Biological X-ray irradiation instrument selection recommendations
In clinical radiation therapy, in order to avoid or reduce the dose of radiation received by normal tissues during the treatment of diseased tissue, there is a strict standard for the selection of therapeutic harnesses.
Electrons, gamma rays, and X-rays can all be used for clinical radiation therapy. Since electrons decay very rapidly with depth, they are only suitable for the treatment of the epidermis. Gamma rays have strong energy and good penetrability, and are usually used for the treatment of deep tumors. The penetration of X-rays is determined by their energy, and the greater the energy penetration, the better the X-rays can be applied to different depths of tumor treatment depending on the energy.
Skin tumors and skin-free tumors are usually treated with superficial X-rays (50-150 kVp, called superficial energy, 90% dose is applied within 5 mm below the surface), and tumors in deeper parts of the body use medium-voltage X-rays (200). -500kVp, called medium voltage energy, more than 90% of the dose can be delivered to a depth zone within 2cm below the surface).
Figure 1: Schematic diagram of superficial X-ray action
Figure 2: Schematic diagram of the action of medium voltage X-ray
Due to its advantages of safety, control, and ease of operation, X-ray irradiators are an inevitable technological advancement in replacing biological applications of gamma ray irradiators. However, in the early stage, even some manufacturers did not realize that the application of X-rays in biology should also consider its energy problem, that is, similar to clinical radiotherapy, it is necessary to select the appropriate type and application for the sample. X-ray energy: superficial X-rays are applied to the irradiation of samples such as cells without considering the influence of depth, and medium-voltage X-rays are used for samples having a large depth such as small animals (such as mice, rats, guinea pigs).
Europe and the United States have a good foundation. At present, 320kV X-rays have been used for small animals. Even in some applications that require superficial X-rays, they can be depressurized to 90-160kV. achieve. In some countries and regions, there is still a large number of mismatches, that is, 160kV X-rays are applied to the illumination of samples that must consider the depth effect, such as small animals.
Scientists and researchers engaged in biological research often do not have the basic knowledge of irradiation, so there is usually a lot of confusion when choosing an X-ray irradiator, and I don't know how to choose. In fact, it is very simple, professional things to the professionals to do! You can explain the purpose, application and needs of your own research to the experts of the Radiation Therapy Department of the top three hospitals. They will definitely give you professional answers and suggestions.
references
[1] Mayles WP, Lake RA, McKenzie AL, Macaulay EM, Morgan HM, Powley SK Report 81 - Physics Aspects of Quality Control in Radiotherapy. IPEM 1998: pp 163-172.
[2] NCRP (National Council on Radiation Protection and Measurements) 1981. Report 69 Dosimetry of X-ray and Gamma-ray Beams for Radiation Therapy in the Energy Range 10 keV to 50 MeV (Bethesda MD: NCRP).
[3] AAPM (American Association of Physicists in Medicine) 1994 Comprehensive QA for radiation oncology: Report of AAPM Radiation Therapy Committee Task Group 40. Med. Phys. 1994; 21: 581–618.
[4] Klevenhagen SC, Aukett RJ, Harrison RM, Moretti C., Nahum AE, Rosser KE The IPEMB code of practice for the determination of absorbed dose for x-rays below 300 kV generating potential (0.035 mm Al - 4 mm Cu HVL 10 - 300 kV generating potential). Phys. Med. Biol. 1996; 41: 2605-2625.
[5] Williams JR, Thwaites DI Radiotherapy Physics: in practice. Oxford University Press, 2000: pp 99-117.
[6] Aukett RJ, Burns JE, Greener AG, Harrison RM, Moretti C., Nahum AE, Rosser KE Addendum to the IPEMB code of practice for the determination of absorbed dose for x-rays below 300 kV generating potential (0.035 mm Al - 4 mm Cu HVL). Phys. Med. Biol. 2005; 50: 2739-2748.
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