Biomedical Engineering Reference
In-Depth Information
This section will outline the developments of deep Raman spectroscopy
from the use of time gating to spatially offset Raman spectroscopy to trans-
mission Raman; a sequence of increasing practical probing depth as advances
have been made. This is counterbalanced by a reduction in depth selectiv-
ity with each new technique. An exploration of the potential use of deep
Raman for breast cancer diagnostics will be used to illustrate the potential
here.
13.4.1 Deep Raman for Breast Cancer Diagnostics
The presence of calcifications on mammography is a feature of particular diag-
nostic significance because this may be the only marker indicating the possible
presence of a malignant breast lesion. While mammography can detect small
masses, areas of distortion, ill-defined densities and microcalcifications not
detectable by physical examination, it relies only on the morphology of the
specimen. This limitation means it gives no definitive criteria for classifying
benign and malignant calcifications. This contributes to the fact that only 10-
25% of mammographically detected lesions are found to be malignant upon
needle biopsy [104, 105].
Microcalcifications can be divided into two types of deposits: type I, which
consist of calcium oxalate dihydrate, and type II, which are composed of cal-
cium phosphates, mainly calcium hydroxyapatite. The type of deposit has
been correlated with disease [106]. Calcium oxalate crystals are mainly found
in benign ductal cysts and rarely found in carcinoma [107], whereas calcium
hydroxyapatite deposits are present in proliferative lesions, which can include
lesions of both benign and malignant pathology [106]. It has been shown
[106] that benign proliferative lesions have calcifications with higher levels
of carbonate than the more pure calcium hydroxyapatites found in malig-
nant lesions. At present, there is no reliable way to distinguish between these
calcification types by mammography. There are differences in the chemical
makeup between the two types of calcification and therefore it is realistic
to propose that Raman spectroscopy should be capable of distinguishing be-
tween them. Indeed, Haka et al. [106] demonstrated this in a well-designed
early study. However, to be truly effective any technique should be able to
be utilised transcutaneously in vivo so as to enable a quick and simplistic di-
agnosis of breast lesions minimising the patient trauma, time delay and high
medical costs of biopsies. We develop all these concepts here using Raman
spectroscopy.
Specimens
Throughout the following studies the specimens involved human and animal
tissues
doped
with
differing
levels
of
powders
representing
breast
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