Spectrum of MRI findings in central nervous system affection in Lyme neuroborreliosis.

Affections of the central nervous system (CNS) rarely occur in Lyme neuroborreliosis (LNB). CNS manifestations can have residual neurological symptoms despite antibiotic treatment. We explored the spectrum of CNS affections in patients with LNB in a tertiary care center in a region endemic for Lyme borreliosis. We retrospectively included patients treated at a tertiary care center from January 2020-December 2021 fulfilling the case criteria for LNB as stated in the current German guideline on LNB. Clinical data, cerebrospinal fluid (CSF) findings and MRI imaging were collected. We included 35 patients with LNB, 24 with early manifestations and 11 with CNS-LNB. CNS-LNB patients had encephalomyelitis (n = 6) or cerebral vasculitis (n = 5). Patients with early LNB and CNS-LNB differed regarding albumin CSF/serum quotient and total protein in CSF. Duration from onset of symptoms until diagnosis was statistically significantly longer in patients with encephalomyelitis. MRI findings were heterogeneous and showed longitudinal extensive myelitis, perimedullar leptomeningeal enhancement, pontomesencephalic lesions or cerebral vasculitis. CNS-LNB can present with a variety of clinical syndromes and MRI changes. No clear pattern of MRI findings in CNS-LNB could be identified. The role of MRI consists in ruling out other causes of neurological symptoms.

Advanced diffusion MRI provides evidence for altered axonal microstructure and gradual peritumoral infiltration in GBM in comparison to brain metastases.

PURPOSE: In contrast to peritumoral edema in metastases, GBM is histopathologically characterized by infiltrating tumor cells within the T2 signal alterations. We hypothesized that depending on the distance from the outline of the contrast-enhancing tumor we might reveal imaging evidence of gradual peritumoral infiltration in GBM and predominantly vasogenic edema around metastases. We thus investigated the gradual change of advanced diffusion metrics with the peritumoral zone in metastases and GBM. METHODS: In 30 patients with GBM and 28 with brain metastases, peritumoral T2 hyperintensity was segmented in 33% partitions based on the total volume beginning at the enhancing tumor margin and divided into inner, middle and outer zones. Diffusion Tensor Imaging (DTI)-derived fractional anisotropy and mean diffusivity as well as Diffusion Microstructure Imaging (DMI)-based parameters Dax-intra, Dax-extra, V­CSF and V-intra were employed to assess group-wise differences between inner and outer zones as well as within-group gradients between the inner and outer zones. RESULTS: In metastases, fractional anisotropy and Dax-extra were significantly reduced in the inner zone compared to the outer zone (FA p = 0.01; Dax-extra p = 0.03). In GBM, we noted a reduced Dax-extra and significantly lower intraaxonal volume fraction (Dax-extra p = 0.008, V­intra p = 0.006) accompanied by elevated axial intraaxonal diffusivity in the inner zone (p = 0.035). Between-group comparison of the outer to the inner zones revealed significantly higher gradients in metastases over GBM for FA (p = 0.04) as well as the axial diffusivity in the intra- (p = 0.02) and extraaxonal compartment (p < 0.001). CONCLUSION: Our findings provide evidence of gradual alterations within the peritumoral zone of brain tumors. These are compatible with predominant (vasogenic) edema formation in metastases, whereas our findings in GBM are in line with an axonal destructive component in the immediate peritumoral area and evidence of tumor cell infiltration with accentuation in the tumor's vicinity.

Broadband directional scattering through a phase difference acquired in composite nanoparticles.

We study the broadband scattering of light by composite nanoparticles through the Born approximation, FEM simulations, and measurements. The particles consist of two materials and show broadband directional scattering. From the analytical approach and the subsequent FEM simulations, it was found that the directional scattering is due to the phase difference between the fields scattered by of each of the two materials of the nanoparticle. To confirm this experimentally, composite nanoparticles were produced using ion-beam etching. Measurements of SiO2 / Au composite nanoparticles confirmed the directional scattering which was predicted by theory and simulations.

Limits of realizing irradiance distributions with shift-invariant illumination systems and finite étendue sources.

When redistributing the light emitted by a source into a prescribed irradiance distribution, it is not guaranteed that, given the source and optical constraints, the desired irradiance distribution can be achieved. We analyze the problem by assuming an optical black box that is shift-invariant, meaning that a change in source position does not change the shape of the irradiance distribution, only its position. The irradiance distribution we can obtain is then governed by deconvolution. Using positive-definite functions and Bochner's theorem, we provide conditions such that the irradiance distribution can be realized for finite étendue sources. We also analyze the problem using optimization, showing that the result heavily depends on the chosen source distribution.

Recent advances in metasurface design and quantum optics applications with machine learning, physics-informed neural networks, and topology optimization methods.

As a two-dimensional planar material with low depth profile, a metasurface can generate non-classical phase distributions for the transmitted and reflected electromagnetic waves at its interface. Thus, it offers more flexibility to control the wave front. A traditional metasurface design process mainly adopts the forward prediction algorithm, such as Finite Difference Time Domain, combined with manual parameter optimization. However, such methods are time-consuming, and it is difficult to keep the practical meta-atom spectrum being consistent with the ideal one. In addition, since the periodic boundary condition is used in the meta-atom design process, while the aperiodic condition is used in the array simulation, the coupling between neighboring meta-atoms leads to inevitable inaccuracy. In this review, representative intelligent methods for metasurface design are introduced and discussed, including machine learning, physics-information neural network, and topology optimization method. We elaborate on the principle of each approach, analyze their advantages and limitations, and discuss their potential applications. We also summarize recent advances in enabled metasurfaces for quantum optics applications. In short, this paper highlights a promising direction for intelligent metasurface designs and applications for future quantum optics research and serves as an up-to-date reference for researchers in the metasurface and metamaterial fields.

Conebeam CT as an Additional Tool in Digital Subtraction Myelography for the Detection of Spinal Lateral Dural Tears.

Lateral dural tears as a cause spontaneous intracranial hypotension occur in ∼20% of patients. Common imaging modalities for their detection are lateral decubitus digital subtraction myelography or dynamic CT myelography. Reports on the use of conebeam CT are scarce. We show 3 patients in whom the targeted use of conebeam CT during digital subtraction myelography was helpful in confirming the site of the leak.

Risk factors for the development of secondary intracranial hypertension in acute cerebral venous thrombosis.

PURPOSE: Intracranial hypertension (IH) can complicate cerebral venous thrombosis (CVT), potentially causing permanent visual loss. Current knowledge on risk factors for the development of IH following CVT is scarce. We applied a compound classifier (CSF opening pressure > 25 cmH2O, papilledema, or optic disc protrusion on MRI) as a surrogate for IH and studied the predictive value of thrombus location, the number of thrombosed segments, and thrombus volume. METHODS: We prospectively included 26 patients with acute CVT and complete MRI data. IH was defined by CSF opening pressure > 25 cmH2O, papilledema, or optic disc protrusion on MRI. Using high-resolution contrast-enhanced venography, we determined the thrombus location, number of thrombosed segments, and thrombus volume. We analyzed their association with IH by logistic regression, their predictive power by the area under the receiver operating characteristic curve, and their association with CSF opening pressure by linear regression. RESULTS: IH occurred in 46% of CVT patients and was associated with higher thrombus volume (AUC 0.759, p = 0.025) and superior sagittal sinus thrombosis both alone (OR 2.086, p = 0.049) and combined with transverse sinus thrombosis (OR 2.014, p = 0.028). Effects in patients presenting CSF opening pressure > 25 cm H2O and the compound classifier were consistent. Thrombus volume > 4 ml was the single most important predictor of higher CSF opening pressure (ß = 0.566, p = 0.035), increasing IH risk. CONCLUSION: Larger thrombus volume, dominant transverse sinus occlusion, and extensive superior sagittal combined with transverse sinus thrombosis were associated with IH. Thrombus volumetry might identify patients at risk for IH and direct further clinical evaluation.

Intracranial Vessel Segmentation in 3D High-Resolution T1 Black-Blood MRI.

We demonstrate the feasibility of intracranial vascular segmentation based on the hypointense signal in non-contrast-enhanced black-blood MR imaging using convolutional neural networks. We selected 37 cases. Qualitatively, we observed no degradation due to stent artifacts, a comparable recognition of an aneurysm recurrence with TOF-MRA, and consistent success in the differentiation of intracranial arteries and veins. False-positive and false-negative results were observed. Quantitatively, our model achieved a promising Dice similarity coefficient of 0.72.

Clinical feasibility of diffusion microstructure imaging (DMI) in acute ischemic stroke.

BACKGROUND: Diffusion microstructure imaging (DMI) is a fast approach to higher-order diffusion-weighted magnetic resonance imaging that allows robust decomposition and characterization of diffusion properties of brain tissue into intra-axonal, extra-axonal, and a free water-compartment. We now report the application of this technique to acute ischemic stroke and demonstrate its potential applicability to the daily clinical routine. METHODS: Thirty-eight patients diagnosed with acute ischemic stroke were scanned using an accelerated multi-shell diffusion-weighted imaging protocol (median delay between onset and MRI scan of 113 min). DMI metrics were calculated and the apparent diffusion coefficient (ADC) derived from conventional diffusion-weighted imaging was used for comparison. The resulting DMI parameter maps were analysed for their potential to improve infarct core delineation, and a receiver-operating characteristic (ROC) analysis was subsequently performed for automated infarct segmentation. RESULTS: Robust parameter maps for diffusion microstructure properties were obtained in all cases. Within the ischemic tissue, an increase in the volume fraction of the intra-axonal compartment was accompanied by a volume fraction reduction in the other two compartments. Moreover, diffusivity was reduced in all three compartments, with intra-axonal diffusivity showing the highest degree of contrast. The intra-axonal diffusion coefficient maps were subsequently found to perform better than single-shell ADC-derived segmentation in terms of automatic segmentation of the infarct core (area under the curve = 0.98 vs 0.92). CONCLUSIONS: The alterations to the ischemic core detected by DMI are in line with the "beading-model" of non-uniform neurite swelling under ischemic conditions. When compared to conventional single-shell diffusion-weighted imaging, DMI metrics are associated with improved discriminative power for delineating and characterizing ischemic changes. This might allow a more detailed assessment of infarct age, severity of damage, the degree of reversibility, and outcome.

Gray-White Matter Blurring of the Temporal Pole Associated With Hippocampal Sclerosis: A Microstructural Study Involving 3 T MRI and Ultrastructural Histopathology.

Hippocampal sclerosis (HS) is often associated with gray-white matter blurring (GMB) of the anterior temporal lobe. In this study, twenty patients with unilateral temporal lobe epilepsy and HS were studied with 3 T MRI including T1 MP2RAGE and DTI/DMI sequences. Anterior temporal lobe white matter T1 relaxation times and diffusion measures were analyzed on the HS side, on the contralateral side, and in 10 normal controls. Resected brain tissue of three patients without GMB and four patients with GMB was evaluated ultrastructurally regarding axon density and diameter, the relation of the axon diameter to the total fiber diameter (G-ratio), and the thickness of the myelin sheath. Hippocampal sclerosis GMB of the anterior temporal lobe was related to prolonged T1 relaxation and axonal loss. A less pronounced reduction in axonal fraction was also found on imaging in GMB-negative temporal poles compared with normal controls. Contralateral values did not differ significantly between patients and normal controls. Reduced axonal density and axonal diameter were histopathologically confirmed in the temporopolar white matter with GMB compared to temporal poles without. These results confirm that GMB can be considered an imaging correlate for disturbed axonal maturation that can be quantified with advanced diffusion imaging.