Background

Synovial hypoxia is a hallmark of rheumatoid arthritis (RA). Photoacoustic (PA) imaging, based on the use of laser-generated US, can detect the oxygenation status of tissue in individuals with RA. However, large studies are lacking, with few investigating the correlation between oxygenation status and disease activity.

Purpose

To measure synovial oxygenation status in participants with RA by using a multimodal PA US imaging system and to determine the correlation between PA imaging–measured oxygen saturation (SO₂) and disease activity.

Materials and Methods

In this prospective observational cohort study, multimodal PA US imaging examinations were performed on small joints of consecutive participants with RA, who were treated at two outpatient rheumatology clinics from 2019 to 2021, and healthy controls. The SO₂ values of the synovium were measured with dual-wavelength PA imaging and classified into three categories—hyperoxia, intermediate oxygenation status, or hypoxia—based on the signal coloration and clustering analysis of the SO₂ values. The correlations of oxygenation status with power Doppler US (PDUS) scoring and clinical disease activity index were evaluated with one-way analysis of variance and the Kruskal-Wallis test with Bonferroni correction.

Results

A total of 118 participants with RA (median age, 55 years [IQR, 41–62 years]; 92 women) and 15 healthy control participants (median age, 37 years [IQR, 33–41 years]; 11 women) were included. The wrist synovium was categorized as hyperoxic in 36 participants with RA, of intermediate oxygenation status in 48 participants, and hypoxic in 34 participants. All control participants had hyperoxic synovial tissues. For participants with RA, hyperoxic synovium had more affluent Doppler US–depicted vasculature than those with hypoxia and intermediate oxygenation status (mean PDUS grade: hyperoxia, 2.7 ± 0.6 [SD]; intermediate, 1.3 ± 0.7; hypoxia, 1.1 ± 0.8; P < .001). Participants with intermediate status synovium had a lower clinical disease activity index than those with hypoxia (intermediate, 11.0 [IQR, 5.0–21.5] vs hypoxia, 26.0 [IQR, 18.0–39.0]; P = .001).

Conclusion

Photoacoustic imaging–detected hypoxia in thickened synovium correlated with less vascularization and higher disease activity in participants with rheumatoid arthritis.

Clinical trial registration no. NCT04297475

© RSNA, 2022

Online supplemental material is available for this article.

中文翻译：

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光声成像滑膜氧合评估类风湿性关节炎疾病活动

背景

滑膜缺氧是类风湿性关节炎 (RA) 的标志。基于使用激光产生的 US 的光声 (PA) 成像可以检测 RA 患者组织的氧合状态。然而，缺乏大型研究，很少有人研究氧合状态与疾病活动之间的相关性。

目的

通过使用多模式 PA US 成像系统测量 RA 参与者的滑膜氧合状态，并确定 PA 成像测量的氧饱和度 (SO 2) 与_疾病活动之间的相关性。

材料和方法

在这项前瞻性观察性队列研究中，对 2019 年至 2021 年在两家门诊风湿病诊所接受治疗的连续 RA 参与者和健康对照者的小关节进行了多模式 PA US 成像检查。使用双波长 PA 成像测量滑膜的SO _{2值，并根据 SO 2}值的信号显色和聚类分析将其分为三类：高氧、中间氧合状态或缺氧。通过单向方差分析和带 Bonferroni 校正的 Kruskal-Wallis 检验评估氧合状态与能量多普勒超声 (PDUS) 评分和临床疾病活动指数的相关性。

结果

共有 118 名 RA 参与者（中位年龄，55 岁 [IQR，41-62 岁]；92 名女性）和 15 名健康对照参与者（中位年龄，37 岁 [IQR，33-41 岁]；11 名女性） . 36 名 RA 参与者的手腕滑膜被归类为高氧状态，48 名参与者的中等氧合状态，34 名参与者的手腕滑膜被归类为缺氧状态。所有对照参与者都有高氧滑膜组织。对于患有 RA 的参与者，与缺氧和中等氧合状态的参与者相比，高氧滑膜具有更丰富的多普勒超声描绘的血管系统（平均 PDUS 等级：高氧，2.7 ± 0.6 [SD]；中等，1.3 ± 0.7；缺氧，1.1 ± 0.8；P<.001）。滑膜处于中间状态的参与者的临床疾病活动指数低于缺氧状态的参与者（中间状态为 11.0 [IQR，5.0–21.5] vs 缺氧状态为 26.0 [IQR，18.0–39.0]；P = .001 ）。

结论

光声成像检测到增厚的滑膜缺氧与类风湿性关节炎参与者的血管形成减少和疾病活动度升高相关。

临床试验注册号 NCT04297475

©北美放射学会，2022

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