Development of low cost instrumentation for non-invasive detection of Helicobacter Pylori

摘要

A new clinical diagnostic instrument for urea breath test (UBT) based non-invasive detection of Helicobacter Pylori is presented here. Its compact and low cost design makes it an economical and commercial alternative for the more expensive Isotope Ratio Mass Spectrometer (IRMS). The instrument is essentially a two channel non-dispersive IR spectrometer that performs high precision ratio measurements of the two carbon isotopomers (~(12)CO_2 and ~(13)CO_2) present in exhaled breath. A balanced absorption system configuration was designed where the two channel path lengths would roughly be in the ratio of their concentrations. Equilibrium between the transmitted channel intensities was maintained by using a novel feedback servo mechanism to adjust the length of the ~(13)C channel cell. Extensive computational simulations were performed to study the effect of various possible interferents and their results were considered in the design of the instrument so as to achieve the desired measurement precision of 1‰. Specially designed gas cells and a custom made gas filling rig were also developed. A complete virtual interface for both instrument control and data acquisition was implemented in LABVIEW. Initial tests were used to validate the theory and a basic working device was demonstrated.