Re: Calibration of blood irr

[mikeg@SLAC.Stanford.EDU (Michael P. Grissom)]

I was once offered a very high strength Sr-90 blood irradiator for
use with the kidney transplantation team from a joint hospital
consortium near the National Institutes of Health in Bethesda, MD.
The purpose of the irradiator was to inactivate immune system cells
that cause graft versus host disease (GVHD) or in some cases to
reduce host versus graft disease (HVGD) by depressing circulating
cells (without damaging bone marrow), the target cells are certain
lymphocytes key to producing the dangerous antibodies/substances that
lead to transplanted organ rejection, which may be inactivated by 
passing blood through the irradiator at a given rate (transit dose 
counts!).  We rejected the offer due to problems with Sr-90 as a 
source and problems with disposition/maintenance of Sr-90 irradiators 
of the type offered.  This may not be the application for Carl's 
institution of course.
------------------------------------------

>        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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Michael P. Grissom
mikeg@slac.stanford.edu
Phone:  (415) 926-2346
Fax:    (415) 926-3030