Philips Chair for Medical Information Technology, RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany. Department of Anaesthesiology and Intensive Care Medicine, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany.
Physiol Meas. 2018 Jun 20;39(6):065004. doi: 10.1088/1361-6579/aac7ae.
Electrical impedance tomography (EIT) is a noninvasive imaging modality that allows real-time monitoring of regional lung ventilation ([Formula: see text]) in intensive care patients at bedside. However, for improved guidance of ventilation therapy it would be beneficial to obtain regional ventilation-to-perfusion ratio ([Formula: see text]) by EIT.
In order to further explore the feasibility, we first evaluate a model-based approach, based on semi-negative matrix factorization and a gamma-variate model, to extract regional lung perfusion ([Formula: see text]) from EIT measurements. Subsequently, a combined validation of both [Formula: see text] and [Formula: see text] measured by EIT against single-photon emission computed tomography (SPECT) is performed on data acquired as part of a porcine animal trial. Four pigs were ventilated at two different levels of positive end-expiratory pressure (PEEP 0 and 15 cm HO, respectively) in randomized order. Repeated injections of an EIT contrast agent (NaCl 10%) and simultaneous SPECT measurements of [Formula: see text] (81Kr gas) and [Formula: see text] (99Tc-labeled albumin) were performed.
Both [Formula: see text] and [Formula: see text] from EIT and SPECT were compared by correlation analysis. Very strong (r = 0.94 to 0.95) correlations were found for [Formula: see text] and [Formula: see text] in the dorsal-ventral direction at both PEEP levels. Moderate (r = 0.36 to 0.46) and moderate to strong (r = 0.61 to 0.82) correlations resulted for [Formula: see text] and [Formula: see text] in the right-left direction, respectively.
The results of combined validation indicate that monitoring of [Formula: see text] and [Formula: see text] by EIT is possible. However, care should be taken when trying to quantify [Formula: see text] by EIT, as imaging artefacts and model bias may void necessary spatial matching.
电阻抗断层成像（EIT）是一种非侵入性的成像方式，可以在重症监护病房床边实时监测区域性肺通气（[公式：见文本]）。然而，为了更好地指导通气治疗，通过 EIT 获得区域性通气-灌注比（[公式：见文本]）将是有益的。
为了进一步探索其可行性，我们首先评估了一种基于模型的方法，该方法基于半负矩阵分解和伽马变量模型，从 EIT 测量中提取区域性肺灌注（[公式：见文本]）。随后，我们对在猪动物试验中采集的数据进行了 EIT 测量的[公式：见文本]和[公式：见文本]与单光子发射计算机断层扫描（SPECT）的联合验证。四只猪分别在两种不同的呼气末正压（PEEP 0 和 15 cm H2O）水平下随机通气。重复注射 EIT 对比剂（10%NaCl），并同时进行[公式：见文本]（81Kr 气体）和[公式：见文本]（99Tc 标记白蛋白）的 SPECT 测量。
通过相关分析比较了 EIT 和 SPECT 的[公式：见文本]和[公式：见文本]。在两种 PEEP 水平下，EIT 和 SPECT 的[公式：见文本]和[公式：见文本]在背-腹方向均具有很强的相关性（r=0.94 至 0.95）。EIT 和 SPECT 的[公式：见文本]和[公式：见文本]在右-左方向的相关性分别为中度（r=0.36 至 0.46）和中度至强（r=0.61 至 0.82）。
联合验证的结果表明，EIT 监测[公式：见文本]和[公式：见文本]是可行的。然而，在尝试通过 EIT 定量[公式：见文本]时应谨慎，因为成像伪影和模型偏差可能会影响必要的空间匹配。
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