Re: Calibration of blood irr

[gfeldman@uci.edu (Gerald Feldman)]

      Reply to: Gary's question about the reason for irradiating blood:

Blood products are irradiated to prevent graft vs host reactions.  When 
blood is given to individuals who have no active immune system (after an 
individual receives total body irradiation for treatment of cancer, for 
example), white cells in the blood may attack the new "host".  Although most 
of the white cells are removed mechanically before transfusion, there are 
always some straglers that may attack the host.  White cells are fairly 
radiosensitive, so irradiation of the blood to about 20Gy will kill off any 
of these remaining cells.





>        Reply to:   RE>Calibration of blood irradiator
>
>Question (probably dumb) for Carl Landis -
>
>May we ask what the purpose of irradiating blood or blood products is? 
>Sterilization?  Could you educate some of us unwashed-masses out here?
>
>--------------------------------------
>Date: 5/18/95 1:14 PM
>To: GARY MANSFIELD
>From: radsafe@romulus.ehs.uiuc.edu
>
> 
>Hello all!
> 
>Have any of you had any experience calibrating a blood irradiator?
>We have just received one at our institution and our other
>physicist, in conversations with the company who
>makes the unit seems to have turned up a misunderstanding on their
>part.  They give you a dose rate to the blood (or blood product)
>as their calibration that they determine in the following way:
> 
>They have a chamber that they can put in the position of the
>center of the container that you put the blood in.  This chamber has
>a cesium-137 factor and buildup.  They get a reading in air and 
>another reading in the same place but with the container filled.  Their
>dose to the blood is then calculated thus:
> 
>(R(air) x 0.87 x R(filled)/R(air))/100 = Dose to blood (Gy)
> 
>What they seem to have done here is to give a dose to _air_ along
>with an attenuation factor of sorts (almost looks like a TAR, doesn't it?). 
>I am reporting this to you second-hand but it appears that they consider
>ratio of R(air)/R(filled) to be a sort of conversion to dose in the blood,
>which we might call the dose to water in the radiation therapy business.
> 
>Any comments?  While you are at it, we are now in the process of
>doing our own calibration with TLD (LiF) chips so if you have any
>sage advice to pass along regarding that we would appreciate it.
> 
>Thanks for any responses!
> 
>Carl F. Landis, II                      clandis@neoucom.edu
>Associate Medical Physicist
>Southside Medical Center                216-740-4409
>345 Oak Hill Ave.                       FAX: 216-740-6581
>Youngstown, OH  44501-0990
> 
>
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>Subject: Calibration of blood irradiator
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***************************************************************************
  Gerald Feldman, M.S.
  Radiation Safety Officer
  UCI Medical Center
  101 City Drive South, Rt. 107
  Orange, California  92668
  Voice:  (714) 456-5607;     FAX:  (714) 634-8639
  E-mail: gfeldman@uci.edu
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