Biomedical Engineering Reference
In-Depth Information
Fig. 3.8
Multicolor
detection: (a) schematics of
the transmission
characteristics of a patterned
color mask. Light from
“green” particles are only
visible through the green area
of the mask. (b) PE and
PECy5 Spherotec Beads
excited at 532 nm and
detected with a red/green
patterned color mask. The
transmission maxima of the
PE bead coincide with
transmission minima of the
PECy5 Bead. With the color
mask spectral information are
converted into time variation
of the detected intensity as
indicated in Fig 3.8b by the
overlaid mask pattern
fluorescence intensity-time pattern. Therefore, they can be identified based on their
emission characteristics in a new way, that is, one that does not need multiple
detectors, multiple filters, or dichroic mirrors.
We have also tested this characterization method by using the superposition
of two periodic red and green masks with corresponding 33 and 23 transmission
periods. PE and PECy5 beads showed clearly distinguishable time patterns in this
setup. In particular, the fast Fourier transformation of the signal showed different
ratios for the contribution of the fast emission frequency (resulting from the red
parts of the mask) and the slow emission frequency (resulting from the green parts
of the mask) for different beads. Based on this information, we characterized beads
automatically while simultaneously determining their fluorescence intensity and
their speed.
3.6
Summary and Outlook
The majority of biological and biomedical tests are performed at major, centralized
clinical laboratories because the availability of compact, robust, and inexpensive
instruments for POC testing is very limited. Yet there are compelling factors driving
