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ESTRO 36 2017
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HDR brachytherapy, using a phase-only cross correlation
localization method.
[1] Beld E. et al. 2015 Proc. Intl. Mag. Reson. Med. 24,
#4151.
[2] De Oliveira A. et al. 2008 MRM
59
1043-1050.
OC-0276 Toward adaptive MR-guided HDR prostate
brachytherapy – Simulation study based on anatomy
movements
M. Borot de Battisti
1
, B. Denis de Senneville
2
, G.
Hautvast
3
, D. Binnekamp
3
, M. Peters
1
, J. Van der Voort
van Zyp
1
, J.J.W. Lagendijk
1
, M. Maenhout
1
, M.A.
Moerland
1
1
University Medical Center Utrecht, Departement of
Radiotherapy, Utrecht, The Netherlands
2
UMR 5251 CNRS/University of Bordeaux, Mathematics,
Talence, France
3
Philips Group Innovation, Biomedical Systems,
Eindhoven, The Netherlands
Purpose or Objective
Dose delivery during a single needle, robotic MR-guided
HDR prostate brachytherapy may be impaired by: (1)
needle insertion errors caused by e.g. needle bending, (2)
unpredictable anatomy movements such as prostate
rotations (induced by the insertion or retraction of the
needle), prostate swelling or intra-procedural rectum or
bladder filling. In this study, a new adaptive dose planning
strategy is proposed to assess the second challenge. The
performance of this approach is evaluated by simulating
brachytherapy procedures using data of 10 patients
diagnosed with prostate cancer.
Material and Methods
Throughout HDR prostate brachytherapy, unpredictable
anatomy movements may cause errors in dose delivery and
potentially, this may result in failure to reach clinical
constraints (e.g. for single fraction monotherapy: D95%
PTV>19 Gy, D10% urethra<21 Gy, D1cc bladder<12 Gy and
D1cc rectum<12 Gy). In this study, a novel adaptive dose
planning pipeline for MR-guided HDR prostate
brachytherapy using a single needle robotic implant
device is proposed to address this issue (Figure 1a). The
dose plan (needle track positions, source positions and
dwell times) and needle insertion sequence are updated
after each needle insertion and retraction with MR–based
feedback on anatomy movements (cf. Figure 1b). The
pipeline was assessed on moving anatomy by simulating
MR-guided HDR prostate brachytherapy with varying
number of needle insertions (from 2 to 14) for 10 patients.
The initial anatomy of the patients was obtained using the
delineations of the prostate tumor and the OAR considered
(urethra, bladder and rectum) on MR images. Each needle
insertion and retraction induced anatomy movements
which were simulated in 2 steps: (1) a typical 3D rotation
of the prostate was imposed (2) a regularization of the
movement in space was then applied. The initial and final
dose parameters were compared in the situations with and
without update of dose plan and needle insertion
sequence.
Results
The computation time for re-planning was less than 90
seconds with a desktop PC. The actual delivered dose
improved with vs. without update of dose plan and needle
insertion sequence: On average, the dose coverage of the
PTV was higher in the situation with vs. without update
(Figure 1c). Moreover, the difference increased with the
number of needle insertions. The dose received by the PTV
in the situation with re-planning was not significantly
different compared to the initial dose plan. Finally, the
dose to the OAR’s was not significantly different between
the initial dose plan and the dose delivered in the situation
with and without update.
Conclusion
This study proposes a new adaptive workflow with
feedback on the anatomy movements for MR-guided HDR
prostate brachytherapy with a single needle robotic
implant device. The assessment of the pipeline showed
that the errors in the dose delivered due to movement of
anatomy can be compensated by updating the dose plan
and the needle insertion sequence based on MRI.