Dose-dependent survival fraction of CHO-K1 cells.

<p>Survival fraction (± SEM) of CHO-K1 cells plotted logarithmically with respect to the mean absorbed dose (± SD) determined by three independent clonogenic cell assays including three different doses each (0 Gy, < 2 Gy, > 2 Gy). Sham-irradiated cells are marked with magenta triangles, homogeneously irradiated cells with blue circles and microbeam treated cells by green stars. A linear-quadratic model was fitted to the survival data (blue and green solid lines) to estimate the relative biological effectiveness. The potential saturation of the survival fraction for microbeam irradiation was estimated by the geometry of the tungsten slit array with 6/7 (solid black line).</p

Fluorescence microscopy images using the γ-H2AX assay.

<p>DNA double-strand breaks in HeLa cells were stained after (A) microbeam irradiation and (B) homogeneous irradiation with a mean dose of 2 Gy, and (C) no irradiation. Equal acquisition, contrast, and scaling settings were applied.</p

Chromosome aberrations—RBE values.

<p>Relative biological effectiveness (RBE) for equivalent dose effect (number of dicentrics (dic) or centric rings (cr) per cell) of microbeam to homogeneous irradiations based on fitted data.</p

Schematic drawing of the microbeam setup at the Munich Compact Light Source (MuCLS).

<p>Accelerated electrons (yellow circles) are circulating in the storage ring at twice the rate as two laser pulses (red circles) in the laser cavity. Upon collision of the laser pulse with the electron bunch at the intersection point, a quasi-monochromatic X-ray beam (cyan) is produced. At a source-distance of ∼ 2 m, the tungsten slit array is positioned in the X-ray beam to create a microplanar radiation field. Directly behind the array, cells are situated in a dedicated cell holder. For dose verification, a radiochromic film is placed behind the cell holder. Live dose monitoring is performed with a photon counting detector at ∼ 16 m distance to the source. (Drawing not to scale).</p

Dose-dependent chromosome aberrations in A_L cells.

<p>Dicentrics (dic) and centric rings (cr) per cell (± SEM) from three individual experiments for mean doses of 0, 1, 1.8, and 2 Gy. Homogeneous irradiation results are shown with blue circles, microbeam irradiation data with green stars and non-irradiated sham data with magenta triangles. Due to its small size, the error bar of the sham irradiation data is not visible at the given scale. A linear-quadratic model was fitted to the data (blue and green, solid and dashed lines). Solid symbols refer to dicentrics, open symbols to centric rings.</p