A high-performance method of deep learning for prostate MR-only radiotherapy planning using an optimized Pix2Pix architecture.

PURPOSE: The first aim was to generate and compare synthetic-CT (sCT) images using a conditional generative adversarial network (cGAN) method (Pix2Pix) for MRI-only prostate radiotherapy planning by testing several generators, loss functions, and hyper-parameters. The second aim was to compare the optimized Pix2Pix model with five other architectures (bulk-density, atlas-based, patch-based, U-Net, and GAN). METHODS: For 39 patients treated by VMAT for prostate cancer, T2-weighted MRI images were acquired in addition to CT images for treatment planning. sCT images were generated using the Pix2Pix model. The generator, loss function, and hyper-parameters were tuned to improve sCT image generation (in terms of imaging endpoints). The final evaluation was performed by 3-fold cross-validation. This method was compared to five other methods using the following imaging endpoints: the mean absolute error (MAE) and mean error (ME) between sCT and reference CT images (rCT) of the whole pelvis, bones, prostate, bladder, and rectum. For dose planning analysis, the dose-volume histogram metric differences and 3D gamma analysis (local, 1 %/1 mm) were calculated using the sCT and reference CT images. RESULTS: Compared with the other architectures, Pix2Pix with Perceptual loss function and generator ResNet 9 blocks showed the lowest MAE (29.5, 107.7, 16.0, 13.4, and 49.1 HU for the whole pelvis, bones, prostate, bladder, and rectum, respectively) and the highest gamma passing rates (99.4 %, using the 1 %/1mm and 10 % dose threshold criterion). Concerning the DVH points, the mean errors were -0.2% for the planning target volume V95%, 0.1 % for the rectum V70Gy, and -0.1 % for the bladder V50Gy. CONCLUSION: The sCT images generated from MRI data with the Pix2Pix architecture had the lowest image errors and similar dose uncertainties (in term of gamma pass-rate and dose-volume histogram metric differences) than other deep learning methods.

Head-and-Neck MRI-only radiotherapy treatment planning: From acquisition in treatment position to pseudo-CT generation.

PURPOSE: In context of head-and-neck radiotherapy, this study aims to compare MR image quality according to diagnostic (DIAG) and radiotherapy (RT) setups; and to optimise an MRI-protocol (including 3D T1 and T2-weighted sequences) for dose-planning (based on pseudo-CT generation). MATERIALS AND METHODS: To compare DIAG and RT setups, signal-to-noise-ratio (SNR) and percentage-image-uniformity (PIU) were computed on T1 images of phantoms and volunteers. Influence of the sample conductivity on SNR was quantified using homemade phantoms. To obtain reliable T1 and T2 images for RT-planning, an experimental design was performed on volunteers by using SNR, contrast-to-noise-ratio (CNR) and mean-opinion-score (MOS). Further, pseudo-CTs were generated from 8 patients T2 images with a state-of-art deep-learning method. These pseudo-CTs were evaluated by mean-absolute-error (MAE) and mean-error (ME). RESULTS: SNR was higher for DIAG-setup compared to RT-setup (SNR-ratio=1.3). A clear influence of the conductivity on SNR was observed. PIU was higher for DIAG-setup (38.8%) compared to RT-setup (33.5%). Regarding the protocol optimisation, SNR, CNR, and MOS were 20.6, 6.16, and 3.91 for the optimal T1 sequence. For the optimal T2 sequence, SNR, CNR and MOS were 25.6, 44.46 and 4.0. In the whole head-and-neck area, the mean MAE and ME of the pseudo-CTs were 82.8 and -3.9 HU. CONCLUSION: We quantified the image quality decrease induces by using an RT-setup for head-and-neck radiotherapy. To compensate this decrease, an MRI protocol was optimised by using an experimental design. This protocol of 15minutes provides accurate images which could be used for MRI-dose-planning in clinical practice.

[MRI-based radiotherapy planning]. / Planification à partir d'imagerie par résonance magnétique en radiothérapie.

MRI-based radiotherapy planning is a topical subject due to the introduction of a new generation of treatment machines combining a linear accelerator and a MRI. One of the issues for introducing MRI in this task is the lack of information to provide tissue density information required for dose calculation. To cope with this issue, two strategies may be distinguished from the literature. Either a synthetic CT scan is generated from the MRI to plan the dose, or a dose is generated from the MRI based on physical underpinnings. Within the first group, three approaches appear: bulk density mapping assign a homogeneous density to different volumes of interest manually defined on a patient MRI; machine learning-based approaches model local relationship between CT and MRI image intensities from multiple data, then applying the model to a new MRI; atlas-based approaches use a co-registered training data set (CT-MRI) which are registered to a new MRI to create a pseudo CT from spatial correspondences in a final fusion step. Within the second group, physics-based approaches aim at computing the dose directly from the hydrogen contained within the tissues, quantified by MRI. Excepting the physics approach, all these methods generate a synthetic CT called "pseudo CT", on which radiotherapy planning will be finally realized. This literature review shows that atlas- and machine learning-based approaches appear more accurate dosimetrically. Bulk density approaches are not appropriate for bone localization. The fastest methods are machine learning and the slowest are atlas-based approaches. The less automatized are bulk density assignation methods. The physical approaches appear very promising methods. Finally, the validation of these methods is crucial for a clinical practice, in particular in the perspective of adaptive radiotherapy delivered by a linear accelerator combined with an MRI scanner.

A single high dose of dexamethasone affects the phosphorylation state of glutamate AMPA receptors in the human limbic system.

Glucocorticoids (GC) released during stress response exert feedforward effects in the whole brain, but particularly in the limbic circuits that modulates cognition, emotion and behavior. GC are the most commonly prescribed anti-inflammatory and immunosuppressant medication worldwide and pharmacological GC treatment has been paralleled by the high incidence of acute and chronic neuropsychiatric side effects, which reinforces the brain sensitivity for GC. Synapses can be bi-directionally modifiable via potentiation (long-term potentiation, LTP) or depotentiation (long-term depression, LTD) of synaptic transmission efficacy, and the phosphorylation state of Ser831 and Ser845 sites, in the GluA1 subunit of the glutamate AMPA receptors, are a critical event for these synaptic neuroplasticity events. Through a quasi-randomized controlled study, we show that a single high dexamethasone dose significantly reduces in a dose-dependent manner the levels of GluA1-Ser831 phosphorylation in the amygdala resected during surgery for temporal lobe epilepsy. This is the first report demonstrating GC effects on key markers of synaptic neuroplasticity in the human limbic system. The results contribute to understanding how GC affects the human brain under physiologic and pharmacologic conditions.

The most fulminant course of the Marburg variant of multiple sclerosis-autopsy findings.

Multiple sclerosis (MS) is usually a chronic and disabling inflammatory disease. Marburg's type of MS is characterized by rapid progression and severe disease course that leads to death within one year after the onset of clinical signs. We describe a fulminant clinical presentation of this malignant subtype of MS and discuss the neuropathological hallmarks as well as differential diagnoses of other fulminant demyelinating diseases. To the best of our knowledge, this is the most fulminant course of this MS variant reported in the literature.

Opsoclonus-myoclonus syndrome associated with Mycoplasma pneumoniae infection in an elderly patient.

Opsoclonus-myoclonus-ataxia syndrome (OMS) is a rare movement disorder characterized by chaotic saccadic, high amplitude, multidirectional and involuntary eye movements usually associated with myoclonus affecting the head, trunk, limbs and signs of cerebellar ataxia, especially the inability to stand and walk. We report a case of a 68 years-old woman, with previous history of diabetes mellitus and systemic hypertension that was referred for evaluation due to headache and low fever for three days. One day after the admission, she developed spatial and temporal disorientation and high-fever (39 °C). On her fourth day in-hospital, while still disoriented, diffuse limb myoclonia and intermittent, multidirectional and chaotic eye movements were noticed. Sorological tests and sputum Mycoplasma real-time PCR were positive on seventh day in-hospital. Patient was treated with Azithromycin and IV Immunoglobulin for five days. On third day after treatment it was noticed significant improvement of ataxia and myoclonia. Completely recovery after macrolydes and IVIg treatment, absence of a malignant neoplasia and knowledge of this entity in pediatric population support that parainfectious OMS associated with M. pneumoniae infections should be considered in the differential diagnosis of OMS in adults.

Edpidemia de fiebre aftosa en Bage, Rs, Brasil, 1980. Evaluacion de dos sistemas de vacunacion / Epidemic of foot-and-mouth disease in Bage, Rs, Brazil, 1980. Evaluation of two systems of vaccination

El programa de control de la fiebre aftosa en Rio Grande do Sul, Brasil, se inicio en 1965. Desde 1979 gran parte del municipio de Bage, en este estado, cuenta con un programa demonstrativo de vacunacion con vacuna antiaftosa inactivada y con adyuvante oleoso producida por el Centro Panamericano de Fiebre AFtosa (CPFA). Durante 1980 el citado municipio fue afectado por una epidemia de febre aftosa producida por el virus O1. El presente trabajo analiza las consecuencias morbidas de la enfermedad en el rebaño sometido a este programa de vacunacion con relacion al resto del rebano bovino del municipio que es vacunado con vacuna de hidroxido de aluminio-saponina, inactivada en velhiculo acuoso (denominado sistema "comercial"). La enfermedad se registro en 73 rebaños de los 1.813 sometidos al sistema "comercial" y en 20 de los 620 pertenecientes al programa de vacuna oleosa, lo que dio tasas de rebaños afectados, con ajuste al tamano, de 5 y 2% respectivamente. Las tasas de morbilidad pra la poblacion bovina del municipio fueron de 45 y 6 por mil, respectivamente, para ambos sistemas de vacunacion. Separando las poblaciones que habian recibido solamente una vacunacion con vacuna oleosa al principio de la epidemia de aquellas que recibieron 2 o mas, las diferencias de morbi-mortalidad entre los grupos fueron mas acentuadas, siendo las tasas de morbilidad y mortalidad por mil bovinos respectivamente de 323 y 9,7 para los sometidos a solamente una vacunacion con vacuna oleosa, y de 29 y 0,08 para los que recibieron dos o mas vacunaciones con vacuna oleosa. Se concluye que la vacunacion con adyuvante oleoso aplicada en forma oficial dio resultados altamente satisfactorios teniendo en cuenta la alta exposicion viral a la que estuvo sometida la poblacion del municipio.