ESTRO 36 Abstract Book

S420 ESTRO 36 2017 _______________________________________________________________________________________________

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 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. Moutinho 1 , H. Freitas 1 , J. Melo 1 , J.F.C.A. Veloso 1 , P.J. Rachinhas 2 , P.C.P.S. Simões 2 , J.A.M. Santos 3 , A. Pereira 3 , J. Silva 3 , S. Pinto 3 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.

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 Fez 1 , M.A. Duch 2 , N. Jornet 1 , M. Lizondo 1 , T. Eudaldo 1 , A. Latorre-Musoll 1 , C. Cases 1 , A. Ruiz 1 , M. Ribas 1 1 Hospital de la Santa Creu i Sant Pau, Servei de Radiofísica i Radioprotecció, Barcelona, Spain 2 Universitat 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). To assess the impact of 2 table tops for these techniques. 2.

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

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