ESTRO 36 Abstract Book

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S413 ESTRO 36
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difference between NFS and EFS was about 6% for 5 mm
field size. Penumbra values were lower than 3 mm for field
sizes up to 15 mm.
Conclusion
Conclusions: CyberKnife OFs measured by Razor showed a
high consistency among different centers and a
comparable variability to data obtained by PTW-60017
routine detector. Comparison between Razor OFs and
PTW-60017 measurements corrected by Monte Carlo
indicated that correction factors for Razor should be
smaller than for PTW-60017 down to 7.5 mm field size. EFS
and penumbra measured over the four centers showed a
good consistency confirming Razor as a good candidate for
small beam relative dosimetry.
PO-0779 New robotic phantom for evaluation of
imaging and radiotherapy of moving structures
H. Arenbeck1, L. Eichert1 , G. Hürtgen2, K. Gester2, I.
Brück2, N. Escobar-Corral2, M. Fleckenstein1, A. Stahl3,
M.J. Eble2
1 Boll Automation GmbH, Research and Development,
Kleinwallstadt, Germany
2 RWTH Aachen University Hospital, Radiooncology and
Radiotherapy, Aachen, Germany
3 RWTH Aachen University, III. Institute of Physics B,
Aachen, Germany
Purpose or Objective
Four dimensional radiotherapy processes that allow an
adaptation to intrafractional motion require increased
accuracy of dose application while displaying increased
technological and procedural complexity and thus
multiplied sources of error. Consequentially, novel 4D
phantoms are required that feature anthropomorphic
structure and motion. In this work, a prototype of such
phantom, which is fit for long term clinical service, is
presented.
Material and Methods
The modular phantom architecture allows different static
and moving human equivalent structures and dose
measurement devices to be placed into the irradiated
region. A new kind of parallel robot generates freely
programmable motion in all Cartesian directions. The
whole system is portable and features similar extension as
a human. Concept, kinematics, construction and software
of a previously presented evaluation model have been
fundamentally refined.
Results
The new components of the robotic phantom are
presented in figure 1. Major technological advancements
with respect to the evaluation model are:
• Robot: A novel kinematic structure has been
found, which reduces the number of joints and
increases stiffness of the mechanics. A fatigue
endurable mechanical construction has been
created. Rapid exchange of the Target core and
inclusion of tethered measurement devices are
now possible via the hollow end effector.
• Modularization: Body and Target can now be
assembled manually and rapidly while ensuring
an absolute positioning accuracy of < 0.1 mm.
Third party phantom structures can be
incorporated and accounted for in a
customizable collision control.
• Software: A control software release has been
developed featuring extended functions,
simplified usage and platform independence.
Figure 2 shows the phantom in a clinical setup. A static
and a respiratory gated CT were performed. Respiration
surrogates were acquired using the C-Rad Sentinel System.
Furthermore, a Cone Beam CT mounted at a linear
accelerator was obtained.
Figure 1: Structure of the robotic phantom
Figure 2: Results of medical imaging
Conclusion
First applications of the phantom under clinical conditions
and purposes revealed feasible physical properties,
functional range and applicability. The platform
technology of the phantom has reached prototype
maturity and can be flexibly adapted to a broad range of
clinical scenarios. For example, both little and high
complexity of human equivalent structure and motion,
both film and ion chamber dosimetry, both air and fluidic
environments, optionally containing radioactive tracers,
are supported. A unique feature of the phantom is its
combination of the described high flexibility with practical
feasibility, efficiency and robustness. Next, real time
robot control capabilities will be extended and clinical
long term studies will be performed.
PO-0780 Feasibility study of beam monitoring system
using AFCRS for proton pencil beam
J.M. Son1, M.Y. KIM2, M.G. Yoon3, D.H. Shin1
1National Cancer Center, Proton therapy Center,
Goyang-si- Gyeonggi-do, Korea Republic of
2Dongnam Inst. Of Radiological & Medical Sciences,
Research Center, Busan, Korea Republic of
3Korea University, Bio-convergence engineering, Seoul,
Korea Republic of