Room: ePoster Forums
Purpose: To evaluate EBT-XD film (Ashland Advanced Materials, Bridgewater NJ) for absolute dose measurement and dose profile evaluation of high dose stereotactic treatment.
Methods: Raystation (RaySearch Laboratories, Stockholm, Sweden) was used for planning and for dose calculation on anthropomorphic head phantom (Integrated Medical Technologies, Troy, NY). Gafchromic EBT-XD was placed into the phantom for the measurements. CBCT was used to position the phantom. Films were exposed to dose ranging from 660-3660 cGy.The film was scanned in landscape orientation using an Epson 10000XL flatbed scanner (Epson America, Long Beach, CA) and processed using Film QA Pro 3 Software (Ashland Advanced Materials). Dose maps were exported to Verisoft software (PTW, Freiburg, Germany) to be compared with calculations. 21 treatments were delivered to the phantom by Infinity/Agility linear accelerator (Elekta, Stockholm, Sweden). Each treatment was measured using axial and sagittal orientation film inserts. For all measurements film was used for dose distribution evaluation, and for 13 of these measurements, film was also used for absolute dose evaluation. Two evaluated patients were treated using 8mm and 10mm cones (Aktina Medical, Congers, NY).
Results: Comparing our sagittal and axial measured films to Raystation there was an average absolute discrepancy of 0.41mm in the Superior-Inferior, 0.11mm in the Anterior-Posterior, and 0.17mm in the Left-Right direction, with the maximum values being 0.9mm, 0.5mm and 0.6mm respectively.On average the absolute dose was Â±2.4% from the expected value produced by Raystation with the maximum being 4.8%.
Conclusion: The data suggests that EBT-XD film with the anthropomorphic IMT phantom is suitable for measuring both absolute dose and dose distribution in high dose intracranial treatments. Our results also indicate that Infinity and Raystation are suitable for delivering stereotactic treatment. However, Infinityâ€™s gantry sag of about 0.8 mm may require a target margin increase in the Superior-Inferior direction.