Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, Missouri 63130, USA.
Opt Lett. 2013 Aug 1;38(15):2800-3. doi: 10.1364/OL.38.002800.
Photoacoustic tomography (PAT) is a hybrid imaging technique that has broad preclinical and clinical applications. Based on the photoacoustic effect, PAT directly measures specific optical absorption, which is the product of the tissue-intrinsic optical absorption coefficient and the local optical fluence. Therefore, quantitative PAT, such as absolute oxygen saturation (sO₂) quantification, requires knowledge of the local optical fluence, which can only be estimated through invasive measurements or sophisticated modeling of light transportation. In this Letter, we circumvent this requirement by taking advantage of the dynamics in sO₂. The new method works when the sO₂ transition can be simultaneously monitored with multiple wavelengths. For each wavelength, the ratio of photoacoustic amplitudes measured at different sO₂ states is utilized. Using the ratio cancels the contribution from optical fluence and allows calibration-free quantification of absolute sO₂. The new method was validated through both phantom and in vivo experiments.
光声断层扫描（PAT）是一种混合成像技术，具有广泛的临床前和临床应用。基于光声效应，PAT 直接测量特定的光吸收，它是组织固有光吸收系数和局部光强度的乘积。因此，定量 PAT，如绝对氧饱和度（sO₂）定量，需要了解局部光强度，这只能通过侵入性测量或复杂的光传输建模来估计。在这封信中，我们利用 sO₂的动力学来规避这一要求。当 sO₂的转变可以同时用多个波长监测时，新方法就可以工作。对于每个波长，利用在不同 sO₂状态下测量的光声幅度的比值。利用该比值可以消除光强度的贡献，实现绝对 sO₂的无校准定量。新方法通过体模和体内实验进行了验证。
