Biomedical Engineering Reference
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and the collection time was 1 second. In their system the measurement, data
analysis, and diagnosis were integrated to allow real-time in vivo disease
diagnosis.
Buschman et al. demonstrated in vivo Raman measurements in live lambs
and sheep using forward-viewing and side-viewing Raman probes with a
2.5 mm diameter [24]. The excitation wavelength and incident power were
830 nm and
100 mW at the tissue, and the exposure time was 10-30 s.
Their experiments were performed during catheterization. After catheteriza-
tion, the probe was guided to the site of the investigation under fluoroscopy.
The in vivo-collected aorta spectra were a simple summation of the aortic wall
and blood signals.
We developed a self-guided intravascular catheter equipped with a forward-
viewing endoscope and side-viewing miniaturized Raman probe [30]. The to-
tal diameter of the catheter was 2 mm. With a water flow arterial model, it
was shown that the side-viewing window of the Raman probe could make
gentle contact with the arterial wall by inflating the balloon incorporated
into the head, as shown in Fig 2.10. Following the suggestions of clinicians,
we also tested the viability of using the catheter for non-contact measure-
ment in blood vessels. The Raman spectra of a phantom target made of
cholesteryl oleate, calcium carbonate, calcium hydroxyapatite, and fluores-
cent powder were successfully obtained in whole blood at a distance of up to
0.4 mm away from the target, using 15 mW at 785 nm and an exposure time of
1-2 s [30].
Small, portable Raman systems that can be used in the clinic are very im-
portant. It is often dicult to obtain ethics committee permission to remove
human specimens from the clinic. The system should be small and tough, and
it must be enough sensitive to detect the weak Raman spectra of biological
tissues. We recommend to check carefully the toughness of Raman spectrom-
eter, CCD detector, and laser as well as performance, before purchasing. It is
warm and humid in the clinic. The system should be air cooled and does not
emit radio wave not to affect clinical instruments.
∼
Fig. 2.10.
Head of the self-guided intravascular catheter (modified from [30]
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