Oswaldo Baffa Departamentode Fsica e Matemtica FFCLRP

transcript

Oswaldo Baffa

Departamento de Física e Matemática

FFCLRP-Universidade de São Paulo

Ribeirão Preto, São Paulo-Brazil

E-mail: baffa@usp.br

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

Why care about dosimetry ?

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

[Swartz, 1972]

Electrons aren’t alone-Hyperfine Interaction

= +1/2

= -1/2

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.

ESR Dosimetry - The aditive dose method

D0 = ???

D0 +D1

D0 +D1+ D2

D0 +D1+ D2 + D3

Amplitude

D1 D2 D3

[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)

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

1,0x10-5

2,0x10-5

3,0x10-5

4,0x10-5

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

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

Added Dose(Gy)0 50 100 150 200

80 (B)

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

Magnetic Field (mT)

-20 0 20 40 60 80 100 120 140 160

2,0x10-3

4,0x10-3

6,0x10-3

8,0x10-3

1,0x10-2

de (a.

Added Dose (Gy)

The Aminoacid Alanine

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

al de E

Campo magnético (G)

Dose Response DL-Alanine

0 5 10 15 20

2,0x10-5

4,0x10-5

6,0x10-5

8,0x10-5

1,0x10-4

1,2x10-4

DL-alanina

r = 0,999

AMP = -2,417E-6 + 5,679E-6*D

ude liq

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

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

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

1.0x10-6

2.0x10-6

3.0x10-6

4.0x10-6

5.0x10-6

6.0x10-6

7.0x10-6

8.0x10-6

sity (

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

2.0x10-6

4.0x10-6

6.0x10-6

8.0x10-6

sity (

Magnetic Field (mT)

20 Gy Pellet

3kGy*Powder

332 334 336 338 340 342

Initial

Initial - R2

Initial - R2-R

Magnetic Field (mT)

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

Isotropic

sity (

Time (min)

0 5 10 15 20

sity (

Dose (Gy)

Dosimetria Retrospectiva de ESR de Cabelo

Necessidade de Novos e mais detalhados Estudos!

-200 0 200 400 600 800

7.5 mW

334 336 338 340 342

al de E

7.5 mW

Sinal de ESR Melanina

App= 107.6

Hpp= 0.98 mT

g = 1.99

120 140 160 180

al de E

Sinal de ESR Indefinida

App= 574.6

Hpp= 5.19 mT

g = 4.29

-200 0 200 400 600 800

7.5 mW

App= 1235

Hpp= 141.5 mT

g = 2.17

0 100 200 300 400 500 600

inal de E

Doses:

O estudo continua .......

Acknowledments Angela Kinoshita

Felipe Chen

Jorge Gomez

Graduate Students

Undergraduate Students

Financial Support:

FAPESP-CNPq-CAPES

Oswaldo Baffa Departamentode Fsica e Matemtica FFCLRP

Documents