The Second Affiliated Hospital of Medical College of Zhejiang University Wang Liancong tumor radiotherapy directorThe direct effect of radia
The Second Affiliated Hospital of Medical College of Zhejiang University Wang Liancong tumor radiotherapy director
The direct effect of radiation on living organisms is the function of the DNA molecular chain, even if DNA single strand or double strand breaks. The indirect effect is mainly on the role of water molecules. Because the cells most by water molecules, water molecules by irradiation after ionization generated free radicals, free radicals with high chemical reactivity, can interact with biological macromolecules and DNA chains, the damage. Studies have shown that radiation therapy for cancer is mainly caused by tumor cell apoptosis.
It has been over 100 years since the invention of radiotherapy is one of the important means for the treatment of malignant tumors, about 60% to 70% of cancer patients in different stages of disease, because of the need to accept radiotherapy for different purposes. WHO (WHO) statistics showed that 45% of malignant tumor can be cured, of which 22% were cured with surgery, radiation therapy to cure 18%, 5% cure for chemotherapy radiotherapy, it is enough to see the progress in this century and its important position in the treatment of tumor.
The development of radiation therapy technology can be divided into 3 stages: primary radiotherapy, conventional radiotherapy and modern radiotherapy, in which there are huge differences between the two completely different techniques of conventional radiotherapy and modern radiotherapy in these two periods. For the majority of tumor, radiotherapy technology is only an auxiliary treatment does not cause serious injury of normal tissue and palliative treatment, while modern radiotherapy is a combination of a series of new technology of stereo positioning technology, radiotherapy equipment and computer technology etc., can correct, accurate and sufficient quantity against tumor tissue, on the part of early tumor, can to achieve the same effect with surgical resection, even better than surgery, less trauma. For conventional radiotherapy and effective disease to continue to vigorously promote the effect of conventional radiotherapy; or to the disease need to re evaluate the treatment by stereotactic radiotherapy techniques such as stereotactic conformal radiotherapy (3D-CRT), stereotactic conformal radiotherapy (IMRT), stereotactic radiotherapy (SRT) or stereo stereotactic radiosurgery (SRS) technology to reduce the normal tissue by the irradiation dose, thereby improving tumor dose, improve the cure rate. The basic principle of stereotactic radiotherapy technology is through computer technology and stereo positioning technology will focus on the accelerator X ray tumor target and destroy all organizations in the region, the radiation dose required or cause the biological effect of target area periphery gradient was dropped, tissue from damage or a slight reversible injury.
A stereotactic conformal radiotherapy (3D-CRT) technology is a way to make the high dose area is consistent with the actual shape distribution in the three-dimensional direction and tumor target irradiation technology. The advantages of conformal radiotherapy is further reduced to vital organs and normal tissue dose, dose distribution and target improvement in the area of tumor dose, and increase the local control rate of tumor, reduce distant metastasis rate. Conformal radiotherapy is achieved according to the GT and MRI provide the target area and the surrounding normal tissue in the direction of three-dimensional position, size and shape of the data, complete the treatment with coordinated movement of automatic control system of accelerator and treatment bed. The technology is currently widely used in clinical treatment with most tumors.
Two, stereotactic conformal intensity-modulated radiation therapy (IMRT) technology by changing the target area of the ray intensity, so that any point in the target area to achieve the ideal dose, so that the dose distribution to achieve a true three-dimensional conformal and uniform dose. IMRT technology of radiotherapy equipment requirements, must have a non uniform irradiation and the target area dose rate varied as needed, IMRT can be ideal to delineate the irradiation target area of any shape, to maximize the protection of the target area inside or outside the target area to normal sensitive organs. In addition to the above advantages, intensity modulated radiotherapy can adjust the dose distribution of several different targets in the target area. The implementation of IMRT at present there are two main ways: one is the dynamic changes using MLC blade spacing size, moving direction and velocity during irradiation is regulated, two is the use of pen type X-ray Cambodia scanning irradiation by hitting the target direction and intensity of the beam and to generate different strength pen type beam conditioning before the target electron beam. For patients with tumor stereotactic tumor with irregular shape, complicated conformal intensity-modulated radiotherapy (IMRT) technical advantages, the technology is currently in clinical radiotherapy has been most experts in general hospital and tumor hospital for daily treatment of head and neck cancer, thoracic and abdominal and pelvic tumors.
Three, the advent of stereotactic radiotherapy (SRS/SRT) is not only a major change in the history of radiation therapy, but also for the development of minimally invasive surgery to inject new vitality. Stereotactic radiosurgery (SRS) by computer and stereo positioning system of the accelerator X ray in tumor target area, 1 times of high-dose irradiation; stereotactic radiotherapy (SRT) by coplanar or non coplanar fields conformal or multi arc fractionated irradiation, the radiation dose distribution in high dimensional direction the target area is highly consistent with tumor. Stereotactic radiotherapy (SRS/SRT) technology of high energy x-ray focusing irradiation in a local target area, destroying all organizations in the region, or caused by the need to achieve a similar biological effect, the effects of surgical, radiation dose peripheral target area gradient sharply reduced from injury or reversible the slight damage. At present, stereotactic radiosurgery by gamma knife radiosurgery, linear accelerator radiosurgery (including X knife and CyberKnife) and charged particle beam radiosurgery (including proton and heavy particle beam therapy). Stereotactic radiotherapy (SRS/SRT) can not only treat the small volume of the malignant tumor, benign tumor and that is not sensitive to radiotherapy and radiation is not sensitive or resistant to the traditional concept of malignant tumors (such as malignant melanoma, renal cell carcinoma) is also effective. The biggest feature of radiosurgery is the small trauma, short treatment time.
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