Computed tomographic colonography(CTC), also called virtual colonoscopy, uses CT scanning and computer post-processing to create two dimensional images and three dimensional virtual views inside of the colon. Computer-aided polyp detection(CAPD) automatically detects colonic polyps and presents them to the user in either a first or second reader paradigm, with a goal reducing examination time while increasing the detection sensitivity. During colonoscopy, the endoscopists use the colonoscope inside of a patient's colon to target potential polyps and validate CAPD found ones. However, there is no direct information linking between CT images and the real-time optical colonoscopy(OC) video provided during the operation, thus endoscopists need to rely largely on their past experience to locate and remove polyps. The goal of this research project is to study the feasibility of developing an image guided colonoscopy(IGC) system that combines CTC images, real-time colonoscope position measurements, and video stream to validate and guide the removal of polyps found in CAPD. System would ease polyp level validation of CTC and improve the accuracy and efficiency of guiding the endoscopist to the target polyps. In this research project, a centerline based matching algorithm has been designed to estimate, in real time, the relative location of the colonoscope in the virtual colonoscopy environment. Furthermore, the feasibility of applying online simultaneous localization and mapping(SLAM) into CT image guided colonoscopy has been evaluated to further improve the performance of localizing and removing the pre-defined target polyps. A colon phantom is used to provide a testing setup to assess the performance of the proposed algorithms. / Master of Science

There are several types of disorders that affect our colon’s ability to function properly such as colorectal cancer, ulcerative colitis, diverticulitis, irritable bowel syndrome and colonic polyps. Automatic detection of these diseases would inform the endoscopist of possible sub-optimal inspection during the colonoscopy procedure as well as save time during post-procedure evaluation. But existing systems only detects few of those disorders like colonic polyps. In this dissertation, we address the automatic detection of another important disorder called ulcerative colitis. We propose a novel texture feature extraction technique to detect the severity of ulcerative colitis in block, image, and video levels. We also enhance the current informative frame filtering methods by detecting water and bubble frames using our proposed technique. Our feature extraction algorithm based on accumulation of pixel value difference provides better accuracy at faster speed than the existing methods making it highly suitable for real-time systems. We also propose a hybrid approach in which our feature method is combined with existing feature method(s) to provide even better accuracy. We extend the block and image level detection method to video level severity score calculation and shot segmentation. Also, the proposed novel feature extraction method can detect water and bubble frames in colonoscopy videos with very high accuracy in significantly less processing time even when clustering is used to reduce the training size by 10 times.

Colonoscopy is used in colorectal cancer (CRC) screening either as an independent screening method (screening colonoscopy) or following a positive result of a primary screening test (eg. fecal occult blood test, FOBT). Preventive colonoscopy is the collective name for screening and FOBT+ colonoscopy. Due to the considerable variability in the detection of colorectal neoplasia between individual endoscopists, colonoscopy quality indicators were introduced. Adenoma detection rate (ADR) and polyp detection rate (PDR) are defined as the proportion of colonoscopies in which at least one adenoma (for ADR) or polyp (for PDR) was detected to the total number of colonoscopies performed. ADR is considered a key indicator of the quality of colonoscopy. Adenoma per colonoscopy (APC), defined as the total number of adenomas detected relative to the total number of colonoscopies performed, is the most accurate indicator currently available. However, APC limit values have not yet been set. Both ADR and APC are validated indicators, but their evaluation is time-consuming and personnel-intensive, which limits their use in clinical practice. The main purpose of the presented work is to simplify the monitoring of colonoscopy quality by introducing a more user-friendly indicator, which does not require histological...

Introdução: A colonoscopia é um dos métodos mais completos de investigação das doenças colorretais, com vantagens por proporcionar a observação da mucosa intestinal, em tempo único e de forma direta e também por ser a técnica de maior acurácia para o diagnóstico de lesões estruturais. Salienta-se que o paciente, ao se deparar com a indicação da colonoscopia, interpreta-a como sendo um exame que provoca desconforto e desencadeia sentimentos de vulnerabilidade, vergonha, medo e ansiedade. Perante estas emoções, o procedimento poderá ser percebido como um fator estresse importante ao paciente e que requer a utilização de estratégias para o enfrentamento da situação de desafio. Objetivo: analisar a percepção de estresse e os estilos de coping em pacientes no período que antecede o procedimento colonoscópico, conforme as variáveis biossociais e clínicas. Material e método: tratase de um estudo descritivo, transversal, exploratório e de campo, com abordagem quantitativa, desenvolvido no Serviço de Endoscopia do Hospital Universitário da Universidade de São Paulo (HU-USP). Foram entrevistados 100 pacientes em período de complementação de preparo, adultos, com solicitação formal para a realização do procedimento colonoscópico. Para esta análise, foram utilizados os instrumentos Escala de Estresse Percebido (PSS 10), o Inventário de Estratégias de Enfrentamento de Folkman e Lazarus (1985) e um roteiro de entrevista semiestruturada para caracterização da população do estudo. Resultados: o perfil biossocial da amostra foi, predominantemente, de mulheres (73%), idade superior a 65 anos (50%), casados ou com companheiros (90%), com pelo menos um filho (38%), com escolaridade superior a oito anos de estudos (33%), que pertenciam as religiões evangélica e católica (48% e 45%, respectivamente), em sua maioria aposentados (48%), com antecedentes clínicos de hipertensão arterial sistêmica (90%) e familiar de câncer de colón (68%); 59% dos pacientes em período de preparo revelaram um nível médio de estresse percebido e os estilos de coping com maiores médias foram o Suporte Social (6,43±1,54), Aceitação da Responsabilidade (5,70±2,41) e Reavaliação Positiva (5,64±1,41). As variáveis sexo, idade, estado civil, escolaridade, tipo de preparo e número de exames realizados previamente foram determinadas, como fatores preditores de estresse nessa população. As correlações estatisticamente significativas deste estudo compreenderam a associação entre o PSS-10 e as estratégias de enfrentamento Confronto, Afastamento, Suporte Social, Aceitação da Responsabilidade e Reavaliação Positiva. Entre estes preditores, houve associação do sexo feminino, da idade superior a 65 anos, dos casados ou com namorado, dos não letrados ou daqueles com 2° grau completo/incompleto, do tipo de preparo ambulatorial e dos pacientes com pelo menos um exame realizado com o PSS-10 e os domínios selecionados. Conclusão: a análise da colonoscopia como fator de estresse é pouco estudada em nosso meio, assim como a associação dos processos de enfrentamento. A percepção de estresse foi maior entre os indivíduos da população da pesquisa quando comparados com a população do estudo de tradução e validação do instrumento. Quanto aos estilos de coping foram observados predomínios dos domínios com foco na emoção. Os resultados desta pesquisa permitiram o desenvolvimento de intervenções voltadas para a diminuição do estresse desses pacientes e que os estilos de enfrentamento encontrados nesta análise sejam utilizados para a melhoria da prática assistencial. / Introduction: Colonoscopy is one of the most complete methods of investigation for colorectal diseases, with several advantages. One is that it makes possible the observation of bowel mucus, directly and in a single session. Another is that it is one of the most accurate ways of diagnosing structural lesions in bowel. It is important to understand that patients who face this procedure interpret the exam as one that provokes discomfort, which leads to feelings of vulnerability, shame, fear and anxiety. In light of the emotional factors involved, the procedure may be viewed as a source of stress for the patient, and so, requires the implementation of strategies for approaching such a challenging situation. Objective: To analyze the perception of stress, according to bio-social and clinical variables, and coping styles of patients during the period preceding a colonoscopy procedure. Methods: This is a descriptive, transversal, field study with a quantitative approach developed by the Endoscopy Service of São Paulo Hospital University (HU-USP). One hundred patients in the preparatory stages were interviewed, of whom 100% were adults who had received a formal referral for the colonoscopy procedure. For the analysis, the following were employed: the Perceived Stress Scale (PSS-10), the Ways of Coping Questionare of Folkman and Lazarus (1985), as well as a semi-structured interview guide whose aim was to characterize the study population. Results: The bio-social profile of the sample population was predominantly female (73%), 65 years or older (50%), married or with a partner (90%) with at least one child (38%). The sample population also consisted of individuals with an eighth-grade or above level of education (33%), who professed a Faith of either Catholic or Evangelical (48% and 45%, respectively), for the most part retired (48%), with a history of hypertension (90%) and a family member with colon cancer (68%); 59% of the patients undergoing preparations revealed a medium level of perceived stress and the coping styles most utilized by these patients were the Social Support style (6,43±1,54), Acceptance of Responsibility Style (5,70±2,41) and Positive Reappraisal style (5,64±1,41). The variables of gender, age, marital status, schooling, type of preparation, and number of exams previously realized proved to be predictive factors of stress among this population. The statistically significant correlations within this study revealed themselves to be an association between PSS-10 and the coping strategies of Confrontive Coping, Distancing, Seeking Social Support, Acceptance of Responsibility and Positive Reappraisal. Among these predictors, an association of female, 65 years, married or with a partner, secondary schooling either complete or incomplete, with a outpatients preparation and patients with at least one procedure conducted style of PSS-10. Conclusion: The analysis of stress in the realization of colonoscopy exams is a little studied area in our field, as is the association of coping processes. The perception of stress was greater among the participants of the study, when compared with the instrument validation population. In terms of coping mechanisms, it was observed that those that focus on emotion were prevalent. The results of this study allow for a development of interventions that focus on diminishing stress in these patients. The results also permit that the coping mechanisms encountered in this analysis be utilized to better the work of care practitioners.

Os exames endoscópicos são considerados procedimentos invasivos, desconfortáveis e estressantes. A colonoscopia, em virtude da necessidade de laxantes para o preparo do cólon, de sua complexidade técnica e do constrangimento devido à maior exposição, causa ansiedade, preocupação e preconceito. No entanto, a colonoscopia é, atualmente, o procedimento de escolha para investigação de enfermidades do intestino grosso de elevada acurácia e possibilidade de realização de procedimentos terapêuticos, mas requer elevada colaboração e tolerância dos pacientes. A tolerância pode ser interpretada de várias maneiras, como aceitação, nível de satisfação e conforto durante o exame, ou disposição para repetir o procedimento. Foi realizado no Centro de Diagnóstico do Serviço de Gastroenterologia Clínica do Instituto Central do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, um estudo observacional prospectivo, longitudinal, com o objetivo de avaliar o nível de tolerância do paciente submetido à colonoscopia e os fatores intervenientes na tolerância. No período de março a dezembro de 2008, foram avaliados 373 pacientes adultos consecutivos, submetidos à colonoscopia eletiva. Foram incluídos pacientes submetidos a exames eletivos, com idade acima de 18 anos, com compreensão e aceitação da entrevista e do procedimento, e que assinaram o termo de consentimento livre e esclarecido. Um inquérito foi aplicado antes, durante e após o exame, a partir de dois questionários: formulário do paciente, preenchido pelo médico pesquisador; e ficha de avaliação médica, preenchido pelos médicos pesquisador e executante. No presente estudo considerou-se tolerância como a disposição do paciente para repetir o exame. Esse questionamento foi aplicado imediatamente na pré-alta, com o indivíduo desperto e orientado, no mínimo duas horas após o procedimento. Os fatores avaliados no pré-exame, durante o exame e no pós-exame foram comparados entre o grupo de pacientes tolerantes e os não tolerantes. Noventa e um por cento dos pacientes avaliados mostraram-se tolerantes à colonoscopia. Maiores níveis de tolerância foram observados em pacientes do sexo masculino (p=0,005; OR=14,8), com idade entre 41 anos e 60 anos (p=0,003; OR=56,92), colaborativos durante o exame (p=0,013; OR=6,15) e que não apresentaram cólica durante o preparo intestinal (p=0,013; OR=5) ou dor abdominal após o procedimento (p=0,032; OR=3,25). Um dos fatores limitantes do presente estudo foi o desconhecimento da razão pela qual o paciente não faria novamente o exame. A diferente graduação dos médicos colonoscopistas, a inclusão de pacientes ambulatoriais e internados submetidos à cirurgia colorretal tornaram a amostra heterogênea, porém mais representativa da prática clínica. Nessa amostra, a dor abdominal associada à colonoscopia foi o elemento mais significativo na caracterização da tolerância / Endoscopic assessments are considered invasive, uncomfortable and stressful procedures. The colonoscopy, due to the need for laxative use for colon preparation, its technical complexity and the embarrassment caused by privacy exposure, results in anxiety, concern and prejudice. However, the colonoscopy is currently the procedure of choice to investigate large bowel disorders, due to its high accuracy and the possibility of performing therapeutic procedures during the examination, but it requires a high degree of collaboration and compliance on the part of the patient. Tolerance can be interpreted in different ways, such as acceptance, level of satisfaction, and comfort during the examination, or willingness to have the procedure repeated. A prospective observational study was carried out at the Diagnostic Center of the Service of Clinical Gastroenterology of Instituto Central of Hospital das Clínicas of the School of Medicine of the University of São Paulo (HCFMUSP), aiming at evaluating the level of tolerance of patients submitted to colonoscopy and the factors that interfere with this tolerance. A total of 373 consecutive adult patients submitted to elective colonoscopy were studied from March to December 2008. The inclusion criteria consisted of patients submitted to elective examinations, aged 18 and older, which understood and agreed with the interview and the procedure and signed the Free and Informed Consent Form. A survey was applied before, during and after the examination, based on two questionnaires: the patients questionnaire, filled out by the medical researcher and the medical assessment file, filled out by the medical researcher and the attending physician. The present study considered the patients tolerance as the willingness to have the procedure repeated. This survey was applied immediately at the pre-hospital discharge, when the patient was conscious and oriented, at least two hours after the procedure. The factors assessed before, during and after the examination were compared between the groups of compliant and non-compliant patients. A total of 91% of the assessed patients showed to be compliant with the colonoscopy. Higher levels of tolerance were observed in male patients (p=0.005; OR=14.8), aged 41 to 60 years (p=0.003; OR=56.92), who collaborated during the examination (p=0.013; OR=6.15) and did not have colic during the intestinal preparation (p=0.013; OR=5) or abdominal pain after the procedure (p=0.032; OR=3.25). One limitation of the present study was the lack of information on why the patient would not have the procedure repeated. The varied degrees of skill presented by colonoscopists, the inclusion of outpatients and inpatients submitted to colorectal surgery made the sample a more heterogeneous one, albeit more representative of clinical practice. In this sample, abdominal pain associated with the colonoscopy was the most significant element in the characterization of tolerance

Various hand-crafted features have been explored for medical image classification, which include SIFT and Local Binary Patterns (LBP). However, hand-crafted features may not be optimally discriminative for classifying images from particular domains (e.g. colonoscopy), as not necessarily tuned to the domain’s characteristics. In this work, I give emphasis on learning highly discriminative local features and image representations to achieve the best possible classification performance for medical images, particularly for colonoscopy and histology (cell) images. I propose approaches to learn local features using unsupervised and weakly-supervised methods, and an approach to improve the feature encoding methods such as bag-of-words. Unlike the existing work, the proposed weakly-supervised approach uses image-level labels to learn the local features. Requiring image-labels instead of region-level labels makes annotations less expensive, and closer to the data normally available from normal clinical practice, hence more feasible in practice. In this thesis, first, I propose a generalised version of the LBP descriptor called the Generalised Local Ternary Patterns (gLTP), which is inspired by the success of LBP and its variants for colonoscopy image classification. gLTP is robust to both noise and illumination changes, and I demonstrate its competitive performance compared to the best performing LBP-based descriptors on two different datasets (colonoscopy and histology). However LBP-based descriptors (including gLTP) lose information due to the binarisation step involved in their construction. Therefore, I then propose a descriptor called the Extended Multi-Resolution Local Patterns (xMRLP), which is real-valued and reduces information loss. I propose unsupervised and weakly-supervised learning approaches to learn the set of parameters in xMRLP. I show that the learned descriptors give competitive or better performance compared to other descriptors such as root-SIFT and Random Projections. Finally, I propose an approach to improve feature encoding methods. The approach captures inter-cluster features, providing context information in the feature as well as in the image spaces, in addition to the intra-cluster features often captured by conventional feature encoding approaches. The proposed approaches have been evaluated on three datasets, 2-class colonoscopy (2, 100 images), 3-class colonoscopy (2, 800 images) and histology (public dataset, containing 13, 596 images). Some experiments on radiology images (IRMA dataset, public) also were given. I show state-of-the-art or superior classification performance on colonoscopy and histology datasets.

Colonoscopy is the current standard for colorectal cancer screening. This procedure requires improvement since it causes patient pain and can even result in injury. Novel colonoscopy devices have to be evaluated to gain information about their performance. At the preclinical stage of the device development the evaluation is typically performed in laboratory experiments. For these experiments an artificial environment is required which can recreate the anatomical and biomechanical features of the colon. A colonoscopy simulator for the evaluation of colonoscopy devices was developed within the ERC funded CoDIR project (Colonic Disease Investigation by Robotic Hydrocolonoscopy). The here developed simulator had to provide a colon phantom with realistic biomechanical properties as well as a sensor setup to measure signals which can be used to quantify the performance of devices which are tested within the simulator. Related literature was reviewed and possible tissue mimicking materials were selected. The suitability of the selected materials was evaluated by testing the frictional and elastic properties of the materials and subsequently comparing the results to those of colon tissue. PVA cryogel was selected as the most suitable material as it exhibits comparable elasticity and coefficients of friction. The tissue mimicking materials were mould casted into phantoms which were designed to represent the anatomical features of the colon. A simulator environment was developed which integrates the phantom as well as force and pressure sensors into a functional system. The sensors measure mesenteric forces and intraluminal pressures which can be related to the performance of tested devices. The simulator allows the arrangement of the sensors and the phantoms in an adjustable, modular approach. The simulator environment was successfully applied in the evaluation of a novel colonoscopy device. The results indicate that PVA cryogels exhibit unique mechanical properties which can be compared to those of colon tissue. The developed colonoscopy simulator provides a promising tool which can aid the development of novel colonoscopy devices.

Os exames endoscópicos são considerados procedimentos invasivos, desconfortáveis e estressantes. A colonoscopia, em virtude da necessidade de laxantes para o preparo do cólon, de sua complexidade técnica e do constrangimento devido à maior exposição, causa ansiedade, preocupação e preconceito. No entanto, a colonoscopia é, atualmente, o procedimento de escolha para investigação de enfermidades do intestino grosso de elevada acurácia e possibilidade de realização de procedimentos terapêuticos, mas requer elevada colaboração e tolerância dos pacientes. A tolerância pode ser interpretada de várias maneiras, como aceitação, nível de satisfação e conforto durante o exame, ou disposição para repetir o procedimento. Foi realizado no Centro de Diagnóstico do Serviço de Gastroenterologia Clínica do Instituto Central do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, um estudo observacional prospectivo, longitudinal, com o objetivo de avaliar o nível de tolerância do paciente submetido à colonoscopia e os fatores intervenientes na tolerância. No período de março a dezembro de 2008, foram avaliados 373 pacientes adultos consecutivos, submetidos à colonoscopia eletiva. Foram incluídos pacientes submetidos a exames eletivos, com idade acima de 18 anos, com compreensão e aceitação da entrevista e do procedimento, e que assinaram o termo de consentimento livre e esclarecido. Um inquérito foi aplicado antes, durante e após o exame, a partir de dois questionários: formulário do paciente, preenchido pelo médico pesquisador; e ficha de avaliação médica, preenchido pelos médicos pesquisador e executante. No presente estudo considerou-se tolerância como a disposição do paciente para repetir o exame. Esse questionamento foi aplicado imediatamente na pré-alta, com o indivíduo desperto e orientado, no mínimo duas horas após o procedimento. Os fatores avaliados no pré-exame, durante o exame e no pós-exame foram comparados entre o grupo de pacientes tolerantes e os não tolerantes. Noventa e um por cento dos pacientes avaliados mostraram-se tolerantes à colonoscopia. Maiores níveis de tolerância foram observados em pacientes do sexo masculino (p=0,005; OR=14,8), com idade entre 41 anos e 60 anos (p=0,003; OR=56,92), colaborativos durante o exame (p=0,013; OR=6,15) e que não apresentaram cólica durante o preparo intestinal (p=0,013; OR=5) ou dor abdominal após o procedimento (p=0,032; OR=3,25). Um dos fatores limitantes do presente estudo foi o desconhecimento da razão pela qual o paciente não faria novamente o exame. A diferente graduação dos médicos colonoscopistas, a inclusão de pacientes ambulatoriais e internados submetidos à cirurgia colorretal tornaram a amostra heterogênea, porém mais representativa da prática clínica. Nessa amostra, a dor abdominal associada à colonoscopia foi o elemento mais significativo na caracterização da tolerância / Endoscopic assessments are considered invasive, uncomfortable and stressful procedures. The colonoscopy, due to the need for laxative use for colon preparation, its technical complexity and the embarrassment caused by privacy exposure, results in anxiety, concern and prejudice. However, the colonoscopy is currently the procedure of choice to investigate large bowel disorders, due to its high accuracy and the possibility of performing therapeutic procedures during the examination, but it requires a high degree of collaboration and compliance on the part of the patient. Tolerance can be interpreted in different ways, such as acceptance, level of satisfaction, and comfort during the examination, or willingness to have the procedure repeated. A prospective observational study was carried out at the Diagnostic Center of the Service of Clinical Gastroenterology of Instituto Central of Hospital das Clínicas of the School of Medicine of the University of São Paulo (HCFMUSP), aiming at evaluating the level of tolerance of patients submitted to colonoscopy and the factors that interfere with this tolerance. A total of 373 consecutive adult patients submitted to elective colonoscopy were studied from March to December 2008. The inclusion criteria consisted of patients submitted to elective examinations, aged 18 and older, which understood and agreed with the interview and the procedure and signed the Free and Informed Consent Form. A survey was applied before, during and after the examination, based on two questionnaires: the patients questionnaire, filled out by the medical researcher and the medical assessment file, filled out by the medical researcher and the attending physician. The present study considered the patients tolerance as the willingness to have the procedure repeated. This survey was applied immediately at the pre-hospital discharge, when the patient was conscious and oriented, at least two hours after the procedure. The factors assessed before, during and after the examination were compared between the groups of compliant and non-compliant patients. A total of 91% of the assessed patients showed to be compliant with the colonoscopy. Higher levels of tolerance were observed in male patients (p=0.005; OR=14.8), aged 41 to 60 years (p=0.003; OR=56.92), who collaborated during the examination (p=0.013; OR=6.15) and did not have colic during the intestinal preparation (p=0.013; OR=5) or abdominal pain after the procedure (p=0.032; OR=3.25). One limitation of the present study was the lack of information on why the patient would not have the procedure repeated. The varied degrees of skill presented by colonoscopists, the inclusion of outpatients and inpatients submitted to colorectal surgery made the sample a more heterogeneous one, albeit more representative of clinical practice. In this sample, abdominal pain associated with the colonoscopy was the most significant element in the characterization of tolerance

This thesis examines the benefits and costs of screening for colorectal cancer in the context of an organised population screening programme. It uses microsimulation modelling to derive an optimally cost-effective screening protocol for various combinations of the available screening tests. ¶ First a mathematical model for the natural history of colorectal cancer is derived, based on analyses of Australian population and hospital-based cancer registries combined with data from published studies. Then a model for population based screening is derived based mainly on data from published screening studies, including the four major published randomised controlled trials of faecal occult blood test (FOBT) screening. These two models are used to simulate the application of a screening programme to the Australian population. The simulations are applied to a period of 40 years following 1990 (the study’s base year), with both costs and benefits discounted back to the base year at an annual rate of 3%.¶ The models are applied to simulating a population screening programme based on FOBT with a colonoscopy follow up of positive tests. This simulation suggests that the optimal application of such a programme would be to offer annual screening to people aged 50 to 84 years. Such a programme would lead to a cumulative fall in years of life lost to colorectal cancer (YLL) of 28.5% at a cost per year of life saved (YLS) of $8,987. These costs and benefits are consistent with those arising from other currently funded health interventions. They are also consistent with the cost per YLS which Australian governments appear willing to pay for health interventions when justified on the basis of cost-effectiveness. The fall in colorectal cancer deaths from this screening programme should be first detectable by a national monitoring system after around three years of screening. However the full benefits from screening would not be realised before around 30 years of screening.¶ These simulations are based on the standard guaiac FOBT, but the results suggest that significant cost-effective gains could be made by using the newer immunochemical FOBT. Further cost-effect gains could be made by offering sigmoidoscopy every five years in addition to annual FOBT.¶ The models are then applied to simulating population screening programmes using colonoscopy and sigmoidoscopy as primary screening tools. Offering colonoscopy every ten years to all people aged from 45 to 85 leads to an overall fall in cumulative YLL of 37.6%, at a cost of $15,585 per YLS. Offering sigmoidoscopy every three years to all people aged 40 to 85 leads to an overall fall in cumulative YLL of 29.1%, at a cost of $4,862 per YLS. Both of these cost and benefit results are also consistent with the cost per YLS which Australian governments appear willing to pay. The fall in deaths with colonoscopy screening would also be detectable after three years of screening but the fall with sigmoidoscopy screening would not be detectable until after six years of screening. Sigmoidoscopy would need around 35 years of screening to reach its potential gains while colonoscopy screening would not reach its full potential during the 40 year screening period.¶ Finally the models are applied to targeting people at higher risk of cancer. The results show that offering colonoscopy every five years to people at higher risk because of a family history of colorectal cancer is a cost-effective addition to the annual FOBT screening programme.¶ An earlier version of chapter two of this thesis has been published as Stevenson CE 1995. Statistical models for cancer screening. Statistical Methods in Medical Research; 4: 19–23.¶ An expanded version of chapter two, along with parts of chapter one, has been published as Stevenson CE 1998. Models of screening. In: Encyclopedia of Biostatistics. Armitage P, Colton T, eds. John Wiley and Sons Ltd, pp 3999–4022.

Koloskopi är en undersökning av tjocktarmen som förväntas öka i antal eftersom studiervisar att screening minskar dödligheten i kolorektalcancer. Patienten kan i vissa falluppleva undersökningen som smärtsam och obehaglig. Sjuksköterskan har enbetydelsefull roll i omvårdnaden. Syftet med studien var att belysa faktorer sompåverkar upplevelsen av smärta och obehag vid en koloskopiundersökning utansedering. Metoden var en litteraturstudie baserad på 19 vetenskapliga artiklar som harkvalitetsbedömts enligt protokoll. Vid analysen skapades tre övergripande kategorier.Fysiska faktorer som påverkar smärtupplevelsen, personlig upplevelse av smärta ochobehag samt patientens erfarenhet. I resultatet framkom följande huvudfynd. Skillnadenmellan hur kvinnor och män upplevde smärta, svårigheter med att mäta och bedömasmärta och obehag samt patientens erfarenhet och dess betydelse för smärtupplevelsen.Det är viktigt med en individanpassad smärthantering. Sjuksköterskan bör ha en adekvatsmärtutbildning och en bred erfarenhet för att kunna ge en god omvårdnad vidkoloskopiundersökningen. / Colonoscopy is an examination of the colon, which is expected to increase in numbersince studies show that screening reduces mortality from colorectal cancer. The patientmay sometimes feel that the examination is painful and unpleasant. The nurse has animportant role in the care of the patient. The aim of this study was to elucidate factorsaffecting the experience of pain and discomfort during a colonoscopy without sedation.The method was a literature review based on 19 scientific articles that have beenassessed according to quality protocols. The analysis generated three broad categories.Physical factors affecting the experience of pain, personal experience of pain anddiscomfort, and the patient's experience. The results revealed the following keyfindings: The difference between how men and women experienced pain, difficulty inmeasuring and assessing pain and discomfort and the patient's experience and itsrelevance to pain. It is important to have an individualized pain management plan. Thenurse should have an adequate pain education and wide experience in order to providegood care during colonoscopy.