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The influence of the MRL fringe field is less than described
by Kok for the pre-clinical prototype, but does still
influence the beam steering of the accelerators in
adjacent treatment rooms. The LUTs of 2 accelerators,
that were situated the closest to the MRL, but outside the
0.5 Gauss line, needed to be adjusted in order to get beam
parameters within tolerances. Adjusting the LUTs fully
corrected the influence of the magnetic fringe field of the
MRL. In case of an unexpected ramp down of the magnet
(i.e. quench) both neighbouring accelerators cannot be
used clinically before the LUTs are adjusted to the new
situation. Adjustment of the LUT can be done in a short
time by experienced personnel, without a dedicated
measurement
device.
References:
Kok et al., Phys. Med. Biol.
54
(2009) N409–N415
OC-0439 Treating patients with Dynamic Wave Arc: first
clinical experience
M. Burghelea
1
, D. Verellen
2
, J. Dhont
1
, C. Hung
3
, K.
Poels
4
, R. Van den Begin
1
, M. Boussaer
1
, K. Tournel
1
, C.
Jaudet
1
, T. Reynders
1
, T. Gevaert
1
, V. Simon
5
, M. De
Ridder
1
1
Universitair Ziekenhuis Brussel- Vrije Universiteit
Brussel, Department of Radiotherapy, Brussels, Belgium
2
GZA Ziekenhuizen- Sint Augustinus – Iridium
Kankernetwerk Antwerpen, Radiotherapy Department,
Antwerpen, Belgium
3
Brainlab AG- Feldkirchen- Germany, R&D RT Motion
Management, Munich, Germany
4
University Hospitals Leuven, Department of Radiation
Oncology, Leuven, Belgium
5
Babes Bolyai University, Faculty of Physics, Cluj-
Napoca, Romania
Purpose or Objective
Dynamic Wave Arc (DWA) is a system-specific non-
coplanar arc technique that combines synchronized
gantry-ring rotation with D-MLC optimization. This paper
presents the clinical workflow, quality assurance program,
and reports the geometric and dosimetric results of the
first patient cohort treated with DWA.
Material and Methods
The RayStation TPS was clinically integrated on the Vero
SBRT platform for DWA treatments. The main difference
in the optimization modules of VMAT and DWA relates to
angular spacing, where the DWA optimization algorithm
does not consider the gantry spacing, but only the
Euclidian norm of the ring and gantry angle. To support
DWA deliveries, the Vero system required some additional
upgrades: an MLC secondary feedback unit upgrade
allowing faster dynamic MLC leaf movement of up to 4
cm/s at isocenter level, and a machine controller offering
gantry-ring synchronous rotations.
The first 15 patients treated with DWA represent a broad
range of treatment sites: breast boost, prostate, lung
SBRT and bone metastases, which allowed us to explore
the potentials and assess the limitations of the current
site-specific DWA template solution. Table 1 provides
further information for each patient case including the
corresponding DWA plan information, while Figure 1
presents the most common used DWA trajectories. For the
DWA verification a variety of QA equipment was used,
from 3D diode array to an anthropomorphic end-to-end
phantom. The geometric accuracy of each arc was verified
with an in-house developed method using fluoroscopy
images.