Multi-modal image fusion for small animal studies in in-line PET /3T MRI

Congrès sous l’égide de la Société Française de Génie Biologique et Médical (SFGBM).National audienceIn the framework of small animal multi-modal imaging, the current progression of the IMAPPI project is illustrated by the design of an in-line PET/MRI prototype, coupled to a dedicated multi-resolution registration method allowing the robust fusion of data coming from both modalities. The first results show a good alignment of the data from tumor imaging at the level of the abdomen

Algorithms for the analysis of 3D magnetic resonance angiography images

Atherosclerosis is a disease of the arterial wall, progressively impairing blood flow as it spreads throughout the body. The heart attacks and strokes that result of this condition cause more deaths than cancer in industrial countries. Angiography refers to the group of imaging techniques used through the diagnosis, treatment planning and follow-up of atherosclerosis. In recent years, Magnetic Resonance Angiography (MRA) has shown promising abilities to supplant conventional, invasive, X-ray-based angiography. In order to fully benefit from this modality, there is a need for more objective and reproducible methods. This thesis shows, in two applications, how computerized image analysis can help define and implement these methods. First, by using segmentation to improve visualization of blood-pool contrast enhanced (CE)-MRA, with an additional application in coronary Computerized Tomographic Angiography. We show that, using a limited amount of user interaction and an algorithmic framework borrowed from graph theory and fuzzy logic theory, we can simplify the display of complex 3D structures like vessels. Second, by proposing a methodology to analyze the geometry of arteries in whole-body CE-MRA. The vessel centreline is extracted, and geometrical properties of this 3D curve are measured, to improve interpretation of the angiograms. It represents a more global approach than the conventional evaluation of atherosclerosis, as a first step towards screening for vascular diseases. We have developed the methods presented in this thesis with clinical practice in mind. However, they have the potential to be useful to other applications of computerized image analysis

Haptic guided seeding of MRA images for semi-automatic segmentation

We investigate how stereo graphics and haptics can be combined to facilitate the seeding procedure in semi-automatic segmentation of magnetic resonance angiography (MRA) images. Real-time volume rendering using maximum intensity projections (MIPs) has been implemented together with a haptic rendering method that provides force feedback based on local gradients and intensity values. This combination allows a user to trace vessels in the image, and to place seed-points directly in the 3D data set. Seed-regions are propagated from the seed-points according to an algorithm that favors bright voxels. An experienced user have tested the interface on whole-body MRA images with promising results. 1

Classification of prostate magnetic resonance spectra using Support Vector Machine

International audienceProstate cancer is the most common cancer in men over 50 years of age and it has been shown that nuclear magnetic resonance spectra are sensitive enough to distinguish normal and cancer tissues. In this paper, we propose a classification technique of spectra from magnetic resonance spectroscopy. We studied automatic classification with and without quantification of metabolite signals. The dataset is composed of 22 patient datasets with a biopsy-proven cancer, from which we extracted 2464 spectra from the whole prostate and of which 1062 were localised in the peripheral zone. The spectra were manually classed into 3 different categories by a spectroscopist with 4 years experience in clinical spectroscopy of prostate cancer: undetermined, healthy and pathologic. We used different preprocessing methods (module, phase correction only, phase correction and baseline correction) as input for Support Vector Machine and for Multilayer Perceptron, and we compared the results with those from the expert. If we class only healthy and pathologic spectra we reach a total error rate of 4.51%. However, if we class all spectra (undetermined, healthy and pathologic) the total error rate rises to 11.49%. We have shown in this paper that the best results are obtained using the pre-processed spectra without quantification as input for the classifiers and we confirm that Support Vector Machine are more efficient than Multilayer Perceptron in processing high dimensional data

In-vivo metabolic characterization of healthy prostate and orthotopic prostate cancer in rats using proton magnetic resonance spectroscopy at 4.7 T.

International audienceBackground To assist the development of new anti-cancer drugs, it is important to identify biomarkers of treatment efficacy in the preclinical phases of drug development. In order to improve the predictivity of preclinical experiments, more realistic animal models are needed, for example, tumors xenografted directly on the prostate gland of rodents. Purpose To characterize the in-vivo metabolism of healthy rat prostate and of an orthotopic human prostate cancer model using proton magnetic resonance spectroscopy (MRS). Material and Methods The highly metastatic and hormone-independent PC3-MM2 human prostate cancer model was implanted into the ventral prostate lobe of three Nude rats. Healthy Nude (n = 6) and Sprague-Dawley (n = 6) rats were also studied for interspecies comparison of normal prostate metabolism. Magnetic resonance imaging and short echo-time (TE 11.2 ms) single voxel PRESS spectroscopy were performed on dorsal (DP) and ventral (VP) prostate as well as tumor at 4.7 T. The metabolic content and volume of dorsal and ventral lobes were characterized as a function of species and age. Results Slightly lower total creatine (tCr)/water (11.3 2.6 vs. 15.3 3.0, NS), but significantly higher Inositol (Ins)/water (18.9 1.9 vs. 6.6 3.3, P < 0.003) and total choline (tCho)/water (15.0 2.1 vs. 5.6 1.1, P < 0.00007) were observed within healthy DP lobes with respect to VP lobes. No significant variation in metabolic content was seen in healthy DP and VP lobes of Nude rats as a function of age, and no species dependence was observed in their metabolic content. For the orthotopic PC3-MM2 tumor, implanted in VP, the tCr/water ratio was significantly lower (3.1 0.9) than neighboring DP (12.8 1.8, P < 0.00003) and healthy VP (15.3 3.0, P < 0.00006). For Ins, the metabolite ratio in PC3-MM2 was close to that of healthy VP (4.3 2.8 vs. 6.6 3.3, p = NS), but much lower than in neighboring DP (19.1 1.3, P < 0.00005). A similar trend was also observed for tCho, where metabolite ratios in PC3-MM2, healthy VP and neighboring DP were 3.5 0.9, 5.6 1.1, and 15.9 0.8, respectively. Conclusion The in-vivo MRS study of healthy prostate and orthotopic prostate cancer is feasible in rats. Such baseline data could be important when following the modifications in metabolism, including during anti-cancer drug development protocols or following radiotherapy

MR-based biomarkers in the diagnosis and the evaluation of the therapeutic response to radiotherapy (ETRR) in prostatic carcinoma (PCa): Implementation of clinical and experimental approaches

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Integrated PET/MRI in preclinical studies State of the art

International audienceThe exquisite tissue contrast of magnetic resonance imaging (MRI), the absence of ionising radiation and the opportunity to obtain new molecular and functional data have strengthened the enthusiasm for coupling MRI rather than computed tomography (CT) to positron emission tomography (PET). When reviewing the current literature one might be surprised by the almost unlimited diversity of what is placed under the name of PET/MRI in the articles. The magnetic field is varying from 0.3 Tesla (T) to 9.4 T, the size of the bore varies also from the wide bore of clinical scanners to volumes limited to a few tens of mL. Many preclinical studies are performed using separate PET and MRI scanners. Sometimes PET and the magnet are in line or sequential. More rarely, fully integrated PET/MRI scanners are used. In that case, mutual interference between PET and MRI has required innovative designs. Initially, the conventional photomultipliers had been installed outside the magnet using long optical fibres. They have now been replaced by avalanche photodiodes (APD), and in the near future silicon photomultipliers (SiPM) could provide an alternative. Tumours and neurological and cardiovascular disorders have been the most studied conditions. Many issues remain to be resolved such as image registration, attenuation correction and animal monitoring. Friendly consoles integrating the control of both imaging modalities also need to be developed

Temozolomide and radiotherapy antitumor efficacy evaluation with magnetic resonance imaging and proton magnetic resonance spectroscopy in human glioma models in nude rats

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