Objective localisation of oral mucosal lesions using optical coherence tomography.

PhDIdentification of the most representative location for biopsy is critical in establishing the definitive diagnosis of oral mucosal lesions. Currently, this process involves visual evaluation of the colour characteristics of tissue aided by topical application of contrast enhancing agents. Although, this approach is widely practiced, it remains limited by its lack of objectivity in identifying and delineating suspicious areas for biopsy. To overcome this drawback there is a need to introduce a technique that would provide macroscopic guidance based on microscopic imaging and analysis. Optical Coherence Tomography is an emerging high resolution biomedical imaging modality that can potentially be used as an in vivo tool for selection of the most appropriate site for biopsy. This thesis investigates the use of OCT for qualitative and quantitative mapping of oral mucosal lesions. Feasibility studies were performed on patient biopsy samples prior to histopathological processing using a commercial OCT microscope. Qualitative imaging results examining a variety of normal, benign, inflammatory and premalignant lesions of the oral mucosa will be presented. Furthermore, the identification and utilisation of a common quantifiable parameter in OCT and histology of images of normal and dysplastic oral epithelium will be explored thus ensuring objective and reproducible mapping of the progression of oral carcinogenesis. Finally, the selection of the most representative biopsy site of oral epithelial dysplasia would be investigated using a novel approach, scattering attenuation microscopy. It is hoped this approach may help convey more clinical meaning than the conventional visualisation of OCT images

DEVELOPMENT OF METHODOLOGIES FOR RAMAN SPECTRAL ANALYSIS OF HUMAN SALIVA FOR DETECTION OF ORAL CANCER

Oral cancer is one of the most common malignancies worldwide, with over 350,000 to 400,000 new cases reported each year. Early detection, followed by appropriate treatment, can increase cure rates to 80 or 90%, and greatly improve the quality of life by minimising extensive, debilitating treatments. Usually, the clinical diagnosis of most head and neck neoplasms, including oral cancer, is performed through time-consuming and invasive biopsies followed by histological examination of the excised tissue and may present psychological trauma and risk of infection to patients. In addition, histological grading can be subjective, as it is based on subtle morphological changes. In this context, saliva is gaining interest as a diagnostic fluid, since it represents a non-invasive, safe, cheap source of complex biomolecular information that can easily be obtained from the oral cavity. In parallel, increased effort is being devoted to developing less invasive early diagnostic modalities for oral cancer, of which novel optical systems, such as Raman spectroscopy, hold great promise. The overall aim of this study is to develop methodologies for analysis of human saliva using Raman spectroscopy with a future applicability for oral cancer diagnosis. In order to optimise the measurement protocol, a number of different microscope configurations, source lasers, and substrates were trialled. Once the measurement protocol was optimised, it was validated using artificial saliva and real human saliva. The individual saliva constituent components as well as the artificial saliva itself were characterised and recorded. Following the standardisation protocol, real human whole saliva samples collected using two different collection methods were subjected to centrifugal filtration. The Raman signal from whole saliva was acquired and analysed through statistical tools, demonstrating the potential for diagnostic applications. Then, the Raman spectroscopic profiles of patients with saliva samples of different oral dysplastic pathologies, such as V epithelial oral dysplasia and oral cancer, were further analysed and spectroscopically assessed. To finalise, confounding factors, such as smoking habits and alcohol consumption, were also assessed in terms of their influence on the Raman classification of these pathologies. This research showed that, Raman spectroscopy was able to successfully discriminate stimulated saliva samples from healthy volunteers and patients with oral cancer or potentially malignant lesions, highlighting the weak influence of confounding factors, such as gender, age, smoking and alcohol consumption. However further studies are still required to improve classification among the different dysplasia grades

State of the art: iterative CT reconstruction techniques

Owing to recent advances in computing power, iterative reconstruction (IR) algorithms have become a clinically viable option in computed tomographic (CT) imaging. Substantial evidence is accumulating about the advantages of IR algorithms over established analytical methods, such as filtered back projection. IR improves image quality through cyclic image processing. Although all available solutions share the common mechanism of artifact reduction and/or potential for radiation dose savings, chiefly due to image noise suppression, the magnitude of these effects depends on the specific IR algorithm. In the first section of this contribution, the technical bases of IR are briefly reviewed and the currently available algorithms released by the major CT manufacturers are described. In the second part, the current status of their clinical implementation is surveyed. Regardless of the applied IR algorithm, the available evidence attests to the substantial potential of IR algorithms for overcoming traditional limitations in CT imaging

Artifacts in magnetic resonance imaging: how it can really affect diagnostic image quality and confuse clinical diagnosis?

Different kinds of artifacts can occur during a magnetic resonance imaging (MRI) scans due to hardware or software related problems, human physiologic phenomenon or physical restrictions. Some of them can seriously affecting diagnostic image quality, while others may simulate or be confused with different pathology. On another word artifact as an artificial feature appearing in an image that is not present in the original investigative object. It is important to recognize these artifacts according to a basic understanding of their origin, especially those mimicking pathology, as they can lead to incorrect diagnosis and cause serious after-effects on patient’s health and outcomes. We presented an overview of the most common MRI artifacts and methods to fix or rectify them. We also provide the original artifacts images and statistics from the Lithuanian University of Health Sciences Kaunas Clinical Hospital, Dept of Radiology, mainly obtained from image databases and some images from data base of other Lithuanian hospitals

The dependency of image quality on acquisition protocol and image processing in chest tomosynthesis

The digital tomosynthesis (DTS) technique is a next generation of the old tomography technique, the use of which has been extended during the past decade. The interest in this technique has increased more and more in Radiology due to its ability to provide threedimensional images by acquiring a number of projection radiographs at lower radiation dose and potentially lower cost than CT in certain clinical situations. Furthermore, there are two main advantages of DTS in comparison with conventional radiography. The first one is that the reconstructed slices reduce the problem of overlaying anatomical structures in a twodimensional image created by conventional radiography. The second one is that DTS has better depth resolution than conventional radiography. The primary aims of the studies in this thesis have been to determine a chest DTS protocol with shorter exposure time then the vendor recommended protocol (12 s) with retained image quality and to investigate the difference in image quality between the protocols with acquisition time 6.3 s and 12 s. In order to compare all available chest DTS protocols, an anthropomorphic phantom with a 12 mm module placed in the center of the right lung was used for the first study. The second study was performed as a prospective human study where the best performing protocols from the first study were compared. In both studies, the observers were instructed to evaluate the image quality based on the pre-defined criteria. The criteria were developed in accordance with the European guidelines and previous studies in combination with the clinical experience of the observers. The data from both studies were analysed with visual grading characteristics (VGC) analysis and the area under the VGC curve (AUGVGC) was used as figure-of-merit. The result of the studies indicates that the chest DTS protocol with the acquisition time of 6.3 s has similar image quality as the reference protocol with acquisition time of 12 s for all quality criteria. The shorter acquisition time may have a great clinical significant for the patient with respiratory impairment. In the future, further studies should be performed to evaluate the diagnostic value of chest DTS in compare with CT in some clinical situations, reduction of radiation dose and cost efficiency within healthcare

Image quality evaluation of eight complementary metalâ oxide semiconductor intraoral digital Xâ ray sensors

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134084/1/idj12241_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134084/2/idj12241.pd

Molecular and Cellular Investigations Relating to Neuroplasticity in Stroke

Stroke is a leading cause of death and the leading cause of adult neurological disability in Australia. The interventions currently available for the management of stroke include intravenous thrombolysis, thombectomy, decompressive hemicraniectomy, antithrombotic therapy, stroke unit care and rehabilitation. The aims of these interventions are to reduce the amount of damage caused by stroke and to support recovery. Currently, there is no method to reverse the damage caused by stroke. The pattern of functional recovery following stroke reveals a critical period of enhanced neuroplasticity. This period is a candidate therapeutic target for post-stroke neurological repair, either by increasing the degree of neuroplasticity that occurs or by extending the duration of enhancement. Experimental interventions that promise to enhance post-stroke neuroplasticity are being investigated. There is extensive evidence that functional recovery can be improved through interruption of endogenous inhibitory mechanisms, which include perineuronal nets (PNNs) and Nogo signalling. Chapter one outlines a review of the literature concerning the pathophysiology of ischaemic stroke, evidence in support of enhanced post-stroke neuroplasticity and evidence in support of potential therapies that target post-stroke neuroplasticity. This review forms the basis for the body of work described in this thesis. Cell-based therapy is one potential way of enhancing recovery from ischaemic stroke. Stem cell transplantation following stroke has resulted in functional improvements in pre-clinical studies. The mechanism of action underlying this effect is unclear, though it is thought to be through the paracrine secretion of neurotrophic cytokines and not through replacement of lost tissue. Intriguingly, both direct intracerebral transplantation and intravascular transplantation are efficacious. For transplanted stem cells to enter the brain from circulation, they must cross the blood-brain barrier (BBB). While this has been shown to occur, the mechanism through which stem cells cross the BBB has not been fully elucidated. Chapter two demonstrates that human dental pulp stem cells (DPSC) can increase BBB permeability through the expression of vascular endothelial growth factor. DPSC conditioned medium caused an increase in permeability of an in vitro model of the BBB and this effect was reversed by blocking the VEGF receptor. These results support the further investigation of intravascular DPSC administration as a treatment for ischaemic stroke. One of the hypothetical mechanisms of action for cell-based therapy is the interruption of PNNs. These are a specialised form of dense ECM within the adult brain and spinal cord that form part of an endogenous system for the inhibition of neuroplasticity. Digestion of PNNs through administration of a bacterial enzyme has been shown to improve outcomes following neurological insults, including stroke. Chapter three demonstrates that DPSC express soluble products that digest PNNs. Application of DPSC conditioned media to in vitro PNN models and brain slices resulted in decreased staining of PNNs. Additionally, DPSC were shown to express active matrix metalloproteinase-2, which digested aggrecan, one of the main PNN components. These results suggest that interruption of PNNs may be a mechanism through which cell-based therapy enhances recovery in the setting of ischaemic stroke. As PNNs are a target for future stroke therapies, it is important to understand the endogenous response of PNNs to stroke. There is evidence in the literature that PNNs are temporarily downregulated after stroke. Numerous studies have demonstrated the temporary downregulation of PNNs after stroke through general staining for the carbohydrate components of PNNs and some of the protein components. However, PNNs are not homogeneous throughout the central nervous system and variations in their composition affect their ability to inhibit neuroplasticity. The response of PNNs to stroke has not yet been fully described. Chapter four addresses this by characterising the expression profile of several PNN components in a mouse stroke model. Following photochemical infarction, there was a temporary decrease in staining of cartilage link protein-1, aggrecan and WFAbinding glycans in the cortex. This effect was more pronounced in the region of the cortex contralateral to the lesion. Additionally, 4-O-sulfated chondroitin, which is the most inhibitory PNNassociated carbohydrate component, was temporarily enriched in the ischaemic border zone. This pattern of regulation may underlie the post-stroke critical period enhanced neuroplasticity. The development of new stroke treatment strategies targeting neuroplasticity is dependent on preclinical in vivo studies. To ensure that pre-clinical studies are mutually comparable, there is a need for a standardised protocol for modelling human stroke. The requirements of this model are that it be reproducible, technically accessible, it must minimise animal suffering and it must accurately model chronic stroke in humans. Many studies use young animals, which recover rapidly and more completely from ischaemic stroke. This is not appropriate for testing stroke therapies for humans as stroke risk is correlated with age. Additionally, middle cerebral artery occlusion is still considered the gold standard for modelling stroke. This is biologically accurate, but is technically difficult, results in variable infarcts and is associated with relatively high mortality and suffering. Chapter five outlines a preliminary study towards the development of a standardised protocol for chronic stroke in aged mice. A photochemical induction method was used, which resulted in reproducible, targeted lesions that were detectable by MRI. This method produced detectable dysfunction of the affected limb at early time points only. These results suggest that further optimisation needs to be done in developing a standardised model of chronic stroke.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 201