Program Information
Reusable, MR-Visible, and Radiosensitive 3D Dosimeters for MR-Guided Radiation Therapy
H Lee1*, G Bosco2 , M Kadbi3 , G Ibbott1 , (1) UT MD Anderson Cancer Center, Houston, TX, (2) Elekta, Atlanta, GA, (3) Philips Healthcare, Cleveland, OH
Presentations
SU-H2-GePD-J(A)-3 (Sunday, July 30, 2017) 3:30 PM - 4:00 PM Room: Joint Imaging-Therapy ePoster Lounge - A
Purpose: To demonstrate the quantitative abilities of novel reusable MR-visible 3D dosimeters incorporating nonhomogeneous components to mimic anatomic heterogeneity for MR-guided radiation therapy. Due to the presence of a strong magnetic field, conventional devices may not be sufficient for QA of multi-beam radiation delivery to anatomies containing air cavities and other structures.
Methods: Dosimeters inside a water-filled head and neck phantom were irradiated using an integrated 1.5T MRI and 7MV linear accelerator (MR-Linac). Each dosimeter was imaged using the MRI component of the MR-Linac immediately before (T1-weighted sequences), in real-time during (balanced-FFE), and after (T1-weighted) irradiation. Five plans ranging from delivery of one to seven beams were used to irradiate four different dosimeters incorporating varying heterogeneous components (solution, gel, and air cavities) and one uniform gel dosimeter. Plans were generated using Monaco TPS, and 3D Slicer was used to perform 3D gamma comparison between the planned and measured doses.
Results: 3D gamma pass rates calculated with 7%/5mm distance-to-agreement criteria were greater than 90% for all dosimeters and all plans except for one dosimeter with a 3 cm air cavity when one or three beams were delivered. Gamma pass rates were similar for dosimeters with heterogeneities when compared to the uniform dosimeter, demonstrating the accuracy of this technique as a QA tool for nonhomogeneous anatomical regions with more complex IMRT or VMAT deliveries.
Conclusion: Novel reusable, MR-visible, and radiosensitive 3D dosimeters can be fabricated with nonhomogeneous regions to mimic anatomical sites as a 3D QA tool for radiation in MR-guided radiation therapy systems. Since these dosimeters demonstrate MR contrast post-irradiation, patient workflow in MR-guided radiation therapy systems can be directly applied to these dosimeters for comparison with TPS calculated doses. In addition, the capability for real-time dose quantification of these dosimeters can be extended for online dose adaptations accounting for motion.
Funding Support, Disclosures, and Conflict of Interest: This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. LH-102SPS.
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