A NOVEL ANALOGUE BIO-IMPEDANCE SYSTEM-ON-A-CHIP FOR MONITORING OF NEONATE LUNG FUNCTION

This research proposes the development of an urgently needed Electrical Impedance Tomography (EIT)-based bio-imaging system for in-vivo monitoring of neonate lung function in Intensive care Units (ITUs). Disorders of lung growth, maturation and breathing control are among the most important problems faced by the neonatologist. Premature birth occurs in 5-10% of all pregnancies, and is frequently accompanied by complications due to lung immaturity. The annual cost to the NHS is estimated in the order of hundreds of millions. One of the key difficulties of neonate ITU monitoring for lung function is that the system must measure the subject in a passive manner, unlike adults who can be asked to perform specific respiratory tasks. EIT is the only solution to this problem. Moreover, EIT is proving to be successful in many clinical applications, an example is the new commercial TSCAN system for detection of breast cancer.The proposed system will provide a non-invasive measure of lung maturity and development, oxygen requirements and lung function, suitable for use in small, unsedated infants. This tool will be routinely used to define the nature and severity of persisting lung disease, and to identify risk factors for developing chronic lung problems. Major limitations of EIT are the inherent common mode errors which result in reduction of the quality of the reconstructed images. These errors are more pronounced in the case of multi-frequency EIT. We have invented a method to address the problem by the use of a novel wideband analogue common-mode enhancement technique which can maximise the overall common-mode rejection ratio (CMRR) and signal-to-noise ratio (SNR). To take full advantage of the capabilities of our wideband CMRR feedback approach, we will use full custom circuit design techniques to create a novel multi-frequency EIT system-on-a-silicon-chip. We have also developed advanced reconstruction methods involving new mesh warping techniques that utilise the boundary information to condition the forward model, taking into account the anatomical details of the problem domain. The end result of this research will be new technology in the form of a wearable device which will minimise disruption when monitoring neonates. This will involve the design of custom made silicon chips, an integrated wearable electrode system, new 3D image reconstruction algorithms and advanced post image processing methodologies. This research will be carried out with the full clinical support of the Portex Anaesthesia, Intensive Therapy and Respiratory Medicine Unit at the world leading children's Hospital, Great Ormond Street, London.