Projection image-to-image translation in hybrid X-ray/MR imaging

The potential benefit of hybrid X-ray and MR imaging in the interventional environment is large due to the combination of fast imaging with high contrast variety. However, a vast amount of existing image enhancement methods requires the image information of both modalities to be present in the same domain. To unlock this potential, we present a solution to image-to-image translation from MR projections to corresponding X-ray projection images. The approach is based on a state-of-the-art image generator network that is modified to fit the specific application. Furthermore, we propose the inclusion of a gradient map in the loss function to allow the network to emphasize high-frequency details in image generation. Our approach is capable of creating X-ray projection images with natural appearance. Additionally, our extensions show clear improvement compared to the baseline method.Comment: In proceedings of SPIE Medical Imaging 201

Posteriore Epilepsien: Ätiologische Aspekte

Background Posterior epilepsies (PE), i.e. focal epilepsies with epileptogenic zones within the posterior parts of the neocortical mantle (parietal, occipital and dorsal temporal lobes), represent a diagnostic and therapeutic challenge encompassing a wide spectrum of possible etiologies. Objective The etiological spectrum of PE is presented. Material and methods Illustration based on the longstanding personal expertise of the authors with examples of findings in personal cases. Results The PE is complex. Knowledge of the broad spectrum of possible etiologies is important in order to be able to reliably identify a PE including its etiology and to offer targeted treatment to selected patients. Successful epilepsy surgery is often possible.Zusammenfassung Hintergrund Posteriore Epilepsien (PE), also fokale Epilepsien mit Ursprungszonen in den hinteren Anteilen des Neokortex (Parietallappen, Okzipitallappen, dorsaler Temporallappen), sind eine diagnostische und therapeutische Herausforderung mit einem großen Spektrum an möglichen Ätiologien. Fragestellung Das ätiologische Spektrum der PE wird dargestellt. Material und Methode Illustration auf der Basis langjähriger eigener Erfahrung und mit Befundbeispielen eigener Fälle. Ergebnisse Die PE ist vielgestaltig. Die Kenntnis des breiten Spektrums der möglichen Ätiologien ist wichtig, um eine PE mit ihrer Ätiologie verlässlich zu erkennen und ausgewählten Patienten eine gezielte Behandlung anbieten zu können. Erfolgreiche Epilepsiechirurgie ist nicht selten möglich

Early intravenous magnesium sulfate and its impact on cerebral vasospasm as well as delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage: a retrospective matched case-control analysis

Introduction Magnesium sulfate (MgSO4) is a potential neuroprotective agent for patients with aneurysmal subarachnoid hemorrhage (aSAH). We analysed the effect of early application of intraoperative intravenous magnesium sulfate (MgSO4) and compared the rate of cerebral vasospasm (CV), delayed cerebral ischemia (DCI) and neurological outcome in two patient cohorts. Material and methods A retrospective matched-pair analysis from patients of a single center in Germany was performed without (group A) and with (group B) MgSO4 application <24 hrs after diagnosis. Pairs were matched according to the known risk factors for DCI and CV (age, Fisher grade, smoking, severity of SAH). Incidence of CV, DCI, and neurological outcome using the modified Rankin Scale (mRS) 3 and 12 months after SAH were recorded. Results 196 patients fulfilled the inclusion criteria. After risk stratification, 48 patients were included in the final analysis (mean±SD age 54.2±8.1yrs, 30 f, 18 m) and were assigned to group A (n=24) or group B (n=24). CV occurred less frequently in group B (33%) than in A (46%). Likewise, DCI was present in 13% (group B) as compared to 42% (group A). After 12 months, 22 patients of group B had a favorable functional outcome (mRS 0 to 3) compared to 15 of group A. Conclusions In this study, the incidence of CV and DCI was lower in patients receiving intravenous MgSO4 within 24 hrs after aneurysmal SAH onset. Favorable functional outcome was more likely in the magnesium group after 12 months of follow-up

Projection-to-Projection Translation for Hybrid X-ray and Magnetic Resonance Imaging

Hybrid X-ray and magnetic resonance (MR) imaging promises large potential in interventional medical imaging applications due to the broad variety of contrast of MRI combined with fast imaging of X-ray-based modalities. To fully utilize the potential of the vast amount of existing image enhancement techniques, the corresponding information from both modalities must be present in the same domain. For image-guided interventional procedures, X-ray fluoroscopy has proven to be the modality of choice. Synthesizing one modality from another in this case is an ill-posed problem due to ambiguous signal and overlapping structures in projective geometry. To take on these challenges, we present a learning-based solution to MR to X-ray projection-to-projection translation. We propose an image generator network that focuses on high representation capacity in higher resolution layers to allow for accurate synthesis of fine details in the projection images. Additionally, a weighting scheme in the loss computation that favors high-frequency structures is proposed to focus on the important details and contours in projection imaging. The proposed extensions prove valuable in generating X-ray projection images with natural appearance. Our approach achieves a deviation from the ground truth of only 6% and structural similarity measure of 0.913 ± 0.005. In particular the high frequency weighting assists in generating projection images with sharp appearance and reduces erroneously synthesized fine details

Voxel-wise lesion mapping of restless legs syndrome in multiple sclerosis

Objective Restless legs syndrome (RLS) is known to be associated with multiple sclerosis (MS) and may be caused by MS lesions in specific cerebral brain regions. Applying a voxel-wise lesion analysis, we tried to identify the contribution of cerebral MS lesions to RLS. Methods In this retrospective study, we established a cohort of people with MS with documented RLS and controls of people with MS without RLS matched disease severity. Diagnosis of MS and RLS was based on the current guidelines. The MS lesions were analyzed on T2-weighted magnetic resonance imaging scans (1.5 or 3 T). After manual delineation, lesion maps were converted into stereotaxic space. We generated a lesion overlap and performed a Liebermeister test with 4000 permutations to compare the absence or presence of RLS voxel-wise between patients with and without lesions in a given voxel. Results Forty of the patients with RLS and MS fulfilled the inclusion criteria. The voxel-wise analysis yielded associations between RLS and MS in the subcortex of the left gyrus precentralis. Conclusion Our voxel-wise analysis shows associations in the subcortex of the left gyrus precentralis. Thus, our data suggests that a dysfunction of the efferent motor system due to cerebral lesions may contribute to the pathophysiology of RLS in MS.Open Access funding enabled and organized by Projekt DEAL.Universitätsklinikum Erlangen (8546