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Medical Sciences100%

Selected Abstracts

Sonographic detection of the optic radiation

ACTA PAEDIATRICA, Issue 10 2005
Annemieke Boxma
Abstract Objective: To describe a region of hyperechoic white matter adjacent to the atrium of the lateral ventricle of preterms, and to speculate on the relevance of detecting preterm white matter injury. Patients and methods: Cranial ultrasound images of 92 preterms of gestational age (GA) 32 wk or less were reviewed. For each infant, one first week standard coronal image was used for measurement of grey values around the para-atrial region of interest (PAROI) relative to the choroid plexus. For verification of the sonographic anatomy, MR images of an adult brain were used. For reference, neuro-anatomical images were compared in several atlases. In a group of nine preterms of similar GA with cystic periventricular leukomalacia (PVL) or MR-confirmed white matter disease, the disappearance of the PAROI was examined. Results: The hyperechoic para-atrial area, subjectively detected in 84% of the patients, was situated bilaterally between the inner end of the lateral fissure and the upper third of the choroid plexus. In white matter caudal to the atrium, the hyperechoic band could be pursued towards the calcarine area. The average ratio of grey value around the PAROI to the choroid plexus was 0.787 (SD=0.072, median 0.791). There was no correlation between PAROI grey value and gestational age. At 26 wk gestational age, the average ratio was 0.781 (n=14), and 0.789 (n=17) at 31 wk. Location of the PAROI agrees with the angle of the upper loop of the optic radiation. None of the nine infants with white matter damage had PAROIs clearly distinguishable from flaring. Conclusion: The symmetrical and unchanged acoustic character between 26 and 31 wk of gestational age argues in favour of the hypothesis that the PAROI is an anatomical structure. The localization of the hyperechoic band supports the hypothesis that it represents part of the optic radiation. Further study is needed to examine the absence of a hyperechoic para-atrial band as a prognostic marker of the extension and severity of white matter injury. [source]

Orientational analysis of planar fibre systems observed as a Poisson shot-noise process

JOURNAL OF MICROSCOPY, Issue 1 2007
SALME KÄRKKÄINEN
Summary We consider two-dimensional fibrous materials observed as a digital greyscale image. The problem addressed is to estimate the orientation distribution of unobservable thin fibres from a greyscale image modelled by a planar Poisson shot-noise process. The classical stereological approach is not straightforward, because the point intensities of thin fibres along sampling lines may not be observable. For such cases, Kärkkäinen et al. (2001) suggested the use of scaled variograms determined from grey values along sampling lines in several directions. Their method is based on the assumption that the proportion between the scaled variograms and point intensities in all directions of sampling lines is constant. This assumption is proved to be valid asymptotically for Boolean models and dead leaves models, under some regularity conditions. In this work, we derive the scaled variogram and its approximations for a planar Poisson shot-noise process using the modified Bessel function. In the case of reasonable high resolution of the observed image, the scaled variogram has an approximate functional relation to the point intensity, and in the case of high resolution the relation is proportional. As the obtained relations are approximative, they are tested on simulations. The existing orientation analysis method based on the proportional relation is further experimented on images with different resolutions. The new result, the asymptotic proportionality between the scaled variograms and the point intensities for a Poisson shot-noise process, completes the earlier results for the Boolean models and for the dead leaves models. [source]

Sonographic detection of the optic radiation

ACTA PAEDIATRICA, Issue 10 2005
Annemieke Boxma
Abstract Objective: To describe a region of hyperechoic white matter adjacent to the atrium of the lateral ventricle of preterms, and to speculate on the relevance of detecting preterm white matter injury. Patients and methods: Cranial ultrasound images of 92 preterms of gestational age (GA) 32 wk or less were reviewed. For each infant, one first week standard coronal image was used for measurement of grey values around the para-atrial region of interest (PAROI) relative to the choroid plexus. For verification of the sonographic anatomy, MR images of an adult brain were used. For reference, neuro-anatomical images were compared in several atlases. In a group of nine preterms of similar GA with cystic periventricular leukomalacia (PVL) or MR-confirmed white matter disease, the disappearance of the PAROI was examined. Results: The hyperechoic para-atrial area, subjectively detected in 84% of the patients, was situated bilaterally between the inner end of the lateral fissure and the upper third of the choroid plexus. In white matter caudal to the atrium, the hyperechoic band could be pursued towards the calcarine area. The average ratio of grey value around the PAROI to the choroid plexus was 0.787 (SD=0.072, median 0.791). There was no correlation between PAROI grey value and gestational age. At 26 wk gestational age, the average ratio was 0.781 (n=14), and 0.789 (n=17) at 31 wk. Location of the PAROI agrees with the angle of the upper loop of the optic radiation. None of the nine infants with white matter damage had PAROIs clearly distinguishable from flaring. Conclusion: The symmetrical and unchanged acoustic character between 26 and 31 wk of gestational age argues in favour of the hypothesis that the PAROI is an anatomical structure. The localization of the hyperechoic band supports the hypothesis that it represents part of the optic radiation. Further study is needed to examine the absence of a hyperechoic para-atrial band as a prognostic marker of the extension and severity of white matter injury. [source]