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Oswaldo Baffa
Departamento de Física e Matemática
FFCLRP-Universidade de São Paulo
Ribeirão Preto, São Paulo-Brazil
E-mail: [email protected]
Abstract Ionizing radiation can create stable free radicals in
solids that can be quantified, in a non-destructiveway, by Electron Spin Resonance (ESR) leading to adosimetric technique. Ionizing radiation canchange the valence of iron ions and the viscosityof certain polymers leading to changes in therelaxation times of protons, allowing the use onuclear magnetic resonance imaging (MRI) toimage three-dimensional dose distribution. Bothtechniques are expected to improve the quality ofmedical care that relay in the use of ionizingradiation.
Absorbed doseAbsorbed dose is defined by the energy absorbed per mass and isgenerally viewed, particularly in epidemiology, as a macroscopic quantity.1Gy=1J/kg
4
Why care about dosimetry ?
DOSE
100%
Radiation Dose-
Tumor Response
Electron Spin ResonanceDosimetry
• Electron spin resonance (ESR) detects systems with non zero magnetic moment (electrons, free radicals, bi-radicals...)
• Experimental technique that allows the measurementsof dose in insulating materials like bone, teeth, alanine,shells, plastics, among others.
• Dosimetric properties of hard tissues, like bones andenamel, have been extensively studied.
Electron Spin Resonance
E = h= gHr
E
Hr
h
+½gH
-½gH
H
[Swartz, 1972]
Electrons aren’t alone-Hyperfine Interaction
E
E
E
E
4
3
2
1
m
m
m
m
m
mI
I
I
I
S
S
= +1/2
= +1/2
= +1/2
= -1/2
= -1/2
= -1/2
E0
Operating parameters: H0= 325 mT (3250 G); H= 20 mT
(200 G) e 4 mT (40 G); t= 2 min; f 9.09 GHz; fm = 100
kHz; P : 5-200 mW; Hm: 0.05-1.6 mT (0.5- 16 G).
- First and second harmonic detection
Sensitivity and precision in concentration measurements of
paramagnetic substances
ESR-X Band Spectrometer
K –Band (24 GHz) ESR Spectrometer
Radiation Effects
Using ESR to measure the dose deposited by
ionizing radiation in different biological
materials like bone, enamel, dentine, alanine;
and non biological like minerals, plastics,
etc... A possible application is retrospective
dosimetry in accidents.
Goals
ESR Dosimetry - The aditive dose method
D0 = ???
D0 +D1
A0
D0 +D1+ D2
D0 +D1+ D2 + D3
A1
A2
A3
D0
Amplitude
Dose
A0
D1 D2 D3
A1
A2
A3
[Ikeya,1993]
Hard Tissue Components Mineral Component-Hydroxyapatite
Ca10(PO4)6(OH)2 + Substituints like F, CO2, etc..
Stable free radicals are formed CO2–
Organic Component
Collagen, proteins, etc…
Unstable signal-unsuitable for dosimetric purposes
ESR Dosimetry with Tooth Enamel
332 334 336 338 340 342
Magnetic Field (mT)
g//
g
Enamel irradiated with 1Gy of 60Co rays
Background signal + CO2- dosimetric signal
332 334 336 338 340 342
Magnetic Field (mT)
Simulated Dosimetric signal
Experimental curve
Background signal
Dosimetric signal simulation
ESR Signal from Enamel
3320 3340 3360 3380 3400 3420 3440
-3,0x10-5
-2,0x10-5
-1,0x10-5
0,0
1,0x10-5
2,0x10-5
3,0x10-5
4,0x10-5
10 Gy
3 Gy
1 Gy
500 mGy
200 mGy
Comparison of Spectra at Different Frequencies
332 334 336 338 340 342 344
Magnetic Field (mT)
846 848 850 852 854 856 858
Magnetic Field (mT)
X band 9 GHz K band 24 GHz
Hydroxyapatite irradiated at 3 Gy
Enamel: ESR Signal (X-band) versus Dose
0 2 4 6 8 10
0
1
2
3
4
5
6
Dose (Gy)
ESR DOSIMETRY OF 89Sr AND 153Sm-IN BONE
The radiation absorbed dose in rabbit bone, delivered by153Sm-EDTMP (samarium-ethylene-diaminetetramethyl-enediphosphonic acid) and 89SrCl2 (strontium chloride), wasmeasured by means of electron spin resonance (ESR). Theseradioisotopes are used in systemic radiotherapy forpalliation of painful bone metastases. Knowledge of the doseis important in order to avoid side effects to bone marrow.The ESR radiation dose signal was calibrated by the additivedose method using cobalt-60 gamma rays. For 153Sm-EDTMPbone doses on three rabbits were (4 2), (51) and (52)cGy.kg/MBq. For 89SrCl2 in one rabbit a dose of(21)Gy.kg/MBq was found..
Scintigraphic image of a rabbit 5 days after IV injection of 153Sm-EDTMP, the dark areas indicate high uptake regions.
ESR spectra of bones irradiated in vivo by 153Sm EDTMP and with added doses in vitro from 60Co gamma radiation
332 334 336 338 340 342 344
-0,000020
-0,000015
-0,000010
-0,000005
0,000000
0,000005
0,000010
0,000015
0,000020
0,000025
Inicial + 201,44 Gy
Inicial + 151,08 Gy
Inicial
Inicial + 50,36 Gy
Campo Magnético (mT)
ESR signal growth of a rabbit bone as function of added dose from 60Co gamma radiation. (A) injected with 153Sm-EDTMP and (B) injected with 89SrCl2 .
0 50 100 150 2000
10
20
30
40
50
60
70
80
90
100
110
(A)
Am
plit
ude/m
ass (
a.u
.)
Added Dose(Gy)0 50 100 150 200
0
10
20
30
40
50
60
70
80 (B)
Am
plit
ude/m
ass (
a.u
.)
Added Dose (Gy)
For 153Sm-EDTMP bone doses were (4 2), (51) and
(52) cGy.kg/MBq. For 89SrCl2 in one rabbit the dose
was (21) Gy.kg/MBq was found..
ACCIDENT DOSE ASSESSMENT WITH ESR
ESR was used to evaluate the dose received by the
right hand medium finger of a worker’s in an
accidental exposure to a radiotherapy Cobalt-60
source. The accident happened in November 1995
in Arequipa, Peru, where a Cobalt unit failed and
the worker trying to fix the problem touched
directly the source for a few seconds.
Schematics of the Accident Scene
Medical HistoryAfter 30 days medical treatment started and the first
diagnosis was burn of II-III degree. The clinical
situation evolved leading to necrosis of the fingers
with increasing pain. In May 1996 the index finger
was amputated and in September 1999 the medium
finger was also amputated. ESR with the additive
dose method with rays of 60Co for calibration was
used for dose reconstruction of a bone sample from
this last finger. A dose of (6.4 1)Gy was found in this
sample.
Aspect of the Hand Immediately After the Accident and after Finger Amputation
ESR Signal and Calibration
332 334 336 338 340 342 344
20 Gy
Magnetic Field (mT)
-20 0 20 40 60 80 100 120 140 160
0,0
2,0x10-3
4,0x10-3
6,0x10-3
8,0x10-3
1,0x10-2
Am
plitu
de (a.
u.)
Added Dose (Gy)
The Aminoacid Alanine
COOH
C
CH
HH N2
COOH
C
CH
NHH
3 3
2
L- alanine D-alanine
The electron interacts with the proton and the 3 protons
of the methyl group, giving a 5 line spectrum with intensity
ratio of 1:4:6:4:1. L-Alanine is more sensitive
Dosimeter Production
X-band ESR first harmonic signal of DL alanine dosimeters after 10Gy with 60Co irradiation
3100 3150 3200 3250 3300
-9,0x10-5
-8,0x10-5
-7,0x10-5
-6,0x10-5
-5,0x10-5
-4,0x10-5
-3,0x10-5
10G
Sin
al de E
PR
(u.a
.)
Campo magnético (G)
Dose Response DL-Alanine
0 5 10 15 20
0,0
2,0x10-5
4,0x10-5
6,0x10-5
8,0x10-5
1,0x10-4
1,2x10-4
DL-alanina
1H
r = 0,999
AMP = -2,417E-6 + 5,679E-6*D
Am
plit
ude liq
uid
a (
u.a
.)
Dose (Gy)
Blood Dosimetry TA-GVHD (transfusion-associated graft-
versus-host disease) is a possible complication of blood transfusion that occurs when viable donor T-lymphocytes proliferate and engraft in inmunodeficient patients after transfusion. Presently, the only method accepted to prevent TA-GVHD is the irradiation of blood and its components before transfusion Moroff G., Luban N.L.C., The Irradiation of Blood and Blood
Components to Prevent Graft-Versus-Host Disease: Technical Issues and Guidelines. Transfusion Medicine Reviews. 11 (1), 15-26. 1997.
Quality Control of Blood IrradiationAlanine Dosimeters
14 16 18 20 22 240
2
4
6
8
10
12
14
16Q
ua
ntity
of D
ose
me
ters
Dose (Gy)
AN ATTEMPT TO USE SWEETENERS AS A MATERIAL FOR ACCIDENT DOSIMETRY
In case of a radiological accident it is important to determine the exposure to radiation of general population. Several materials can be used to reconstruct the exposed dose. Tooth enamel has been studied for a long time and now the procedures to determine the dose are well established for in vitromeasurements. Many materials have been investigated by different techniques: sugar, wall bricks, roof tiles, plastics, watch glass, ruby present in watches, medicines carried by persons and shell button, among others. In this work an attempt is made to use sweeteners as a possible accident dosimeter material. They are becoming increasingly common and more likely to find them. Sweeteners based on saccharine, cyclamate, stevia and aspartame were acquired in local stores and ESR spectrum was recorded before and after gamma irradiation. Spectrum simulation demonstrated that there are two main radicals with g=2.0063, A=1.6mT and g=2.0048, A=5mT due to Lactose. For the better characterization of spectroscopic and dosimetric properties of these materials, higher microwave frequency (K-Band, ~24GHz) was also employed. Experiments in X-Band (~9GHz) showed that low dose level of 500mGy can be measured with this material demonstrating the potential use of sweeteners for retrospective dosimetry.
Espectro ESR de Adoçantes
332 334 336 338 340 342
Doce MenorR
GoldR
SteviaR
Radical R1
Radical R2
Magnetic Field (mT)
O ESR spectrum
of Stevita®,
Gold® and Doce
Menor® after
3kGy dose of
gamma radiation
and spectral
simulation of the
radicals R1:
g=2.0063,
A=1.6mT and R2:
g=2.0033, A=5mT
Stevia
Espectro de ESR da Lactose emBanda X e K
844 846 848 850 852 854 856 858 860
Magnetic Field (mT)
K-Band
X-Band
0 2 4 6 8 10 12 14 16 18
0.0
1.0x10-6
2.0x10-6
3.0x10-6
4.0x10-6
5.0x10-6
6.0x10-6
7.0x10-6
8.0x10-6
R1
R2
ES
R S
ign
al In
ten
sity (
a.u
.)
Microwave Power1/2
Comportamento em banda K dos
espectros dos radicals R1 and R2 em
função da potência
332 334 336 338 340 342 344
-8.0x10-6
-6.0x10-6
-4.0x10-6
-2.0x10-6
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
ES
R s
ign
al In
ten
sity (
a.u
.)
Magnetic Field (mT)
20 Gy Pellet
3kGy*Powder
R1
R2
332 334 336 338 340 342
Initial
Initial - R2
Initial - R2-R
1
Magnetic Field (mT)
R2
R1
Isotropic
0 1000 2000 3000 4000 5000 6000 7000
2.0x10-3
4.0x10-3
6.0x10-3
8.0x10-3
1.0x10-2
1.2x10-2
1.4x10-2
1.6x10-2
1.8x10-2
2.0x10-2
2.2x10-2
2.4x10-2
2.6x10-2
2.8x10-2
R1
R2
Isotropic
ES
R s
ign
al In
ten
sity (
a.u
.)
Time (min)
0 5 10 15 20
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
R1
R2
ISO
ES
R s
ign
al In
ten
sity (
a.u
.)
Dose (Gy)
40
Dosimetria Retrospectiva de ESR de Cabelo
Necessidade de Novos e mais detalhados Estudos!
41
Dosimetria Retrospectiva de ESR de Cabelo
42
Dosimetria Retrospectiva de ESR de Cabelo
-200 0 200 400 600 800
-800
-600
-400
-200
0
200
400
600
Sin
al d
e E
SR
(x1
03)
Campo Magnético (mT)
10 mW
-200 0 200 400 600 800
-800
-600
-400
-200
0
200
400
600
800
Sin
al d
e E
SR
(x1
03)
Campo Magnético (mT)
7.5 mW
43
Dosimetria Retrospectiva de ESR de Cabelo
334 336 338 340 342
-50
0
50
Sin
al de E
SR
(x10
3)
Campo Magnético (mT)
7.5 mW
Sinal de ESR Melanina
App= 107.6
Hpp= 0.98 mT
g = 1.99
120 140 160 180
-1000
-800
-600
-400
-200
0
200
400
600
800
Sin
al de E
SR
(x10
3)
Campo Magnético (mT)
10 mW
Sinal de ESR Indefinida
App= 574.6
Hpp= 5.19 mT
g = 4.29
-200 0 200 400 600 800
-800
-600
-400
-200
0
200
400
600
800
Sina
l de
ESR
(x10
3 )
Campo Magnético (mT)
7.5 mW
App= 1235
Hpp= 141.5 mT
g = 2.17
0 100 200 300 400 500 600
-2000
0
2000
S
inal de E
SR
(x1
03)
Campo Magnético (mT)
Doses:
0 Gy
1 Gy
2 Gy
3 Gy
44
Dosimetria Retrospectiva de ESR de Cabelo
O estudo continua .......
Acknowledments Angela Kinoshita
Felipe Chen
Jorge Gomez
Graduate Students
Undergraduate Students
Financial Support:
FAPESP-CNPq-CAPES