Biomedical Engineering Reference
In-Depth Information
Fig. 8.11.
Cancer imaging using OCT. OCT can identify neoplastic changes at
varying stages of tumor growth. Top image set: Morphological OCT and histological
imaging of (
a
,
b
) normal and (
c
,
d
) late-stage carcinogen-induced mammary tumor in
a rat model. The tumor (t) mass is evident compared to the low-backscattering adi-
pose (a) cells. Bottom image set: Early-stage ductal changes detected in this model
using OCT and confirmed with histology. Ducts are imaged in cross-section (
a
,
b
)
and through a longitudinal section (
c
,
d
). Figure modified and used with permission
from [67]
characterized [68, 69]. In contrast to fluorescent probes, which are commonly
used as contrast agents in fluorescence, confocal, and multiphoton microscopy,
new classes of optical contrast agents suitable for OCT must be based on mech-
anisms other than the detection of incoherently emitted fluorescence because
OCT detects only coherent light. Agents that alter the local scattering or
absorption properties are used (Fig. 8.14), such as oil-filled microspheres that
have scattering nanoparticles of melanin, gold, carbon, or iron-oxide either
embedded in their protein shell or encapsulated in their liquid-filled core [70].
Fluorescence-based microscopy techniques have the advantage of very low
background signal in the absence of autofluorescence. This advantage can also
be obtained in OCT by using novel dynamic contrast agents that are physically
modulated in space using an external magnetic or electric field [71,72]. While
