ESTRO 36 Abstract Book

S766 ESTRO 36 _______________________________________________________________________________________________

melanoma patient with the lesion of 3-cm diameter localized in a sole of right foot. The superficial lesion was bordered by a catheter and covered with a water- equivalent bolus. Using treatment planning system SERA, the tumor is depicted as a region surrounded by the catheter with 5-mm thickness, and also skin is depicted as the other region except for tumor with 3-mm thickness from body surface. A water-equivalent bolus was delineated as water. This was placed into air in calculation in condition with no bolus. For comparison with bolus-like effect of a covered collimator, the outline of an imaginary collimator cover was set as a mass of polycarbonate or a water tank filled with water with 20-50-mm thickness. For calculation of photon-equivalent dose (Gy-Eq), blood 10B concentrations, 10B tumor/blood concentration ration, and CBE factor for 10B(n,α)7Li reaction were assumed to be 25 ppm, 3.5, 4.0. Tolerance dose of the skin was regarded as 18 Gy-Eq. Results In condition with no bolus, irradiation time was 121.6 min, and tumor Dmax and Dmean were 125 Gy-Eq, and 74.3 Gy- Eq, respectively. In condition with water-equivalent bolus technique, irradiation time was 72.1% decreased (33.9 min) compared with no bolus condition. Also tumor Dmax and Dmean were 54.4 Gy-Eq and 45.0 Gy-Eq, and the dose homogeneity was dramatically improved. Skin Dmax became greatly less than tolerable dose (11.5 Gy-Eq, 59.6% decrease).The bolus-like effect of covered collimator with a mass of polycarbonate or water tank was not sufficient. Dose homogeneity and irradiation time was largery worse than the condition with a water-equivalent bolus. Conclusion Although this study was examined for a single case of melanoma patient, our results revealed that water- equivalent bolus technique could have a great effectiveness on dose improvement of AB-BNCT for superficial cancers. EP-1437 New Cobalt-60 system for reference irradiations and calibrations C.E. Andersen 1 1 DTU Nutech Technical University of Denmark, Center for Nuclear Technologies, Roskilde, Denmark Purpose or Objective Cobalt-60 plays an important role as reference beam quality in radiation dosimetry and radiobiology. Only few systems are available on the commercial market for the therapeutic dose range (~1 Gy/min), and it is therefore of interest for research and calibration laboratories that a new irradiator (Terabalt T100 Dosimetric Irradiator) has been introduced by UJP Praha, Czech Rebublic. In 2013, DTU Nutech in Denmark acquired the first unit of this new model, and the purpose of this contribution is to report on (i) the main characteristics of this gamma irradiator found during the commissioning work, and on (ii) additional developments carried out in order to apply the irradiator for highly precise, automated (i.e. computer controlled) irradiations. Material and Methods The irradiator has a fixed horizontal beam axis about 110 cm above the floor. A collimator system enables field sizes from 5x5 cm 2 to 40x40cm 2 at the reference point at 100 cm from the source. The irradiator is equipped with a GK60T03 cobalt-60 source having an activity of 250 TBq corresponding to a dose rate of about 1.1 Gy/min at the reference point (Sep. 2016). The source is fully computer controlled. A special rig of 10x10 cm 2 aluminum profiles has been designed in collaboration with UJP Praha. This rig is equipped with a water-tank lift and an xyz-stage for precise positioning of ionization chambers and other dosimeters at the reference point. An optical system is

Figure 1 shows registered images of the original patient image (a), phantom 1 (b), and phantom 2 (c). Tissue density was more accurate in phantom 2, despite some small holes not being filled with bone resin.

Conclusion Two phantoms were created, one with a single material, and a second with two materials (tissue and bone). These two phantoms provide an ability to more closely simulate the patient and provide a means to more accurately measure dose delivered in a patient surrogate. EP-1436 A newly designed water-equivalent bolus technique enables BNCT application to skin tumor. K. Hirose 1 , K. Arai 1 , T. Motoyanagi 1 , T. Harada 1 , R. Shimokomaki 1 , T. Kato 1 , Y. Takai 1 1 Southern TOHOKU BNCT Research Center, Radiation Oncology, Koriyama, Japan Purpose or Objective The accelerator-based boron neutron capture therapy (AB- BNCT) system was developed in order to enable the installation of safe hospital BNCT. An important feature of AB-BNCT system is its capability of delivering great doses to deep-seated tumors under condition in which a beryllium target and neutron-beam-sharping assembly are adjusted for production of epithermal neutron that is applicable for more types of tumor localization.Conversely, AB-BNCT is less suitable for superficial cancers, such as malignant melanoma. In this study, we developed a newly water-equivalent bolus technique that has no production of prompt gamma ray and no influence on complicating dose calculation, and we evaluated the effect of this technique on treatment quality for a case of malignant melanoma patient. Material and Methods A water-equivalent bolus was prepared as follows. Urethane foam was cut down into the size of 3-cm larger than the superficial lesion, infiltrated with distilled water with deaeration, and covered with a thin film. The simulated patient was played by a healthy man and simulated condition was originated from a malignant