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MAGIC-F Dosimetric Signal in a High Dose Rate Brachytherapy Clinical Source: Influence of Radio-Induced Polymeric Chains' Radius of Gyration
A QUEVEDO*, P Nicolucci , University of Sao Paulo, Ribeirao Preto, Brazil
Presentations
TU-C3-GePD-T-5 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Therapy ePoster Lounge
Purpose: In this work, the MRI transverse relaxation time (R2) of MAGIC-f was compared with the radius of gyration of the radio-induced polymeric chains as a function of a wide dose range from a HDR ¹⁹²Ir clinical source.
Methods: The dose-response curve, given as R2 versus dose, and the radius of gyration of polymeric chains in MAGIC-f as a function of dose were compared to study the correlation between the gel's dosimetric signal and gel polymerization. Doses from 0 to 20 Gy were used to construct the dose-response curve. The samples were read 24 h after irradiation in a Philips 3.0 T MRI tomograph, using a multi-spin echo sequence with repetition time of 6000 ms and echo-time of 15 ms.The static light scattering experiments were conducted with a He-Ne laser (632.8 mm wavelength) aligned to a 90° light polarizer. The laser incidence in the sample was in the same direction of the irradiation. Intensities of light scattering were measured from 0° to 110°. The weight average molecular weight and the radius of gyration of polymeric chains were calculated for the irradiated and non-irradiated gel samples.
Results: The signals in the dose-response curve ranged from 0.60x10⁻³ to 6.02x10⁻³ ms⁻¹ and weight average molecular weight obtained was 1.32x10⁴ gmol⁻¹ as the dose varied from 0 to 20 Gy. The radius of gyration ranged from 2.74x10⁻⁷ m to 4.48x10⁻⁷ m in the dose range analyzed. The results have shown that R2 and radius of gyration increase with dose up to aproximately 10 Gy and then both tend to a saturated response.
Conclusion: The correlation between the radius of gyration and the dosimetric signal of MAGIC-f has been verified for a wide dose range. It has been shown that both R2 and the polymeric chain tend to a saturation for than 10 Gy.
Funding Support, Disclosures, and Conflict of Interest: CAPES (Coordination of Superior Level Staff Improvement); HC (Hospital of Clinics)
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