BLOOD IRRADIATORS - TECHNIQUE, DOSIMETRY AND SUGGESTIONS TO QUALITY ASSURANCE

Background: For avoidance of a transfusion associated graft versus hos t reaction, the irradiation of blood products is vital. Normally, a do se of 30 Gy is considered to be necessary, and the minimum acceptable dose is 25 Gy and should not be fallen below. In the USA, already appr oximately 420 specific sites were in operation in 1992. In Germany, at present approximately 67 of such devices are operated. Material and M ethods: By means of thermoluminescence dosimeters, the dose and its di stribution in the beaker was determined at 15 sites. The radiation tim e for 5 Gy had been taken from the exposure table of the respective in stitute. Results: Referring to the asis of rotation, deviations of up to 57% occurred, an average deviation of 27% was typical. At 10 instit utes, in areas of the beaker the minimal dose of 25 Gy was fallen belo w. Only 8 institutes reached a mean dose in the beaker of 30 Gy or mor e. The largest value for the mean dose was found to be 38.8 Gy. Conclu sions: A setup of quality assurance procedures for blood irradiators i s necessary, The irradiation time table must be calculated according t o measurements in a water-filled beaker. The dose distribution along t he axis of rotation of the beaker should be 30 Gt and should not vary by more than +/- 2,5%. The dose at the inner wall of the beaker should not be more than 40 Gy. At present not all devices can keep these sta ndards.