Radiation Dose to I-131 Labelled Cells

[kgordon@cc.UManitoba.CA]

I've got a question about estimating the radiation dose received by I-131 

labelled cells, and wonder if any of my fellow radsafers with expertise in 

microdosimetry can offer assistance. 
 
One of my immunology researchers is very anxious to know the radiation dose 

received by tumour cells during I-131 labelling process and after a four-day 

period post-labelling. Technical details as follows: 

1. 37 KBq (1 uCi) I-131 is added to 1 million cells suspended in 5 ml fluid in 

a test 
tube, then incubated for 4-6 hours.

2.  After incubation, cells are washed three times after which cells are 

counted.  Labelled fraction of I-131 on cells is usually between 1.6 to 3.2 

KBq.

3.  Entire lot of labelled cells are then suspended in a very small volume 

(0.1 ml) of fluid which is drawn up into a syringe and injected as a "clump" 

into one subcutaneous site on a mouse.  

4.  It is assumed that, once in-vivo, the cells stay relatively packed 

together and do not disperse.   

5. Mouse undergoes whole body counting immediately and at certain time 

intervals post injection.  

6. As the cells die and break down, radioiodine is released and excreted very 

rapidly via the urinary tract.  50% of iodine on injected cells is usually 

excreted within 24 hours. The clearance rate of radioiodine from the mouse is 

an index of cell death. 

5. The mouse is terminated 4 days post injection. 

Can you give me an estimate of:

a) the radiation dose these cells would have received during the 4 - 6 hour 

labelling
process with 37 KBq I-131 and 

b) the radiation dose to the labelled cells that survive the 4-day in-vivo 

period.


Thanks in advance.


Karin Gordon
Radiation Safety Office		phone	(204) 787-2903
Health Sciences Centre		fax	(204) 787-1313
PW-160, 820 Sherbrook St. 	Email	kgordon@cc.umanitoba.ca
Winnipeg, MB 
R3A 1R9