Biomedical Engineering Reference
In-Depth Information
Fig. 3.10.
Transcutaneous Raman spectra of dog tibia positioned at the medial
side of the left tibia at the diaphysis, with 2 mm of overlying tissue.
a
Aver-
aged (
n
= 500) transcutaneous spectra (
grey
) and exposed bone (
n
= 100) spec-
tra (
black
).
b
Recovered bone spectrum at ring/disk spacings between 3.5 and
13.8 mm (reprinted with permission from [20]. Copyright (2007) Society for Applied
Spectroscopy)
Non-invasive Cancer Detection
As discussed in [Chap. 13], SORS and transmission Raman are applicable to
the non-invasive detection of the chemical composition of calcifications within
breast tissue. Their detection, with the high chemical specificity inherent to
Raman spectroscopy, opens the prospect of non-invasive identification of as-
sociated malignant and benign lesions, thus providing additional diagnostic
power to more established techniques (such as X-ray mammography) which
are blind to chemical composition. The current protocol following detection
of suspect calcifications by X-ray mammography is a needle biopsy, which in
most cases (70-90%) results in the detection of a benign lesion. The potential
for the non-invasive characterisation of the chemical make up of calcifications
buried deep within tissue was conceptually demonstrated by Baker et al. [54],
Stone et al. [55] and Matousek et al. [56] using Kerr-gated Raman, SORS
and transmission Raman on chicken breast tissue phantoms. The penetration
depths achieved were 0.9, 8.7 and 16 mm, respectively.
The research in this area builds on the earlier work of Haka et al. [57] who
found that excised calcifications can be classified into two groups using Raman
spectroscopy: type I - calcium oxalate dihydrate (cod) and type II - calcium
hydroxyapatite (hap). Calcium oxalate crystals are mainly found in benign
ductal cysts while calcium hydroxyapatite is found in both carcinoma and in
benign breast tissue; the chemical specificity of Raman spectroscopy identifies
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