或肾脏、心脏和肝脏（n=5）高极化[1-¹³C]丙酮酸 MRI。在交叉实验中使用动态、代谢物选择性成像，[1-¹³C]乳酸分别用 0°或 90°翻转角激发。确定[¹³C]碳酸氢盐 SNR 和[1-¹³C]丙酮酸到[¹³C]碳酸氢盐的表观转化（k）。此外，还进行了模拟以确定用于检测[1-¹³C]乳酸和[¹³C]碳酸氢盐的 SNR 最佳翻转角方案。
在大脑中，当未激发[1-¹³C]乳酸时，[¹³C]碳酸氢盐 SNR 升高 64%（5.8±1.5 比 3.6±1.3；1.2 到 3.3 点增加；p=0.0027）。[1-¹³C]乳酸饱和时，表观 k 降低 25%（0.0047±0.0008 s 比 0.0034±0.0006 s；95%置信区间，0.0006-0.0019 s 增加；p=0.0049）。这些效应在肾脏、心脏或肝脏中不存在。模拟表明，在 TR 为 1 s 的大脑中，[¹³C]碳酸氢盐、[1-¹³C]乳酸和[1-¹³C]丙酮酸的翻转角分别为 60°、15°和 10°时，可获得最佳[¹³C]碳酸氢盐 SNR。
[1-¹³C]乳酸的射频饱和脉冲特异性地限制了大脑中[¹³C]碳酸氢盐的检测，这可能是由于乳酸从星形胶质细胞向神经元穿梭所致。我们的结果对需要检测[1-¹³C]碳酸氢盐的研究中的实验设计具有重要意义。
