Design Of LED Photothermal Therapeutic System Based On ARM And Preliminary Experimental Study

Photothermal therapy is a kind of physiotherapy method of which the majorphysical factors are light and heat. In photothermal therapy, photochemical effect andheat effect are produced by the irradiation of light on human tissue with a specificwavelength, which are used as the treatment of skin diseases, gunecological diseases aswell as superficial cancers and other diseases. Photothermal therapy has the advantagesof noninvasive, small side effect, and also the combination of other treatments, so it hasbeen widely used in clinical practice. The thermal effect can cause the tissuetemperature rise, and the temperature reflects the absorbed dose of radiation duringphotothermal therapy. For some diseases, only in a certain range of temperaturethreshold, photothermal therapy can achieve the desired therapeutic effect. Thereforethe temperature directly reflects the effect of photothermal therapy, and is the parameterthat needs to be controlled in clinical treatment. The control of tissue’s temperature canguide the photothermal therapy, making it safer and more effective. But in general thephotothermal treatment apparatus are lack of the function controlling the tissue’stemperature.For the real-time monitoring of tissue’s temperature during the irradiation, a designof LED photothemal therapeutic system based on S3C2440with ARM920T architectureand embedded operating system is presented. With the semiconductor technology gotgreat progress, high power LED light source can be used as an ideal radiation source forphotothermal therapy. The hardware of system comprises driving part of LED lightsoure、temperature acquisition part、microprocessor and interactive compents. For thecharacteristics and luminous of high power LED array, the current of the constantdriving circuit with LM3406chip as the core is up to1.2A, and the circuit has PWMdimming function. Infrared temperature measurement module TN901using thermopilesensor acquires the target temperature, and through the SPI interface the temperaturesignal is transmitted to the microprocessor S3C2440. S3C2440peripheral circuitincludes the serial port、USB interface、JTAG interface and LCD touch screen, whichrealize the system communication、debugging、data transmission and human-computerinteraction. Software design of the system is divided into two parts: driver andapplication software. The driver is written according to the hardware, and the GUI isdesigned under the Qt Creator intergrated development environment. The user interface includes the treatment parameter setting interface、PID interface and temperature curvedrawing interface. According to the requirement of temperature control during thephotothermal therapy, the traditional PID algorithm is improved, adding the integralseparation process. The target temperature and tissue temperature acquired by TN901are calculated to adjust the duty cycle of PWM signal, and then to adjust the LEDoutput optical power density resulting in the precise control of temperature.After the completion of LED photothermal therapy system， the system’sparameters were tested. The multimeter and laser energy meter were used to measurethe LED operating current and output power density varied with PWM duty cycle. Theresult showed that the PWM signal can modulate these two parameters linearly. Thefresh pigskin was selected as the isolated tissue sample in the photothermal therapysimulation experiment in which temperature control performance was tested. Theexperiment result showed that the effect and quality of temperature’s control are goodand high, the maximum overshoot is not more than1℃, and that the steady-state error is±0.5℃. The system can meet the requirement of the temperature control duringphotothermal therapy. The effect of photothermal therapy with the red light asirradiation source on exercise-induced skeletal muscle fatigue and skeletal musclerecovery in humans was studied preliminary. The finger force signals collected in thevolunteer experiment were analyzed. After the analysis of the experiment, someimprovement suggestions were proposed for further study. All of these lays a foundationfor further in-depth study.