UV-klimaat monitoring systeem ; beschrijving van testresultaten

In 1989 is een project gestart om het UV-klimaat in Nederland te bepalen. Het doel is het bepalen van het biologisch relevante UV-klimaat op het aardoppervlak. De meetgegevens moeten kennis verschaffen over het huidige biologisch relevante UV-klimaat en de afhankelijkheid van atmosferische parameters. Verder zullen meetgegevens over meerdere jaren geanalyseerd worden op eventuele trends in het UV-klimaat. Tevens zullen met de data UV-overdrachtsmodellen gevalideerd kunnen worden. In een eerste fase is in 1990 en 1991 een definitiestudie uitgevoerd naar de eisen die aan een dergelijke meetopstelling moeten worden gesteld. Het resultaat was een aanbeveling voor het gebruik van een combinatie van twee instrumenten ; een spectroradiometer voor metingen van in het bijzonder het UV-B en een spectrograaf voor een instantane meting van het totale UV spectrum. De spectroradiometer bestaat uit een dubbele monochromator met een photon counting detectie systeem. Dit systeem moet voldoen aan bepaalde eisen zoals een groot dynamisch bereik, een laag donkersignaal, een laag strooilichtniveau en een hoge golflengte-nauwkeurigheid en -reproduceerbaarheid. Dit zijn belangrijke parameters voor een accurate meting van de steile flank in het zonnespectrum in het UV-B golflengtegebied. De spectrograaf bestaat uit een enkele monochromator met een diode array voor een meting van in het bijzonder het UV-A. De voordelen van de combinatie zijn uitvoerig beschreven in de definitiestudie. In 1992 is de opstelling gebouwd en geinstalleerd in een mobiele container. De container is lichtdicht en temperatuur-gestabiliseerd binnen +/- 1 graden C. De mobiliteit biedt de mogelijkheid deel te nemen aan internationale vergelijkingen van UV meetapparatuur en metingen te verrichten in gebieden met verschillende milieu-omstandigheden. In de bouwperiode is ook optica ontwikkeld, dat het licht afkomstig van de integrerende bol inkoppelt in de spectrometers. Het is een periscoop-achtig systeem bestaande uit twee lenzen en twee spiegels. Na het gereedkomen (eind 1992) is de opstelling eind 1992 en begin 1993 getest of deze voldeed aan de in de definitiestudie gestelde eisen. Sinds april 1993 worden op reguliere basis metingen verricht. Dit rapport beschrijft het systeem zoals het functioneerde in 1993 en 1994. De verschillende componenten van de opstelling worden beschreven evenals het besturen van de opstelling. De testresultaten worden bediscussieerd. De resultaten laten zien dat de opstelling voldoet aan de meeste van de gestelde eisen. Het is gebleken dat het photon counting signaal gecorrigeerd moet worden voor dode tijd. Strooilicht in de dubbele monochromator is gereduceerd door aanpassingen aan de wand tussen de twee monochromators en bij de in- en uitkoppel spleten. Het is nu kleiner dan het donker signaal. De cosinus respons van de integrerende bol is beter dan voor diffusers. Echter voor bepaalde hoeken van inval, waarbij het oppervlak tegenover de uitgang van de bol verlicht wordt, vertoont de integrerende bol een overrespons in vergelijking tot de cosinuswet. Strooilicht in de enkele monochromator van de spectrograaf is een, nog op te lossen, probleem. Een methode voor het controleren van de golflengte-stabiliteit van de spectrometers is ontwikkeld. Hierbij wordt de Fraunhofer structuur op het gemeten spectrum vergeleken met de structuur van een buitenaards spectrum. Het calibreren van het systeem voor het meten van absolute irradiantie niveaus en de controle van de calibratie-stabiliteit worden nog onderzocht. Onderzoek naar het gebruik van een calibratie-unit heeft uitgewezen dat het gebruik van een dergelijke unit de calibratie- nauwkeurigheid aanzienlijk verslechtert. Geen van de internationaal gerenommeerde standaard laboratoria levert standaard lampen voor gebruik in een behuizing. Voor de controle van de stabiliteit wordt momenteel een 200 Watt lampbehuizing ontwikkeld. Aangezien het slechts een relatieve meting van een 200 Watt lamp betreft is de stabiliteit van de lamp de enige eis. Als laatste wordt het monitoring protocol voor 1994 gegeven en worden enkele voorlopige resultaten getoond.In 1989, a project was started to collect information on the current UV climatic conditions and changes in the Netherlands. The goal of the project is to obtain knowledge of the biologically relevant UV climate at the earth's surface. The experimental data should lead to knowledge on the present biologically relevant UV radiation and its dependence on atmospheric conditions as well as determination of long-term trends in the biologically relevant UV climate. Furthermore, the measurements are to be used to validate UV transfer models.This report describes the optical system and the mobile container as they operate since 1993. The different components and the operation of the system are discussed and test results are given. The tests show that most requirements, such as wavelength accuracy, spectral bandwidth, dark signal and dynamic range, are met. Correction of the photon-counting signal for the dead time in the detection electronics was found to be necessary. Stray light in the spectroradiometer is reduced by adapting the interior of the instrument, and is smaller than the darksignal. The cosine response of the integrating sphere is superior to that of diffusors. However, for specific angles of incidence where the area opposite the exit port of the sphere is illuminated, the sphere shows an overresponse with respect to the cosine law. Stray light in the spectrograph is still a problem to be solved.DGM/SV

Effectieve UV-straling in Nederland

In dit rapport worden de meetresultaten en eerste analyses van de spectrale UV-metingen gepresenteerd, zoals die zijn verkregen met de bij het RIVM ontwikkelde spectrale UV-meetsysteem, dat sedert april 1993 operationeel is. De spectrale meetgegevens zijn in dit rapport geanalyseerd met betrekking tot effecten van variaties van de dikte van de ozonlaag, bewolking en aerosolen. Metingen zijn vergeleken met modelberekeningen van de UV-transfer voor onbewolkte situaties en een empirische methode is ontwikkeld en toegepast voor de analyse van de invloeden van bewolking en aerosolen. Bewolking en aerosolen reduceren de effectieve UV jaardosis met circa 35%. De methoden zijn gebruikt voor het berekenen van de effectieve UV jaardoses in de periode van 1991-1994. De resultaten zijn vergeleken met een referentie jaarsom, gebaseerd op gemiddelde ozonwaarden in de periode van 1972-1993 en een gemiddelde reductie door bewolking en aerosolen. Vergeleken met de referentie jaarsom is de voor bewolking en aerosolen gecorrigeerde berekende jaardosis in 1991 3% lager, de jaardosis in 1992 5% hoger en in 1993 12% hoger. De voor bewolking en aerosolen gecorrigeerde jaardosis in 1994 was ruim 8% hoger dan de referentie jaarsom, hetgeen inhoudt dat de sterke opwaartse trend van 1992 en 1993, die mogelijk is beinvloed door de vulkaanuitbarsting van de Pinatubo in 1991, niet wordt voortgezet. Niettemin is de jaardosis in 1994 beduidend hoger dan de jaardosis in 1991 en de referentie dosis.This report presents the observations and first analysis of the spectral and effective UV-irradiance levels in the Netherlands (at 52o N) obtained with the UV-monitoring system developed at RIVM and operational since April 1993. The spectral data have been analysed with respect to effects of variations of thickness of the ozone layer, cloud cover and aerosols. Measurements were compared with UV-transfer model calculations for cloudless situations. An empirical method is developed and applied for the evaluation of cloud and aerosol effects on atmospheric UV-transfer. Clouds and aerosols were found to reduce the yearly effective UV dose by 35% compared to clear sky estimates. The method is used to analyse yearly effective UV doses in the Netherlands in the period 1991-1994. The results are compared to a reference yearly UV dose, based on average ozone values over 1972-1993, and average cloud and aerosol reductions. Compared to the reference yearly dose the cloud and aerosol corrected yearly doses in 1991 were 3% lower, the doses in 1992 5% higher, and in 1993 12% higher. The cloud and aerosol corrected yearly dose for 1994 was 8% higher than the reference yeardose. Thus the sharp upward trend observed in 1992 and 1993, which might have been influenced by the volcanic eruption of the Pinatubo in 1991, has not been continued. Nevertheless, the 1994 estimates are consistently higher than the 1991 values and the reference dose.DGM/SVS/SN

Hirnmetastasen – interdisziplinär zu einer personalisierten BehandlungBrain metastases–Interdisciplinary approach towards a personalized treatment

The incidence, treatment and prognosis of patients with brain metastases have substantially changed during the last decades. While the survival time after diagnosis of cerebral metastases was on average a maximum of 3–6 months only 10 years ago, the survival time could be significantly improved due to novel surgical, radiotherapeutic and systemic treatment modalities. Only a few years ago, the occurrence of brain metastases led to a withdrawal from systemic oncological treatment and the exclusion of drug therapy studies and to a purely palliatively oriented treatment in the sense of whole brain radiation therapy (WBRT) with or without surgery. The increasing availability of targeted and immunomodulatory drugs as well as adapted radio-oncological procedures enable increasingly more personalized treatment approaches. The aim of this review article is to demonstrate the progress and complexity of the treatment of brain metastases in the context of modern comprehensive interdisciplinary concepts

Visualization and Classification of Deeply Seated Collateral Networks in Moyamoya Angiopathy with 7T MRI

This study aimed to evaluate morphologic patterns and the delineation of deeply seated collateral networks using ultra-high-field MRA in comparison with conventional DSA in 15 patients. Sequences acquired at 7T were TOF-MRA with 0.22 X 0.22 X 0.41 mm(3) resolution and MPRAGE with 0.7 X 0.7 X 0.7 mm(3) resolution. The relevant deeply seated collateral networks were classified into 2 categories and 6 pathways. A total of 100 collateral networks were detected on DSA; 106, on TOF-MRA; and 73, on MPRAGE. Delineation of deeply seated collateral networks was comparable between TOF-MRA and DSA. The authors demonstrate excellent delineation of 6 distinct deeply seated collateral network pathways in Moyamoya angiopathy. BACKGROUND AND PURPOSE: Collateral networks in Moyamoya angiopathy have a complex angioarchitecture difficult to comprehend on conventional examinations. This study aimed to evaluate morphologic patterns and the delineation of deeply seated collateral networks using ultra-high-field MRA in comparison with conventional DSA. MATERIALS AND METHODS: Fifteen white patients with Moyamoya angiopathy were investigated in this prospective trial. Sequences acquired at 7T were TOF-MRA with 0.22 x 0.22 x 0.41 mm(3) resolution and MPRAGE with 0.7 x 0.7 x 0.7 mm(3) resolution. Four raters evaluated the presence of deeply seated collateral networks and image quality in a consensus reading of DSA, TOF-MRA, and MPRAGE using a 5-point scale in axial source images and maximum intensity projections. Delineation of deeply seated collateral networks by different imaging modalities was compared by means of the McNemar test, whereas image quality was compared using the Wilcoxon signed-rank test. RESULTS: The relevant deeply seated collateral networks were classified into 2 categories and 6 pathways. A total of 100 collateral networks were detected on DSA; 106, on TOF-MRA; and 73, on MPRAGE. Delineation of deeply seated collateral networks was comparable between TOF-MRA and DSA (P = .25); however, both were better than MPRAGE (P < .001). CONCLUSIONS: This study demonstrates excellent delineation of 6 distinct deeply seated collateral network pathways in Moyamoya angiopathy in white adults using 7T TOF-MRA, comparable to DSA

The cerebellum is involved in processing of predictions and prediction errors in a fear conditioning paradigm

Prediction errors are thought to drive associative fear learning. Surprisingly little is known about the possible contribution of the cerebellum. To address this question, healthy participants underwent a differential fear conditioning paradigm during 7T magnetic resonance imaging. An event-related design allowed us to separate cerebellar fMRI signals related to the visual conditioned stimulus (CS) from signals related to the subsequent unconditioned stimulus (US; an aversive electric shock). We found significant activation of cerebellar lobules Crus I and VI bilaterally related to the CS+ compared to the CS-. Most importantly, significant activation of lobules Crus I and VI was also present during the unexpected omission of the US in unreinforced CS+ acquisition trials. This activation disappeared during extinction when US omission became expected. These findings provide evidence that the cerebellum has to be added to the neural network processing predictions and prediction errors in the emotional domain

Visualization and Classification of Deeply Seated Collateral Networks in Moyamoya Angiopathy with 7T MRI

BACKGROUND AND PURPOSE Collateral networks in Moyamoya angiopathy have a complex angioarchitecture difficult to comprehend on conventional examinations. This study aimed to evaluate morphologic patterns and the delineation of deeply seated collateral networks using ultra-high-field MRA in comparison with conventional DSA. MATERIALS AND METHODS Fifteen white patients with Moyamoya angiopathy were investigated in this prospective trial. Sequences acquired at 7T were TOF-MRA with 0.22 × 0.22 × 0.41 mm resolution and MPRAGE with 0.7 × 0.7 × 0.7 mm resolution. Four raters evaluated the presence of deeply seated collateral networks and image quality in a consensus reading of DSA, TOF-MRA, and MPRAGE using a 5-point scale in axial source images and maximum intensity projections. Delineation of deeply seated collateral networks by different imaging modalities was compared by means of the McNemar test, whereas image quality was compared using the Wilcoxon signed-rank test. RESULTS The relevant deeply seated collateral networks were classified into 2 categories and 6 pathways. A total of 100 collateral networks were detected on DSA; 106, on TOF-MRA; and 73, on MPRAGE. Delineation of deeply seated collateral networks was comparable between TOF-MRA and DSA ( = .25); however, both were better than MPRAGE ( < .001). CONCLUSIONS This study demonstrates excellent delineation of 6 distinct deeply seated collateral network pathways in Moyamoya angiopathy in white adults using 7T TOF-MRA, comparable to DSA

Improved cerebral time-of-flight magnetic resonance angiography at 7 Tesla--feasibility study and preliminary results using optimized venous saturation pulses.

PURPOSE: Conventional saturation pulses cannot be used for 7 Tesla ultra-high-resolution time-of-flight magnetic resonance angiography (TOF MRA) due to specific absorption rate (SAR) limitations. We overcome these limitations by utilizing low flip angle, variable rate selective excitation (VERSE) algorithm saturation pulses. MATERIAL AND METHODS: Twenty-five neurosurgical patients (male n = 8, female n = 17; average age 49.64 years; range 26-70 years) with different intracranial vascular pathologies were enrolled in this trial. All patients were examined with a 7 Tesla (Magnetom 7 T, Siemens) whole body scanner system utilizing a dedicated 32-channel head coil. For venous saturation pulses a 35° flip angle was applied. Two neuroradiologists evaluated the delineation of arterial vessels in the Circle of Willis, delineation of vascular pathologies, presence of artifacts, vessel-tissue contrast and overall image quality of TOF MRA scans in consensus on a five-point scale. Normalized signal intensities in the confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter were measured and vessel-tissue contrasts were calculated. RESULTS: Ratings for the majority of patients ranged between good and excellent for most of the evaluated features. Venous saturation was sufficient for all cases with minor artifacts in arteriovenous malformations and arteriovenous fistulas. Quantitative signal intensity measurements showed high vessel-tissue contrast for confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter. CONCLUSION: The use of novel low flip angle VERSE algorithm pulses for saturation of venous vessels can overcome SAR limitations in 7 Tesla ultra-high-resolution TOF MRA. Our protocol is suitable for clinical application with excellent image quality for delineation of various intracranial vascular pathologies

Comparative analysis of CGUARD embolic prevention stent with Casper-RX and Wallstent for the treatment of carotid artery stenosis

Stent protected Angioplasty of extracranial carotid artery stenosis using the dual-layered CGUARD stent is a novel treatment option. In this study we evaluate the feasibility and the safety of the CGUARD in symptomatic and asymptomatic patients in comparison to Casper-RX and Wallstent. This is a multi-center study of consecutive patients treated with the CGUARD, Casper-RX and Wallstent at two German high volume neurovascular centers between April 2017 and May 2018. Patient characteristics, neuroimaging data and angiographic outcome were retrospectively analyzed. The primary end points of the study were acute occlusion of the carotid stent and symptomatic intracerebral hemorrhage (sICH). Carotid artery stenting was performed in 76 patients; of those 26 (34%) were treated with the CGUARD, 25 (33%) with Casper-RX, and 25 (33%) with Wallstent. In 58/76 (76%) cases carotid artery stenosis was symptomatic with a median baseline National Institutes of Health Stroke Scale of 4. Angioplasty and stenting as part of a mechanical thrombectomy for acute ischemic stroke was performed in 25/76 (33%) patients. Baseline patient characteristics were similar between the treatment groups, except for a higher portion of scheduled cases in the Casper-RX group. There were no significant differences in the rate of acute in stent occlusions (CGUARD, 2/26 (8%); Casper-RX, 1/25(4%), Wallstent, 1/25 (4%)) and postinterventional sICH (1/26 (4%), 0/25(0%), 0/25 (0%)). Clinical outcome at discharge did not differ between groups. Treatment of carotid artery stenosis using CGUARD is feasible with a good safety profile comparable to that of Casper-RX and Wallstent. (C) 2020 Elsevier Ltd. All rights reserved

Treatment of complex neurovascular lesions: an interdisciplinary angio suite approach

Objective: The objective of this study was to analyse our initial experience using an interdisciplinary angio suite approach to neurosurgical treatment of complex neurovascular lesions and expound technical feasibility and possible applications. Subjects: Six out of 451 patients with cranial or spinal neurovascular lesions were surgically treated in the angio suite (biplane angiographic system) during a 28-month observation period. Clinical baseline data, radiological and intraoperative findings as well as clinical and radiological outcome were assessed. Results: A ventral spinal perimedullary arteriovenous malformation, a ventral spinal perimedullary fistula, two diffuse frontal dural arteriovenous fistulas, a multifocal temporal arteriovenous malformation and a partially embolized fronto-temporo-basal dural arteriovenous fistula were successfully treated with angiographically confirmed complete occlusion and unimpaired neurological condition of the patients at the 12-month follow up. Conclusion: This study demonstrates the feasibility of this approach and points out possible indications, namely ventrally located spinal lesions and diffuse, deep seated cranial lesions