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publicado em 12/11/2013 às 12h19:00
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Dosimeter analyzes blood irradiation in a simpler and faster

In blood banks, the machine controls the recommended dose irradiation of blood, decreasing the viability of T lymphocytes

 
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Vision Research PhD developed at the University of São Paulo (USP) has enabled the creation of a chemical dosimeter that can be prepared and analyzed by professional blood bank faster and simpler than those currently available.

The dosimeter is used to measure the absorbed dose, i.e., energy received that certain medium after being exposed to ionizing radiation. In blood banks, it helps control the recommended dose irradiation of blood, the technique used to reduce the viability of T lymphocytes (immune cells) in donated blood, which reduces the patient the risk of rejection of organ or tissue transplant .

To obtain this result, the researcher Luke Sacchini Del Lama characterized and adapted Fricke dosimeter Xylenol Gel (FXG). Usually held in the dosimetry devices that radiate blood is made with dosimeters, or film radiocrômicos with Fricke solution. But these methods are time consuming because many dosimeters are used, which should be read unitarily. With our dosimeter and our systematic auferição and benchmarking, this process can be done in minutes, explains.

According Del Lama, FXG is a radiochromic dosimeters type, ie changes its color according to what is spent and also interacts with radiation analogously to the tissue. The physical principle responsible for the inference of the dose absorbed by FXG is the radio-induced oxidation of ferrous ions (Fe +2) ions present in the solution in ferric (Fe +3), the latter being pigmented by xylenol orange (XO). His analysis is mainly carried out by optical methods, while others, such as MRI and photoacoustic, may also be employed, explains the researcher.

The main methods used in the research for the characterization and adaptation of FXG for the dosimetry associated with blood irradiation were based on calibration curves, which related the optical response of the FXG due to the absorbed dose to different changes in the composition of the dosimeter, and theoretical comparisons, which related parameters of interaction of radiation with matter between the dosimeter and blood, says Del Lama.

According to the researcher, the irradiation of blood is recommended for specific cases, such as for transfusion in immunocompromised patients, people who are affected by some type of disability in basic mechanisms of defense, usually due to some surgical intervention, such as bone marrow transplant marrow, cardiac surgery, vascular, gastrointestinal and abdominal, liver transplant and pancreoesplênico due to treatment of tumors such as neuroblastoma, lung carcinoma, glioblastoma, cervical cancer, renal adenocarcinoma, or due to some congenital deficiency. Moreover, the irradiation of blood is also recommended for cases between blood donations family.

The irradiation of blood prevents a reaction rare, but fatal, known as Graft-versus-Host Disease Associated with Transfusion (TA-GVHD). The agents of reaction are T lymphocytes, which act on the immune system of the human body. When these cells present in donor blood, identify any incompatibility with the patient's system, begin to multiply and attack some systems in the body of the receiver. In a few days, they cause tissue necrosis and marrow failure.

The researcher points out that Del Lama leading organizations governing the irradiation of blood, as the American Association of Blood Banks (AABB), the American agency FDA and European guide quality control, recommend irradiation of blood to different clinical syndromes, with absorbed doses ranging from 15 to 50 Gy (Gray, unit of measurement of the absorbed dose) depending on the selected tab, this measurement being made by means of dosimeters.

Source: USP
   Palavras-chave:   Dosimeter    Dosimeter Fricke Xylenol Gel    Fricke solution    USP    T lymphocytes    Lucas Sacchini Del Lama    Health   
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