ESTRO 36 Abstract Book

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S409 ESTRO 36 2017
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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
Purpose or Objective
PBS, recently developed, scans a tumor with very precise
beam of protons that’s accurate within millimeters,
sparing the healthy surrounding tissues. But it is able to
harmful rather than conventional radiotherapy if the beam
is not accurately irradiated as planned. It is very important
to measure beam width and spot center of the proton
pencil beam for the accurate delivery of dose to the target
volume with a good conformity. We have developed the
beam monitoring system using Array of Fiber-Optic
Cerenkov Radiation Sensor (AFCRS), and conducted
feasibility study for proton pencil beam.
Material and Methods
We have developed a fine segmented detector array to
monitor PBS. A prototype beam monitor system using
AFCRS has been developed for real-time display of the
pencil beam status during the PBS mode operation. The x-
y monitoring system with 128 channel readout is mounted
to the snout for the in-situ real time monitoring. Beam
widths and spot centers of various energies are measured.
Two dimensional Gaussian fit is used to analyze the beam
width and the spot center. The ability of this system to
evaluate Lynx system (Scintillator-based sensor with CCD
camera) and EBT3 for PBS was compared.
Results
The measured Gaussian widths using AFCRS changes from
13 to 5 mm for the beam energies from 100 to 226 MeV.
The beam widths of PBS using the AFCRS are well matched
with the data acquired by a Lynx system and EBT 3 film.
In addition, spot centers for 226 Mev PBS beams are also
well matched with RTP system.
Conclusion
The dosimetric performance of the newly developed
system based on AFCRS was comparable to that of the Lynx
system and EBT3 film. Not only measuring the spot profile
but also monitoring dose map by accumulating each spot
measurement will be available.
PO-0781 A characterisation of EBT3 Gafchromic film for
relative and absolute dosimetry
I. Billas1, H. Bouchard2, A. Subiel1, I. Silvestre1, S. Duane1
1National Physical Laboratory, Radiation Dosimetry,
Middlesex, United Kingdom
2Université de Montréal, Département de physique,
Montréal, Canada
Purpose or Objective
The aim of this work is to investigate the variation in dose
response of Gafchromic EBT-3 film within each film and
across films from different boxes and lots. In this way the
uncertainty of relative and absolute dosimetry using EBT-
3 film is quantified and its potential for use in small field
and MRI-guided radiotherapy is better understood.
Material and Methods
Sheets of Gafchromic EBT-3 film were uniformly irradiated
in a cobalt-60 beam in increments of 1 Gy up to a
cumulative dose of 10 Gy. Films were scanned repeatedly
before the first irradiation and after each step. Software
for image processing and analysis was implemented in