1 Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland.
2 Quantitative RedOx Sensing Team, Department of Basic Medical Sciences for Radiation Damages, Chiba, Japan .
Antioxid Redox Signal. 2018 May 20;28(15):1378-1393. doi: 10.1089/ars.2017.7391. Epub 2018 Jan 9.
Electron paramagnetic resonance imaging (EPRI) is capable of generating images of tissue oxygenation using exogenous paramagnetic probes such as trityl radicals or nitroxyl radicals. The spatial distribution of the paramagnetic probe can be generated using magnetic field gradients as in magnetic resonance imaging and, from its spectral features, spatial maps of oxygen can be obtained from live objects. In this review, two methods of signal acquisition and image formation/reconstruction are described. The probes used and its application to study tumor physiology and monitor treatment response with chemotherapy drugs in mouse models of human cancer are summarized. Recent Advances: By implementing phase encoding/Fourier reconstruction in EPRI in time domain mode, the frequency contribution to the spatial resolution was avoided and images with improved spatial resolution were obtained. The EPRI-generated pO maps in tumor were useful to detect and evaluate the effects of various antitumor therapies on tumor physiology. Coregistration with other imaging modalities provided a better understanding of hypoxia-related alteration in physiology.
The high radiofrequency (RF) power of EPR irradiation and toxicity profile of radical probes are the main obstacles for clinical application. The improvement of RF low power pulse sequences may allow for clinical translation.
Pulsed EPR oximetry can be a powerful tool to research various diseases involving hypoxia such as cancer, ischemic heart diseases, stroke, and diabetes. With appropriate paramagnetic probes, it can also be applied for various other purposes such as detecting local acid-base balance or oxidative stress. Antioxid. Redox Signal. 28, 1378-1393.
电子顺磁共振成像（EPRI）能够使用外源性顺磁探针（如三苯基自由基或氮氧自由基）生成组织氧合的图像。顺磁探针的空间分布可以使用磁场梯度来生成，就像在磁共振成像中一样，并且可以从其光谱特征中获得来自活体对象的氧的空间图谱。在这篇综述中，描述了两种信号采集和图像形成/重建的方法。总结了所使用的探针及其在研究肿瘤生理学和监测人类癌症小鼠模型中化疗药物治疗反应的应用。
通过在时域模式中的 EPRI 中实施相位编码/傅里叶重建，避免了频率对空间分辨率的贡献，并获得了具有改进空间分辨率的图像。EPRI 生成的肿瘤内 pO 图可用于检测和评估各种抗肿瘤疗法对肿瘤生理学的影响。与其他成像方式的配准提供了对缺氧相关生理变化的更好理解。
EPR 辐照的高射频（RF）功率和自由基探针的毒性特征是临床应用的主要障碍。RF 低功率脉冲序列的改进可能允许进行临床转化。
脉冲 EPR 血氧测定法可以成为研究涉及缺氧的各种疾病（如癌症、缺血性心脏病、中风和糖尿病）的有力工具。通过适当的顺磁探针，它也可以应用于各种其他目的，如检测局部酸碱平衡或氧化应激。抗氧化。氧化还原信号。28,1378-1393。
