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

13/15COMPARASION: TLD-UV

SUNVISION 240, Dinamic FAN solarium machine

NUCTECH MT1213LH(C) (J) (E)

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