Memory-Efficient Training for Fully Unrolled Deep Learned PET Image Reconstruction with Iteration-Dependent Targets

We propose a new version of the forward-backward splitting expectation-maximisation network (FBSEM-Net) along with a new memory-efficient training method enabling the training of fully unrolled implementations of 3D FBSEM-Net. FBSEM-Net unfolds the maximum a posteriori expectation-maximisation algorithm and replaces the regularisation step by a residual convolutional neural network. Both the gradient of the prior and the regularisation strength are learned from training data. In this new implementation, three modifications of the original framework are included. First, iteration-dependent networks are used to have a customised regularisation at each iteration. Second, iteration-dependent targets and losses are introduced so that the regularised reconstruction matches the reconstruction of noise-free data at every iteration. Third, sequential training is performed, making training of large unrolled networks far more memory efficient and feasible. Since sequential training permits unrolling a high number of iterations, there is no need for artificial use of the regularisation step as a leapfrogging acceleration. The results obtained on 2D and 3D simulated data show that FBSEM-Net using iteration-dependent targets and losses improves the consistency in the optimisation of the network parameters over different training runs. We also found that using iteration-dependent targets increases the generalisation capabilities of the network. Furthermore, unrolled networks using iteration-dependent regularisation allowed a slight reduction in reconstruction error compared to using a fixed regularisation network at each iteration. Finally, we demonstrate that sequential training successfully addresses potentially serious memory issues during the training of deep unrolled networks. In particular, it enables the training of 3D fully unrolled FBSEM-Net, not previously feasible, by reducing the memory usage by up to 98% compared to a conventional end-to-end training. We also note that the truncation of the backpropagation (due to sequential training) does not notably impact the network’s performance compared to conventional training with a full backpropagation through the entire network

Argumentaire pour une utilisation plus large de la photochimiothérapie extracorporelle chez l’enfant

International audienceThe management of immune diseases in children remains challenging , although significant advances have been made. In addition to pharmacological approaches, extracorporeal photochemotherapy (ECP) is distinctive in its ability to provide immunomodulation without immune suppression or toxicity. However, in practice, this therapy is not widely used because of logistical issues and the lack of robust clinical pediatric studies. Here, we discuss the potential clinical applications of ECP in children and emphasize the need for a rigorous and specifically pediatric clinical evaluation of ECP. ß 2010 Elsevier Masson SAS. All rights reserved. Résumé Malgré l'apport des biothérapies, le traitement des maladies dysim-munitaires sévères et des conflits allogéniques de l'enfant reste difficile et entaché de nombreuses complications. Dans ce contexte, la photo-chimiothérapie extracorporelle (PCE) (thérapie cellulaire qui repose sur l'effet immunomodulateur des cellules mononucléées du patient, prélevées par aphérèse et exposées ex vivo aux rayons ultraviolets A [UVA] en présence de psoralène) a l'avantage notable d'induire une tolérance immunitaire sans générer d'immunosuppression systémique ni de toxicité a ` court, moyen ou long terme. Cette immunomodulation fait intervenir notamment la génération de lymphocytes T régulateurs (T reg). Malgré cela, la PCE est peu utilisée en raison de ses contraintes logistiques et du manque de données cliniques. Nous proposons une revue des indications reconnues et potentielles de la PCE en pédiatrie. Nous insistons sur la nécessité d'une e ´valuation clinique spécifique a ` l'enfant qui ne peut se concevoir sans la participation active des cliniciens pédiatres en particulier dans le domaine de la transplanta-tion et des maladies auto-immunes et inflammatoires

Les radiodermites après procédures interventionnelles guidées par rayons X

International audienceRadiodermatitis is a common side effect of radiation therapy. However, despite being characterized by quasi-geometric shapes and typical sites, it remains a little-known complication of fluoroscopy-guided procedures. Fluoroscopy-induced chronic radiodermatitis can occur several months or even years after the irradiating procedure itself. It presents as a poikilodermal, depilated, sclerotic, and occasionally ulcerated plaque. Confusion with other skin diseases can lead to delayed diagnosis. There are few medical treatment options. Surgical treatment is possible for chronic radiodermatitis only, but is so complex that it is only suitable for serious cases. Risk factors for developing fluoroscopy-induced chronic radiodermatitis have been identified but remain difficult to control.Les radiodermites sont un effet indésirable fréquent de la radiothérapie. Pourtant, bien qu’elles soient caractérisées par des formes quasi géométriques et des localisations typiques, elles constituent aussi une complication méconnue des procédures interventionnelles guidées par rayons X (PIGRX). En particulier, les radiodermites chroniques peuvent survenir plusieurs mois, voire années, après la procédure irradiante. Elles se présentent sous forme d’une plaque poïkilodermique dépilée, scléreuse, parfois ulcérée. La confusion avec d’autres dermatoses peut conduire à un retard diagnostique. Il existe peu d’options de traitement médical. Pour les radiodermites chroniques uniquement, le traitement chirurgical est possible, mais sa complexité doit le faire réserver aux cas les plus graves. Les facteurs de risque de développer une radiodermite chronique après PIGRX ont été identifiés, mais restent difficilement maîtrisables

Rapid Desensitization to Adalimumab Is Associated With Decreased Basophil Sensitivity

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Stratégies diagnostiques et thérapeutiques dans le mélanome : apport des différentes techniques de médecine nucléaire

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Radiothérapie interne du mélanome métastatique par [131I]ICF01012 : phase I

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