Purpose-To report an image segmentation algorithm that was developed to provide quantitative thickness measurement of 6 retinal layers in optical coherence tomography (OCT) images. Design-Prospective cross-sectional study.Methods-Imaging was performed with time and spectral domain OCT instruments in 15 and 10 normal healthy subjects, respectively. A dedicated software algorithm was developed for boundary detection based on a 2-D edge detection scheme, enhancing edges along the retinal depth while suppressing speckle noise. Automated boundary detection and quantitative thickness measurements derived by the algorithm were compared with measurements obtained from boundaries manually marked by 3 observers. Thickness profiles for 6 retinal layers were generated in normal subjects.Results-The algorithm identified 7 boundaries and measured thickness of 6 retinal layers: nerve fiber layer (NFL), inner plexiform layer and ganglion cell layer (IPL+GCL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer and photoreceptor inner segments (ONL +PIS), and photoreceptor outer segments (POS). The root mean squared error (RMSE) between the manual and automatic boundary detection ranged between 4 and 9 microns. The mean absolute values of differences between automated and manual thickness measurements were between 3 -4 microns, and comparable to inter-observer differences. Inner retinal thickness profiles demonstrated minimum thickness at the fovea, corresponding to normal anatomy. The OPL and ONL+PIS thickness profiles displayed a minimum and maximum thickness at the fovea, respectively. The POS thickness profile was relatively constant along the scan through the fovea.Conclusions-The application of this image segmentation technique is promising for investigating thickness changes of retinal layers due to disease progression and therapeutic intervention.

Background It has been well documented that along with tonsillar herniation, Chiari Malformation Type I (CMI) is associated with smaller posterior cranial fossa (PCF) and altered CSF flow and tissue motion in the cranio-cervical junction (CCJ). Objective This study assesses the relationship between PCF volumetry and CSF and tissue dynamics toward a combined imaging-based morphologic-physiologic characterization of CMI. Multivariate analysis is employed to identify the subset of parameters that best discriminates CMI from healthy. Methods Eleven length and volumetric measures of PCF, including volume, crowdedness, and 4th ventricle volume, four measures of CSF and cord motion in the CCJ, and five global intracranial measures, including intracranial compliance and pressure, were measured by MRI in 36 symptomatic CMI subjects (28F, 37±11 years) and 37 control subjects (24F, 36±12 years). The CMI group was further divided based on symptomatology into “typical” and “atypical” subgroups. Results Ten of the 20 morphologic and physiologic measures were significantly different between the CMI and the control cohorts. These parameters also had less variability and stronger significance in the typical CMI compared with the atypical. The measures with the most significance were clival and supraocciput lengths, PCF crowdedness, normalized PCF volume, 4th ventricle volume, maximal cord displacement (p<.001), and MR measure of ICP (p=.007). Multivariate testing identified cord displacement, PCF crowdedness, and normalized PCF as the strongest discriminator subset between CMI and controls. MRICP was higher in the typical CMI cohort compared with the atypical. Conclusion The identified 10 complementing morphologic and physiologic measures provide a more complete and symptomatology relevant characterization of CMI than tonsillar herniation alone.

BACKGROUND AND PURPOSE Dolichoectasia (DE) is a vasculopathy that consists of abnormal elongation and dilatation of arteries. The objective of this study is to evaluate the frequency of DE in an unselected population and assess different diagnostic methods. METHODS The Northern Manhattan Study is a multiethnic population based cohort of stroke-free participants. The definition proposed for DE was total cranial volume (TCV)-adjusted arterial diameter ≥2 SD. Other methods studied included visual assessment, unadjusted arterial diameters cutoff, Smoker's criteria and basilar artery (BA) volume. RESULTS A total of 718 subjects were included in the analysis (mean age 71.6 ± 8.0 years, 40% men, 61% Hispanic). Using the TCV-adjusted DE definition, 19% of the sample had at least one dolichoectatic artery. In 7% of the subjects, two or more arteries were affected. The BA was the most common dolichoectatic artery. Reproducibility for arterial diameter measurements was good to excellent (.70–.95), while for visual assessment ranged from fair to good (.49–.79). CONCLUSIONS A TCV-adjusted intracranial arterial diameter ≥2 SD is proposed as a useful DE definition. The variability in the prevalence of DE depending on the methods used underscores the need to agree on a reliable, universal definition of DE.

Long-duration exposure to microgravity is associated with an increase in periventricular WMH in astronauts. This increase was linked to an increase in ventricular CSF volume documented in ISS astronauts. There was no associated change in or abnormal levels of WMH volumes in deep white matter as reported in U-2 high-altitude pilots.