The integumental appendages of the turtle shell: An evo-devo perspective

The turtle shell is composed of dorsal armor (carapace) and ventral armor (plastron) covered by a keratinized epithelium. There are two epithelial appendages of the turtle shell: scutes (large epidermal shields separated by furrows and forming a unique mosaic) and tubercles (numerous small epidermal bumps located on the carapaces of some species). In our perspective, we take a synthetic, comparative approach to consider the homology and evolution of these integumental appendages. Scutes have been more intensively studied, as they are autapomorphic for turtles and can be diagnostic taxonomically. Their pattern of tessellation is stable phylogenetically, but labile in the individual. We discuss the history of developmental investigations of these structures and hypotheses of evolutionary and anomalous variation. In our estimation, the scutes of the turtle shell are an evolutionary novelty, whereas the tubercles found on the shells of some turtles are homologous to reptilian scales.Peer reviewe

Automatic 3D extraction of pleural plaques and diffuse pleural thickening from lung MDCT images

Pleural plaques (PPs) and diffuse pleural thickening (DPT) are very common asbestos related pleural diseases (ARPD). They are currently identified non-invasively using medical imaging techniques. A fully automatic algorithm for 3D detection of calcified pleura in the diaphragmatic area and thickened pleura on the costal surfaces from multi detector computed tomography (MDCT) images has been developed and tested. The algorithm for detecting diaphragmatic pleura includes estimation of the diaphragm top surface in 3D and identifying those voxels at a certain vertical distance from the estimated diaphragm, and with intensities close to that of bone, as calcified pleura. The algorithm for detecting thickened pleura on the costal surfaces includes: estimation of the pleural costal surface in 3D, estimation of the centrelines of ribs and costal cartilages and the surfaces that they lie on, calculating the mean distance between the two surfaces, and identifying any space between the two surfaces whose distance exceeds the mean distance as thickened pleura. The accuracy and performance of the proposed algorithm was tested on 20 MDCT datasets from patients diagnosed with existing PPs and/or DPT and the results were compared against the ground truth provided by an experienced radiologist. Several metrics were employed and evaluations indicate high performance of both calcified pleura detection in the diaphragmatic area and thickened pleura on the costal surfaces. This work has made significant contributions to both medical image analysis and medicine. For the first time in medical image analysis, the approach uses other stable organs such as the ribs and costal cartilage, besides the lungs themselves, for referencing and landmarking in 3D. It also estimates fat thickness between the rib surface and pleura (which is usually very thin) and excludes it from the detected areas, when identifying the thickened pleura. It also distinguishes the calcified pleura attached to the rib(s), separates them in 3D and detects calcified pleura on the lung diaphragmatic surfaces. The key contribution to medicine is effective detection of pleural thickening of any size and recognition of any changes, however small. This could have a significant impact on managing patient risks

Diagnostic and prognostic biomarkers of malignant pleural mesothelioma

Malignant Pleural Mesothelioma (MPM) is an aggressive intrathoracic malignancy with an overall poor prognosis. MPM is associated with asbestos exposure but has a long latency period between exposure and disease development. Incidence of MPM in the UK is therefore still rising, predicted to reach a peak in 2020. The majority of patients with MPM present with breathlessness, frequently due to a pleural effusion and/or chest pain. Diagnosis of MPM can be difficult. Radiological detection of early stage MPM in particular can be challenging, as pleural tumour, nodularity or significant pleural thickening may not be evident. Diagnosis is further complicated by the low yield of pleural fluid cytology examination in MPM and pleural biopsy is therefore usually required to allow definitive diagnosis. This can be achieved under image guidance, at surgical thoracoscopy or at local anaesthetic thoracoscopy (LAT). A significant number of patients are either elderly or have co-morbidity precluding general anaesthesia and surgical thoracoscopy. Image-guided pleural biopsy is not always feasible, particularly in the absence of significant pleural thickening. LAT remains a limited resource in the UK. A non-invasive biomarker of MPM, which could be performed early in the patient’s presentation, and that could be available to most hospitals, would therefore be a major clinical advance, allowing clinicians to direct appropriate patients to specialist centres with access to LAT and specialist MDT input where MPM appears likely. There have been several potential blood biomarkers identified in the mesothelioma literature, including the most widely studied, Mesothelin, and more recently Fibulin-3 and SOMAscan™. Unfortunately study results have been variably limited by retrospective study design, inconsistent sampling time points, inconsistent results and lack of external validation, therefore despite initial promising results, none of these biomarkers have entered routine clinical practice for diagnosis. Similarly, utility of imaging biomarkers such as perfusion Computed Tomography (CT), Positron Emission Tomography (PET) and Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI) has been limited by high radiation dose, limited availability, and requirement for bulky (and therefore late stage) disease for assessment respectively. In chapter 2, study design, recruitment and preliminary results of the DIAPHRAGM (Diagnostic and Prognostic Biomarkers in the Rational Assessment of Mesothelioma) study are reported. A prospective, multi-centre study was designed, recruiting patients with suspected pleural malignancy (SPM) at initial presentation to secondary care services, from a mixture of academic and more clinical units in the UK and Ireland, in addition to asbestos-exposed control subjects. In one of the largest biomarker studies in mesothelioma to date, 639 patients with SPM and 113 asbestos-exposed control subjects were recruited over three years. Data cleaning is being finalised by the Cancer Research UK Clinical Trials Unit Glasgow at the time of writing. Preliminary results reveal that 26% (n=154) patients recruited to the SPM cohort were diagnosed with MPM, 33% (n=209) had secondary pleural malignancy and 34% (n=218) were diagnosed with benign pleural disease. A final diagnosis is awaited in 7% (n=47) at the time of writing. SOMAscan™ and Fibulin-3 biomarker analyses are ongoing and DIAPHRAGM will definitively answer the question of diagnostic utility of these blood biomarkers in routine clinical practice, in a ‘real-life’ MPM population, relative to that of Mesothelin. In chapter 3, contrast-enhanced MRI was performed in patients with suspected MPM and a novel MRI biomarker of pleural malignancy defined (Early Contrast Enhancement – ECE). ECE was defined as a peak in pleural signal intensity at or before 4.5 minutes after intravenous Gadobutrol administration. ECE assessment was successfully performed in all patients who underwent contrast-enhanced MRI. This included patients with pleural thickening 0.533AU/s), indicative of high tumour vascularity, was associated with poor median overall survival (12 months vs. 20 months, p=0.047). Staging of MPM represents an additional challenge to clinicians. This is due to the complex morphology and often rind-like growth pattern of MPM. In addition, delineation of pleural disease from adjacent structures such as intercostal muscle and diaphragm can be difficult to assess, particularly at CT, which is the most commonly used imaging modality for diagnostic and staging assessment in MPM. Current clinical staging frequently underestimates extent of disease, with a significant proportion of patients being upstaged at time of surgery, and is limited by high inter-observer variability. Recent studies have reported the prognostic significance of CT-derived tumour volume; however, many of these studies have been limited by the laborious or complex nature of tumour segmentation, significant inter-observer variability or challenges encountered in separating pleural tumour from adjacent structures, which are often of similar density. MRI is superior to CT in the detection of invasion of the chest wall and diaphragm in MPM. In Chapter 4, MRI was used to quantitatively assess pleural tumour volume in 31 patients with MPM using novel semi-automated segmentation methodology. Four different segmentation methodologies, using Myrian® segmentation software were developed and examined. Optimum methodology was defined, based on the accuracy of volume estimates of an MRI phantom, visual-based analysis, intra-observer agreement and analysis time. Using the optimum methodology, there was acceptable error around the MRI phantom volume (3.6%), a reasonable analysis time (approximately 14 minutes), good intra-observer agreement (intra-class correlation coefficient (ICC) 0.875) and excellent inter-observer agreement (ICC 0.962). Patients with a high MRI-estimated tumour volume (≥300cm3) had a significantly poorer median overall survival (8.5 months vs. 20 months) and was a statistically significant prognostic variable on univariate (HR 2.273 (95% CI 1.162 – 4.446), p=0.016) and multi-variate Cox proportional hazards model (HR 2.114 (95% CI 1.046 – 4.270), p=0.037)

Measurement of treatment response and survival prediction in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare cancer of the mesothelial cells of the visceral and parietal pleurae that is heterogeneous in terms of biology, prognosis and response to systemic anti-cancer therapy (SACT). The primary tumour forms an unusual, complex shape which makes survival prediction and response measurement uniquely challenging. Computed tomography (CT) imaging is the bedrock of radiological quantification and response assessment, but it has major limitations that translate into low sensitivity and high inter-observer variation when classifying response using Response Evaluation Classification In Solid Tumours (mRECIST) criteria. Magnetic resonance imaging (MRI) tools have been developed that overcome some of these problems but cost and availability of MRI mean that optimisation of CT and better use for data acquired by this method are important priorities in the short term. In this thesis, I conducted 3 studies focused on, 1) development of a semi-automated volumetric segmentation method for CT based on recently positive studies in MRI, 2) training and external validation of a deep learning artificial intelligence (AI) tool for fully automated volumetric segmentation based on CT data, and, 3) use of non-tumour imaging features available from CT related to altered body composition for development of new prognostic models, which could assist in selection of patients for treatment and improving tolerance to treatment by targeting the systemic consequences of MPM. The aim of Chapter 3 is to develop a semi-automated MPM tumour volume segmentation method that would serve as the ground truth for the training of a fully automated AI algorithm. A semi-automated approach to pleural tumour segmentation has been developed using MRI scans which calculated volumetric measurements from seed points - defined by differential tumour enhancement - placed within a pre-defined volume of pleural tumour. I extrapolated this MRI method using contrast-enhanced CT scans in 23 patients with MPM. Radiodensity values – defined by Hounsfield units (HU) - were calculated for the different thoracic tissues by placing regions of interest (ROI) on visible areas of pleural tumour with similar ROIs placed on other thoracic tissues. Pleural volume contours were drawn on axial CT slices and propagated throughout the volume by linear interpolation using volumetric software (Myrian Intrasense® software v2.4.3 (Paris, France)). Seed points based on the radiodensity range of pleural tumour were placed on representative areas of tumour with regions grown. There were similarities in median thoracic tissue HU values: pleural tumour, 52 [IQR 46 to 60] HU; intercostal muscle, 20.4 [IQR 11.9 to 32.3] HU; diaphragm, 40.4 [IQR 26.4 to 56.4] HU and pleural fluid, 11.8 [IQR 8.3 to 17.8] HU. There was also reduced definition between MPM tumour and neighbouring structures. The mean time taken to complete semi-automated volumetric segmentations for the 8 CT scans examined was 25 (SD 7) minutes. The semi-automated CT volumes were larger than the MRI volumes with a mean difference between MRI and CT volumes of -457.6 cm3 (95% limits of agreement -2741 to +1826 cm3). The complex shape of MPM tumour and overlapping thoracic tissue HU values precluded HU threshold-based region growing and meant that semi-automated volumetry using CT was not possible in this thesis. Chapter 4 describes a multicentre retrospective cohort study that developed and validated an automated AI algorithm – termed a deep learning Convolutional Neural Network (CNN) - for volumetric MPM tumour segmentation. Due to the limitations of the semi-automated approach described in Chapter 3, manually annotated tumour volumes were used to train the CNN. The manual segmentation method ensured that all the parietal pleural tumour was included in the respective volumes. Although the manual CT volumes were consistently smaller than semi-automated MRI volumes (average difference between AI and human volumes 74.8 cm3), they were moderately correlated (Pearson’s r=0.524, p=0.0103). There was strong correlation (external validation set r=0.851, p<0.0001) and agreement (external validation set mean AI minus human volume difference of +31 cm3 between human and AI tumour volumes). AI segmentation errors (4/60 external validation set cases) were associated with complex anatomical features. There was agreement between human and AI volumetric responses in 20/30 (67%) cases. There was agreement between AI volumetric and mRECIST classification responses in 16/30 (55%) cases. Overall survival (OS) was shorter in patients with higher AI-defined pre-chemotherapy tumour volumes (HR=2.40, 95% CI 1.07 to 5.41, p=0.0114). Survival prediction in MPM is difficult due to the heterogeneity of the disease. Previous survival prediction models have not included measures of body composition which are prognostic in other solid organ cancers. In Chapter 5, I explore the impact of loss of skeletal muscle and adipose tissue at the level of the third lumbar vertebra (L3) and the loss of skeletal muscle at the fourth thoracic (T4) vertebrae on survival and response to treatment in patients with MPM receiving chemotherapy. Skeletal and adipose muscle areas at L3 and T4 were quantified by manual delineation of relevant muscle and fat groups using ImageJ software (U.S. National Institutes of Health, Bethesda, MD) on pre-chemotherapy and response assessment CT scans, with normalisation for height. Sarcopenia at L3 was not associated with shorter OS at the pre-chemotherapy (HR 1.49, 95% CI 0.95 to 2.52, p=0.077) or response assessment time points (HR 1.48, 95% CI 0.97 to 2.26, p=0.0536). A higher visceral adipose tissue index (VFI) measured at L3 was associated with shorter OS (HR 1.95, 95% CI 1.05 to 3.62, p=0.0067). In multivariate analysis, obesity was associated with improved OS (HR 0.36, 95% CI 0.20 to 0.65, p<0.001) while interval VFI loss (HR 1.81, 95% CI 1.04 to 3.13, p=0.035) was associated with reduced OS. Overall loss of skeletal muscle index at the fourth thoracic vertebra (T4SMI) during treatment was associated with poorer OS (HR 2.79, 95% CI 1.22 to 6.40, p<0.0001). Skeletal muscle index on the ipsilateral side of the tumour at the fourth thoracic vertebra (Ipsilateral T4SMI) loss was also associated with shorter OS (HR 2.91, 95% CI 1.28 to 6.59, p<0.0001). In separate multivariate models, overall T4SMI muscle loss (HR 2.15, 95% CI 102 to 4.54, p=0.045) and ipsilateral T4SMI muscle loss (HR 2.85, 95% CI 1.17 to 6.94, p=0.021) were independent predictors of OS. Response to chemotherapy was not associated with decreasing skeletal muscle or adipose tissue indices

Lung cancer screening in the NELSON trial: balancing harms and benefits

__Abstract__ In this thesis, the harms and benefits of lung cancer screening using low-dose computed tomography were investigated. Data of the Dutch-Belgian NELSON trial were used to quantify its harms and benefits and develop strategies to improve the balance between them. If the NELSON trial demonstrates that low-dose CT screening is an effective method to reduce mortality from lun

Extracellular lipid particles in atherosclerosis and aortic stenosis

Aortic stenosis and athrosclerosis are slowly progressing diseases. Being clinically silent, as they start developing decades before they cause symptoms, cardiovascular diseases and atherosclerosis in particular, are the leading cause of morbitidy and mortality in the Western world. Lipid accumulation begins both in the artery walls and in the aortic valves before any clinical signs of atherosclerosis or aortic stenosis can be detected. While atherosclerotic lesions are characterized with cells filled with lipid droplets i.e. foam cells, and they are found to be calcified only in the late stages of atherosclerosis, the stenotic aortic valve leaflets contain both lipid droplets and calcified nodules already in early lesions. The proteoglycan matrix common to artery wall and aortic valve leaflets retains the entering lipoprotein particles that are then enzymatically and oxidatively modified. Such modifications have an ability to transform the non-inflammatory plasma lipoprotein particles into crystals and particles that can induce sterile inflammation in the various intimal and valvular cells. This thesis was set to study the distribution and characteristics of the extracellular lipid and to reveal the origin of the extracellular lipid particles. Prior to the analyses of the isolated extracellular lipid particles, the human carotid artery plaques were imaged with three-dimensional electron microscopy and sections of human coronary arteries were analyzed with imaging mass spectrometry to study the spatial distribution of lipids in different stages of atherosclerosis. In the human coronary arteries, the lipid domains found in advanced atherosclerotic lesions were different from the domains found in atheroma-stage artery sections, and even more different from healthy sections of coronary arteries. In the human carotid artery plaques, cholesterol crystals were found to be large sheets or needle-like structures, and they appeared to be growing out from large lipid particles in the intima. For the purpose of studying the chemical and physical characteristics of the extracellular lipid particles, the extracellular particles were isolated from aortic valve leaflets and coronary artery plaques. The lipid particles were examined with multiple tools to study their lipid composition, protein composition, protein structure, size, and density. The extracellular lipid particles, both in human aortic valve leaflets and human carotid arteries, were found to be derived from plasma lipoproteins, mainly from low density lipoprotein (LDL) or very low density lipoprotein (VLDL). Apart from multiple small exchangeable lipoproteins, like apolipoprotein (apo) E, apoA-family, and apoC-family, the particles contained mainly apolipoprotein B-100 (apoB-100), the integral protein of LDL and VLDL, and they contained features which suggest that they were multiply modified. Another goal was to find which modifications would change the intimal or valvular extracellular lipid particles to such fused and aggregated lipid particles that were found in the valves and intimal plaques, and which modifications would induce a sterile inflammatory response similar to the response the extracellular lipid particles induce. To study the possible culprit modifications, both the extracellular lipid particles, in vitro-generated cholesterol crystals, and LDL that was modified by lipolysis, proteolysis, and oxidation, were applied to human primary monocyte-derived macrophages. Both the isolated extracellular lipid particles and LDL modified with a combination of phospholipolysis by PLA2 and cholesterol esterase were found to be able to activate a multiprotein complex inflammasome in human primary monocyte-derived macrophages in vitro, and to induce the secretion of proinflammatory cytokines. According to the results of this thesis, the lipid particles in the arterial intima and in the aortic valve are active components of atherosclerosis and aortic stenosis. They can induce the cells in the intima and in the valve to produce inflammatory cytokines and thus can affect the progress of these diseases.Aorttastenoosi eli aorttaläpän kalkkinen kovettumatauti ja ateroskleroosi eli valtimokovettumatauti ovat hitaasti eteneviä tauteja. Koska nämä sydän- ja verisuonitaudit kehittyvät piilossa oireita aiheuttamatta jopa vuosikymmenten ajan, ne ovat yhä edelleen suomalaisten ja läntisen maailman kuolinsyytilastojen kärjessä. Lipidit eli rasva-aineet alkavat kertyä sekä aorttaläppään että valtimoiden seinämään jo paljon ennen kuin mitään kliinisiä merkkejä on havaittavissa. Ateroskleroosissa plakit ovat tyypillisesti täynnä rasvapartikkeleita eli lipidipartikkeleita ja soluja, jotka ovat täynnä rasvapisaroita (vaahtosoluja) ja ne kalkkiintuvat vasta taudin myöhäisvaiheessa. Aorttaläpissä on sen sijaan yhtä aikaa sekä lipidipartikkeleita ja kiteytynyttä kalkkia. Sekä aorttaläpässä että valtimon seinämässä on proteoglykaanikerros, johon lipidipartikkelit tarttuvat kiinni. Kiinni tarttuneet lipidipartikkelit voivat voivat muokkaantua entsyymien vaikutuksesta tai hapettumisen seurauksena. lipidipartikkelien muokkaantuminen voi saada aorttaläpän tai valtimon sisäkerroksen solut reagoimaan steriilillä tulehdusreaktiolla tai muokkaantuneet lipidipartikkelien sisältämä kolesteroli voi kiteytyä suuriksi kolesterolikiteiksi. Tässä väitöskirjassa tutkittiin solunulkoisten lipidipartikkeleiden ominaisuuksia ja niiden levittäytymistä solujen väliseen tilaan. Siten pyrittiin selvittämään solunulkoisten lipidipartikkeleiden alkuperä. Ihmisen kaulavaltimoiden seinämästä valmistettiin malleja kolmiulotteisten elektronimikroskooppikuvien avulla ja ihmisen sepelvaltimoleikkeitä tutkittiin kuvantavalla massaspektrometrilla. Näin saatiin selville, kuinka lipidipartikkelit sijaitsivat valtimoiden seinämässä. Terveiden sepelvaltimoiden lipidipartikkelikertymien laatu ja paikka erosivat aterooma-vaiheen plakkien lipidipartikkelikertymistä ja vielä enemmän ne erosivat pitkälle edenneestä ateroskleroottisesta plakista. Ihmisen kaulavaltimoiden plakeissa kolesterolikiteet olivat sekä neulamaisia että suuria levyjä ja ne näyttivät kasvavan suoraan suurista lipidipartikkeleista. Kemiallisten ja fysikaalisten ominaisuuksien selvittämiseksi lipidipartikkelit eristettiin sekä aorttaläpistä että kaulavaltimoista. Niistä tutkittiin lipidikoostumusta, proteiinikoostumusta, proteiiniosan rakennetta, partikkelien kokoa ja tiheyttä. Sekä aorttaläpän että kaulavaltimon lipidipartikkeleiden havaittiin olevan peräisin plasman apolipoproteiini (apo)B-100:aa sisältävistä lipoproteiinipartikkeleista, todennäköisimmin joko kevyen lipoproteiinin (LDL) tai erittäin kevyen lipoproteiinin (VLDL) partikkeleista. Partikkelit sisälsivät apoB-100:n lisäksi myös pieniä vaihdettavia apolipoproteiineja, kuten apolipoproteiini (apo) E:tä, apoA-proteiiniperheen ja apoC-proteiiniperheen apolipoproteiineja. ApoB-100 (LDL:n ja VLDL:n tärkein rakenneproteiini) oli yleisin löydetty proteiini. Lipidipartikkeleissa nähtiin merkkejä moninkertaisesta muokkautumisesta. Tutkimuksen toisena tavoitteena oli saada selville, miten aorttaläpän ja valtimon sisäseinämään jääneet lipidipartikkelit muuntuvat plasman lipoproteiineista suuriksi fuusioituneiksi ja aggregoituneiksi lipidipartikkeleiksi. Lisäksi haluttiin tietää, mitkä muokkausmekanismit muuntaisivat lipoproteiinit niin, että solut reagoisivat steriilillä tulehdusreaktiolla eli inflammasomi-kompleksin aktivaatiolla. Mahdollisia muuntumismekanismeja tutkittiin muokkaamalla LDL-partikkeleita lipolyyttisillä ja proteolyyttisillä entsyymeillä ja hapettamalla niitä. Näin muokattuja LDL-partikkeleita ja kaulavaltimoista eristettyjä lipidipartikkeleita annettiin ihmisen plasmasta eristetyistä monosyyteistä erilaistetuille makrofageille. Sekä solunulkoiset lipidipartikkelit että fosfolipolyysillä muokatut plasman lipoproteiinit saivat koeolosuhteissa makrofagit reagoimaan inflammasomin aktivaatiolla ja tuottamaan tulehdusvälittäjäaineita. Väitöskirjan tulosten mukaan voidaan todeta, että lipidipartikkelit aorttaläpässä ja valtimon sisäseinämässä ovat oleellinen osa aorttastenoosin ja ateroskleroosin syntyprosessissa. Ne saavat aorttaläpän ja valtimon sisäseinämän solut tuottamaan tulehdusvälittäjäaineita ja vaikuttavat siten sekä aorttastenoosin että ateroskleroosin etenemiseen

Small animal clinic and surgery

As part of the last step in concluding the Master’s degree in veterinary medicine, the current report was carried out. It is divided in three parts. The first part includes statistics regarding pathologies or symptoms of animals brought to Priory Veterinary Surgeons during the traineeship, with brief detailing of a disease or procedure relevant to each clinical and surgical area of small animal medicine. The second part is a review of available literature regarding canine non-Hodgkin lymphoma addressing its aetiology, diagnosis, immunophenotypes, presentations, therapeutics and prognosis. The third and last part is a description of a canine lymphoma case in a 9-year-old border collie with data regarding the diagnosis, management and the treatment protocol; Resumo: Clínica e Cirurgia de Pequenos Animais - O seguinte relatório foi elaborado como parte da última etapa para completar o mestrado em medicina veterinária. Está dividido em três partes. A primeira parte inclui a estatística das patologias ou sintomas dos animais que foram levados à Priory Veterinary Surgeons durante o período de estágio curricular, com um abreve revisão de uma doença ou procedimento relevante a cada área da clínica e cirurgia de medicina de animais de companhia. A segunda parte é uma revisão da literatura disponível sobre linfoma não-Hodgkin canino abordando a sua etiologia, diagnóstico, imunofenótipo, manifestação clínica, tratamento e prognóstico. A terceira e última parte é uma descrição de um caso de linfoma não Hodgkin canino de um border collie de 9 anos com dados sobre o diagnóstico, acompanhamento e tratamento

Maladies péritonéales : place et apport de l'imagerie par résonance magnétique

Magnetic resonance imaging (MRI) allows news approaches to improve diagnostic and therapeutic issues related to peritoneal diseases. This technique requires using dedicated protocols and has a learning curve. After a literature review on peritoneal imaging highlighting the role of MRI and its potential underutilization, the purpose of this work was to study the contribution of MRI in two models of diffuse peritoneal diseases. The first model concerned endometriosis. Using dedicated protocols, studies on digestive and diaphragmatic involvements reported high performance for providing a useful mapping of lesions for both diagnosis and surgical planning. The second model concerned peritoneal carcinomatosis. The purpose was to assess the contribution of MRI in selecting patients for curative surgery. The first study, performed in a large cohort, reported a very low impact of the different imaging techniques in the selection of non-resectable patients. Using a new approach combining MRI and computed tomography (CT), the second study demonstrated a substantial improvement in quantitative lesion assessment, although remaining sub optimal. With a qualitative approach evaluating signs of non-resectability, the third study showed MRI had better sensitivity than CT for the detection of non-resecable small bowel involvements in pseudomyxoma peritonei. MRI, thanks to its high contrast resolution, provides unique information. Used as reference technique or in addition to other techniques, MRI optimizes patient managementDe nouvelles approches sont possibles en imagerie par résonance magnétique (IRM) pour répondre aux principaux enjeux diagnostiques et thérapeutiques liés aux maladies péritonéales. Cette technique implique l'utilisation de protocoles dédiés et une courbe d'apprentissage. Après une revue de la littérature sur l'imagerie péritonéale mettant en perspective la place de l'IRM et sa potentielle sous utilisation, l'objectif de ce travail a été d'étudier l'apport de cette technique dans deux modèles de maladies péritonéales diffuses. Le premier modèle concernait l'endométriose. En utilisant des protocoles adaptés, les études sur les atteintes digestives et diaphragmatiques ont démontré qu'une cartographie lésionnelle utile au diagnostic et à la prise en charge chirurgicale gynécologique pouvait être obtenue avec de hauts niveaux de performance. Le second modèle concernait la carcinose. La problématique était d'évaluer l'apport de l'IRM dans la sélection des patients candidats à une chirurgie menée à visée curative. La première étude menée sur une grande cohorte a démontré un très faible impact des différentes techniques d'imagerie dans la sélection des patients non résécables. La seconde étude, proposant une nouvelle approche de la quantification des lésions en combinant l'IRM au scanner, a rapporté une amélioration relative du bilan lésionnel, bien qu'encore infra optimale. Avec une approche qualitative centrée sur la recherche de signes de non résécabilité, la troisième étude a démontré que l'IRM avait une meilleure sensibilité que le scanner pour détecter les atteintes non résécables de l'intestin grêle dans le pseudomyxome péritonéal. L'IRM, grâce à sa haute résolution en contraste, offre des informations uniques. Utilisée comme technique de référence ou en complément des autres techniques en fonction de la nature des lésions à explorer, elle permet d'optimiser la prise en charge des patient