16 electrodes. Image quality can be further improved by constructing an EIT system with active surface electrodes, which significantly reduce signal loss, artifacts, and interferences associated with cables as well as cable length and handling. In contrast to spatial resolution, temporal resolution of EIT (0.1 milliseconds) is much higher than in CT or MRI (0.1 seconds). Applications Lung (a-EIT, td-EIT) EIT is particularly useful for monitoring lung function because lung tissue resistivity is five times higher than most other soft tissues in the thorax. This results in high absolute contrast of the lungs. In addition, lung resistivity increases and decreases several-fold between inspiration and expiration which explains why monitoring ventilation is currently the most promising clinical application of EIT since mechanical ventilation frequently results in ventilator-associated lung injury (VALI). The feasibility of EIT for lung imaging was first demonstrated at Rensselaer Polytechnic Institute in 1990 using the NOSER algorithm. Time difference EIT can resolve the changes in the distribution of lung volumes between dependent and non-dependent lung regions and assist in adjusting ventilator settings to provide lung protective ventilation to patients during critical illness or anesthesia. Most EIT studies have focused on monitoring regional lung function using the information determined by time difference EIT (td-EIT). However absolute EIT (a-EIT) also has the potential to become a clinically useful tool for lung imaging, as this approach would allow one to directly distinguish between lung conditions which result from regions with lower resistivity (e.g. hemothorax, pleural effusion, atelectasis, lung edema) and those with higher resistivity (e.g. pneumothorax, emphysema). The above image shows an EIT study of a 10-day-old baby breathing normally with 16 adhesive electrodes applied to the chest. Image reconstruction from absolute impedance measurements requires consideration of the exact dimensions and shape of a body as well as the precise electrode location since simplified assumptions would lead to major reconstruction artifacts. While initial studies assessing aspects of absolute EIT have been published, this area of research has not yet reached the level of maturity which would make it suitable for clinical use. In contrast, time difference EIT determines relative impedance changes that may be caused by either ventilation or changes of end-expiratory lung volume. These relative changes are referred to a baseline level, which is typically defined by the intra-thoracic impedance distribution at the end of expiration. Time difference EIT images can be generated continuously and right at the bedside. These