Human Electrical-Impedance-Tomography Reconstruction Models

Assessment of CT-derived Thoracic Electrical-Impedance-Tomography Finite Element Models

Current EIT analyses are based on the assumption of a circular thorax-shape and do not provide any information on lung borders. The aim is to obtain the body and lung border contours of male subjects by multi-detector computed tomography (MDCT) in defined thresholds of anthropometric data (gender = male; height; weight) for calibration of more realistic EIT reconstruction models.

A major drawback of EIT is its relatively poor spatial resolution and its limitation in measuring changes in bioimpedance as compared to a reference state (and not absolute quantities). Therefore, the technique cannot differentiate between extrapulmonary structures (muscles, thorax, heart, large vessels, spine, etc.) and non-aerated lung tissues - which is a major limitation for the clinical use of information derived from EIT-imaging. Moreover, current EIT-reconstruction algorithms are based on the consideration of a complete circular thoracic shape and do not take into account the body contours and lung borders.

The investigators are convinced that EIT-derived dynamic bedside lung imaging can be advanced by morphing computed tomography (CT) scans of the respective thoracic levels with concomitant EIT images - thus enhancing EIT-image information with CT-data. Integrating the anatomy of thoracic shape and lung borders provided by high-spatial resolution multi detector CT-scans (MDCT) with high-temporal resolution EIT has the potential to improve image quality considerably. This data can be used to compute mean EIT-reconstruction models that further offer the possibility to develop novel and clinically meaningful EIT parameters.

Therefore, the investigators hypothesize that by integration of CT-scan information of body and lung contours (and by computing different EIT reconstruction models) the current methodological limitations of EIT technology can be overcome.

Inclusion Criteria:

• spontaneous breathing male subjects
• age > 18,
• clinical indication for thoracic CT scanning,
• matching of weight and height to the predefined model-thresholds

Exclusion Criteria:

• pre-existing chronic pulmonary disease
• skin lesions / wounds in the thoracic plane where the EIT SensorBelt will be attached
• known allergy against any ingredient of the used ContactAgent
• abnormalities in thoracic shape as defined by the radiologist in charge (e.g. extreme kyphosis, funnel chest, pigeon breast, multiple rip fractures)
• pneumothorax
• pace maker (external and internal)
• other implanted electrical devices
• other methods measuring bioimpedance