ABSTRACT
BACKGROUND: To identify the most appropriate dose for the prevention of transfusion-associated graft-versus-host disease, the radiosensitivity of T cells has been determined in blood bags irradiated with X-rays produced by a linear accelerator and gamma rays derived from the cesium-137 source of a specific irradiator. In this study, the influence of doses ranging from 500 to 2500 cGy was investigated on T cells isolated from red blood cell (RBC) units preserved with ADSOL and irradiated with a cobalt teletherapy unit. STUDY DESIGN AND METHODS: A thermal device consisting of acrylic and foam was constructed to store the blood bags during irradiation. Blood temperature was monitored with an automated data acquisition system. Dose distribution in the blood bags was analyzed based on isodose curves obtained with a polystyrene phantom constructed for this purpose. The influence of cobalt-60 gamma radiation on T cells was determined by limiting-dilution analysis, which measures clonable T cells. T-cell content of the mononuclear cell population plated was assessed by flow cytometry with a monoclonal antibody specific for CD3. RESULTS: Blood temperature ranged from 2 to 4.5 degrees C during irradiation. Dosimetry performed on the phantom showed a homogenous dose distribution when the phantom was irradiated with a parallel-opposite field. A radiation dose of 1500 cGy led to the inactivation of T cells by 4 log, but T-cell growth was observed in all experiments. At 2500 cGy, no T-cell growth was detected in any of the experiments and a greater than 5 log reduction in functional T cells was noted. CONCLUSION: The results showed that a dose of 2500 cGy completely inactivates T cells in RBC units irradiated with cobalt-60 source.
Subject(s)
Erythrocyte Transfusion , Gamma Rays , Graft vs Host Disease/prevention & control , Leukocyte Reduction Procedures , T-Lymphocytes/radiation effects , Adenine , Blood Preservation , Cobalt Radioisotopes , Cold Temperature , Dose-Response Relationship, Radiation , Glucose , Humans , Leukocyte Reduction Procedures/instrumentation , Leukocyte Reduction Procedures/methods , Mannitol , Quality Control , Sodium Chloride , X-RaysABSTRACT
BACKGROUND AND OBJECTIVES: Irradiation of whole blood and blood components before transfusion is currently the only accepted methodology to prevent transfusion-associated graft-vs.-host disease. In the present work, we developed an automated system for blood bag storage during irradiation, using a teletherapy unit. MATERIALS AND METHODS: A device with two thermal compartments was constructed in acrylic and foam, for the storage of blood bags during irradiation. An automatic acquisition system, coupled with an amplifier and a thermal-sensitive probe, were developed to check blood temperature during irradiation. A polystyrene phantom was constructed to simulate the volume of blood routinely irradiated. The dose distribution was measured in the phantom using thermoluminescent dosimeters and represented in terms of isodose curves. RESULTS: The thermal device kept the blood temperature below 6 degrees C for more than 2 h. Our system allowed the simultaneous irradiation of two different blood components while maintaining a constant temperature. The temperature monitoring system remained invariant (0.2 degrees C) over the whole irradiation interval. Phantom dosimetric results showed a homogeneous dose distribution when the phantom was irradiated, using rotational fields with a 2 r.p.m. frequency. CONCLUSIONS: The methodology developed in the present work provides appropriate storage conditions during irradiation of both red blood cells and platelet blood components using a teletherapy unit.
Subject(s)
Blood Banking/methods , Blood/radiation effects , Radioisotope Teletherapy/instrumentation , Blood Preservation/instrumentation , Equipment Design , Graft vs Host Disease/prevention & control , Humans , Phantoms, Imaging , Quality Control , Radiometry , TemperatureABSTRACT
An x-ray sensitometer is used to measure the characteristic curve of radiographic films exposed with fluorescent intensifying screens. The series of relative exposures, necessary to cover the full density range of the film, can be obtained by either time-scale or intensity-scale sensitometric methods. We have developed a convenient method of exposing film-screen systems for time-scale sensitometry. In this method, during exposure the x-ray kilovoltage, tube current and x-ray intensity remain constant and a geometric series of exposures of the film is modulated by varying the exposure time. This time variation can be obtained when a lead disc with different sector openings is rotated in front of the film system by a stepping motor. The conditions normally used are 70 kVp x-rays, 3.5 mm Al total filtration at the tube, and 2.4 m focal spot-film distance. This exposure latitude gives a complete characteristic curve of film-screen systems.
Subject(s)
X-Ray Film , Calibration , Fluorescence , Sensitivity and Specificity , Time Factors , X-RaysABSTRACT
A transfusão de sangue e dos componentes celulares contendo linfócitos vivos pode resultar na doença do Enxerto-Versus-Hospedeiro (DEVH) em pacientes imunocomprometidos. Ela pode ser prevenida pela irradiação dos componentes do sangue antes da transfusão. Este trabalho apresenta uma visão da realidade brasileira na prática de prevenção da doença, e apresenta proposta de otimização do problema.