11/19/2014
EORTC meeting for Radiation Therapy Technologists:
RTT’s role in the modernization of radiotherapy
10th October 2014, Villejuif (Grand Paris),
France
Elekta Stereotactic Body Frame:
transmission modelled by Monte Carlo
and Collapsed Cone algorithm for VMAT
treatment planning
Ilenia Iarrusso
University of Torino, Italy
Equipe:
• 4 Physicists
+
4 Dosimetrists
• Management of DICOM images;
• Contouring of some OAR (Organ At Risk) in CT simulation scan;
• Planning of 3D treatment plans;
• Patient Specific Quality Assurance (the focal point of this
study);
• LINAC QC.
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11/19/2014
Our Department:
structure and
organization
I will speak
about
Our study:
purpose,
methods and
discussion
Patient specific
Quality
Assurance
control
Our Department:
structure and
organization
I will speak
about
Our study:
purpose, methods
and discussion
Patient specific
Quality
Assurance
control
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11/19/2014
ELEKTA MOSAIQ Vers. 2.4.1
LINAC 1 Elekta SL75
X 6; Align RT
Philips Brilliance Big Bore
CT-Simulation, Tumor L.O.C.,
4D-CT; Clarity
LINAC 2 Elekta Synergy
Velocity
X 4-6 , MLCi2, cone beam CT,
Clarity, Intuity
Elekta ABAS; Anatom-e
LINAC 3 Elekta Precise
Atlas based autosegmentation
X 6-10-25; e, MLCi2, EPID,
Clarity
LINAC 4 Elekta Axesse
Elekta Monaco 3.3
Monte-Carlo Systems
Film-and paperless
since 2010
X 6-10-15; e, Beam Modulator,
cone beam CT, Integrity 1.1,
Symmetry, Intuity, 4D-Autoscan
Gammknife
Perfexion 2014
IORT Linac
Elekta/Nucletron
Masterplan vers. 4.3
Connection to unit 1
Radioterapia SGAS
(3 Linacs)
Distance 3 km
Novac-7 NRT
Connection to unit 2
Radioterapia S. Anna
(1 Linac)
Distance 500 m
LINAC Elekta Synergy
2 Linac Siemens
Primus
LINAC Elekta Synergy
X 6; e, MLC, EPID
X 6-18; e, MLC, EPID
HDR Brachytherapy
The Department of Radiation Oncology of University of Torino is directed by
Prof. Umberto Ricardi and the staff is composed of:
9 Radiation Oncologists
13 Residents
4 Medical Physicist
4 Dosimetrists
15 RTT
Dedicated ward to assist critical patients and a Day Hospital for
chemotherapy and to carry out a supportive care.
UNIVERSITA’ DEGLI STUDI DI TORINO
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11/19/2014
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11/19/2014
Our Department:
structure and
organization
I will speak
about
Our study:
purpose, methods
and discussion
Patient specific
Quality
Assurance
control
UNIVERSITA’ DEGLI STUDI DI TORINO
This is the phantom used
by Dosimetrist for Patient
Specific QA
UNIVERSITA’ DEGLI STUDI DI TORINO
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11/19/2014
Scandidos
Delta4
Detector type
Diode
Resolution(mm)
5/10
# of Detectors
1069
Max field size
20
Weight kg
(detector/phantom)
24
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- VMAT plan is approved.
- Plan parameters are copied to a phantom (Verification Plan)
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11/19/2014
- Delta 4 phantom CT
Phantom density
override and couch
absorption
For no-coplanar arcs,
beams are arranged to
remove couch angle
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- Positioning and centering of Delta 4 phantom on the couch
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11/19/2014
The planar
measured dose is
compared to that
calculated by TPS
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- Dosimetrist and Medical Physicist analyze the results
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11/19/2014
- The agreement is acceptable if the percentage of points with value of
Gamma Index < 1 is ≥ 90%; When this value is < 90%, we perform a
specific procedure:
Yes
Percentage of
point ≥ 90%
VMAT – QA is
approved
No
Verification of
workflow
Measure is
repeated
VMAT – QA
is approved
Re-export
Step and
Shoot
VMAT – QA is
approved
UNIVERSITA’ DEGLI STUDI DI TORINO
Our Department:
structure and
organization
I will speak
about
Our study:
purpose, methods
and discussion
Patient specific
Quality Assurance
control
UNIVERSITA’ DEGLI STUDI DI TORINO
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11/19/2014
The purpose of this study was to verify the influence of the
transmission of the Elekta Stereotactic Body Frame (ESBF) in VMAT
treatment planning:
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- Selection of one patient with Liver tumor for Stereotactic Body
Radiation Therapy (SBRT) and planning of a treatment of 60 Gy in
three fractions, using beams with energy of 6 MeV.
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- Acquisition of CT images of the Delta 4 phantom, positioning it on
the Elekta Stereotactic Body Frame (ESBF)
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- Calculation of VMAT QA with and without ESBF, using Monte Carlo
and Collapsed Cone algorithm.
Dose calculated
using Collapsed Cone
algorithm with and
without ESBF
Dose calculated
using Monte Carlo
algorithm with and
without ESBF
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- Verification of the plan, positioning the phantom with and without
the ESBF on the couch and acquisition of the dose.
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- Analysis of results and comparison between the two TPS
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Gamma Index passing rates for the two considered algorithms
110
100
90
80
70
60
50
Gamma Index 2mm / 2%
40
Gamma Index 3mm / 3%
30
20
10
0
Monaco
Masterplan
Without ESBF absorption
Monaco
Masterplan
With ESBF absorption
UNIVERSITA’ DEGLI STUDI DI TORINO
Evaluation of ESBF absorption for VMAT treatment by means of
patient specific QA procedure
If absorption is considered, we can find lower agreement between
measured and calculated doses
Metal artifacts?
Considering ESBF absorption, Monaco TPS better than Masterplan
TPS
AAPM TG 119 (90%).
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The use of ESBF introduces an increased value of
uncertainty in treatment planning for liver SBRT
Monte
Carlo
algorithm
may
overcome
this
uncertainties
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