Temperature and X-irradiation strength effects on acid production and color changes in solid chemical radiation dosimete

Potsaid, M. S.

Shibata, S.

English

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I t . $ . 
SEMWJMIAL- 
July 1, 1966 
w\sA Research Grant N s G  719 
Radiology Dl3p-t 
Massachusetts General H o s p i t a l  
SOLID MEMICAL RADIATION DOSIMETER 
Majic S .  Potsaid, M.D. 
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EFFECTS OF PIiYSICAL STATES (34 ACID PROIXICI'ION 
AND COLOR W c ; E  IN THE fW SYSl€M* 
S. Shibata, MOD.' 
* From the Departmnt of Radiology, Massachusetts General Hospital, 
Boston, Massachusetts, 02114. 
1. Associate Radiologist, Massachusetts General Hospital; and 
Assistant Clinical Professor i n  Radiology, Harvard Medical School, 
Bostcm. 
2. Research Fellow, Massachusetts General Hospital, Boston. 
- 1- 
c 
, 
INTRODUCTION 
This report is concerned with further investigations into 
certain physical and chemical aspects of the IIAP sol id  chemical 
dosimeter, which records the spatial  distribution of radiation. 
?he HAP system (Halogenated - compound - - Azo dye - - Paraffin 
matrix) allows changes i n  the concentration of the various 
components thereby making possible fomla t ions  closely equiva- 
lent  t o  sof t  tissue i n  t e r n  of electron density and the effective 
atomic nunber (Z). 
?he following series of experiments are reported: 
1. 
2. 
3. 
Effect of temperature and physical state.  
Correlation of acidproduction with electron density and Z. 
Factors influencing the peak response. 
-2- 
. 
MATERIALS AND METIDD 
For ?Ae acid productim studies a liquid paraffin (e.g. heavy 
mineral o i l )  instead of solid paraffin a t  room tenperature was 
found to be the matrix of choice because acid extraction w a s  
M)X complete and reproducible. 
compound used and the dye was dimethylaminoazobenzene, 
s ta te  of the mixture was obtained by cooling in a deep freeze 
capable of temperaturns dawn t o  82O C. 
done with deionized dis t i l led water, hkasurements of pH were 
w i t h  a Beckman Model No GS meter. 
&lorofom w a s  the halogenated 
?he sol id  
Extraction of  acid was 
For the l igh t  transmittance masurement studies paraffin 
was blended with chloroform and the dye a t  65 t o  70° C in  making 
the translucent so l id  slabs. As stated i n  previous reports, the 
base OT matrix was considered as the solvent in the concentration 
calculations of  molality, 
- 3- 
RESULTS 
1. Effects of Temperature and Physical State 
A. Acid productim 
The s a m  f o m l a t i o m o f  the mineral o i l  HAP dosimeter 
w e r e  irradiated with X-rays in t h e i r  l iquid as w e l l  as t he i r  
sol id  s ta tes  and the acid production determined. 
mch more acid produced in the l iquid state as compared t o  
the s a m  f o m l a t i m  irradiated as a solid. This difference 
is clearly i l lus t ra ted  by Figures 1 and 2. 
"here was  
B. Transmittance measurements of color response 
'Ihe s m  f o m l a t i a n s  of the paraffin base IW dosimeter 
w e r e  irradiated at different temperatures and al lmed to  
equilibrate at room temperature for  the l ight  transmittance 
measurements. 
change at  the lower temperatures. 
Figure 3 shows that  there w a s  less color 
2. Correlation of Acid Production with Electron Density 
and Effective Atomic Number 
A. Acid production 
"he frozen so l id  mineral o i l  HAP dosimeter with chloroform 
cmcentrations ranging from 0.5 to  3.0 molal w e r e  irradiated 
with X-rays having effective energies of 25 keV and 100 keV 
as well as gamna rays from Coblat 60, which is considered t o  
have an effective energy of 1.25 MeV. "he absorbed dose (rads) 
and the G values for  the various f o m l a t i o n s  exposed to  the 
different radiation sources were correlated with acid produced. 
- 4- 
These data rre plo-ted in  Figure 4 and show that  there is 
more acid produced in  the higher concentrations of chloroform 
irradiated w i t h  higher radiation energies. 
B. Transmittance masuremats of color response 
Color danges were masured as the amomt of l i gh t  trans- 
iixitted t!!m& %!e &Liter  befare a d  after imdiatim of 
0.8 an solid-paraffin base slabs within a phantom of the 
same chloroform concentration, 
greater with the higher chloroform concentrations and greater 
with the higher radiation energies as seen in Figure 5, 
The change of color was  
3, Factors Influencing the Peak Respmse in  the HAP System 
It w a s  pmviously reported that  relatively law concentra- 
tions of halogenated organic canpound (chloroform o r  bromoform) 
gave the most color change with radiation, This effect was 
considered as due to the physical s t a t e  of the paraffin and/or 
p l a s t i c  matrix. 
this lesponse w a s  not consistent. 
seems t o  show a cantinually increasing sensi t ivi ty  with higher 
concentrations of halogenated hydrocarbon whereas the small 
addition of other substances such as microcrystalline wax or 
plast ics  can produce the peak response. 
trace m t s  of water may be responsible for the peak response 
i n  som instances. More work needs t o  be done to  elucidate 
t h i s  phenomnon, 
Upon further examinatim it was found that 
Paraffin alme as the matrix 
I t  also appears that  
-5- 
BIBLIOGRAW 
Potsaid, M.S., and Irie, G. Paraffin base halogenated hydrocarbon 
chemical Qsimeters. Radiology, 77:61-65 , 1961. 
Potsaid, M.S., and Irie, G. An in-phantom radiation detector. 
New England J. Med., 265 :1135-1139, 1961. -
Potsaid, M.S. Dosimeters: Solid t'Phantm.'' IN:  The Encyclopedia 
of X-rays and Gamna-Rays. Editor, G. Clark. Reinhold Publishing 
Corporation, New York, 1963, pp, 279-290. 
Potsaid, M.S., and Umezawa, T. Ionizing radiation color measurements 
of the IiAP dosimeter. h r .  J. Roentgenol., 93(3):715-724, 1965. - 
Potsaid, M.S., and Umzawa, T. The effects of chemical concentrations 
and chemical modifiers on the HAP dosimeter, Amer. J. Roentgenol., 
93 (3) : 725-732, 1965 . -
Potsaid, M.S., Shibata, S. ,  and McClymont, J.C. Effects of  visible,  
ultraviolet  and ionizing electromagnetic radiation on the HAP 
dosimeter containing sol id  halogenated compounds, sensit izers and 
stabilizers. Report t o  NASA on Research Grant NsG 719: Solid 
Chemical Radiation Dosimeter, Decenber 15, 1964. 
Potsaid, bl.S., Umzawa, T., Shibata, S., and Koehler, A.M. Proton 
Report t o  NASA on Research G r a n t  dosimetry using the HAP system, 
N s G  719: Solid aemical Radiation Dosimeter, December 20, 1965. 
Potsaid, M.S., Umezawa, T., and Shibata, S. Beta ray dosimtry using 
the HAP system. 
Chemical Radiation Dosimeter, kcenher 20, 1965. 
Report to  NASA on Research Grant N s G  719: Solid 
-6- 
15 
iu 
Frozen solid state 
5 
(-82" C) 
/00 KeV X-my 
0 1500 3000 4500 
RAD 
FIGURE 1 
Effect of Physical State (during irradiatim) 
and X-ray Photon Energy m Acid Production. 
- 7- 
40 20 0 -20 -40 -60 - 80 
T€MP. "C 
FIGURE 2 
Effect of Temperature at the Time of Irradiation on the Quantity 
of Acid Produced by X-rays w i t h  an Effective Energy of 100 keV. 
c 
i 
- 8- 
? 
IO0 
50 
10 
E F F E C T  OF T E M P E R A T U R E  D U R I N G  R A D I A T I O N  
20°C 
500 1000 
A/R DOSE I N  ROC'NTGENS 
FIGURE 3 
Effect of Tenprature on Sensitivity (color change as measured 
by transmitted light) of the Paraffin-Based HAP Dosimeter. 
-9- 
EFFECT OF RADIATION ENERGY A N D  C O N C E N T R A T I O N  
ON A C I D  P R O D U C T I O N  
5 -  
4 -  
cr, 
lu 
5 
3 -  s 
Q3 2 -  
I -  
3.0 Molal 
2.0 
I .o 
0.5 
10 100 100 0 
X-RA Y €ff€#? G Y fKe V) 
FIGURE 4 
Effect of Photon Energy and Chloroform Concentration on the G Value 
(amount of acid resulting from every 100 ev of energy absorbed). 
-10- 
i 
a- 
EFFECT OF RADIATION ENERGY AND CONCENTRATION ON SENSITIVITY 
IO'  I I I 1- 
1000 2000 3000 
RADS 
FIGURE 5 
Effect of Photon Energy and Chloroform Cmcentratim on 
Sensitivity (color change) of Solid Paraffin Rase Slabs. 
-11- 


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