Calibration of blood irradiator -Reply

[FRAMEP@ORAU.GOV]

Carl Landis wrote in part:

>They have a chamber that they can put in the position of the
>center of the container that you put the blood in. .. 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)
 
>Any comments? 

The equation seems odd because the R(air) values cancel out.
In your message you also refer to the R(air)/R(filled) ratio. Let me
work on the (probably incorrect and therefore I am wasting everyones
time) assumption that the equation is 

(R(air) x 0.87 x R(air)/R(filled))/100 = Dose to blood (Gy)

A reading in air in roentgen (R(air)?) x 0.87/100 gives the dose to
the air in Gy. If we multiply this by [uen/p(blood)]/uen/p(air)] we
get the dose to blood in Gy where uen/p is the mass energy absorption
coefficient. Perhaps it has been decided that R(air)/R(filled), is a
reasonable approximation for [uen/p(blood)/[uen/p(air)].

Thats idle speculation and hand waving but I couldn't resist.

>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.

You should get lots of good ideas here. Let me mention one thing
because I/we once got burned because of the dose resonse issue.

If you are going to use them above 100 rad or so, and I assume these
are not for personnel dosimetry purposes, the response of LiF goes
supralinear. You might want to calibrate at multiple points in the
same dose range that you will measure. 


Good luck. Time to go home. 

Paul Frame
Professional Training Programs
Oak Ridge Associated Universities
framep@orau.gov