A clinical accelerator with seven x-ray energies of (4,6,8,10,15,18 and 25) MV will be operated i...

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Metrological Standards and Traceability System Research On Dosimetry Of Clinical Accelerator


According to Medical Device Directory which is released by State Food and Drug Administration, medical accelerator is an important medical device categorized as medical high-energy-ray therapy equipment. In China, there is one person diagnosed with cancer once every 15 seconds. Among all those patients, about 70% of them need to receive radiation therapy.  The accuracy of radiation dose in radiation therapy is so crucial that it directly affects the treatment’s effectiveness and could possibly jeopardize patient’s life. As one of all cancer therapies, radiation therapy has its irreplaceable position. Since medical accelerator has many advantages, such as: it can generate a high dose rate in a small radiation field and causes less damage to normal cells and tissues, it is widely applied in radiation therapy. However, once the therapeutic dose is out of control, it may cause fatal damage to the patient. According to World Health Organization’s official report, 38% of radiotherapy medical accidents are due to errors in information transfer process. Consequently, a medical accelerator which can provide itself with accurate and consistent measurement is urgently needed.



A clinical accelerator with seven x-ray energies of (4,6,8,10,15,18 and 25) MV will be operated in the Second Experimental Base. The standard devices will be installed to measure the reference radiation from 4 MV to 25 MV. The parameters of the radiation field, such as photon energy, absorbed dose and its distribution, flatness, penumbra, stability, will be measured and simulated in detail.

The graphite calorimeter has been operated to measure the absorbed dose to water in 60Co gamma radiation, and will be used to measure the absorbed dose for photon of the accelerator. The project aims to determine basic data for radiation physics, develop standards and codes of practice for clinical dosimetry, and finally establish the primary standard of water absorbed dose for photon radiation from 4 MV to 25 MV and take part in the BIPM.RI(I)-K6 comparison.

Standard equipment for medical accelerator output dose will be fabricated, for clinic accelerator measurement of dose and dose parameters, to study high-energy photons absorbed dose to water and transfer method, the output parameters for clinical medical accelerator test and its calibration.

This project aims to establish primary standard and national second standard, verification regulations and calibration specification, and to establish water absorbed dose tracing system for high-energy photons. As an outcome of the project, a research platform with a high-energy photon beam reference radiation field will be built. It will serve for radiotherapy quality control, thus to enhance the nation’s metrology capability in radiology and related field.