In vivo quantification of accumulating abdominal fluid using an electrical impedance tomography hemiarray

A new method to image and quantify intra-abdominal haemorrhage using electrical impedance tomography (EIT) was tested in vivo. Supine peritoneal dialysis patients were monitored using an 8-electrode hemiarray placed on the anterior abdomen. EIT measurements were recorded using the EPack II data acquisition system before, during, and after the administration of dialysate. The amount of dialysate infused was recorded synchronous with EIT measurements and used as a control. Tomographic images of impedance change were reconstructed using a weighted, sensitivity-based method and then post-processed to obtain a quantitative estimate of the total dialysate volume added and the rate of dialysate administration. Our preliminary study included two subjects, one male and one female, each of whom participated for two sessions spaced about 6 months apart. Data collected from these sessions indicated that with an in vivo SNR of about 35 dB the EPack II can detect accumulations larger than about 100 ml, with a quantification uncertainty of about 50 ml. The rate of accumulation was determined in less than 2 min. This method shows promise for automated detection of other pathologies, eg ascites, and is adaptable to detecting conductive accumulations in other anatomy.