Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America.
PLoS One. 2013 Aug 6;8(8):e69657. doi: 10.1371/journal.pone.0069657. Print 2013.
Radiation retinopathy is a possible post-treatment complication of radiation therapy. The pathophysiologic mechanism is hypothesized to be microvascular in origin, but evidence is limited. In an effort to study retinal oxygenation in these patients, we herein evaluate the repeatability and variability of retinal oximetry measurements in subjects who had previously received radiation and make comparisons to a cohort of unirradiated subjects.
Using retinal oximetry, a non-invasive imaging modality, we performed in vivo measurements of arteriole (SaO2) and venule SO2 (SvO2) in subjects (n = 9, 18 retinas) who had received incidental radiation to their retinas (≥ 45 Gy to one retina) and in healthy subjects (n = 20, 40 retinas). A total of 1367 SO2 observations on 593 vessels in 29 persons were analyzed to assess three sources of variance in vessel SO2: 1) variance in repeated measurements of the same vessel ("repeatability"), 2) variance in different vessels within the same subject ("within-subject variability"), and 3) variance between subjects ("between-subject variability").
Retinal oximetry measurements were highly repeatable in both irradiated patients and unirradiated subjects. The within-subject variability of SvO2 and SaO2 measurements constituted the highest component of variance in both groups and was significantly higher in venules vs. arterioles (relative effect size 1.8, p<0.001) and in irradiated subjects vs. unirradiated subjects (relative effect size 1.6, p<0.001).
Retinal oximetry is a highly repeatable technology and can be reliably used to study vascular oxygenation in irradiated subjects. Different vessels within the same subject exhibit a high degree of variability, suggesting that pooled analyses of multiple vessels are most likely to be informative of regional retinal oxygenation. Finally, irradiated subjects exhibited significantly higher within-subject variability in SO2 measurements, suggesting that radiation may cause regional alterations in retinal oxygen delivery and/or metabolism.
放射性视网膜病变是放射治疗后可能出现的一种治疗后并发症。其病理生理机制推测源于微血管，但证据有限。为了研究这些患者的视网膜氧合情况，我们在此评估了既往接受过放射治疗的患者的视网膜血氧测量的重复性和可变性，并与未接受放射治疗的患者进行了比较。
使用视网膜血氧计，一种非侵入性的成像方式，我们对 9 名（18 只眼）接受过视网膜偶然放射治疗（一只眼接受 45Gy 以上放射治疗）的患者和 20 名（40 只眼）健康患者进行了活体测量。对 29 名患者的 593 条血管共进行了 1367 次 SO2 观察，以评估血管 SO2 的三种方差来源：1）同一血管重复测量的方差（“重复性”）；2）同一患者内不同血管的方差（“个体内变异性”）；3）个体之间的方差（“个体间变异性”）。
视网膜血氧计测量在放射治疗患者和未接受放射治疗的患者中均具有高度重复性。SvO2 和 SaO2 测量的个体内变异性是两组中最高的方差组成部分，且在静脉中明显高于动脉（相对效应大小 1.8，p<0.001），在放射治疗患者中明显高于未接受放射治疗的患者（相对效应大小 1.6，p<0.001）。
视网膜血氧计是一种高度可重复的技术，可可靠地用于研究放射治疗患者的血管氧合情况。同一患者内的不同血管表现出高度的变异性，这表明对多个血管的汇总分析最有可能提供有关局部视网膜氧合的信息。最后，放射治疗患者的 SO2 测量个体内变异性明显更高，这表明放射治疗可能导致视网膜氧输送和/或代谢的局部改变。
