Tran H T, Guo Q, Schumacher D J, Buxton R B, Mattrey R F
Department of Radiology, University of California, San Diego Medical Center, USA.
Acad Radiol. 1995 Sep;2(9):756-61. doi: 10.1016/s1076-6332(05)80485-4.
There is a linear relation between the T1 relaxation rate of fluorine-19 (19F) of perfluorochemicals (PFCs) and the partial pressure of the oxygen (pO2) dissolved in the PFC. A line scan technique was used to overcome the significant chemical shift and low signal-to-noise ratio (SNR) of in vivo 19F magnetic resonance imaging. This study was designed to determine whether the line scan technique could detect the effect of oxygen on 19F T1. In addition, its ability to detect changes in intracellular pO2 when the inspired gas was raised from 20% to 100% O2 also was investigated.
The T1 relaxation rate of samples of perflubron emulsion diluted from 3.5% to 70% w/v and equilibrated with N2-O2 gas mixtures (pO2 range = 10-450 mm Hg) was measured using the line scan technique. The gas and emulsion pO2 were measured with a blood gas analyzer. The liver T1 relaxation rate was measured in three rabbits given 5 ml/kg perflubron emulsion 4 and 8 days earlier as they breathed room air and then 100% O2. We used a prototype cylindrical coil double-tuned to hydrogen-1 (1H) and 19F and selected a line through the liver. The scanning parameters yielded a voxel size of 20 x 20 x 15.6 mm. Liver and blood samples were obtained postsacrifice for perflubron concentration measurement.
A linear relation between the 19F T1 relaxation rate (1/T1) of the 3.5% w/v emulsion and dissolved pO2 was established with a slope of 0.0033 (sec-1/mm Hg) and a correlation coefficient of .991. As the PFC concentration increased by 1,900%, the slope increased by 21.2%. The 1/T1 for the liver was 0.182 +/- 0.004 sec-1 at baseline. It increased to 0.247 +/- 0.022 sec-1 when rabbits breathed 100% O2 (p = .023), which corresponded to an increase in intracellular pO2 of 19.7 mm Hg. The liver-to-blood PFC concentration ratio was 500:1.
In vitro measurements with the line scan technique replicated the established linear dependence of 1/T1 on pO2. In vivo measurements indicated a 20-mm Hg increase in intracellular pO2 of liver phagocytes when the inspired gas was changed from 20% to 100% O2.
全氟化合物（PFCs）中氟 - 19（¹⁹F）的T1弛豫率与溶解在PFC中的氧分压（pO₂）之间存在线性关系。采用线扫描技术来克服体内¹⁹F磁共振成像中显著的化学位移和低信噪比（SNR）。本研究旨在确定线扫描技术是否能检测到氧对¹⁹F T1的影响。此外，还研究了在吸入气体从20% O₂升高到100% O₂时，其检测细胞内pO₂变化的能力。
使用线扫描技术测量从3.5%重量/体积稀释到70%重量/体积并与N₂ - O₂混合气体（pO₂范围 = 10 - 450 mmHg）平衡的全氟溴辛烷乳液样品的T1弛豫率。用血气分析仪测量气体和乳液的pO₂。在三只兔子于4天和8天前分别给予5 ml/kg全氟溴辛烷乳液后，在它们呼吸空气然后呼吸100% O₂时测量肝脏T1弛豫率。我们使用了一个双调谐到氢 - 1（¹H）和¹⁹F的原型圆柱形线圈，并选择一条穿过肝脏的线。扫描参数产生的体素大小为20×20×15.6 mm。在处死动物后获取肝脏和血液样本以测量全氟溴辛烷浓度。
建立了3.5%重量/体积乳液的¹⁹F T1弛豫率（1/T1）与溶解的pO₂之间的线性关系，斜率为0.0033（秒⁻¹/mmHg），相关系数为0.991。随着PFC浓度增加1900%，斜率增加21.2%。肝脏的1/T1在基线时为0.182±0.004秒⁻¹。当兔子呼吸100% O₂时，它增加到0.247±0.022秒⁻¹（p = 0.023），这对应于细胞内pO₂增加19.7 mmHg。肝脏与血液的PFC浓度比为500:1。
线扫描技术的体外测量重现了已确立的1/Tl对pO₂的线性依赖性。体内测量表明，当吸入气体从20% O₂变为100% O₂时，肝脏吞噬细胞的细胞内pO₂增加20 mmHg。
