ESTRO 36 Abstract Book

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S420 ESTRO 36 2017
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Conclusion
This abstract shows greater dosimetric differences due to
sinus filling in a 1.5T magnetic field for plans optimised
with an empty cavity. Without a B-field plans optimised
on full and empty cavities show similar results.
The dose to the PTV is also less conformal optimising on
an empty cavity due to hotspots caused by the ERE close
to the surface shown by a higher effect for the max dose
to 2% of the Target. The results indicate that optimising
with a full sinus cavity makes the plan more robust to the
Lorentz force and therefore to changes in filling.
PO-0797 Studies on optical fiber dosimeters for in-vivo
dosimetry in HDR brachytherapy
L. Moutinho1, H. Freitas 1, J. Melo1, J.F.C.A. Veloso1, P.J.
Rachinhas2, P.C.P.S. Simões2, J.A.M. Santos 3, A. Pereira3,
J. Silva3 , S. Pinto3
1 University of Aveiro, Physics Department, Aveiro,
Portugal
2 CHUC, Radiology, Coimbra, Portugal
3 IPO-Porto, Radiotherapy, Porto, Portugal
Purpose or Objective
Dose verification and quality assurance in radiotherapy
should be assessed in order to provide the best treatment
possible and minimize risks for patient. Notwithstanding,
due technical constraints in certain treatments there’s no
such tools capable to perform real-time dose
measurement. An ideal dosimeter for prostate
brachytherapy should provide real-time and in-vivo dose
measurement, present high sensitivity and no
dependencies on energy, dose and dose rate and
temperature. Also should be detectable in the anatomic
volume to check its position, easy to use and calibrate and
not expensive/disposable use of its implantable part.
Material and Methods
We developed a fiber optic dosimeter suitable for real-
time dose monitoring in breast and prostate
brachytherapy, thus opening the possibility for real-time
dose correction.
The dosimeter comprehends a sensitive optical fiber probe
of 1mm or 0.5 mm diameter where a 5 mm length
scintillating optical fiber is coupled. The clear optical
fiber providing scintillation light guidance into the
photodetectors.
Results
The first round of in-vitro tests in clinical ambient allowed
to demonstrate that fiber optical based dosimeters are
suitable for dosimetry in regimes such the ones in HDR
prostate brachytherapy. The versatility of this kind of
device and easiness of use allows application in other
radiotherapy modalities. The dosimeter response was
evaluated under irradiation with a 10.07 Ci Ir-192 HDR-
brachytherapy The dosimeter shows a linear response with
dose and is capable of detecting µGy dose variations like
an ionization chamber.
Conclusion
The first round of in-vitro tests in clinical ambient allowed
to demonstrate that fiber optical based dosimeters are
suitable for dosimetry in regimes such the ones in HDR
prostate brachytherapy. The versatility of this kind of
device and easiness of use allows application in other
radiotherapy modalities.
The dosimeter shows a linear response with dose and is
capable of detecting µGy dose variations like an ionization
chamber.
PO-0798 Identification of areas of high-risk skin toxicity
in SBRT and IMRT treatments
P. Carrasco de Fez1, M.A. Duch2, N. Jornet 1, M. Lizondo1,
T. Eudaldo1, A. Latorre-Musoll1, C. Cases 1, A. Ruiz1, M.
Ribas 1
1Hospital de la Santa Creu i Sant Pau, Servei de
Radiofísica i Radioprotecció, Barcelona, Spain
2Universitat Politècnica de Catalunya, Institut de
Ciències Energètiques, Barcelona, Spain
Purpose or Objective
The AAPM TG176 shows examples of dramatic unexpected
skin effects. This work is aimed:
1. To develop an in-phantom method to identify
what areas of skin could be exposed to high
doses and are of potential risk in order to decide
where to perform skin in vivo dosimetry on SBRT
(3DCRT) and IMRT treatments (sliding windows).
2. To assess the impact of 2 table tops for these
techniques.
Material and Methods
• Two Clinac 2100 CD (Varian) with the Exact
Couch, one with the Exact Couch top (carbon
fiber grid) and one with the IGRT Couch top
• EBT3 films+Film QA Pro 2014 Software
(Ashland)+EPSON EXPRESSION 10000XL scanner