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Dose Distribution of Praseodymium-142 Microspheres in Microcapillary Using Radiochromic Film Dosimetry and Applications in Hepatocellular Carcinoma Microsphere Brachytherapy

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C Ferreira

M Ferreira*, K Rasmussen , J Jung , East Carolina Univ, Greenville, NC


SU-E-T-112 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: This work verified simulations of beta-minus emitter Praseodymium-142 (Pr-142) for microsphere brachytherapy by performing absolute dose measurements for Pr 142 microspheres in a microcapillary as a simplified model for a single blood vessel for the treatment of Hepatocellular Carcinoma (HCC).

Methods:Pr-142 microspheres (mass: 0.169g, average diameter: 29.7±3.9μm) were activated by thermal neutron activation at the University of Missouri Research Reactor. Experimental setup consisted of a microsphere solution (initial activity 36.6mCi in 0.1ml of sterile water) within a glass microcapillary (internal and external diameter: 305μm and 453μm, respectively) placed for 51h in a custom made Gammex Solid Water™ phantom. GAFCHROMIC™ EBT2 film calibrated with a 6MeV electron beam was used to access the dose fall-off of microspheres. The microcapillary was modeled in MCNPX2.6 in order to compare with experiments.

Results: The radial dose fall-off on the transverse plane due to scatter and attenuation in the solid water phantom was analyzed using ImageJ for both film and MCNPX2.6 simulations. Isodose analysis showed close agreement among the methods used, i.e. measurements and simulations agree within 3.9% for doses below 1600cGy. Experimental and simulated doses obtained at 0.5 cm radially from the source were 1547cGy and 1610cGy respectively. Discrepancies for points close to the microcapillary surface were observed between MCNPX2.6 and measurements due to film saturation for high doses. Dose due to Pr-142 3.7% gamma emission was below the threshold of detection for the film.

Conclusion: A detailed dosimetric study was performed for Pr-142 glass microspheres within a single microcapillary. MCNPX2.6 simulations were verified by means of direct measurement. Based on these results, Pr-142 appears to be a viable choice of radionuclide for treating HCC.

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