Development Of The Electronic Control System Of A New Medical Water Scalpel

Water-jet technology or water scalpel is the real cold cutting technology, which was first applied to industry. Through a series of superchargers, high-energy water with high pressure is generated and jets from nozzle (φ0.1-0.35mm) with a high speed of almost one kilometer per second, which will cause strong incising force in contact with the surface of an object. Medical water scalpel is of the same mechanism with the industrial, and it can help accomplish micro-invasive surgery by selectively incising body tissues with effective protection of vessels and neural. Since the technology was first applied to medical field in1982when Professor Barter and Papachristou did liver resection successfully, it has been fully developed over the last few decades and experiences now universal application in many surgical fields such as urology, brain surgery, orthopedics, ENT, ophthalmology, etc.Apart from the ability to incise soft tissues, medical water scalpel is of great characteristic in its selectively incising as well as incision cleaning ability without thermal damage to tissues, which is an incomparable advantage in tissue surgeries rich of vessels and neural. As a result of the frequent natural disasters nowadays, there maybe a large number of the wounded with complex injuries, and to minimize mortality, timely and effective wound cleaning method is of great significance. This paper is mainly about the study on electronic control system of equipment, which is a hard-core of the equipment. Through the control system, individual mechanical components can be coordinated and unified and constitute an organic whole to implement its specific functionality. I chose single chip microcomputer (SCM) C8051F040from Cygnal Corporation which uses CIP-51microcontroller core with a maximum speed25MIPS and full compatibility with MCS-51instruction set. As a developing direction for current8bits SCM system, C8051F040has8x8bits wide I/O port, all of which can be set accordingly as open-drain or push-pull output mode.In the second chapter of this text, I made an overall design of the control system with the research contents as the following several aspects:1) Communication with the human-computer interaction interface (HII):in this device, a serial port RS232was used to realize interaction between control system and the HII.2) Communication with the driving system: composed of two brushless DC motors and the appropriate drivers, the driving system powers the device.485bus modes were chosen for communication between control system and the motor drivers.3) Acquisition and processing of signals from foot switch: foot switch helps control the operation process, and it is important for control system to timely acquire switching signals and send instruction to driving devices to start/pause effectively.4) Detection and alarm control of pressure signals:proper incising pressure regulation during operation is vital to avoid injury of vessels, neural and the surrounding tissue. Thus, abnormal pressure alarm is required in the control system. 5) Implementing the control for negative pressure suction (NPS) system: The NPS system will help clean up the waste during operation in time to maintain a clear vision and improve environment of operating room.6) Implementing the control for automatic stripping mechanism: the medical water scalpel device developed this time adopted disposable and sterile design. All the components in contact with water in operation will be replaced through this automatic stripping mechanism after operation.Each module of the control system was introduced in detail in chapter three including SCM choosing, acquisition and processing of pressure and optoelectronic signals, design of digital-to-analogue conversion (DAC), NPS and alarming component. An active filter circuit was added into the signal acquisition circuit to effectively eliminate electromagnetic interference (EMI) in the original signal. Acousto-optic model was applied in the design of alarm module with an intermittent noise and a red twinkling LED to warn the medical workers when the alarm activated.In chapter four, I analyzed the factors that influenced the stability of pressure and came up with some solutions. The factors included:1. Whether the air in hyperbaric chamber was fully removed;2. Tightness of the whole system;3. Oriented conduction of the one-way valve;4. Starting and accelerating time of the driving motor. The use of energy accumulator and especially the phase based control method significantly declined the pressure fluctuations in working and the incising pressure was also adjustable from0MPa to8.0MPa making it relatively satisfactory.When it comes to chapter five, human-oriented interface was designed based on Modbus protocol. Users could set the operating parameters and monitor the real-time status in case of equipment fault. When choosing the HII type, I took into account three issues:1. Whether the HII suits in function and size for the designed device;2. Whether the chosen HII could vividly show and conveniently set the operating parameters;3. Cost performance of the HII.Some results of liver tissue incision experiments were showed in chapter six. The whole experiment took15min and incision6min, and when the pressure was set at3MPa, the liver tissue was smoothly incised withholding almost all the blood vessels. The feasibility and practicability of this medical water scalpel were proved in subsequent tissue incising experiments which would make it a potential operative tool for special operations.In the last chapter, a summary and several suggestions of the research were raised:1) Optimization in mechanical structure of the one-way valve is needed to help stabilize the output of water jet.2) There are still some questions in stroke and load-carrying design of the automatic stripping mechanism and improvements are required to conveniently replace the disposable components.3) Disposable components by one-step plastic mould processing will help with sterilized operation, good tightness and weight reduction.Compared with the past debridement equipment, there have been great improvements in mechanical structure and control method. In addition, this research has some innovations:1) A new type of medical water scalpel debridement equipment has been developed with simple structure, small size, light weight as well as a concept of sterile design.2) In terms of control, phase based control method was used which significantly declined the pressure fluctuations. 3) Concept of modular design made it possible to fast locate and easily remove faults.