FIRST MOBILE LINEAR ACCELERATORS IN SERBIA
- PRELIMINARY TLD RESULTS -
Olivera Marinkovic(*), Vedrana Prokic(**), Stefan Rafailovic(*), Zoran Mirkov(**)
(*) Serbian Radiation Protection and Nuclear Safety Agency, Belgrade(**) Serbian Institute of Occupational Health “Dr Dragomir Karajovic”, Belgrade
2/15
THERMOLUMINESCENT DOSIMETRYSerbian Institute of Occupational Health “Dr D. Karajovic”
Those were the days:- PC 286- DOS
and still operate:- REMSMENU software - CGCD Programme
(Computerised Glow Curve Deconvolution)
Harshaw TLD Reader Model 6600 (12th serial unit) and 12000 dosimeters (LiF:Mg,Ti) were bought 1991
Come to the Laboratory for personal dosimetry in January, 1992.
ETAM Method for Exposure Conditions Reconstruction
Marinkovic, Olivera1; Spasic Jokic, Vesna2
1 Serbian Institute of Occupational Health “Dr Dragomir Karajovic”, Belgrade2 Faculty of Technical Sciences, University of Novi Sad, SERBIA
Third European IRPA Congress 2010 June 1418, Helsinki, Finland
4/15ETAM
Elapsed time correlate with one-shot exposure Broadly applicable ETAM
Exposure Time Assessment Method
5/15
Glow curve shape:
a) short elapsed time; b) long elapsed time
between irradiation and read-out
a)
a)
b)
LiF Fading
6/15
A card has two chips (ii) & (iii)beneath different filters!
CARD HOLDERS
STANDARD FILTERED HOLDER
- Tissue equivalent filter- Skin equivalent filter
7/15GLOW CURVE SHAPE
a) “regular”
b) (ii) “regular” (iii) “irregular”
-Many causes for irregularity.-Permanent crystal defect.-Non ionizing excitation.
8/15Mobile Container/Vehicle Inspection System
- Serbia has a few 6 MeV NUCTECH MT1213LH- Improvement of cross border control
- Cross border area usually is not too big
Three decades of mobile linear accelerators in human medicine in China !!!
9/15DOSIMETRY – points of measurement
MT1213LH
beam
A
N
M
B C D E F
G
P
HIJK
O
L
Ambient dose equivalent rate (μSv/h)
point B C E F G H I J L K
value 0.15 0.6 1.2 1.1 1.3 0.8 0.2 0.09 0.08 0.08
PROTEKTIVE LINE (FENCE)
10/15TLD RESULTS
A set of TL dosemeters (two crystals per card packed in standard filtered holders, has been placed around NUCTECH MT1213LH Mobile Container/Vehicle Inspection System at different distances to collect radiation during a month.
At the same time, eight TL dosimeters which were exposed to three scans were read-out three hours later (Table 2). Crystal (ii) has position below 1 cm tissue equivalent filter and crystal (iii) has position below skin equivalent filter.
11/15TLD RESULTS – Table 2
No.
TLDbar-code
Three scans (TLD in air)Distance from spot
(different angles)
Check crystals (**)
(ii) (nC) (iii) (nC)(*) (ii) (nC) (iii) (nC)(*)
H 11039 0.9709 1.75959 11 m right back 13.25 12.85
C 4232 1.0630 7.64617 19 m left front 13.52 13.86
D 2510 0.8061 1.60664 9 m left front 13.16 13.84
I 2985 1.0260 5.64319 9 m central back 13.60 12.85
F 4158 0.8874 7.79779 8 m right front 13.15 13.91
J 4033 1.9780 11.6002 13 m left back 14.12 14.07
E 4223 1.0360 1.33133 6 m central front (beam) 12.68 13.21
B 10244 1.1740 2.01362 25 m left front 12.37 12.74
- 5537 0.8372 2.60281 Not exposed (background) 13.35 12.40
- 4113 0.8786 1.24128 Not exposed (background) 13.74 13.54
average 1.06572 4.324269 13.294 13.3286
stdev 0.340241 3.628713 0.505573 0.592033
12/15ULTRAVIOLET RADIATION
TLDs exposed to ultraviolet radiation
SUNVISION 240, Dinamic FAN solarium machine
Exposure 20 minutes
READ OUT AFTER 20 HOURS
HEATING EFFECT
14/15DISCUSION
This paper doesn’t give integral values for doses but strongly testify on intensive low energy field around linac.
Average signal (in nC) for TLDs exposed two months around linac was only 50% higher than for TLDs exposed one day (low energy peak, spontaneous contamination ) .
Are we sure that health risk is well known?
Gaius Flavius Valerius Aurelius Constantinus commonly known as Constantine I, (272-337)Birthplace: Naissus, Illyria (modern-day Niš, Serbia)
The Edict of Milan (Edictum Mediolanensium, 313) was a letter signed by emperors Constantine I and Licinius
that proclaimed religious toleration in the Roman Empire
THANK YOU FOR YOUR ATTENTION