Abstract Book

S1235

ESTRO 37

are calibrated simultaneously). Measured correction factor for R1 diode in B setup are 1.213 and 1.205 for probes T9112- 1725 and 9112-1469 respectively. It gives differences 7.2% and 6.4% with pure inverse square law values, or 6.8±0.5% is the averaged lack scatter factor for R1 diode. The similar measurements for R2 diode were done: the averaged lack scatter factor is 1.5±0.5%. Conclusion Using PTW MultiSoft Software for simultaneously calibration of PTW T9112 five-fold semiconductor rectum probe ( correction algorithm based on inverse square law ) without taking into account lack scatter factor PTW 9193 type phantom for semiconductor detectors results to unexpectedly high systematic errors in diode calibration coefficients: 6.8±0.5% for R1, R5 diodes and 1.5±0.5% for R2, R4 detectors. EP-2235 Commissioning of the first Papillon+ for breast intra operative radiotherapy unit C. Dejean 1 , M. Gautier 1 , W. Ouakkad 1 , D. Lam Cham Kee 1 , J. Gérard 1 1 Centre Antoine Lacassagne, Academic Physics, Nice, France Purpose or Objective Purpose: to report commissioning of first Papillon+ ™ (Ariane Medical Systems) unit for breast IORT. Material and Methods Materials and methods: Papillon + is using low energy x rays to deliver intra operative treatment for breast cancer. It uses a switchable 30/50 kV Xray generator and an hollow rod anode tube (rhenium target) associated with spherical applicators ranging from 30 to 50 mm diameters. Measurements were realised with a calibrated plane parallel ionisation chamber (PTW 23342) associated to Unidos E electrometer (PTW) and s Soft XRay Slab phantom or gafchromic films EBT3. Were measured repeatability, reproducibility, half value layer (HVL), homogeneity, output and delivery time by an independent chronometer. To mimic reference conditions presented in IAEA TRS398, for each applicator diameter, the equivalence thickness was designed to be positioned at the exit of the Xray tube (micronode). This accessory will permit an easier way of measurement. Results Results: security tests were conform with the IEC60601, especially concerning treatment interruption. Only results concerning 50kV (energy clinically used) are presented here. Repeatability of results were lower than 1% and reproducibility 1.5%. Applicator diameter (mm) FSD (mm) HVL (mmAl) 30 15 0.65 35 17.5 0.75 40 20 0.85 45 22.5 1 50 25 1 Table1: results obtained for the different applicators If we compare the spherical applicator to a terrestrial globe, the results of homogeneity for a 35mm and a 45mm applicator diameter are respectively : in latitude 7.3% and 6.5%; in longitude 7.4% and 4.7%. Dose rate in reference conditions (30mm diameter applicator) will be settled to 30Gy/min by adjusting mA level. Conclusion Characteristics of this new device are congruent with medical physics expectations. The characteristics of this new device make it possible to deliver intraoperative treatments in senology for a dose of 20Gy in less than 2 minutes. The anaesthesia duration is thus little

Electronic Poster: Brachytherapy: Physics

EP-2234 Measurement of lack scattering factor for PTW 9193 INVIVO phantom in irridium-192

brachytherapy V. Stserbakov 1

1 North-Estonian Regional Hospital Cancer Center, Department of Radiotherapy and Oncology, Tallinn, Estonia Purpose or Objective The size of PTW 9193 type afterloading calibration phantom is much smaller than size of big water phantom for which it is assumed that 'full scattering conditions” are executed and due to 'lack of scattering” for afterloading phantom it can be expected that inverse square law works very roughly in this case. The purpose of this work to measure lack scattering factor for R1 and R5 INVIVO diodes of PTW T9112 rectum probe when all 5 detectors are calibrated simultaneously . Material and Methods Two setups of adapter for five-fold semiconductor rectum probe (Fig., 1), are used: first (Fig., A), when probe with adapter was situated in its ordinary position (R3 diode located just opposite the radiation source 3, in closest position to the source, like a Farmer chamber 4, and , second (Fig., B), where diodes with adapter was shifted up by 3 cm, using insert tube (Fig., 6), and where in this case R1 diode is positioned in opposite and closest position to the radiation source. 2 cm diameter acrylic cylinder (Fig., 5) used as a scattering conditions compensator. For excluding angular dependence of diodes sensitivity the fluoroscopic imaging was done to find and take into account detector angle sensitivity plateau (angle 0°). Measurements were done for 0° and 180° degree detector positions. Results were averaged in order to eliminate non-symmetric diode location inside the cable. MultiSoft Software (S09002) program calibration procedure was used for calibration R1 detector when all 5 diodes (R1-R5) are calibrated simultaneously. Calibration of R1 diode in B and A setups we consider as true and approximate respectively and difference between these calibrations gives us 'lack scattering” factor. It was used the GammaMed Plus afterloader (Ir-192). As a reference chamber was taken the 0.6 cc Farmer chamber placed inside the adapter (Fig., 4) on the opposite side of the phantom. Figure. PTW 9193 phantom setups A and B for diodes calibration.

Results For measurements it was used two rectal probes. Correction factors for R1, R5 and R2, R4 detectors stored in MultiSoft Software are: 1.1406 and 1.0343 respectively (as results of exact inverse square law calculations of software in calibration procedure when all 5 detectors