Maria Skłodowska-Curie Memorial Cancer Centre and Institute of Oncology, Warsaw, Poland
8th ECMP, Athens, 11-13.09.2014
Dosimetry audits in radiotherapy in Poland
W. Bulski, K. Chełmiński, J. RostkowskaMedical Physics Department
Bielsko--Biała
Rzeszów
Kielce
Katowice
Olsztyn
Bydgoszcz
Szczecin
Zielona Góra
Poznań
Łódź
Warszaw a
Gdynia
Gdańsk
Białystok
Lublin
Brzozów
Kraków
W rocław
Opole
Gliwice
Słupsk
Tarnów
Wałbrzych
Radiotherapy centres in Poland as of 2013:30 radiotherapy centres
0102030405060708090
100110120130
1985 1990 1995 2000 2005 2010 2015
lata
liczb
a
Co-60
linacs
total
Radiotherapy equipment in Poland as of 2013:About 115 accelerators in 30 centres
For over 20 years a postal audit (IAEA methodology) has been carried out to check the TPS dose calculations in a homogenous
phantom (water) in reference and variousnon-reference conditions.
SAD
d=10 cm
TLD
SSD
d=10 cm
TLD
Non-reference conditions,Non-reference conditions,on axison axis, , MLCMLC shaped fields shaped fields
reference (1)
„small” (2)
„irregular” (5)
„inverted Y” (4)
„circular” (3) „irregular”+wedge (6)
MLC shaped photon beams from linear accelerators; dose calculated with TPS vs. measured with TLD. D(stated) - dose stated by the participant,
D(TLD) - dose determined by the SSDL
Results of the postal audit in 2012:
0,90
0,95
1,00
1,05
1,10
0 10 20 30
RT centre code
D(T
LD
) / D
(sta
ted
)
10x10
small
circular
inverted Y
irregular
irregular with wedge
In the above example all results were within the ± 5% level. Only 10 out of 168 results (6%) were over ±3.5% level.
This allowed us for adoption of the levels of the evaluation of the results:acceptance level ± 3,5%, and intervention level ± 5%.
Such levels are adopted by the IAEA only in the case of Secondary Standard Dosimetry Laboratories (SSDL).
However, all the measurements were done in a homogenous (water) phantom.
In the radiotherapy Treatment Planning Systems (TPS) various calculation algorithms are used and they accuracy of dose calculations in heterogenous medium has to be verified.
For this reason a heterogeneous cubic-shape phantom has been designed within a Coordinated Research Project of the IAEA.
Materials and methods• The heterogeneous phantom was developed in the
frame of an IAEA Coordinated Research Project. • The phantom consists of frame made with
polystyrene and of bone and lung inhomogeneity slabs.
• Special inserts allow to position TLD capsules within the polystyrene below the bone or lung material and also within the lung equivalent material.
• There are also inserts for positioning an ionization chamber.
• The comparisons were performed for a number of various TPS and for a number of various linear accelerators in radiotherapy departments in Poland.
15 cm
15
cm
10
cm
2 cm
2 cm
5 cm
2 cm
2 cm
2 cm
15 cm
15
cm
5 cm
2 cm
2 cm
2 cm
2 cm
2 cmBone
15 cm
2 cm
2 cm
2 cm
2 cm
2 cm
10
cm
15
cm 5 cmLung
15 cm15 cm
15 cm
10
cm
15 cm
15
cm
10
cm
2 cm
2 cm
5 cm
2 cm
2 cm
2 cm
15 cm
15
cm
10
cm
2 cm
2 cm
2 cm
2 cm
5 cm
2 cm
2 cm
2 cm
15 cm
15
cm
5 cm
2 cm
2 cm
2 cm
2 cm
2 cmBone
15 cm
2 cm
2 cm
2 cm
2 cm
2 cm
10
cm
15
cm 5 cmLung
15 cm15 cm
15 cm
10
cm
The phantom consists of a frame made of polystyrene and inhomogeneitis - bone or lung equivalent exchangeable slabs.
polystyrene
bone
lung
IAEA heterogeneity phantom with cassettes for TLD or films and ionization chamber cavity inserts.
Beam Radiationunit
TLD set #
User stated (TPS)
dose [Gy]
IAEA (measured)dose [Gy]*
deviation relative**to IAEA
mean dose [%]
IAEA mean dose
/User stated
dose
6 MV Clinac 2300CD
P(Polystyrene)
2,00 1,99 0,7 0,99
BP(Bone)
2,00 1,99 0,3 1,00
LP(Lung on-axis)
2,00 2,04 -1,6 1,02
LL(Lung off-axis)
2,28 2,22 2,9 0,97
Pencil beam algorithm, X6 MV, Warsaw, Poland
EXAMPLE RESULTS OF IAEA/WHO TLD POSTAL DOSIMETRIC QUALITY AUDIT
IAEA – HETEROGENEITY PHANTOM AUDITRESULTS FROM PILOT STUDY IN POLAND
PERFORMED BY SSDL-WARSAW
• Irradiaton of TLD capsules• Ionizing chamber measurements using dedicated inlet
Irradiation conditions (same for all detectors):• beam quality: 6MV• field size: 6 cm x 6 cm• SSD = 90 cm
Ten radiotherapy centers (of 30 total in Poland), six TPS types with alternative algorithms were examined giving 15 TPS/Algorithm/Linac combinations
No. TPS Algorithm Linac
1 Panther 5.01 EP Siemens Artiste
2 PrecisePlan 2.16 PBC Elekta Synergy
3 Eclipse 7.3 PBC Varian Clinac 2300
4 MasterPlan 4 PBC Varian Clinac 2300
5 Eclipse 8.2 PBC Varian Clinac 2300
6 Panther 5.01 CCC Siemens Artiste
7 CMS XiO 4.62 CCC Elekta Synergy
8 MasterPlan 4 CCC Siemens Primus
9 MasterPlan 4 CCC Varian Clinac 2300
10 MasterPlan 4 CCC Elekta Synergy
11 Eclipse 8.2 AAA Varian Clinac 2300
12 Eclipse 10.0 AAA Varian Clinac EX-S
13 Eclipse 8.6 AAA Varian Clinac 2300
14 Eclipse 11.0 AAA Varian Clinac 2300
15 Monaco 3.2 MC Elekta Synergy
PBC – Pencil Beam Convolution
AAA – Analytical Anisotropic Algorithm
MC – Monte-Carlo
EP – fast photon effective path
CCC – Collapsed Cone Convolution)
TLD – POLYSTYRENE
The TLD capsules were located in the polystyrene material at 10 cm depth. The plan was normalized to 100% for 2 Gy at 10 cm depth..
TLD – BONE
The TLD capsules were located under the bone tissue equivalent material at 10 cm depth. The plan was normalized to 100% for 2 Gy at 10 cm depth.
TLD – LUNG
In case of lung tissue equivalent material the TLD capsules were located in two positions:
in lung tissue, under lung tissue slab at 10
cm depth.
The plan was normalized to 100% for 2 Gy in the point at 10 cm depth.
Results
• Ten Polish radiotherapy centers (of 30 in total) were audited. • Six different TPSs and eleven calculation algorithms were
examined. • Generally, most of the results from TLD measurements were
within 5% tolerance. • Differences between doses calculated by TPSs and measured
with TLD did not exceed 4% for bone and polystyrene equivalent materials.
• Under the lung equivalent material, on the beam axis the differences were lower than 5%, whereas within the lung and off the beam axis – in some cases were around 7%.
• For algorithms which use point kernel convolution/superposition and density variation in 3D with modeling of lateral electron and photon transport (CCC, AAA) the calculated doses were usually underestimated compared to the TLD measurements.
National audit system of TPS in Poland within the IAEA pogramme with the CIRS
Phantom
Ten radiotherapy centres , seven TPS systems with various algorythms. Test cases were planned and measured for 31 combinations of beams of various energies and various calculation algorythms.
IAEA SUPPORTED AUDIT OF TPS IN POLAND
CC – Collapsed ConeAAA –Anisotropic Analytic AlgorithmPBC – Pencil Beam ConvolutionFPH – Fast Photon AlgorithmFFT – Fast Fourier Transform Convolution
31 combination of TPS x algorithm x beam energy were tested in 10 audited centers
0% 20% 40% 60% 80% 100%
CC4
FFT4
PBC4
AAA 6MV
AAA 6MV
AAA 6MV
CC 6MV
CC 6MV
CC 6MV
CC 6MV
CC 6MV
FFT 6MV
PBC 6MV
PBC 6MV
PBC 6MV
PBC 6MV
FPH 6MV
AAA 15MV
AAA 15MV
AAA 20MV
CC 15MV
CC 15MV
CC 15MV
CC 15MV
CC 15MV
FFT 15MV
PBC 15MV
PBC 15MV
PBC 15MV
PBC 15MV
FPH 15MV
TP
S c
alc
ula
tio
n a
lgo
rith
m, b
ea
m e
ne
rgy
% OF CASES PASSING THE TESTS
IAEA SUPPORTED AUDIT OF TPS IN POLAND
CC – Collapsed ConeAAA –Anisotropic Analytic AlgorithmPBC – Pencil Beam Convolutionother:FPH – Fast Photon AlgorithmFFT – Fast Fourier Transform Convolution
31 combination of TPS x algorithm x beam energy were tested in 7 audited centers
0%
20%
40%
60%
80%
100%
CC AAA PBC other
TPS calculation algorithm
% O
F R
ES
UL
TS
PA
SS
ING
TH
E
TE
ST
S
4-10MV
15-20 MV
0%
5%
10%
15%
20%
25%
30%
35%
40%
CC AAA PBC other
TPS calculation algorithm
FR
AC
TIO
N O
F R
ES
UL
TS
OU
TS
IDE
A
CC
EP
TA
NC
E
4-10MV
15-20 MV
IAEA SUPPORTED AUDIT OF TPS IN POLAND
CC – Collapsed ConeAAA –Anisotropic Analytic AlgorithmPBC – Pencil Beam Convolutionother:FPH – Fast Photon AlgorithmFFT – Fast Fourier Transform Convolution
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Case 1 Water Point 3 (0°)
Case1 Lung Point 9 (0°)
Case1 Bone Point 10 (0°)
Case 2 Water Point 1 (0°)
Case 2 Water Point 3 (0°)
Case 4 Water Point 5 (0°)
Case 4 Water Point 5 (90°)
Case 4 Water Point 5 (180°)
Case 4 Water Point 5 (270°)
Case 4 Water Point 5 SUM
Case 4 Lung Point 6 (0°)
Case 4 Lung Point 6 (90°)
Case 4 Lung Point 6 (180°)
Case 4 Lung Point 6 (270°)
Case 4 Lung Point 6 SUM
Case 4 Bone Point 10 (0°)
Case 4 Bone Point 10 (90°)
Case 4 Bone Point 10 (180°)
Case 4 Bone Point 10 (270°)
Case 4 Bone Point 10 SUM
Case 5 Water Point 2 (0°)
Case 5 Lung Point 7 (0°)
Case 6 Water Point 3 (45°)
Case 6 Lung Point 7 (45°)
Case 6 Bone Point 10 (45°)
Case 7 Water Point 5 (0°)
Case 7 Water Point 5 (90°)
Case 7 Water Point 5 (270°)
Case 7 Water Point 5 SUM
Case 8 Water Point 5 (30° Table 90°)
Case 8 Water Point 5 (G90)
Case 8, Water, Point 5, (Gantry 270°)
Case 8 Water Point 5 SUM
tes
t
% of Audits PASS
IAEA SUPPORTED AUDIT OF TPS IN POLAND
0
1
2
3
4
5
6
7
8
9
10
100% 80% 60%
%PASS
Nu
mb
er
of
au
dit
ed
co
mb
ina
tio
ns
o
f b
ea
m, T
PS
, alg
ori
thm
Conclusions
• Over the last 20 years the postal TLD audits fulfilled their role and remain the primary and well established dosimetric audit method;
• The measurements allow to the detect limitations of TPS calculation algorithms. The audits performed with the use of the IAEA heterogeneous phantom seem to be an effective tool for detecting errors in radiotherapy procedures.
• The variety of new sophisticated heterogenous phantoms allow for thorough testing of TPS performance, for detecting computing algorithm’s limitations and corrections in treatment planning procedures.
• New irradiation modalities (tomotherapy, CyberKnife, etc.) require specific methods of dosimetric audits which are now being elaborated in a number of radiotherapy centres.
Maria Skłodowska-Curie Memorial Cancer Centre and Institute of Oncology, Warsaw, Poland
8th ECMP, Athens, 11-13.09.2014
Thank you for your attention
W. Bulski, K. Chełmiński, J. RostkowskaMedical Physics Department