Gas Path Design For Lung Cancer Exhaled Gas Detection

Lung cancer has become a major threat to human health. In recent years, with thecontinuous decline on China’s air quality, the incidence of lung cancer has showed arising trend, WHO forecasts that China would have the largest population of patientswith lung cancer by2025. The early diagnosis of lung cancer could greatly improve thesurvival rate of patients. Compared with the traditional detection methods for lungcancer which is expensive, complex detecting, invasive and has a high rate ofmisdiagnosis, breath detection based on biochemical sensor technology not only lowercost, higher sensitivity, faster response, simpler structure, more importantly, it isnon-invasive and device miniaturization, so it is expected to screening for early lungcancer.The human exhaled gas contains physiological metabolism, research hasdemonstrated that there is a relation between lung cancer and some kinds of VOCs inexhaled gas, which could be used as a marker of lung cancer detection. The biggestdifficulty in exhaled gas detection is the extremely low content of VOCs (order ofPPb). Lung cancer breath diagnosis is a kind of detecting method rising in recent years,there is no device of exhaled gas collection, target enrichment or gas standardization. Inview of this, this paper aims to provide a gas path system contains of exhaled gascollection, target enrichment, accurate temperature and humidity control. At the sametime, provide technical and design support for clinical application.In this paper, the main study completed as follows:1. Analyze the process of exhaled gas detection based on biochemical sensor.Design a set of innovative gas path system with simple structure and comprehensivefunctions which is based on summary of the design requirements and the lack ofexisting system. According to the target of concentration, propose the idea ofenrichment-module-entered “multi-layer cycles”. Finish the design which include“enrichment cycle” and “testing cycle” for ensuring the function and simplify the gaspath. The gas path system contains of exhaled gas collection, target enrichment,accurate temperature and humidity control for lung cancer patients’ breath gas to ensurethe stable reaction condition of breath gas and biochemical sensor.2. Due to the high sensitivity of the biochemical sensor, impurities will affect thetest results. Therefore, the gas path system and the gas reactor should have good air tightness. In view of the existing gas reactor has a bad air tightness, make a design toimprove the airproof performance.3. Based on the functional requirements of the lung cancer breath detection system,the system consists of a host computer and a slave computer. As a host computer, ARMcontrols the working process, take the job of Image acquisition and result analysis; Asthe slave computer, PIC16F877A controls the gas path system. According to the actionand function of the gas path system and PIC16F877A, design a set of system which wascomposed by power-supply module, air-storage module, mini-pump andelectromagnetic-valve driver module, temperature control module, temperature andhumidity monitoring module and communication module. The MCU control procedureswas completed in the environment MPLAB in accordance with the testing process.4. The sub-module hardware is tested one by one, and then blending experimentalgas whose target is benzene is concentrated by the assembled system and its function isconfirmed.The main innovation of this paper as follow:Propose the idea of VOCs enrichment-module-entered “multi-layer cycles”.Design a set of innovative gas path system with simple structure and comprehensivefunctions.A summary was given at the end of the paper. Some views for the futuredevelopment direction ware also put forward.