Download 2D_image_reconstruction_for_IMRT

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3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Motivation
The RADIA project
Detector characteristics
Characterization of the system (setup and
data analysis)
Algorithm for 2D dose map reconstruction
(setup, theory and tests)
Conclusions and perspectives
Bibliography
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Radiotherapy plays an important role in the treatment of a wide range of
cancers
Very important: monitoring the dose delivered to the patient
A novel dosimetric system based on silicon detector for radiotherapy
treatment verification.
Advantages:
silicon detectors have good radiation hardness;
on line treatment verification -> for example, no need of film development;
acceptable spatial resolution;
reproducibility;
dose maps in the axial plane.
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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TWO DETECTORS
A feasibility study:W1 SS 500
New detector based on BB7 technology
A commercial Single Sided
Silicon Strip Detector
(SSSSD)
Patent at OEMP (Oficinal Española de Patentes
y Marcas), Ministry of Industry & Commerce:
Number P201101009 (13/09/2011)
Dual chip SSSSD, designed
by our group, following
clinical constraints
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Mechanical system
BOX
Siemens Linac in 6 MV photon
mode
SLAB PHANTOM
Irradiation tests performed
at the Virgen Macarena
Hospital in Seville
Detector placed perpendicularly to
the beam
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Complete characterization of the system in terms of:
(a)linearity:
The response
of each strip
is linear as
function of
irradiation
time
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Complete characterization of the system in terms of:
(b) uniformity:
a
fundamental
step to
establish a
common
ground
behavior for
the strips of
each
detector
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Complete characterization of the system in terms of:
(c)
Percentage
Depth Dose
(PDD): study
of the dose
at different
depth in solid
water,
compared to
the ionization
chamber
data
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Complete characterization of the system in terms of:
(d)
Penumbra:
penumbra is
defined as
the region
located
between
20% and 80 %
of the
maximum
dose level
along X and
Y directions
Detector irradiated by asymmetric fields
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Old system
setup
Dose maps in the axial plane
Detector parallel to the beam field
Cylindrical phantom: new project
Housing the detector
• Versatile and rotating phantom;
• homogeneus: water equivalent
material;
• Able to house different detectors
(films, ionization chambers, strip
detectors,..)
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Mathematical algorithm for dose map reconstruction based on:
Radon Transform
+∞
𝑅 𝑓(𝑥, 𝑦) = 𝑔 𝑥 ′ , 𝜗 =
𝑓(𝑥 ′ cos 𝜗 − y′ sin 𝜗, 𝑥′ sin 𝜗 + 𝑦′ cos 𝜗)𝑑𝑦′
−∞
𝑔 𝑥 ′ , 𝜗 : our set of data for each angle θ
f(x,y): the function representing the dose map we want to reconstruct
To solve the equation: back projection theorem
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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𝜋
𝑔 𝑥 ′ , 𝜗 ∗ 𝐹 −1 (|𝑘|)𝑑𝜗
𝑓 𝑥, 𝑦 =
0
Filter
Real case with the detector
Discretization is needed
The dose in each pixel is reconstructed by the formula:
d(𝑥𝑖 ,𝑦𝑗 ) = n ∗ a
180/Δ𝜗 ∗
𝑑
𝑞=1
(𝑥′𝑖𝑗𝑞 ,𝜗)∆𝜃
Where:
• a is the strip lenght,
• n is the number of strips,
• q is the number of measurements,
• Δθ is the angular step between consecutive measurements.
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Dual chip SSSSD: 32 strips for
both detectors
SSSSD: 16 strips (developed by M.A.
Cortés Giraldo, University of Seville)
Simulated dose map image of a circle (R=9 mm) for both the systems
Reconstructed area
48x48 mm2
64x64 mm2
Image resolution
3 mm
2 mm
Angular range
0º-180º
0º-90º
Angular step
5º
3º
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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•
The new detection system shows good performances in
radiotherapy conditions;
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A preliminary, complete characterization of the system as a
dosimeter has been done;
Work to be done :
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New set of measurements, with the new cylindrical phantom;
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Calibration of the system in such configuration;
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Implementation of new algorithm for dose map reconstruction
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Appreciated contributions to make this project a success have been received
from the silicon detector manufacturer, Micron Semiconductor Ltd., web:
www.micronsemiconductor.co.uk (Dr Susanne Walsh Design /Colin D.Wilburn
Director), ATI Sistemas S. L., www.atisistemas.com (Mrs. Marta Trueba) and
Instalaciones Inabensa.
Radia Collaboration
Department of Atomic, Molecular and Nuclear Physics, University of Seville:
GETERUS group (M. A. Cortés Giraldo, M. I. Gallardo, J. M. Quesada), J. M.
Espino (also CNA), M. C. Ovejero and A. Selva.
University Hospital “Virgen Macarena”, Seville (SAS): R. Arráns, H. Miras.
National Accelerator Centre (CNA): Z. Abou-Haïdar, M. Alvarez, M. C.
Battaglia, A. Bocci.
Department of Electronic Engineering, University of Seville: A. Pérez Vega-Leal
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 201416
(1) A. Bocci, M. A. Cortés-Giraldo, M. I. Gallardo, J. M. Espino, R. Arráns, M. A. G. Alvarez, Z.
Abou-Haïdar, J. M. Quesada, A. Pérez Vega-Leal, and F. J. Pérez Nieto, “Silicon strip
detector for a novel 2D dosimetric method for radiotherapy treatment verification”,
Nucl. Instrum. Methods Phys. Res., Sect. A. 673, 98 (2012).
(2) Z. Abou-Haïdar, A.Bocci, M. A. G. Alvarez, J.M. Espino, M.I. Gallardo,
M.A. Cortés-Giraldo, M.C. Ovejero, J.M. Quesada, R. Arráns, M. Ruiz Prieto,
A. Pérez Vega-Leal y F.J. Pérez Nieto. “Output factor determination for
dose measurements in axial and perpendicular planes using a silicon strip detector”,
Phys. Rev. ST Accel. Beams 15,042802 (2012).
(3) M.A.Cortés-Giraldo, M.I. Gallardo, R. Arráns, J.M. Quesada, A. Bocci, J.M. Espino,
Z. Abou-Haïdar and M. A. G. Alvarez, "Geant4 simulation to study the sensitivity of
a Micron silicon strip detector irradiated by a Siemens PRIMUS linac", Progress in
Nuclear Science and Technology, Vol. 2, pp. 191-196 (2011).
(4) Patent at the OEMP - Oficina Española de Patentes y Marcas – Ministry of Industry
& Commerce: Number P201101009 (13/09/2011).
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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Thank you
Any questions?
3rd oPAC Topical Workshop on Beam Diagnostics, CIVIDEC, Vienna, 8th-9th May 2014
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