(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: Enfolded within vertebral structures, the spinal cord is the most difficult organ to be protected during the spine stereotactic body radiotherapy (SBRT). In this work, we performed 3D dose distribution delivered to the spinal cord during SBRT treatments using Gafchromic EBT3 film
Methods: An acrylic phantom of 26 pieces of several thicknesses (3 mm- 20 mm) was built at the Institute of Physics at UNAM. Gafchromic EBT3 film was calibrated in the 6 MV x-ray reference field and read in an Espson 11000XL document scanner at 300 dpi using 48 bit color depth. The phantom was CT-scanned and introduced into the TPS to simulate the patient. A total of 9 beamlets have been delivered during the treatment to impart an absorbed dose of 15.54 Gy maximum within the tumor volume.
Results: Preliminary results indicate that the absorbed dose within the spinal cord measured with the film are about 2.3 Gy to 2.85 Gy over the complete length of the tumor volume versus 2.55 Gy-3.19 Gy suggested by the treatment planning system (TPS). These values are significantly smaller that these reported in the literature where dose up to 12 Gy has been reported for single fraction.From a simple observation, one can argue that qualitative agreement is found between the TPS and the Gafchromic film measurements. High gradients were successfully reproduced as indicated in the TPS to have spinal cord preservation.
Conclusion: 3D dose distribution for spine stereotactic body radiotherapy have been qualitatively compared with that given for the treatment planning system showing good agreement. To achieve such a goal, a strict protocol should be followed for an accurate dosimetric quality assurance verification.AcknowledgementWe acknowledge C. Ruiz-Trejo, E Lopez-Pineda and R C Ronquillo-Gomez for technical support. This work was partially funded by UNAM-PAPIIT IN115117, Royal-Society-Newton-Advance-Fellowship NA150212
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