Tissue engineering is limited by inability to create early and adequate blood supply. In-vivo DCE-MRI has imaged angiogenesis in soft tissues, yet has not been considered in hard tissues. Bilateral critical defects created in parietal bones of eighteen adult rabbits were left void, treated with haluronic acid acellular matrix (HA-ACM), or HA-ACM impregnated with vascular endothelial growth factor (VegF). DCE- MRI was acquired at weeks 1,2,3,6, and 12. Histologic analysis of HA-ACM treated defects demonstrated quantitatively greater immature bone formation, increased quantity and larger blood vessels compared to void. Statistically significant greater angiogenesis evidenced by quantitative perfusion on MRI supported histologic findings. DCE MRI is a novel means of imaging angiogenesis in grafted bone defects. DCE-MRI discerns physiologically important phases of angiogenesis: Initial vasoactive response, vessel network initiation, establishment, and pruning. DCE-MRI is adaptable to non-invasive study of candidate tissue engineered constructs and in evaluating scaffolds and treatments on angiogenesis.

Tissue engineering is limited by inability to create early and adequate blood supply. In-vivo DCE-MRI has imaged angiogenesis in soft tissues, yet has not been considered in hard tissues. Bilateral critical defects created in parietal bones of eighteen adult rabbits were left void, treated with haluronic acid acellular matrix (HA-ACM), or HA-ACM impregnated with vascular endothelial growth factor (VegF). DCE- MRI was acquired at weeks 1,2,3,6, and 12. Histologic analysis of HA-ACM treated defects demonstrated quantitatively greater immature bone formation, increased quantity and larger blood vessels compared to void. Statistically significant greater angiogenesis evidenced by quantitative perfusion on MRI supported histologic findings. DCE MRI is a novel means of imaging angiogenesis in grafted bone defects. DCE-MRI discerns physiologically important phases of angiogenesis: Initial vasoactive response, vessel network initiation, establishment, and pruning. DCE-MRI is adaptable to non-invasive study of candidate tissue engineered constructs and in evaluating scaffolds and treatments on angiogenesis.

Background Ultrasmall superparamagnetic particles of iron oxide (USPIO)- enhanced magnetic resonance imaging (MRI) can detect tissue-resident inflammatory macrophages and identify cellular inflammation. Clinical studies using this non-invasive technique are now emerging. Objectives The aims of this thesis were (i) to determine whether USPIO-enhanced MRI can detect and serially monitor myocardial inflammation after myocardial infarction (MI) using single and repeated USPIO administration, (ii) to report a range of normal R2* (1/T2*) values at 1.5 tesla (T) and 3 T in healthy myocardium and other tissues before and after USPIO administration, (iii) to determine whether USPIO-enhanced MRI can detect myocardial inflammation in acute myocarditis, and (iv) to determine whether USPIO-enhanced MRI can detect myocardial inflammation in patients with a prior cardiac transplant. Methods Thirty-one patients were recruited following acute MI and followed up for 3 months with repeated T2 and USPIO-enhanced T2* mapping 3 T MRI. Twenty healthy volunteers were recruited: 10 imaged each at 1.5 T and 3 T. T2 and USPIO-enhanced T2* mapping MRI was conducted. Fourteen patients with suspected acute myocarditis underwent T2 and USPIO-enhanced T2* mapping 3 T MRI, with further imaging at 3 months. Eleven patients with prior cardiac transplant underwent T2 and USPIO-enhanced T2* mapping 1.5 T MRI with further imaging at 3 months. Regions of interest within the myocardium, along with other tissues, were selected for analysis. Pre-contrast T2 values, and the change in R2* due to USPIO from baseline to 24 hours after USPIO were compared for each region of interest. Results In patients with MI, USPIO uptake in the infarct zone peaked at days 2-3, and greater USPIO uptake was detected in the infarct zone compared to remote myocardium in the first 2 weeks after myocardial infarction. In contrast, T2-defined myocardial oedema peaked at days 3-9 and remained increased in the infarct zone throughout the 3-month follow up period. Histology confirmed colocalisation of iron and macrophages within the infarcted, but not the non-infarcted, myocardium. In healthy volunteers, we reported a range of normal myocardial and tissue R2* values at baseline, and following USPIO. Tissues showing greatest USPIO enhancement were organs of the reticuloendothelial system: the liver, spleen and bone marrow. Myocarditis was confirmed in 9 of the 14 suspected cases of myocarditis. There was greater myocardial oedema, but no demonstrable difference in USPIO enhancement, in inflamed myocardial regions in patients with myocarditis when compared to healthy myocardium. We recorded an improvement in cardiac function and reduced imaging measures of inflammation after 3 months. Ten patients with cardiac transplant were retained for analysis. Measures of myocardial oedema were greater in patients with cardiac transplant than healthy volunteers. There was no difference in the change in R2* due to USPIO between patients with transplantation and healthy volunteers. Imaging recordings did not change when repeated at 3 months. Conclusions Myocardial macrophage activity can be detected using USPIO-enhanced MRI in the first 2 weeks following acute MI. This observed pattern of cellular inflammation is distinct, and provides complementary information to, the more prolonged myocardial oedema detectable using T2 mapping. In patients with acute myocarditis, USPIO-enhanced MRI does not provide additional clinically relevant information to standard clinical MRI sequences. This suggests that tissue-resident macrophages do not provide a substantial contribution to the myocardial inflammation in this condition. Stable patients with cardiac transplantation have increased myocardial T2 values, consistent with resting myocardial oedema or fibrosis. In contrast, USPIO-enhanced MRI is normal and stable over time suggesting the absence of chronic macrophage-driven cellular inflammation. In conclusion, this imaging technique holds promise as a non-invasive method of assessing and monitoring macrophage-driven myocardial inflammation after myocardial infarction with potential application to diagnosis, risk stratification and assessment of novel anti-inflammatory therapeutic interventions. It remains to be determined whether USPIO-enhanced MRI may be able to identify myocardial inflammation in other myocardial inflammatory conditions including acute cardiac transplant rejection.

L'évaluation non-invasive de la myéline dans la substance blanche du système nerveux central est fondamentale pour le suivi de pathologies telles que la sclérose en plaques. La myéline est majoritairement constituée de lipides et de protéines : du fait des nombreuses interactions dans ces macromolécules, les temps de relaxation transversale sont très courts (T2 < 1 ms), rendant indétectables ces signaux par des séquences conventionnelles. Les méthodes standards d’imagerie par RMN pour la caractérisation de la myéline reposent sur la modélisation des interactions entre les protons aqueux et la structure myélinisée. Néanmoins, la sélectivité et la robustesse de ces méthodes indirectes peuvent être remises en cause. Les séquences à temps d’écho ultracourt (UTE – TE < 1 ms) permettraient de faire l’acquisition directe des signaux issus de la matrice semi-solide de la myéline. Le développement de telles méthodes pour la mise en contraste positif et sélectif de la myéline sur système préclinique est l’objet de cette thèse. La validation de chacune des méthodes a été menée sur modèle murin ex vivo en confrontant des animaux sains et démyélinisés. Les résultats à partir des méthodes UTE montrent une sélectivité significative à la démyélinisation, suggérant l’adéquation de la technique pour l'évaluation de la myéline dans la substance blanche. / Non-invasive evaluation of white matter myelin in the central nervous system is essential for the monitoring of pathologies such as multiple sclerosis. Myelin is essentially composed of lipids and proteins: because of the numerous interactions between these macromolecules, the transverse relaxation times are very short (T2 < 1 ms), and their signals are undetectable using conventional sequences. Standard MRI methods for the characterization of myelin rely on the modeling of the interactions of aqueous protons with myelinated structures. Nonetheless, the selectivity and robustness of such indirect methods are questionable. Ultrashort echo time sequences (UTE – TE < 1 ms) may allow to directly detect the signals arising from the semi-solid spin pool of myelin. The main objective of this thesis consists in developing such methods in order to generate a positive and selective contrast of myelin using a preclinical imaging system. Validation of each method was carried out using an ex vivo murine model by confronting healthy and demyelinated animals. Results show a significant selectivity of the UTE methods to demyelination, suggesting that the technique is promising for white matter myelin monitoring.

abstract: Modern medical conditions, including cancer, traumatic brain injury, and cardiovascular disease, have elicited the need for cell therapies. The ability to non-invasively track cells in vivo in order to evaluate these therapies and explore cell dynamics is necessary. Magnetic Resonance Imaging provides a platform to track cells as a non-invasive modality with superior resolution and soft tissue contrast. A new methodology for cellular labeling and imaging uses Nile Red doped hexamethyldisiloxane (HMDSO) nanoemulsions as dual modality (Magnetic Resonance Imaging/Fluorescence), dual-functional (oximetry/ detection) nanoprobes. While Gadolinium chelates and super paramagnetic iron oxide-based particles have historically provided contrast enhancement in MRI, newer agents offer additional advantages. A technique using 1H MRI in conjunction with an oxygen reporter molecule is one tool capable of providing these benefits, and can be used in neural progenitor cell and cancer cell studies. Proton Imaging of Siloxanes to Map Tissue Oxygenation Levels (PISTOL) provides the ability to track the polydimethylsiloxane (PDMS) labeled cells utilizing the duality of the nanoemulsions. 1H MRI based labeling of neural stem cells and cancer cells was successfully demonstrated. Additionally, fluorescence labeling of the nanoprobes provided validation of the MRI data and could prove useful for quick in vivo verification and ex vivo validation for future studies. / Dissertation/Thesis / Masters Thesis Bioengineering 2014

Técnicas de aquisição paralelas e hardware dedicados vem sendo desenvolvidos desde a década de 1980 para reduzir o tempo de aquisição de imagens via ressonância magnética (IRM). Uma bobina do tipo phased array é um dispositivo do tipo receptor, que usa múltiplas bobinas (canais) cada qual com seu próprio circuito de detecção para adquirir simultaneamente os sinais que formam uma imagem ou espectro via IRM. Exemplos de técnica de imagem paralela que usa bobinas tipo phased array são Sensitivy Enconding (SENSE) e GeneRalized Autocalibrating Partial Parallel Acquisition (GRAPPA). Sampled array é o nome de um método proposto neste trabalho em que cada canal de uma bobina multicanal é responsável por adquirir de forma independente o sinal da sua amostra de modo que cada sinal de amostra é endereçado ao seu canal específico. Neste trabalho, descrevemos o desenvolvimento de uma bobina phased array de quatro canais para anatomia de cabeça de rato usando circuito impresso flexível para operar em um sistema de IRM pré-clínico de 2T com objetivo de validar o método de construção e uso de circuito flexível como bobina de recepção. Também desenvolvemos uma bobina de quatro canais para realizar simultaneamente a imagem de quatro sementes na mesma varredura para validar o método Sampled Array com objetivo de melhorar a qualidade da imagem e simultaneamente acelerar experimentos de múltiplas amostras. Os resultados mostram que a bobina de circuito impresso phased array, em comparação com uma bobina de enrolamento de fio regular, forneceu uma boa relação sinal / ruído (RSR) e possui geometria mais adequada à anatomia por ser flexível. Além disso, o processo de fabricação da bobina seja facilitado desde que toda a bobina é construída como um protótipo de circuito impresso. Os bons resultados da bobina sampled array mostraram o método como promissor para imageamento de múltiplas amostras com aumento de RSR e diminuição de tempo de experimentos em relação ao uso de bobinas de canal único. / Parallel techniques and dedicated hardware has been developed since the 1980s to reduce acquisition time on Magnetic Resonance Imaging (MRI) scanners. A phased array is a receiver only mode device concept, which uses multiple channels (coils) with their own detection circuits to simultaneously acquire MRI or localized spectroscopic signals. An example of parallel imaging technique that uses phased array coils is Sensitivy Enconding (SENSE). Sampled array is the name proposed in this work for a method in which each channel of a multichannel coil is responsible to acquire independently the signal from its sample so that each sample signal is addressed to its specific channel. In this work, we describe the development of a four-channel phased array coil for rat head anatomy using flexible printed circuit board (PCB), to operate on a 2T pre-clinical MRI scanner to validate the construction method and usage of flexible PCB as a receiver coil. We also developed a four-channel sample array coil to simultaneously perform the imaging of four seeds at the same scan, to validate the proposed method to improve image quality at the same time accelerating multiple seed imaging for agriculture studies. The results show that phased array PCB coil as compared to a regular wire winding coil provide good signal-to-noise ratio (SNR) imaging with more adequate geometry to the anatomy by being flexible. In addition, the coil manufacturing process is facilitated since the entire coil is constructed as a PCB prototype. The sample array imaging showed as a promising method for multiple sample increasing SNR and time to do experiments.

O uso de agentes de contraste em técnicas de diagnóstico por imagem é uma prática médi-ca rotineira. Certos compostos, presentes em agentes de contraste, possuem propriedades paramagnéticas que podem afetar os sinais da tomografia por ressonância magnética, \"Mag-netic Resonance Imaging\"(MRI). Em estudos aplicados ao trato gastrintestinal (GI), os meios de contraste são amplamente utilizados por via endovenosa, mas também podem ser admi-nistrados oralmente. Porém, a adoção do uso oral é limitada, principalmente, porque os agentes convencionais são caros e causam, geralmente, efeitos colaterais. Desta forma, a-presentamos a caracterização e os resultados preliminares da implementação da polpa do fruto da Euterpe olerácea para um possível uso clínico como agente de contraste oral em MRI do trato GI. A polpa da Euterpe olerácea, conhecida como Açaí, de origem amazônica, apre-senta um aumento de sinal de MRI ponderado em T1 equivalente ao do Gd-DTPA e, tam-bém, um decréscimo de sinal em imagens ponderadas em T2. Investigamos propriedades intrínsecas que possam estar correlacionadas com o aumento de sinal em T1 e à opacidade em T2. O espectro de absorção atômica revelou a presença de íons Fe, Mn e Cu no Açaí, o que contribui para o valor susceptométrico encontrado de -4,83 . 10-6. Essa medida fomen-ta a hipótese de que as mudanças de contraste nas imagens são devido à presença de mate-rial paramagnético, revelando um contraste clinicamente satisfatório nas porções superiores do trato GI. Estudos preliminares indicaram que a homogeneidade e a intensidade do sinal da polpa do Açaí (Euterpe olerácea), no estômago, e duodeno, são próximos daquele encon-trado em agentes convencionais. Além disso, ele não apresentou efeito colateral algum. Devido ao aumento de contraste associado ao Açaí, podemos observar a parede gástrica de forma singular. Ainda, este agente contribuiu para o diagnóstico das vias pancreática e biliar em exames de colangiopancreatografia por ressonância magnética, Magnetic Resonance Colan-giopancreatography (MRCP), com seqüências ponderadas em T2, por reduzir o sinal das alças intestinais. / The use of contrast agents is a common practice in medical imaging protocols. Paramagnetic properties of certain compounds present in contrast agents can affect Magnetic Resonance Imaging (MRI) signals. For abdominal applications, they are usually injected, but may also be administered orally. However, their use as a routine technique is limited, mainly due to the lack of appropriate oral contrast agent. Standard agents are expensive and cause, generally, some kind of side effect. We herein present the preliminary characterization and results for implementation of Euterpe olerácea (popularly named Açaí) as a possible clinical oral contrast agent for MRI of the gastrointestinal (GI) tract. The pulp of Açaí, a fruit from the Amazon area, presented an increase in T1-weighted MRI signal, equivalent to that of Gd-DTPA, and a signal decrease in T2-weighted images. We looked for intrinsic properties that could be responsible for the T1 signal enhancement and T2 opacification. Atomic Absorption spectra revealed the presence of Fe, Mn and Cu ions in Açai. The presence of such ions contribute to the susceptometric value found of -4.83 x 10-6 . This finding assents with the hypothesis that image contrast changes were due to the presence of paramagnetic material. The first measurements in vivo demonstrate a clear increase of contrast due to signal intensity and homogeneity in stomach and bowel walls with the pulp of Açaí, which look like the effects related to standard agents. Consistently, the increase in T1-weighted and the opacification in a T2-weighted acquisition was evident, revealing a biphasic contrast on gastric tissues. Besides, the pulp does not present any side effect. It still has contributed to the diagnostic of pancreatobiliary system at Magnetic Resonance Cholangiopancreatography (MRCP), by reducing overlap of the surround tissues and those structures.

The brain ages, and with it come alterations in its micro- and macro-structure which reflect in its morphology and functioning. Changes in the brain structure and functional coupling between regions can be assessed with neuroimaging, and, more specifically, magnetic resonance imaging (MRI). Using MRI data from two stages (Pilot and Enhanced) of the Nathan Kline Institute Rockland Sample (NKI-RS), totalling 613, free of neurodegenerative diseases, and right-handed, participants aged 18 to 85 years old, we measured gray-matter parameters such as cortical volume, cortical thickness, and cortical surface area, and also volume of subcortical structures. We also measured cortico-cortical functional connectivity, defined either as the Pearson correlation coefficient and partial correlation coefficient, bivariate instantaneous Granger causality and Granger causality, and generalized partial directed coherence (GPDC). GPDC was evaluated in five frequencies between the four pairs of regions displaying the strongest evidence for linear thinning, measured by their associated t-statistic, and its alterations alongside aging were assessed using a multivariate approach based on Dirichlet Regression. We also studied spatial associations between patterns of morphometric and connectivity alterations. We reproduced generalized age-related atrophy reported in the literature in cortical volume (90% of the studied structures), surface area (68%) and thickness (90%), and volumetric atrophy of several subocortical structures. We observe a positive association in the joint distribution of the expected cortical thickness at 18 years old and the yearly percentage reduction in cortical thickness. We showed, projecting these two quantitities into their principal axes and analyzing the spatial distribution of the scores, that the first principal component correlates with neocortical granularity while the second principal component represents cortical type admixture. On functional connectivity, we gathered evidence for overall increased Pearson correlation coefficient (6% of the connections in the Pilot NKI-RS and 2% in the Enhanced NKI-RS), with proportionally smaller number of decreases (0.1% in the Pilot NKI-RS and 0.3% in the Enhanced NKI-RS). The Pearson partial correlation coefficient between 12 out of 65 homotopic region pairs shows a pattern of decline with age, suggesting inter-hemispheric disconnection. However, predictive causality, as measured by both Granger causalities, do not share the same degree of changes observed in the correlational metrics. We observe increased GPDC from several regions to themselves in many frequencies (25% out of a total of 40 self-connections), indicating a degree of disconnection to the other regions. Given seed regions, we uncovered spatially distributed significant patterns of association between the standardized effect of age on the connectivity to its targets and on their targets thicknesses. Regions with smaller evidence for age-related thinning, such as several occipital areas, tend to have fewer alterations in functional connectivity than regions with greater evidence for age-related thinning, like many frontal regions. We hypothesize that regions showing a negative association (5% of the seed regions) are part of compensatory systems, being increasingly correlated with regions displaying most atrophy. Regions showing a positive association (5%) do not have compensatory mechanisms available, and therefore are losing connectivity to atrophyc regions. Overall, we found evidence for brainwide alterations in connectivity and cortical and subcortical morphometry throughout the human adult lifespan. We also found a specifc pattern of associations between the atrophic trends and age-related alterations in connectivity in the brain / O cérebro envelhece, e com isso vêm à tona alterações em sua micro e macroestrutura que se refletem em sua morfologia e funcionamento. Mudanças na estrutura cerebral e acoplamento funcional entre suas regiões podem ser averiguadas através da neuroimagem, e, mais especificamente, imagem por ressonância magnética (IRM). Usando dados de IRM das duas etapas (Pilot and Enhanced) do Nathan Kline Institute Rockland Sample (NKI-RS), totalizando 613 participantes destros, livres de doenças neurodegenerativas, com idade entre 18 e 85 anos, medimos parâmetros de substância cinzenta como volume, espessura, e área de superfície corticais, e também volume de estruturas subcorticais. Também medimos conectividade funcional cortico-cortical, definida como o coeficiente de correlação de Pearson, coeficiente de correlação parcial de Pearson, causalidade instântanea de Granger e causalidade de Granger bivariadas, e coerência parcial direcionada generalizada (GPDC). A GPDC foi medida em cinco frequências entre quatro pares de regiões que demonstraram a mais forte evidência para diminuição da espessura cortical linearmente, medido pela estatística-t associada, e suas alterações ao longo do envelhecimento foram estudadas usando uma abordagem multivariada baseada na Regressão de Dirichlet. Também estudamos associações espaciais entre padrões de alterações morfométricas e na conectividade. Reproduzimos a atrofia generalizada devido à idade reportada na literatura no volume cortical (90% das estruturas estudadas), área de superfície (68%) e espessura (90%), e atrofia volumétrica de várias estruturas subcorticais. Observamos uma associação positiva na distribuição conjunta do valor esperado da espessura cortical aos 18 anos de idade e a redução percentual anual na espessura cortical. Mostramos, ao projetar ambos em seus eixos principais e analizar a distribuição espacial desses índices, que a primeira componente principal correlaciona-se com a granularidade neocortical enquanto que a segunda componente principal representa o tipo cortical. Sobre a conectividade funcional, colhemos evidências para um aumento geral no coeficiente de correlação de Pearson (6% das conexões no Pilot NKI-RS e 2% no Enhanced NKI-RS), com menor proporção de decréscimos (0.1% no Pilot NKI-RS e 0.3% no Enhanced NKI-RS). O coeficiente de correlação parcial de Pearson entre 12 de 65 pares de regiões homotópicas demonstra um padrão de declínio com a idade, sugerindo desconexão inter-hemisférica. No entanto, a causalidade preditiva, como medida através de ambas as métricas de causalidade de Granger, não aparenta o mesmo grau de mudanças observado nas medidas correlacionais. Observamos aumentos na GPDC de várias regiões para si próprias em muitas frequências (25% de um total de 40 auto-conexões), que indica um grau de disconexão às outras regiões. Dadas regiões semente, revelamos padrões significativos espacialmente distribuídos de associação entre efeitos padronizados da idade na conectividade para seus alvos e das espessuras dos alvos. Regiões com menor evidência para o desbastamento relacionado com a idade, como várias áreas occipitais, tendem a ter menos alterações em sua conectividade funcional que regiões com maior evidência suportando o desbastamento cortical relacionado à idade, como diversas regiões frontais. Hipotetizamos que regiões cuja associação é negativa (5% das regiões semente) são parte de sistemas compensatórios, estando correlacionadas com regiões que demonstram os maiores graus de atrofia de modo crescente. Regiões cuja associação é positiva (5%) não teriam mecanismos compensatórios à disposição, e portanto perdem conectividade para regiões atróficas. No geral, encontramos evidências para alterações na conectividade e na morfometria cortical e subcortical no cérebro todo ao longo da extensão da vida adulta humana. Também achamos um padrão específico de associações entre tendências atróficas e alterações na conectividade cerebral devido à idade

Abstract The purpose of this study was to evaluate the value of 0.23T low-field magnetic resonance imaging (MRI) and nanocolloid (NC) scintigraphy in assessing joint pathology associated with rheumatoid arthritis (RA). Fat suppression methods combined with contrast media enhancement aid in distinguishing enhancing inflamed tissue from the surrounding fat, especially in the imaging of arthritic joints. The feasibility and image quality of a phase-shift water-fat MRI method for fat suppression at low-field 0.23T open configuration MR scanner was evaluated. The technique was combined with contrast-enhanced imaging to assess the conspicuity of synovial hypertrophy in the joints of 30 RA patients. Improved conspicuity and delineation of synovitis was detected with this method. However, because of a great amount of manual post processing, future development is needed to make this method more feasible. Contrast-enhanced MRI and NC scintigraphy may provide objective and quantitative information about the inflammatory activity in arthritic joints. The value of quantitative and semiquantitative measures of inflammation derived from NC scintigraphy and low-field MRI of the wrist joint of 28 early RA patients was evaluated. Furthermore, it was investigated whether these parameters have predictive value of further erosive development during two years of follow-up. Strong correlations were detected between the NC scintigraphy and MRI measures, and these parameters were associated with laboratory markers of inflammation. During the two-year follow-up, the initial MRI and NC scintigraphy measures were closely related with the progression of wrist joint erosions. Small erosive-like bone defects can occasionally be found in wrist MRI of patients without clinically overt arthritis. The prevalence of these lesions was studied in bilateral wrist MRI examinations of 31 healthy persons. Small lesions resembling erosions were detected in 14 out of 31 subjects. Altogether 24 of the 930 wrist bones evaluated showed such lesions (3%). Thus small changes resembling erosions can be found in the wrist MRI of healthy subjects; the significance of these findings must always be interpreted with reference to the clinical picture. In conclusion, early RA patients with high local inflammatory activity, as detected by NC scintigraphy and MRI are at risk of developing further bone damage. Furthermore, in the follow-up of early RA patients, if clinically sustained response is not achieved, these methods help to identify patients who need more intensive drug treatment.

Background: Angiogenesis is the process by which new blood vessels develop from existing vasculature and is a critical step in all tumours to facilitate growth beyond a few millimetres. As this process is largely inactive in physiological circumstances in adults, it represents an attractive therapeutic target in oncology. Drugs that target the angiogenic process are classified as anti-angiogenic agents. The first anti-angiogenic drug to be approved by the FDA was bevacizumab; a recombinant humanized monoclonal antibody against VEGF. Randomised studies in colorectal cancer (and other solid malignancies) have reported prolonged progression free survival and overall survival for bevacizumab. However, standard radiological criteria, Response Evaluation Criteria In Solid Tumours (RECIST), although widely employed to assess response to therapy in clinical trials, are generally insensitive to the predominantly cytostatic effects of anti-angiogenic and other targeted therapies. Alternative methods of predicting or assessing early response to such agents are needed, particularly given the cost and toxicity implications of such treatments. However, biomarkers to aid selection of patients for anti-angiogenic therapies, including bevacizumab, remain elusive. Purpose: To investigate Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI), Diffusion Weighted Imaging (DWI) and circulating angiocytokines, measured using an ELISA multiplex, as prognostic markers in patients with metastatic colorectal cancer treated with bevacizumab and chemotherapy. Results: Seventy patients were treated. DCE-MRI and DWI parameters showed good reproducibility with coefficient of variation between 3.7 to 23% for parameters. The median progression free survival, the primary end point of the trial, was 9.3 months. The overall response rate was 44%. The clinical variables which were significant for progression free survival on univariate analysis were: performance status (p=0.005), CEA (p=0.04) and serum LDH (p=0.005). Biomarkers which were significant for progression free survival on univariate analysis were serum VEGF-A (p=0.02), serum HGF (p=0.005), sVEGFR-2 (p=0.02). In each case, low values of the biomarker were associated with improved outcome. Multivariate analysis identified Ktrans (p=0.015), performance status (p=0.008) and serum HGF (p=0.003) as the most significant predictors of progression free survival. A prolonged progression free survival was associated with a good ECOG performance status, high Ktrans and low serum HGF.Conclusions: Whilst these results are encouraging, future work is required to establish whether HGF and Ktrans are prognostic markers for metastatic colorectal cancer and their precise role in the prediction of patients likely to benefit from treatment with bevacizumab.