|
Fluorescence guidance in brain tumor resection is performed intra-operatively where bleeding is included. When using
fiber-optical probes, the transmission of light to and from the tissue is totally or partially blocked if a small amount of
blood appears in front of the probe. Sometimes even after rinsing with saline, the remnant blood cells on the optical
probe head, disturb the measurements. In such a case, the corresponding spectrum cannot be reliably quantified and is
therefore discarded. The optimal case would be to calculate and take out the blood effect systematically from the
collected signals. However, the first step is to study the pattern of blood interference in the fluorescence spectrum. In this
study, a fiber-optical based fluorescence spectroscopy system with a laser excitation light of 405 nm (1.4 J/cm2) was
used during fluorescence guided brain tumor resection using 5-aminolevulinic acid (5-ALA). The blood interference
pattern in the fluorescence spectrum collected from the brain was studied in two patients. The operation situation was
modeled in the laboratory by placing blood drops from the finger tip on the skin of forearm and the data was compared to
the brain in vivo measurements. Additionally, a theoretical model was developed to simulate the blood interference
pattern on the skin autofluorescence. The blood affects the collected fluorescence intensity and leaves traces of oxy and
deoxy-hemoglobin absorption peaks. According to the developed theoretical model, the autofluorescence signal is
considered to be totally blocked by an approximately 500 μm thick blood layer.
|
