Wild Jim M, Fichele Stan, Woodhouse Neil, Paley Martyn N J, Kasuboski Larry, van Beek Edwin J R
Unit of Academic Radiology, University of Sheffield, UK.
Magn Reson Med. 2005 May;53(5):1055-64. doi: 10.1002/mrm.20423.
A method for 3D volume-localized quantification of pO2 in the lungs is presented that uses repetitive frame 3D gradient-echo imaging of (3)He. The method was demonstrated by experiments on (3)He phantoms containing known concentrations of O(2) and in vivo on a group of three healthy human volunteers. The results were compared with those obtained by equivalent 2D thin-slice and 2D projection methodologies, and were found to be consistent with published results from the 2D projection methodologies (pO(2) = 0.09-0.18 bar). Studies performed on the same subject, on three separate occasions, demonstrated a repeatability of pO(2) measurement to within 14% using the 3D technique. Experimental differences between the 2D and 3D methods were substantiated with theoretical and numerical analyses of the signal decay, which took into account the effects of out-of-slice diffusion as a source of error in the thin-slice 2D experiments. It is shown that the 2D thin-slice technique systematically underestimates pO2 when there is significant gas diffusion (factor of 4 underestimate for D = 0.9 cm(2)s(-1) representative of free (3)He in air).
本文介绍了一种用于肺部pO2的三维体积定位定量方法，该方法使用(3)He的重复帧三维梯度回波成像。该方法通过在含有已知O(2)浓度的(3)He模型上进行实验，并在一组三名健康人类志愿者身上进行体内实验得到了验证。将结果与通过等效二维薄片和二维投影方法获得的结果进行了比较，发现与二维投影方法公布的结果一致（pO(2)=0.09-0.18巴）。在同一受试者上进行的三次独立研究表明，使用三维技术时，pO(2)测量的重复性在14%以内。二维和三维方法之间的实验差异通过信号衰减的理论和数值分析得到了证实，该分析考虑了切片外扩散作为薄片二维实验中误差来源的影响。结果表明，当存在显著的气体扩散时，二维薄片技术会系统性地低估pO2（对于代表空气中自由(3)He的D = 0.9 cm(2)s(-1)，低估因子为4）。
