Choroid plexus volume in multiple sclerosis vs neuromyelitis optica spectrum disorder: a retrospective, cross-sectional analysis

BACKGROUND AND OBJECTIVES: The choroid plexus has been shown to play a crucial role in CNS inflammation. Previous studies found larger choroid plexus in multiple sclerosis (MS) compared with healthy controls. However, it is not clear whether the choroid plexus is similarly involved in MS and in neuromyelitis optica spectrum disorder (NMOSD). Thus, the aim of this study was to compare the choroid plexus volume in MS and NMOSD. METHODS: In this retrospective, cross-sectional study, patients were included by convenience sampling from 4 international MS centers. The choroid plexus of the lateral ventricles was segmented fully automatically on T1-weighted MRI sequences using a deep learning algorithm (Multi-Dimensional Gated Recurrent Units). Uni- and multivariable linear models were applied to investigate associations between the choroid plexus volume, clinically meaningful disease characteristics, and MRI parameters. RESULTS: We studied 180 patients with MS and 98 patients with NMOSD. In total, 94 healthy individuals and 47 patients with migraine served as controls. The choroid plexus volume was larger in MS (median 1,690 µL, interquartile range [IQR] 648 µL) than in NMOSD (median 1,403 µL, IQR 510 µL), healthy individuals (median 1,533 µL, IQR 570 µL), and patients with migraine (median 1,404 µL, IQR 524 µL; all p < 0.001), whereas there was no difference between NMOSD, migraine, and healthy controls. This was also true when adjusted for age, sex, and the intracranial volume. In contrast to NMOSD, the choroid plexus volume in MS was associated with the number of T2-weighted lesions in a linear model adjusted for age, sex, total intracranial volume, disease duration, relapses in the year before MRI, disease course, Expanded Disability Status Scale score, disease-modifying treatment, and treatment duration (beta 4.4; 95% CI 0.78-8.1; p = 0.018). DISCUSSION: This study supports an involvement of the choroid plexus in MS in contrast to NMOSD and provides clues to better understand the respective pathogenesis

Precise modelling of coaxical germanium detectors in preparation for a mathematical calibration

In preparation for the planned mathematical efficiency calibration of a whole-body counter, models of the four HPGe detectors have to be developed as input for Monte Carlo simulations. The results for two of the detectors are presented here. With the initial detector models, based on data provided by the manufacturer, calculated efficiencies for various photon energies and measuring geometries were 10-20% Loo high compared with the measured efficiencies. To obtain more reliable information about the constructional features, scanning measurements with collimated radiation were performed at the front window and the sides of each detector. Using the information from these measurements, the initial detector model was improved by comparing the measured efficiencies with efficiencies calculated by the Monte Carlo code MCNP 4C2 and correcting the model by an iterative process if necessary. Finally, the quality of the detector models was verified by measurements with uncollimated point sources, which were placed in 77 different positions on a 10 cm x 10 cm grid on the stretcher of the whole-body counter. For all photon energies and all source positions the deviation between measured and simulated efficiencies was found to be less than 3%. (C) 2007 Elsevier B.V. All rights reserved

Precise modelling of coaxial germanium detectors in preparation for a mathematical calibration

In preparation for the planned mathematical efficiency calibration of a whole-body counter, models of the four HPGe detectors have to be developed as input for Monte Carlo simulations. The results for two of the detectors are presented here. With the initial detector models, based on data provided by the manufacturer, calculated efficiencies for various photon energies and measuring geometries were 10-20% Loo high compared with the measured efficiencies. To obtain more reliable information about the constructional features, scanning measurements with collimated radiation were performed at the front window and the sides of each detector. Using the information from these measurements, the initial detector model was improved by comparing the measured efficiencies with efficiencies calculated by the Monte Carlo code MCNP 4C2 and correcting the model by an iterative process if necessary. Finally, the quality of the detector models was verified by measurements with uncollimated point sources, which were placed in 77 different positions on a 10 cm x 10 cm grid on the stretcher of the whole-body counter. For all photon energies and all source positions the deviation between measured and simulated efficiencies was found to be less than 3%. (C) 2007 Elsevier B.V. All rights reserved