Biomedical Engineering Reference
In-Depth Information
Advanced Pathology
Raman spectroscopy as an adjunct to current diagnostic tools offers many
benefits to the histopathologist in evaluating excised tissue samples.
Histopathology observes changes in tissue morphology through the disease
process. However, it is likely that these architectural changes are driven by
early biochemical changes within tissue. The qualitative analysis of such vari-
ations provides important clues in the search for a specific diagnosis [67], and
the quantitative analysis of biochemical abnormalities is important in measur-
ing the extent of the disease process, designing therapy and evaluating the ef-
ficacy of treatment. Raman spectroscopy probes the biochemistry of the tissue
sample, and therefore can potentially detect pre-malignant changes within the
tissue before morphological changes are evident in histopathological sections,
enabling an earlier diagnosis and improved prognosis. Indeed there is scope
for Raman to provide prognostic information identifying which patients are
more likely to develop cancer. Raman mapping (see also Chap. 5) can rapidly
provide biochemical information across an unstained tissue section. Raman
provides the additional benefit of an objective diagnosis in comparison to the
subjectivity of histopathology, where low levels of inter-observer agreement
[6, 68] characterise some critical decisions, for example, whether to perform
treatments involving radical surgical excision, radiotherapy, or chemotherapy,
which carry risks of mortality and substantial complications [69]. Current
significant technological improvements leading to rapid sample scanning are
making unstained molecular imaging a real prospect as a histopathological
tool [70].
Deep Probing
Until very recently Raman spectroscopy was a technique applied to the sur-
face of the specimen of interest, thus limiting the molecular specific probe
for disease to the near surface of outer or hollow inner organs. One of the
main problems with the use of Raman spectroscopy for in vivo measurements
of biological tissue is that the collected Raman signal decreases when prob-
ing at greater tissue depth, causing the surface Raman signal and fluores-
cence to be significantly stronger than the sub-surface Raman signal. Use of
confocal Raman microspectrometry has enabled specific volumetric sampling
up to a maximum of 100-200
m in turbid media such as human tissues.
However a number of significant cancers originate in organs deep within the
body, for example, breast and prostate cancer and lymph node metastatic
involvement. Breast cancer is now the most common cancer in the UK and
incidence rates have increased by more than 50% over the last 25 years. The
accurate and safe diagnosis of breast cancer is a significant issue in the UK,
with annual incidence of 44,000 women and around 300 men. Early diag-
nosis of the disease allows more conservative treatments and better patient
outcomes.
μ
Search WWH ::
Custom Search