988 / 1082
S972
ESTRO 36 2017
_______________________________________________________________________________________________
in the SagiPlan® TPS in order to perform the applicator
reconstruction based on the markers and pre-defined
template, based on the 3D applicator model, loaded in
SagiPlan®.
The presented technique could be expanded to any rigid
applicator and other image modalities, under condition of
the adequate selection of the markers. It is necessary to
mention, that positioning of the accessory attachments on
the applicator is very easy and does not affect integrity or
other characteristics of the product.
Conclusion
We designed several accessory attachments for the
markers to be placed on Vienna applicator, which allow
easy, fast and precise reconstruction. This technique can
be expanded for other applicator types. Additionally it
permits to resolve the practical issue of the marker
availability for the reconstruction in MRI
.
EP-1796 Dosimetric comparison between TG43/TG186
algorithms and manual/inverse optimization in
brachytherapy
T. Brun
1
, E. Torfeh
1
1
Institut Universitaire du Cancer Toulouse - Oncopole,
DIPM, Toulouse, France
Purpose or Objective
For brachytherapy planning treatment, different types of
algorithms are used for calculate and optimize the dose
distribution. In Toulouse, reference treatment plans are
calculated with the software Oncentra Brachy which is
based on the formalism TASK GROUP 43 (TG43) and
manual optimization.
The aim of this project is to compare two algorithms dose
calculation: TG43, which does not take into account the
heterogeneities vs. TG186, which takes into account the
heterogeneities. This comparison was realized for
gynecological, anal canal, prostate, H&N and skin
treatments in order to strengthen clinical practices on the
prescribed dose.
Finally, in order to improve the dosimetric quality and
harmonize clinical practices, a second study was done to
evaluate the difference between a manual optimization
and an automatic inverse optimization algorithm with
Hybrid Inverse Planning Optimization (HIPO).
Material and Methods
For this study, 38 patients dose plans were calculated with
the reference dosimetry using the TG43 and a manual
optimization. A dosimétric comparaison for each plans was
done with the dose calculation algorithm based on the
TG186 and the optimisation algorithm HIPO.
Finally, to study the conformity and consistency of the
different algorithms, both COnformity INdex (COIN) and
Homogeneity Index (HI) were calculated for the different
cases.
Results
Considering the comparison between the TG43 and TG186
and the most relevant criteria, dosimetric data does not
show a significant difference for gynecological, anal canal,
prostate, H&N and skin plans. But results for prostate and
H&N plans were relevant: a decrease of 13.75% for V50Gy
with the TG186 is obtained. This difference is accentuated
with the high dose. For the lead, an increase of 21.6% for
D25% with the TG186 is obtained (Fig 1).
Regarding the optimization algorithms HIPO/manual and
considering the most relevant criteria, there is no
significant difference on the target volumes on the D90%.
For the two optimizations, the mean value respects the
dosimetric constraints for the 5 cases of treatment
(difference of 4.3% for the gynecological case, 4.4% for the
anal canal case, 1.2% for the prostate case, 0.7% for ENT
case, and 6.4% for skin case). Furthermore, the inverse
optimization algorithm HIPO shows less fluctuation with
respect to manual optimization and results are more
homogeneous. The value obtained for the COIN and HI for
HIPO were higher than those obtained for a manual
optimization in the 5 cases especially for the prostate case
(Table 1).
Conclusion
The difference between the TG43 and the TG186 is for
most clinical cases not significant for target volumes and
OARs except sources in the case of the prostate, as well
as lead in cases of H&N. The use of HIPO optimization
algorithm has shown a real advantage in the robustness of
calculation. Moreover, HIPO enables a reduced dwell time
by position, so a total treatment time shorter than the
ones obtained with manual optimization.
EP-1797 Dosimetric characterization of MOSFET
detectors for Ir-192 and feasibility for in vivo dosimetry.
R. Fabregat Borrás
1
, S. Ruiz-Arrebola
1
, M. Fernández
Montes
1
, E. Rodríguez Serafín
1
, J.T. Anchuelo Latorre
2
,
M.T. Pacheco Baldor
1
, J.A. Vázquez Rodríguez
1
, M.M.
Fernández Macho
1
, D. Guirado
3
, P.J. Prada
2
1
Hospital Universitario Marqués de Valdecilla,
Radiophysics, Santander, Spain
2
Hospital Universitario Marqués de Valdecilla, Radiation
Oncology, Santander, Spain
3
Hospital Universitario San Cecilio, Radiophysics,
Granada, Spain
Purpose or Objective
There is a recognized interest in developing in vivo
dosimetry (IVD) as an effective method of independent
treatment verification for HDR BT treatments [1]. The
purpose of current study was to perform a dosimetric
characterization of MOSFET TN-502RDM from Best Medical
Canada in order to optimize their use in HDR BT
treatments delivered with the Ir-192 source contained in
Flexitron afterloader (Nucletron-Elekta).