Hall Morales Ryan D, Sun Hongjing, Hong Ong Yi, Zhu Timothy C
Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
Proc SPIE Int Soc Opt Eng. 2022 Jan-Feb;11940. doi: 10.1117/12.2609937. Epub 2022 Mar 4.
Accurate dosimetry is crucial for the ongoing development and clinical study of photodynamic therapy (PDT). Current dosimetry standards range from less accurate methods involving measurement of only light fluence and photosensitizer concentration during treatment, to significantly improved methods such as singlet oxygen explicit dosimetry (SOED), a macroscopic model that includes an additional important parameter in its dosimetric calculations: ground-state oxygen concentration ([O]). However, neither of these models is a method of direct dosimetry. Multispectral singlet oxygen luminescence dosimetry (MSOLD) shows promise in this regard but requires significant improvement in signal quality and remains to be validated in a clinical setting. In this study, we validate a linearly increasing MSOLD signal with an InGaAs photodiode detector for increasing concentration (0 mg/kg to 200 mg/kg) in tissue-simulating phantoms containing photofrin, calculating a calibration curve based on 1270 nm peak-intensity signal and area under the curve for background-subtracted singlet oxygen emission. Additionally, we validate MSOLD against the current clinical dosimetry standard, SOED, through simultaneous measurement of SOED parameters and MSOLD signal for varying concentrations (50 μM - 300 μM). Finally, we investigate the effects of using very high gain amplification on InGaAs photodiode detectors to amplify the MSOLD signal for use in clinical models. We show that a calibration curve relating photosensitizer concentration (PS) and MSOLD signal can be established. Additionally, we demonstrate good correlation between MSOLD signal and SOED-calculated [O]. However, we show that when using high amplification on InGaAs photodiodes for long illumination times, the inherent instability in these detectors becomes apparent.
精确的剂量测定对于光动力疗法（PDT）的持续发展和临床研究至关重要。当前的剂量测定标准范围较广，从不太精确的方法（仅在治疗期间测量光通量和光敏剂浓度）到显著改进的方法，如单线态氧显式剂量测定法（SOED），这是一种宏观模型，在其剂量计算中包含一个额外的重要参数：基态氧浓度（[O]）。然而，这些模型都不是直接剂量测定方法。多光谱单线态氧发光剂量测定法（MSOLD）在这方面显示出前景，但需要在信号质量上有显著改进，并且仍有待在临床环境中验证。在本研究中，我们使用铟镓砷光电二极管探测器验证了在含有光卟啉的组织模拟体模中，随着浓度从0 mg/kg增加到200 mg/kg，MSOLD信号呈线性增加，基于1270 nm峰值强度信号和背景扣除后的单线态氧发射曲线下面积计算校准曲线。此外，我们通过同时测量不同浓度（50 μM - 300 μM）下的SOED参数和MSOLD信号，将MSOLD与当前临床剂量测定标准SOED进行了验证。最后，我们研究了在铟镓砷光电二极管探测器上使用非常高的增益放大来放大MSOLD信号以用于临床模型的效果。我们表明可以建立光敏剂浓度（PS）与MSOLD信号之间的校准曲线。此外。我们证明了MSOLD信号与SOED计算的[O]之间具有良好的相关性。然而，我们表明，当在铟镓砷光电二极管上长时间使用高放大倍数时，这些探测器固有的不稳定性就会显现出来。
