The significant achievements of medical science over the last century are evident in the increasing age of
the global population, however this now brings new problems, the most prominent being the growth in the
number of people suffering from dementia. Over half the people with dementia in the UK are sufferers of
Alzheimer's disease, a condition in which intraneuronal neurofibrillary tangles and extraneuronal senile
tangles take over neurons prompting their death. A definitive diagnosis is still only currently available
post-mortem, whilst current symptom based processes of elimination are far from perfect, especially when
the only treatments available are symptom inhibiting drugs. Principal component analysis (PCA) of the
Raman spectra taken from brain tissue has proved to be a potential tool in the diagnosis. However, this
work now has to be refined in order to progress to tissue less associated with the symptoms of Alzheimer's
disease. The first step of this has already been taken in progressing from frontal tissue to occipital tissue
point spectra taken at random positions from bulk tissue. Now we present initial work into acquiring
Raman spectral maps from across a tissue area, in pursuit of identifying unique plaque and tangle spectra.
These spectra are presented alongside synthetic β-Amyloid spectra, in a study of the role that the peptide
plays in the biomarker spectra, and how this information can aid the PCA of bulk tissue, and point towards
a Raman spectroscopic test on less sensitive tissue, such as blood.
Within the next 50 years Alzheimer's disease is expected to affect 100 million people worldwide. The progressive decline in the mental health of the patient is caused by severe brain atrophy generated by the breakdown and aggregation of proteins, resulting in β-amyloid plaques and neurofibrillary tangles. The greatest challenge to Alzheimer's disease lies in the pursuit of an early and definitive diagnosis, in order that suitable treatment can be administered. At the present time, definitive diagnosis is restricted to post-mortem examination. Alzheimer's disease also remains without a long-term cure. This research demonstrates the potential role of Raman spectroscopy, combined with principle components analysis (PCA), as a diagnostic method. Analyses of ethically approved ex vivo post-mortem brain tissues (originating from frontal and occipital lobes) from control (3 normal elderly subjects and 3 Huntingdon's disease subjects) and Alzheimer's disease (12 subjects) brain sections, and a further set of 12 blinded samples are presented. Spectra originating from these tissues are highly reproducible, and initial results indicate a vital difference in protein content and conformation, relating to the abnormally high levels of aggregated proteins in the diseased tissues. Further examination of these spectra using PCA allows for the separation of control from diseased tissues. The validation of the PCA models using blinded samples also displays promise for the identification of Alzheimer's disease, in conjunction with secondary information regarding other brain diseases and dementias. These results provide a route for Raman spectroscopy as a possible non-invasive, non-destructive tool for the early diagnosis of Alzheimer's disease.
Alzheimer's disease currently affects over 800,000 people in the UK, and this figure is set to exceed 1.5 million by 2050. The disease causes a severe breakdown of the brain, resulting in the progressive decline in the mental health of the patient. It also remains without a long-term cure. A definitive diagnosis of the disease can only be gained at post-mortem, whilst other technologies are limited to monitoring the physical breakdown of the brain. The early identification of the chemicals responsible for the disease, and their structure, is therefore essential for improved diagnosis, treatment and care. This research demonstrates the use of Raman spectroscopy, and principle components analysis, as a method for the diagnosis, and examination of, the specific proteins responsible for Alzheimer's disease. Analyses of ethically approved ex vivo brain tissues from normal elderly (n=3), Alzheimer's disease (n=12) and Huntingdon's disease (n=3) brain sections (from the frontal and occipital lobes) are presented. Subsequently, a further 12 blinded individual samples were examined and the preliminary results are presented. Spectra originating from these tissues are highly reproducible, and results indicate a vital difference in protein content and protein conformation, relating to the abnormally high levels of aggregated proteins in the diseased tissues. Principle components analysis has been shown to differentiate normal elderly tissues from diseased tissues. These results show great promise for the early identification of Alzheimer's disease, and secondary information regarding other brain diseases and dementias. These results demonstrate the potential use of Raman spectroscopy as a possible non-invasive, non-destructive tool for the early diagnosis of Alzheimer's disease.
In recent years, the use of Raman spectroscopy for the detection and diagnosis of disease has steadily grown within the research field. However, this research has primarily been restricted to oncology. This research expands the use of Raman spectroscopy as a potential tool for the diagnosis of Alzheimer's disease, which is currently the most prevalent, and fastest growing type of dementia in the Western world. Using a commercial Raman spectrometer (Renishaw PLC ®, UK) flash frozen post-mortem ex vivo brain tissue sections were illuminated using a high power (20mW) 830 nm near infrared diode laser, and subsequently spectra were gained in the region of 2000–200 cm-1 from a 10 second accumulation time. Ethical approval was gained for the examination of 18 individual donors exhibiting varying states of Alzheimer's disease, Huntingdon's disease and their corresponding age-matched healthy controls. Following on from previous preliminary studies, the Raman spectra were found to be highly reproducible, and when examined further, the spectra showed differences relating to the content and structure of the proteins in the individual brain samples, in particular, the beta-amyloid protein structure found in Alzheimer's disease patients. Principle components analysis further determined these protein structural changes, with Alzheimer's disease and Huntingdon's disease samples being defined from the healthy controls, and from each other.
The ability to delineate structural information in medical images is important for accurate diagnoses and will often depend on how the image is presented. Various methods of signal and image processing have been explored to improve this process across a wide range of medical imaging techniques. We present the application of chromatic analysis, a measurement technique developed for colorimetry applications, for signal processing of optical coherence tomography (OCT) images in human tissue. In particular, specific characteristics in the optical signal relating to various structural features are identified using chromatic filters and this information is used to process the OCT image. The technique was developed using mathematically simulated OCT signals and the applied to experimental OCT images of human tissue biopsy samples of the oesophagus. In the processed images, reflecting surfaces are highlighted and background noise is reduced to improve image interpretation.
Alzheimer's disease is one of the most common forms of dementia, and causes steady memory loss and mental regression. It is also accompanied by severe atrophy of the brain. However, the pathological biomarkers of the disease can only be confirmed and examined upon the death of the patient. A commercial (Renishaw PLC, UK) Raman system with an 830 nm NIR diode laser was used to analyse brain samples, which were flash frozen at post-mortem. Ethical approval was sought for these samples. The Alzheimer's diseased samples contained a number of biomarkers, including neuritic plaques and tangles. The Raman spectra were examined by order to differentiate between normal and Alzheimer's diseased brain tissues. Preliminary results indicate that Alzheimer's diseased tissues can be differentiated from control tissues using Raman spectroscopy. The Raman spectra differ in terms of peak intensity, and the presence of a stronger amide I band in the 1667 cm-1 region which occurs more prominently in the Alzheimer's diseased tissue. These preliminary results indicate that the beta-amyloid protein originating from neuritic plaques can be identified with Raman spectroscopy.
We have applied a spectroscopic system capable of monitoring the fluorescence dynamics of photosensitiser at micron-scale locations within individual cells. This report shows that the accumulation of protoporphyrin IX (PpIX) within the nucleus of formalin-fixed keratinocytes, fibroblasts, and a metastatic squamous carcinoma cell line, following incubation with 5-aminolaevulinic acid (ALA), is dependent upon both incubation time and cell proliferation status. We
demonstrate that the process of photobleaching can be monitored via the depletion in PpIX fluorescence emission during exposure to 532 nm laser light. All spectra show a progressive reduction of the 634 nm PpIX peak - following a bi-exponential decay which is consistent with a singlet oxygen mediated process. The rate of photobleaching, when plotted as a function of light dose, increases with reduced incident laser power. The generation of the hydroxyaldehyde-chlorin photoproduct, as monitored by the increase in fluorescence emission centred on 672 nm, is also greatest when the lowest laser power is applied. When light is delivered in two fractions, there is evidence of PpIX fluorescence recovery during the dark period, and an increase in bleaching rate at the onset of the second exposure. These results are in qualitative agreement with measurements performed in vivo which demonstrate that the photodynamic dose is dependent upon fluence-rate and oxygen status.
A pulsed terahertz imaging system has been developed for potential use in vivo. Few data are available regarding the optical properties of human tissue at terahertz frequencies. This work demonstrates
transmission measurements through human ex vivo tissue sections, and determines broadband refractive indices, and broadband and frequency dependent absorption coefficients. The data presented here are the first systematic measurements of this type. Significant differences were found between a numbers of human tissue types.
Terahertz frequency spectroscopic imaging studies of teeth are reported. The aim is to establish the characteristic properties of enamel and dentine at these high frequencies. Changes to the THz characteristics as a result of various types of tooth abnormalities are reported showing the potential of this technique for dental diagnosis