ESTRO 36 Abstract Book

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S971 ESTRO 36 2017
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On figures:
a) Assembly for rapid strand radioactivity measurement.
1- short transport container; 2- tweezers to hold strand;
3- cylindrical tube (barrel); 4- sterile coating; 5- plastic
container; 6- rapid strand seeds; 7- well-chamber. b)
Measured values of Rapid strand seeds radioactivity. c)
Strand cutting procedure devices. 8- Transport container
with cut-outs for 'safely and clean outside cutting” of
required strand; 9- spacing jig; 10- seat for container to
prevent its rotation on the table; 11- cut-out for finger in
container to prevent rotating of spacing jig inside the
container. d) Removing of cut-up strands from container.
12- container; 13- metal shielding cover; 14- lead glass;
15- seat for container.
Results
Summarizing the measurement of every single seed
activity might be found the intra-op calibration factors for
rapid strand (containing 4/5/6 seeds) inserted into well-
chamber. They are: total activity 2,20 mCistrand 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. Otal1, J. Richart1, C. Domingo1, S. Rodriguez 1, P.
Rodriguez-Meijide2, I. Fotina2, M. Santos1, J. Perez-
Calatayud3
1 Hospital Clinica Benidorm, Radiotherapy, Benidorm,
Spain
2 Eckert & Ziegler BEBIG GmbH, Marketing, Berlin,
Germany
3Hospital 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 ).
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