1. Identification of a 3D dosimeter best-suited for use by the RPC M. Heard, G. Ibbott, D. Followill, R. White, E. Jackson, M. Salehpour

2. Motivation RPC has a family of anthropomorphic phantoms Phantoms use TLD and film Radiation treatments are 3D A 3D dosimeter is needed

3. Which 3D dosimeters? There are many 3D formulations to choose from –BANG ®, MAGIC, MAGAT, PAGAT, VIPAR, PRESAGE™, etc.

4. Purpose Characterize several different 3D dosimeters and identify one best- suited for the RPC’s needs.

5. 3D Formulations Investigated PAGAT (polymer gel) 1 –manufactured in-house BANGkit™ (polymer gel) 2 –Supplied by MGS Research Inc. PRESAGE™ (radiochromic dosimeter) 3 –Supplied by Heuris Pharma 1 Venning, A.J., et al., Investigation of the PAGAT polymer gel dosimeter using magnetic resonance imaging. Physics in Medicine & Biology, 2005. 50(16): p. 3875-88. 2 Murakami, Y., et al., Evaluation of the basic properties of the BANGkit™ gel dosimeter. Phys. Med. Biol., 2007. 52(8): p. 2301-2311. 3 Adamovics, J. A. and M.J. Maryanksi, Characterisation of PRESAGE™: A new 3-D radiochromic solid polymer dosemeter for ionising radiation. Radiation Protection Dosimetry, 2006.

6. Polymer Gels –Made of water, gelatin, and monomers –Irradiation initiated polymerization process –Polymers change the optical turbidity and relaxation properties of the gel PRESAGE™ –Composed of a polyurethane matrix doped with leuco dye –Dosimeters are optically clear before irradiation –Irradiation causes exposed areas to turn blue UnirradiatedIrradiated

7. Determined the dose response up to 10 Gy using 6 MV photons for 3 batches of each formulation Determined the dose resolution and inter- batch reproducibility 2 Gy5 Gy10 Gy PAGAT dosimeters irradiated to different doses

8. A half-blocked field was used to irradiate a batch of each formulation Doses of 2 Gy, 5 Gy, and 8.25 Gy were delivered –Multiple dosimeters irradiated at each dose level Radiochromic film also irradiated using a half-blocked field Determined the dosimetric accuracy, spatial accuracy, and intra-batch reproducibility

9. Imaging PRESAGE™ dosimeters imaged with optical CT Polymer gels were imaged with optical CT and MRI Bruker 4.7T scanner Optical CT system

10. Dose response of PAGAT imaged with OCT. Error bars represent one standard deviation.

11. Dose resolution of PAGAT imaged with OCT

12. PRESAGE™ irradiated to 8.25 Gy using a half blocked field

14. PRESAGE™ irradiated to 2 Gy using a half blocked field

15. Characteristics Evaluated 1.Dosimetric accuracy 2.Dose resolution 3.Cost 4.Intra-batch reproducibility 5.Monotonic dose response 6.Spatial accuracy 7.Linear dose response 8.Inter-batch reproducibility

16. Summary Dose response differs by more than 4% between batches of each 3D dosimeter formulation Intra-batch reproducibility > 2% for all dosimetry systems OCT system resulted in inaccuracies at low OD PAGAT polymer gel with OCT imaging was selected as the dosimetry system to be tested in the RPC’s phantoms

17. Thank You