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S985
ESTRO 36
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rapid strand (containing 4/5/6 seeds) inserted into well-
chamber. They are: total activity 2,20 mCi
strand of 4 seeds
produce 121,4 pC/10s corrected for pressure and
temperature reading of electrometer, overall activity 3,28
mCi
strand of 6 seeds
gives 181,6 pC/10s corrected for pressure
and temperature reading of electrometer.
Conclusion
Described quality control procedure provide confidence
that total seeds radioactivity of implanted into patient in
LDR brachytherapy procedure correspond to intended
value. Sterile conditions for rapid strands are guaranteed
and therefore procedure can be accepted for intra-op
using. The exposure dose received by personal during this
procedure is negligibly small.
EP-1795 A novel MRI markers system in applicator
reconstruction for brachytherapy
A. Otal
1
, J. Richart
1
, C. Domingo
1
, S. Rodriguez
1
, P.
Rodriguez-Meijide
2
, I. Fotina
2
, M. Santos
1
, J. Perez-
Calatayud
3
1
Hospital Clinica Benidorm, Radiotherapy, Benidorm,
Spain
2
Eckert & Ziegler BEBIG GmbH, Marketing, Berlin,
Germany
3
Hospital Clinica Benidorm/Hospital La Fe,
Radiotherapy, Benidorm/Valencia, Spain
Purpose or Objective
ABS and GEC-ESTRO recommend magnetic resonance
imaging (MRI) in T2-sequence as preferable modality in
image-guided
brachytherapy
for
gynecological
malignancies. On the other hand, widespread availability
of the applicator libraries in the brachytherapy treatment
planning systems (TPS) allows global approach to the issue
of the applicator modeling. The aim of this work is to
present a method to incorporate complete applicator
geometries in SagiPlan, (not only single channels), based
on the technical data available from manufacturer and
then develop a marking system which allows recognizing a
defined applicator (Vienna-type applicator of Eckert &
Ziegler BEBIG) in the MR image series with utmost possible
precision for the library reconstruction.
Material and Methods
The investigated applicator model is Vienna-type
applicator, consisting of tandem with a ring for possible
interstitial component from Eckert&Ziegler BEBIG (Berlin,
Germany) together with a model available in the library of
the SagiPlan® TPS from Eckert&Ziegler BEBIG.
3D model of the applicator was reconstructed
independently, using open-source modeling software
FreeCAD
(www.freecad.org).
The presented reconstruction technique is based on the
placement of three vitamin A capsules, clearly visualized
in T2 MRI, embedded in the material layer giving enough
contrast for the capsule recognition. The position of the
marking capsules with respect to the applicator geometry
is known precisely, due to placement of the attachments
in 3D model reconstructed in FreeCAD and verified against
technical specifications of the applicator. The accessory
attachments to the applicator are produced on the 3D
printer from polylactide polymer material (PLA) and carry
the marking capsules inside.
Results
In order to validate the accuracy of the reconstruction
with use of the model described above, we acquired T2
MRI sequence of the Vienna applicator in water with
accessory attachments in place. The images were entered
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.