lic. pedro antonio pérez
DESCRIPTION
Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry. Lic. Pedro Antonio Pérez. Facultad de Matemática, Astronomía y Física Universidad Nacional de Córdoba. Outlines & main goals. - PowerPoint PPT PresentationTRANSCRIPT
Preliminary study about the feasibility of
developing novel analysis methods based
on visible light absorption for Fricke
dosimetryLic. Pedro Antonio Pérez
Facultad de Matemática, Astronomía y Física Universidad Nacional de Córdoba
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To develop a simple and versatile dosimetric method capable of determining changes in matter (Xylenol Orange added Fricke gel) due to ionizing radiation.
To design and construct a preliminar device (hardware and software) in order to quantify absorbed dose by means of visible light absorption.
To establish applicability limits of extremely simple devices.
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
Outlines & main goals
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Nowadays, the development of novel dosimetric techniques has become great interests.
Optical analysis: Standard Fricke solution presents maximum absorption at 294nm (ultraviolet).
X. O. Fricke gel has maximum absorption at 585nm (visible).
Spatial resolution can be obtained fixing the X.O. Fricke solution to a gel matrix.
X. O. Fricke gel dosimeters, which constitute tissue-equivalent media for radiotherapy purposes, are capable of providing real 3D dose mapping.
Introduction
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke
dosimetry
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Boltzmann Radiation Transport Equation
Parallel beam
ma>>ms
Theoretical Background
drIrIrIntc
ssa
m
mm ,4
ˆ1
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Contiuous light source
Then,
Wich solution is the Lambert-Beer eq.
zI
dsenzIzIdrIrI
a
sa
ssa
m
m
mm
mm
24
,4
zzI
kzzI
tzI
crIn
tc
,0,0
ˆ1ˆ1
zIdzzdI
am
zIaeIzI m 0
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
Theoretical Background
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From L-B
Light absorption law
z≈Cd, then And the Optic al Density differences result:
zIzI m
0
ln
dCA
zA m
d
a
II
OD 10log
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
Theoretical Background
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Dosimeter preparation: Chemical composition
Protocol
Materials and methods
Comp. H2O G. H2O F. G.P.S. X.O. Sulf. Fe+2 H2SO 4
100ml 50ml 47ml 3,0389g 0,0125g 0,0196g 1,39ml
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Experimental Set Up: Dispositive description
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
Materials and methods
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Developed software:Get image Get red channel
Calculate XCM Calculate 2° moment
Calculate s (Rm)
Get ROI
Get definitive image
Calculate VM on new ROI and new s
Materials and methods
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Radiation facilities:
Conventional X-Ray tube
W anode. Mo cathode. V=40kV. 40mA
CLINAC
Varian 6/100
Materials and methods
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Results Experimental Set Up characterization. Preliminary tests.
Repetitivty and stability of the sistem source-dosimeter-camera
Results:
Stability: I=25,6+0,6 Repetitity: I=26,7+0,4
Diference on both modes: 4%
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Software validation by Gauss function
Some results
Some distributions
(ic,jc) y s escrito (ic,jc) calculado(50,25) y 10 (50,25)(25,50) y 10 (25,50)(50,50) y 5 (50,50)(75,75) y 5 (75,75)
Measurement and data processing Experimental Set Up characterization. Preliminary tests.
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Software validation
2 VM known functions
Constant I píxel to píxel (VM) Variable I pixel to pixel (ROI)
Results:
Fixed I: VM=1, s=0 Variable I:
Measurement and data processing Experimental Set Up characterization. Preliminary tests.
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Characterization of the developed device for optical analysis
Results: Serie 1: OD=0,16+0,01. Error: 6,7%. Serie 2: characteristic curve “exposition time-response”
Measurement and data processing On X-Ray tube.
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Two elaboration series to be irradiated by means of CLINAC: characteristic curve of “dose-response” and “depth dose” (to compare with standard dosimetric system -ionization chamber).
One elaboration serie to be irradiated by means of X-Ray tube and repeat the experience to obtain characteristic curve “exposition-response”
Measurement and data processing On CLINAC
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Irradiated samples
Dose on depth and comparison with ionization
chamber
Preliminary measurementsOn CLINAC – in-depth dose
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Discussion, conclusions and outlook
Software validation It has been verified the correct determination of relevant qquantities (VM, Rm,
CM and ROI). It has been established the consistency for the realization of the diferent steps
relative to communication with hardware, signal acquisition and data interpretation and subsequent processing.
Response of the integral system (source-dosimeter-software) It was possible to stablish the REPRODUCIBILITY (non-distinguishable), stability
(less than 1.6%) and repetitivity (less than 2.4%). The reults show clearly linearity region, as it was expected, even with supra and
sub linear zones. Response curves, which have been found to be indistinguishable, demonstrated
the reproducibility of the whole dosimeter elaboration procedure.In addittion
Device dimensions (20cm side box) allow its portability, therefore improving its comfortability for CLINAC measurements.
Preliminary PDD determination, as compared with ionization chamber, show hopeful results.
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry
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Main conclussions It was demonstrated that, even considering extremely simplcity
of the the device component, it is possible to develop suitable systems capable of determining absorbed dose by means of visible light transmittance measurements, particularly with radiochromic dosimeters.
Perspectives A lot of future improvements are been considered for the
developed device regarding its applicability limits and accuracy. Specially, a better detector quality may improve significantly the overall performance.
Several techniques devoted to 1D and 2D dose mapping are under investigation.
Discussion, conclusions and future lines
P. Pérez, V. Galván, M. Valente - Preliminary study about the feasibility of developing novel analysis methods based on visible light absorption for Fricke dosimetry