Development Of Wireless Real-time Fractional Flow Reserve Measurement System

In recent years,cardiovascular disease has become the leading cause of death worldwide.With the development of our society,advances in medical technology,people’s living standards and medical conditions have a lot of progress.However,studies have shown that,due to rising levels of cardiovascular disease risk factors,coupled with the trend of population aging on our population cardiovascular disease morbidity and mortality increased year by year.China is currently the number of patients with cardiovascular disease 2.3 million people die each year from cardiovascular disease,the number of nearly 350 million people.In 2011,in China the number of deaths of cardiovascular disease deaths listed second in the world.And cardiovascular disease in general is associated with atherosclerosis.As technology advances,methods for evaluation of coronary artery disease gradually innovation,developed from the former "gold standard" Coronary Angiography(CAG)to Intravascular Ultrasound(IVUS)and Optical Coherence Tomography(OCT)technology.However,these techniques can only produce clearer images of vascular lesion,but cannot make an accurate assessment of the physiological function of coronary artery lesions,that these technologies are not clearly the nature of coronary artery stenosis,only with the diagnosis of the doctor’s experience to judge,this often leads to underestimate or overestimate the severity of disease.In order to better assess the functional significance of coronary artery stenosis,there is a new evaluation method for physiological function of coronary stenosis lesion,that is the evaluation of coronary artery stenosis is caused significant myocardial ischemia,Pijls and other scholars put forward a new concept named fractional flow reserve(FFR)in 1993.Fractional flow reserve is defined as the ratio of the presence of stenosis maximum the myocardium blood flow(Qsmax)and assuming the absence of stenosis maximum blood flow(Qnmax),and establish a corresponding pressure-flow equation.Compared with previously widely used in clinical technologies,such as CAG,IVUS,OCT,this parameter really describe the function of vascular stenosis affects to what extent.The past experience of the physician to determine the need for stent placement converted to quantization parameter guide,avoiding underestimate or overestimate the degree of stenosis of coronary lesions,which can reduce medical malpractice or avoid overtreatment.Theoretically,coronary fractional flow reserve is not influence by hemodynamic factors(such as blood pressure,heart rate and myocardial contractility,etc.),it can be used for multi-vessel disease and good reproducibility,and gradually received wide attention and application.At present,the parameter can only be measured by the measurement devices produced by two American companies St.Jude or Volcano.The device is divided into two parts,one is the pressure guide wire which maintaining the size and have installed an ultra-miniature sensor of the guide wire tip.The ultra-miniature sensor is used to measure the coronary blood pressure;Second is the measurement host,it transmits the signal and makes it into the most waveforms for health care workers to use.However,due to the level of domestic production technology lagged behind and the monopoly of foreign companies,at present China has no independent development of coronary artery pressure guidewire and fractional flow reserve measurement system in real time.Therefore,it takes a lot of money to have a coronary flow reserve measurement,some hospitals even up to ten thousands Yuan or even more,which is a heavy burden for most of our country’s cardiovascular patients.In addition,the current real-time measurement of coronary flow reserve fraction is still a cable transmission system and there will be the risk of infection during the surgery.Under the premise of no self-developed coronary artery pressure guidewire and fractional flow reserve system real-time measurement system,this article proposes a design of real-time wireless FFR measurement system.Wireless real-time measurement of fractional flow reserve system based.on ARM core.and microcontroller can achieve real-time wireless measurement technology.A reasonable design of hardware and software achieved dynamic compensation and sensor measurements to improve the accuracy of measurement.This paper developed a wireless real-time measurement of fractional flow reserve system prototype,the prototype system is simple to operate,and with touch-screen operation can improve the way of convenience and accuracy during surgery.First,the paper describes the definition of fractional flow reserve and the structure of pressure guidewire and detailed analysis of the working principle of the pressure sensor,temperature drift and the compensation method and then introduced all sorts of signal conditioner chip.After an in-depth analysis of each signal conditioner chip,signal conditioner chip PGA309 and MAX1454 are choose to compensate the pressure guidewire,and describes the basic structures and compensation principles of PGA309 and MAX1454.Paper then describes the hardware design of the measurement system.As the use of wireless transmission,so the hardware design of the whole measuring system is divided into two specific parts:the host computer system and slave system.The slave system uses STC15F2K60S2 microcontroller as the control,respectively,based on two kinds of signal conditioner chip PGA309 and MAX1454 designed two schemes.The slave system circuit uses a modular design,mainly about the power supply module,pressure guidewire data storage module,signal conditioning chip module,microcontroller module,and wireless communication module.Using the power chip SPX3819 provides precision power for the entire slave system,the microcontroller STC15F2K60S2 configures the signal conditioner chip based on the data stored in EEPROM,using ADS1115 to collect the data and transmitted to STC15F2K60S2 MCU through I2C,and then MCU communicates with hosts on the data processing and real-time display by Bluetooth.The host system using ARM-based embedded systems.It can achieve a touch display;perform aortic pressure signal acquisition and systems with lower data transmission,processing and storage.In order to meet the design requirements,selection of Samsung’s S5PV210 microprocessors,ARM CortexTM-A8 core,clocked at up to 1 GHz,with a wealth of on-chip resources,such as:4-channel UART,I2C 3-channel,LCD controller and touch screen control and so on.By connecting SDRAM,Flash,and LCD with touch screen can be composed of a fully functional embedded systems.Using 1024x600 resolution precision of 10.1 in LCD resistive touch screen,a touch screen to replace the traditional keyboard,simple instrument operation,display more clearly.The experiment tested the hardware circuit basically meet the requirements.Then the article describes the software part of the measurement system.Software design is also divided into the host computer system and slave system,also introduced the host system and slave system programming environment and programming language.The slave system using C language programming ideas designed according to a modular design and achieves some functions of each subroutine including reading pressure guidewire information stored in EEPROM,configuring signal conditioner chip,communicating with the host transmission by wireless transmission modules,so that the slave system the overall structure of software systems clear,readable,easy to maintain and debug,so that the whole structure software of slave system is clear,readable,easy to maintain and debug.Finally,the performances of the two designs were simulated experiments and contrast.Testing experimental mainly includes three parts:First,the performance test of PGA309 scheme;Second,performance testing of MAX1454 scheme;Third,the performance comparison of two schemes PGA309 and MAX1454.U-shaped tube used in the experiment simulated the internal state of the blood vessel.Amount of water was injected in the U-shaped tube to simulate blood.Pump is the pressure source,and mercury manometer is used to read the pressure value.One end of the U-shaped tube is connected the pump and mercury manometer through three way valve,the other end of the U-shaped tube is the pressure guidewire and keep it sealed.After ensuring sealed,PGA309 and MAX1454 precision of experimental tests carried out respectively.Change within the U-shaped tube water temperature,respectively,temperature drift testing experimental about MAX1454 and PGA309 are performed.After the experiment,the experimental data of the two schemes were analyzed.The conclusion that PGA309 and MAX1454 can simultaneously meet the accuracy requirements of the system to measure,MAX1454 has the same effect with the PGA309.Simulation results show that the system is reliable.However,the temperature compensation parameters of PGA309 is calculated complex,the MAX1454 is relatively easy to calculate,so using MAX1454 is more operational than PGA309.