Optical spectra and the corresponding blood similarity parameters.

<p>Spectra acquired from one volunteer for subcutaneous needle (upper panes) and intravascular needle positioning (lower panes), as confirmed by positive blood aspiration. Left: full spectra, indicating the intensity of light received by the stylet (linear arbitrary units, a.u.) as a function of the wavelength (nanometers, nm). Center: an enlarged image of the spectrum that is used to determine the blood similarity parameter B (dashed lines indicate the wavelengths that are used for the calculation). Right: Ln (natural logarithm) of the blood similarity parameter as calculated for these two acquisitions.</p

All blood similarity parameters.

<p>Overview of all blood similarity parameters (B) determined for the different measurement locations in all volunteers. Results are plotted as the average natural logarithm Ln (B) (crosses), with standard deviations determined for the set of spectra acquired at each measurement location in each subject. Volunteer 14 was excluded. Because of the considerable differences in blood similarity parameters (B) between the two groups, more details in the data are visible by plotting Ln(B) instead of B directly.</p

Consort flowchart of the study.

<p>Consort flowchart of the study.</p

Picture of the console and needle tip.

<p>Picture of the console (upper part) and needle tip with optical stylet (lower part). The drawing demonstrates the needle, which is connected to the console. The console is just a drawing and not an accurate image of the real one. The picture of the needle tip shows the two fibers and indicates the measuring volume.</p