SU-E-T-526: Irradiation of Human Cell Lines Using Carbon Ions: Real Time Dosimetry Using Gaf-Chromic Film

Authors

  • Lin Y,

    1. Massachusetts General Hospital and Harvard Medical School, Boston, MA
    2. NASA Space Radiation Laboratory, Brookhaven National Laboratory, Upton, NY
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  • La Tessa C,

    1. Massachusetts General Hospital and Harvard Medical School, Boston, MA
    2. NASA Space Radiation Laboratory, Brookhaven National Laboratory, Upton, NY
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  • Rusek A,

    1. Massachusetts General Hospital and Harvard Medical School, Boston, MA
    2. NASA Space Radiation Laboratory, Brookhaven National Laboratory, Upton, NY
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  • Held K

    1. Massachusetts General Hospital and Harvard Medical School, Boston, MA
    2. NASA Space Radiation Laboratory, Brookhaven National Laboratory, Upton, NY
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Abstract

Purpose:

The purpose of this study is to investigate and quantify several factors affecting biological effects of carbon ions such as cell type, dose, energy and position where the cells are irradiated along the pristine Bragg curve.

Methods:

Experiments to quantify clonogenic cell survival in three human lung cancer cell lines and a fibroblast cell line were performed at the NASA Space Radiation Laboratory, BNL, Upton, USA. A system of water or media-filled T25 flasks lined up along the beam axis was designed so that the cell-containing surfaces of the flasks were placed at specific depths along the Bragg curve. Gaf-chromic films were placed between the flasks to monitor the dose distribution in the sample as soon as the irradiation was finished. Additional studies were conducted at four selected depths along the Bragg curve to obtain full cell survival dose response curves for the four cell lines.

Results:

The percent depth dose of the beams was determined using an ionization chamber and showed that the physical Bragg peak is at 22.5 cm water depth. However, the clonogenic cell survival data indicated that the maximum cell killing occurred at 21.5 cm. Gaf-chromic films revealed some inhomogeneity in the dose distribution on the flasks near the peak, presumably due to lack of scattering from the sides of the flasks, which might account for the differences. Depending on the cell line and radiation dose, the maximum cell killing (i.e., the greatest RBE) is at the 21.5 (the peak) or 24 cm (distal fall off) depth.

Conclusion:

There is a difference in biological effect along the Bragg curve of a carbon ion beam, indicating an elevated RBE at or beyond the end of the range. Gaf-chromic films are proven to be effective in monitoring the 2D irradiation pattern to the flasks.

Research supported by NIH/NCI through grant no. R21 CA182259.

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