ESTRO 36 Abstract Book

226 / 1082

S213 ESTRO 36 2017
_______________________________________________________________________________________________
with 131-I [2]. A very recent approach is the use of CLI for
the analysis of ex vivo fresh tumor specimens removed
during neurosurgery [3].
From the radiotherapy side there has been considerable
interest in the possible use of CLI to monitor external-
beam radiation therapy. The main dosimetric parameters
that could be measured are the percent depth dose (PDD)
and the lateral dose profile of the radiation beam. It has
been hypothesized that these parameters can be directly
measured by imaging the CR induced in a water phantom
as a surrogate of the dose.
In the literature it has been shown that due to the
anisotropy of the CR emission some differences arise
between the CR-derived and the true dose profiles, these
differences in the PDD and lateral dose profile can be
taken into account by using correction factors derived
from Monte Carlo simulations [4].
A more practical approach to reduce the effect of
Cerenkov emission anisotropy is adding a CR-excitable
fluorophore to the water in the phantom, the addition of
a fluorophore allows more accurate estimation of the PPD
[5].
The use of CLI for real-time portal imaging during
CyberKnife radiation therapy was also investigated by
irradiating a water tank phantom. Imaging at 30 frames
per second was acquired showing that CLI is a feasible tool
to image dynamic and static objects [6].
An interesting development is the use of CR to visualize in
real time the dose delivery during radiation therapy [7],
more precisely it has been shown that it is possible to
visualize the surface dose during the treatment.
In conclusion, the use of CLI in the RT field could lead to
a novel approaches to perform QA and real time in vivo
dosimetry
References
[1] Jelley JV 1958 Cerenkov Radiation and Its
Applications (London: Pergamon)
[2] Spinelli, AE, Ferdeghini, M, Cavedon, C, Zivelonghi, E,
Calandrino, R, Fenzi A. et al, First human
Cerenkography. J Biomed Opt. 2013;18:020502.
[3] Spinelli AE, Schiariti MP, Grana CM, Ferrari M,
Cremonesi M, Boschi F. Cerenkov and radioluminescence
imaging of brain tumor specimens during neurosurgery.J
Biomed Opt. 2016 1;21(5):50502.
[4] Glaser AK, Davis SC, McClatchy DM, Zhang R, Pogue
B.W. Gladstone, D.J. Projection imaging of photon beams
by the Cerenkov effect. Med Phys. 2013;40:012101.
[5] Glaser AK, Davis SC, Voigt WH, Zhan R, Pogue BW,
Gladstone DJ Projection imaging of photon beams using
Čerenkov-excited fluorescence. Phys Med Biol.
2013;58:601–619.
[6] Roussakis Y, Zhang R, Heyes G, Webster G, Mason S,
Green S, Pogue B, Dehghani H. Real-time Cherenkov
emission portal imaging during CyberKnife®
radiotherapy. Phys Med Biol. 2015 Nov 21;60(22):N419-
25.
[7] Jarvis LA, Zhan R, Gladstone DJ, Jiang S, Hitchcock
W, Friedman O.D. et al . Cherenkov video imaging allows
for the first visualization of radiation therapy in real
time. Int J Radiat Oncol Biol Phys. 2014;89:615–622.
Symposium: Adaptive radiotherapy (both anatomical
and ‘functional’ changes)
SP-0404 Development and Clinical Implementation of
Image Registration and Dose Accumulation
K. Brock1
1 MD Anderson Cancer Center, Imaging Physics, Houston,
USA
Image registration is challenging in simple cases of
deformable tissues. In the presence of anatomical and
functional changes, these challenges can substantially
increase. This presentation will evaluate the translation
of standard deformable image registration techniques to
challenging cases of anatomical and function
response. Limitations of the techniques in the adaptive
scenario will be discussed and validation techniques will
be described. Although all registration techniques have
uncertainties, once understood and quantified, the
clinical application of these registration techniques can
often improve the treatment in the adaptive radiotherapy
treatment paradigm. One of the primary uses of
deformable image registration for adaptive radiotherapy
is dose accumulation, including the accumulation of dose
assessed on each treatment fraction as well as the
propagation of the initially planned dose onto the adaptive
or replanning image. This process generates a wealth of
data that can overwhelm a clinical process. Strategies will
be discussed for distilling this data down into meaningful
data that can be clinically evaluated. This presentation
will also illustrate dose accumulation workflows that are
clinically feasible as well as the use of deformable
registration for dose propagation between an initial and
adaptive planning image.
Objectives for this presentation include:
1. Describing techniques and limitations of image
registration in the presence of anatomical and functional
changes
2. Addressing the question: how accurate is accurate
enough for clinical use
3. Illustrating a workflow for dose accumulation that is
clinically feasible 4. Strategies for reporting dose
accumulation results
SP-0405 Adaptive strategies to account for anatomical
changes
J.J. Sonke 1
1Netherlands Cancer Institute, Radiotherapy
department, Amsterdam, The Netherlands
Geometric uncertainties limit the precision and accuracy
of radiotherapy. In room imaging techniques are now
readily available to reimage the patient prior to and
during treatment. Typically, these images are used to
reposition the patient and thus minimize target
misalignment. Anatomical changes, however, frequently
occur during treatment but cannot be accurately
corrected for using a couch shift. Adaptive radiotherapy,
on the other hand, utilizes an imaging based feedback loop
to adjust the treatment plan and thus has to potential to
account for such anatomical changes. In this presentation,
the magnitude and frequency of anatomical changes will
be exemplified and various adaptive protocols will be
described. Finally, current challenges and future
perspective of adaptive strategies to account for
anatomical changes will be discussed.
SP-0406 Adaptive strategies to account for functional
changes
I. Toma-Dasu1
1Karolinska Institutet, Medical Radiation Physics,
Stockholm, Sweden
The progress and technological development of functional
and molecular techniques for imaging tumours has offered
the possibility of redefining the target in radiation therapy
and devising the treatment in an innovative manner
accounting for relevant biological information on
metabolic, biochemical and physiological factors known to
be related to poor treatment response. Thus, dose
painting approaches have been proposed based on the
hypothesis that local recurrence is related to resistant foci
not eradicated by the currently prescribed doses, which
might however be controlled by delivering non-
homogeneous dose distributions targeting specific tumour