Advances in equipment for tumor photodynamic therapy

Abstract

Photodynamic therapy (PDT) is a new technique for interventional minimally invasive therapy of cancer. It has many advantages such as less trauma, low toxicity, quick recovery, good selectivity and adaptability, and repeatable/palliative treatment. It uses the photodynamic reaction between photosensitizer and oxygen molecules under the light condition, so that tumor cells can be damaged and even be killed, to cure cancer. PDT equipment is a new type of medical equipment which is used in PDT for cancer treatment. Its main components include the light source, the light transmission system, the control system and the monitoring system. Stable and flexible PDT equipment can greatly improve the curative effect of PDT, which will promote the applications of PDT clinically. This paper is mainly a summary and analysis of the vital structures of PDT equipment for cancer, including the light source, optical transmitting system, optical power and temperature detection and control system, blood oxygen concentration monitoring system, as well as the photosensitizer concentration monitoring and tumor localization devices. Light source is the most important part of the device. Different types of light sources can be used in different clinical occasion. Despite the traditional light sources such as LED or lasers, some new light sources are also invented, thus giving more choices to the clinical application. In choosing the appropriate light source, the wavelength and output power is also vital for the clinical effect. To keep the output power stable is still the challenge in the design of light sources. The optical transmitting system guides the light to the tumor in deep, which can be flexible in design according to the different organs and the structure of tissues. The parameters which are needed to be detected and controlled include the temperature, optical power, blood oxygen concentration, photosensitizer concentration. The stability of these parameters guarantee the treatment effect of individual treatment, and some new methods and techniques are invented recently and are still to be developed. Image navigation system is an auxiliary for PDT. It can be achieved by existing imaging technology such as the ultrasonic imaging and MRI. The establishment of image model can also help to analyze the therapeutic schedule and plan the route of treatment. These medical images give PDT an accurate positioning of the region of interest, so that certain regions can get the appropriate light dose, thus broaden the scope of PDT to adapt, showing great value of development. There are also techniques devoting to designing intelligent PDT instrument such as remote control and the portable devices, which will make PDT more flexible for patients to receive the treatment. At present, these structure and designs mentioned above are mostly developed separately, so the PDT equipment which integrates the fundamental structure with advanced monitoring and controlling system is required to be invented. The research and development of the devices for PDT are not relatively mature and specialized enough, and has not yet formed a commercialized scale, but some progress has been made in the key parts of PDT equipment. Nowadays most researches are focused on the light source and optical transmission structure, but there will be more development space for PDT parameters monitoring, image navigation, tumor positioning and other technological problems, which will improve the stability and reliability of PDT equipment, promoting the PDT equipment to be better used in clinical.