More than 40,000 patients undergo treatment for superficial venous incompetence (varicose veins) in the UK each year. Previously the majority underwent conventional surgery with its associated inconvenience and morbidity. Endovenous laser ablation (EVLA) is a relatively new minimally invasive technique that abolishes superficial venous reflux and is an alternative treatment for some patients. Although early studies have shown it to be safe and effective for great saphenous vein (GSV) reflux there remain many questions relating to optimizing the technique and the range of patients for whom it is suitable. This thesis evaluates factors that may influence EVLA efficacy for GSV reflux and other sites of deep to superficial venous incompetence (small saphenous, anterior accessory GSV, paradoxical reflux). It also assesses changes in venous haemodynamics after EVLA which has led to recommendations on improving treatment outcomes. Further, a prospective database of patients undergoing EVLA and conventional surgery has been maintained (clinical and duplex ultrasound follow-up at 6, 12 & 52 weeks, quality of life data) which has provided additional evidence on the management of patients with varicose veins. Briefly, these studies have confirmed that laser energy density (J/cm) is the crucial factor determining successful truncal vein ablation following EVLA and that appropriate patients can continue warfarin therapy without compromising the safety or efficacy of treatment. Other studies demonstrate the transition of ablated truncal veins from a non-compressible “thrombosed” vein to becoming non-visible 1 year after EVLA. Further, sapheno-femoral junction (SFJ) tributaries remain patent and competent with no adverse impact on clinical outcome whilst SFJ neo-vascularisation occurs much less often after EVLA than surgery. In patients with persistent below-knee GSV incompetence after EVLA residual symptoms are more likely and there is a greater need for sclerotherapy for residual varicosities. A RCT subsequently confirmed that extended ablation of the below-knee GSV achieved superior outcomes.

While minimally invasive surgery is replacing open surgery in an increasing number of surgical procedures, it still poses risks such as unintended tissue damage due to reduced visual and haptic feedback. Surgeons assess tissue health by analysing mechanical properties such as compliance. The literature shows that while both types of feedback contribute to the final percept, visual information is dominant during compliance discrimination tasks. The magnitude of that contribution, however, was never quantitatively determined. To determine the effect of the type of visual feedback on compliance discrimination, a psychophysical experiment was set up using different combinations of direct and indirect visual and haptic cues. Results reiterated the significance of visual information and suggested a visio-haptic cross-modal integration. Consequently, to determine which cues contributed most to visual feedback, the impact of force and position on the ability to discriminate compliance using visual information only was assessed. Results showed that isolating force and position cues during indentation enhanced performance. Furthermore, under force and position constraints, visual information was shown to be sufficient to determine the compliance of deformable objects. A pseudo-haptic feedback system was developed to quantitatively determine the contribution of visual feedback during compliance discrimination. A psychophysical experiment showed that the system realistically simulated viscoelastic behaviour of compliant objects. Through a magnitude estimation experiment, the pseudo-haptic system was shown to be successful at generating haptic sensations of compliance during stimuli indentation only by modifying the visual feedback presented to participants. This can be implemented in research and educational facilities where advanced force feedback devices are inaccessible. Moreover, it can be incorporated into virtual reality simulators to enhance force ranges. Future work will assess the value of visual cue augmentation in more complicated surgical tasks.

The adsorption of salivary proteins to enamel is critical for the protection against acid demineralisation but it is unclear which proteins are involved in protection or the mechanism by which they act. The aim was to investigate salivary protein adsorption and protection using powdered synthetic hydroxyapatite, powdered enamel and natural enamel as substrates and to characterise the specific salivary proteins providing protection. Human whole salivary proteins and its purified fractions were adsorbed to the various substrates and challenged with acid. Adsorbed proteins were characterised by SDS-PAGE and their protective efficacy determined by spectrophotometric assay of phosphate released into the acid during dissolution. A significantly higher degree of protection was provided by salivary proteins when adsorbed to natural enamel surfaces. It was found that the protective species in saliva reside in a small subset comprising 15% of the total protein and efficacy is dependent on conformation. The desorption of salivary proteins during an acid challenge correlated with loss of protection and it was hypothesised that the proteins desorbed during the challenge may be the protective species. Protein S100-A8 and S100 were identified as members of these putative protective proteins. Many proteins (including protein S100-A8 and S100) remained adsorbed to enamel even after 19 acid challenges but they were not protective. Size exclusion chromatography under non-denaturing conditions resulted in co-elution of two proteins identified as α-amylase and cystatin. Their adsorption behaviour was dependent on the actual substrate used. This thesis demonstrates that the use of powdered substrates may not be ideal substitutes for natural enamel surfaces when investigating salivary protein adsorption and the effect of salivary proteins on enamel demineralisation. This is an important consideration as correctly identifying the protective species and understanding the mechanism of protection will inform the development of prophylactic/therapeutic peptides for clinical use in dry mouth cases.

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The purpose of this thesis is to identify new methods of improving the delivery and assessment of minimally invasive surgery (MIS), particularly under the constraint of monoscopic MIS visualisation. In this thesis, the role of visual spatial ability in the acquisition of surgical skills is first investigated. A psychometric test is used to elucidate the correlation between spatial ability and complex tasks, and highlight the need for more quantitative assessment of visuomotor behaviours in laparoscopic procedures. To this end, a wavelet-based analysis framework for instrument trajectory analysis is developed for extracting intrinsic motion behaviours. This is used to provide an insight into subconscious integration of the visual and motor axes in a depthless operative field. The issue of monoscopic visualisation of the operative field in MIS is also addressed and a method of improving depth perception by digitally enhancing a "weak" shadow cast by a secondary light source is proposed. By performing experiments on MIS novices, significant improvements in depth perception by the use of the proposed technique are demonstrated. Finally, eye tracking is used to study the difference in visual behaviour between laparoscopic novices and experts. A distinct visual behaviour of instrument tool-tip tracking during instrument manoeuvring is observed among the novices but not the experts, and this behaviour is shown to be repeatable in both groups. These results provide an important insight into how the cognitive, motor and visual stimuli are integrated during MIS surgery, as well as how the surgeons compensate for the depthless operative field. These findings can be used for the development of more focussed training curricula and the development of improved MIS instruments for its safe practice.

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This PhD thesis addresses the question of how we define, measure and improve surgical judgment and decision making, and how junior surgeons may be trained in these skills. The introduction to the thesis outlines the importance of surgical decision making, and the rationale for undertaking this research. An overview of relevant cognitive psychology research is presented, and the methodologies used in the experimental chapters of the thesis are described in detail. The introduction concludes with a systematic review of published empirical work on surgical decision making. The first two empirical studies are qualitative in nature, using interviews and simulation. They address how we define surgical decisions and their relationship to the process of care, including how surgeons subjectively view their own decision making, and whether we can draw inferences from observation of the process in action. Subsequent experimental chapters focus on the measurement of the quality of judgments of risk - a pre-decisional process in which likely outcomes of surgery are evaluated and estimated. Judgment analysis methodology is used to measure surgeons' performance at estimating surgical risks, with evaluation of whether the method shows construct validity, and whether feedback derived from judgment analysis tasks can be used as a teaching tool. The final empirical section of the thesis develops the theme of training junior surgeons in understanding risk and becoming better decision-makers. The process of developing, piloting, implementing and evaluating of a course module aiming to improve surgical trainees' approaches to decision making is presented. Finally the discussion reflects on the strengths and weaknesses of the studies, and outlines the implications of the work for clinical practice, training of junior surgeons, and future research.

Previous evidence has shown that standards of performance in gastrointestinal endoscopy are variable and that there are disparities in training outcomes. Many changes have been made recently to both training and assessment of endoscopy in the UK. However, no prospective methods of evaluating their outcome have been put in place. The aims of this research were to evaluate current and new training processes and assessments in order to quality assure the outcomes and improve the training process. Two audits were undertaken demonstrating improvements in colonoscopy training over 5 years within a single region and in trainee perceptions of their training nationally. Two studies were done investigating a novel computer colonoscopy simulator for assessment of colonoscopic skills, demonstrating excellent construct validity. A multi-centre randomised controlled trial evaluated the use of this simulator in novice training, which was shown to be equivalent to standard bed-side training with a high degree of skills transfer to real-life colonoscopy. Assessment tools for therapeutic endoscopic procedures were developed, validated and used to quality assure a course in therapeutic endoscopy. This course resulted in significant improvements in practical skills for three of the four therapeutic procedures following training. Web-based training and assessment modules for lesion recognition at capsule endoscopy were developed, validated and piloted. This demonstrated the effectiveness of using new training methodologies for skills improvement in this area. A training course for radiographers in virtual colonoscopy was developed and the training evaluated. This demonstrated competence in practical performance and improvements in knowledge and interpretative skill. Finally, two qualitative studies on non-technical skills in endoscopy were undertaken in order to widen the assessment domains from purely knowledge and skill. An interview study provided the basis for development of a nontechnical skills taxonomy and a video-analysis study resulted in production of a marker system for professional behaviour within gastrointestinal endoscopy.