**Abbreviations**

in **Figure 11** are expected to be approximately anatomically symmetrical and thus, signal drifts in the non-normalized images most likely result from insufficient washing and equilibration and also prolonged measurement times (that were here 14 h). This is of course not overcome by background subtraction and normalization with a constant factor. In contrast, pixelwise normalization reduces excessive values and increases too small intensities in relation to the

**Figure 11.** Comparison between images that were normalized using different strategies. Shown are non-normalized images (*left*), congruent to constant factor normalized images (*middle*), and pixelwise normalized images (*right*) of 13C, 23Na, and 64Zn in section derived from mouse brain. The normalization was performed on the basis of the image of 34S (*left*) and the corresponding area of interest (*middle*). The pixelwise normalization of 34S (*right*) shows the theoretical

In order to take into account that absolute element concentrations vary due to slightly different measurement conditions, normalization is essential to make data sets comparable. It is necessary to minimize deviations originated by measurement errors or measurement-related

Generally, normalization is highly dependent on the sample type and the selected reference, but in each case, the normalization reference should be distributed as homogeneous as

homogeneity obtained by decreasing and increasing signal-drift distorted values.

fluctuations, especially in the form of signal drifts.

**4. Conclusion**

reference isotope which significantly improves the image quality (**Figure 11**).

412 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

