SU‐GG‐I‐85: Mixed Dose Distribution of Electron and Photon Beams through the Magic F Polymer Gel and Penelope Code

• Published in: Medical Physics 2010-06, Vol.37 (6), p.3121-3121
• Main Authors: Pianoschi, T, Alva, M, Takeda, F, Alves, T, Haddad, C, Nicolucci, P
• Format: Article
• Language: English
• Subjects: Dosimetry; Electron beams; Electron radiation effects; Gels; Magnetic resonance imaging; Medical imaging; Monte Carlo methods; Photons; Polymers; Sequence analysis
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3468118

Purpose: Evaluate the improvement of the dose distributions in treatments using mixed photon and electron beams through polymer gel dosimetry with MAGIC‐f and Monte Carlo simulation using PENELOPE. Method and Materials: A cylindrical phantom with dimensions of 10 cm diameter and 12 cm height was homogeneously filled with MAGIC‐f and was irradiated with 6 MV for photon and 12 MeV for electron. Fields of 3 × 7 cm2 at 100 cm SSD were used to deliver a prescribed dose of 8 Gy for each beam. The phantom analysis followed a previous developed protocol in which an MRI image is registered one day after irradiation in a 3.0 T MRI scanner using a head coil, a multiple spin echo sequence with 16 echos, TE = 22.5 ms and TR = 3000 ms. From the MRI base images R2 values were calculated on a pixel‐by‐pixel basis to produce R2 maps which are related the absorbed dose. The same geometry used in the irradiation process was simulated by PENELOPE with spatial resolution of 1 mm. The depth doses and dose profile were used to compare the results from experiments (MAGIC‐f) and simulation. Results: The comparisons between PENELOPE and MAGIC‐f showed maximum differences of 3.0% and 3.2 %, inside the volume of the 90% isodose for the profile and for the PDP curves, respectively. Typically electron treatment, in 90% isodose, beginning in 0.2 cm for 12 MeV, compared this with the study mixed field was of 0.9 cm, protecting 0.7 cm of the healthy tissue. Conclusions: The comparison preliminary between the dose distribution for PENELOPE and MAGIC‐f showed that gel dosimeter could be used in radiotherapy, for special applications, as photons and electrons mixed fields. Besides of the concordance found, more measurements will be done.