AbstractID: 8001 Title: Beta and photon dosimetry with MAGIC acrylic gels and MD55-2
radiochromic films
The new MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) acrylic gels and
MD55-2 radiochromic films were evaluated for dosimetry in conventional and intravascular
brachytherapy. The energy and dose rate dependence of their response was investigated. The detectors
were irradiated with ISO standard x-ray beams of 19.2, 32.1, 64.1, 119.2, and 216.2 keV mean energy
at PTB, with Cs-137 gamma rays at PTB and Yale, and with 6 MV LINAC x-rays at Yale. Electron
irradiations were performed using Sr-90/Y-90 beta rays at PTB and a 6 MeV LINAC beam at Yale. At
PTB, reference dosimetry of the photon beams was performed with the primary standards for air
kerma; an extrapolation chamber was used for the beta source. At Yale, an ion chamber with a Co-60
dose-calibration traceable to NIST was used. To minimize wall-shielding and self-attenuation effects,
MAGIC gels were prepared in thin glass vials irradiated in free air. MD55-2 radiochromic film pieces
were irradiated on and inside "solid water" phantoms. The response of the two dosimeters is fairly
independent of radiation quality for high energy photons and electrons. Consistently with the mass
energy absorption coefficients, the response decreases with decreasing photon energies. MD55-2
under-responds by over 40% compared to Cs-137 gamma rays, while MAGIC has a much flatter
response decreasing by about 10%. For the Sr-90/Y-90 irradiations, the depth dose profiles from the
two systems are in substantial agreement. Finally, once the signal is fully developed (2 days postirradiation), neither system shows significant dose rate effects.