Grayscale median measurements are highly reproducible when obtained from the same US system with similar gain settings. Grayscale median values differ significantly across gain values and between systems. Researchers should consider the impact of US system and gain settings on GSM values when working to minimize system- and operator-dependent factors.

A wide bandwidth, dual polarized, modi¯ed four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical re°ectors for Tianlai, a radio interferometer designed for 21 cm intensity mapping. Simulations of the feed antenna beam patterns and scattering parameters are compared to experimental results at multiple frequencies across the 650-1420 MHz range. Simulations of the beam patterns of the combined feed array/re°ector are presented as well.

The purpose of this study was to determine the relationship between symptomatic status, transcranial Doppler (TCD) microemboli presence and plaque histopathology findings. TCD was performed on 60 subjects (37 symptomatic, 23 asymptomatic) prior to undergoing clinically indicated carotid endarterectomy. The frequency of microemboli signals was not significantly different between symptomatic and asymptomatic subject groups (p=0.88) and there were no differences observed in the macroscopic or histopathology scoring of these plaques (p-values all > 0.05). The presence of microemboli was associated with an ulceration score (regardless of symptomatic or asymptomatic status, p=0.034), with a one level increase in ulceration rating associated with an odds ratio of 5.86 (95%[CI] 1.55, 43.4). These findings suggest that both symptomatic and asymptomatic subjects may have plaque with similar features of instability and ability to create emboli. Thus, identifying new ways to measure plaque instability may provide important information for optimizing treatment to prevent future stroke.

Introduction: Traditional Doppler measures have been used to predict cognitive performance in patients with carotid atherosclerosis. Novel measures, such as carotid strain indices (CSI) have shown associations with cognitive performance. We hypothesized that lower mean middle cerebral artery (MCA) velocities, higher bulb-internal carotid artery (ICA) velocities, MCA pulsatility index (PI) and CSI would be associated with poorer cognitive performance in individuals with advanced atherosclerosis. Methods: Neurocognitive testing, carotid ultrasound, transcranial Doppler and CSI were performed on 40 subjects scheduled for carotid endarterectomy. Kendall tau correlations were used to examine relationships between cognitive tests and the maximum peak systolic velocity (PSV) (from bulb, proximal, mid or distal ICA), mean MCA velocity and PI (on surgical side) and CSI (maximum axial, lateral and shear strain indices used to characterize plaque deformations with arterial pulsation). Cognitive measures included age adjusted indices of verbal fluency, verbal and visual learning/memory, psychomotor speed, auditory attention/working memory, visuoconstruction, and mental flexibility. Results: Participants were median age 71.0 (IQR 9.75) years, 26 male (65%) and 14 female (35%). Median stenosis was 70.00 (IQR 10.00) percent. Traditional Doppler parameters, PSV, mean MCA velocity and MCA PI did not predict cognitive performance (p values all >0.05). Maximum strain values were significantly associated with cognitive performance (p<0.05). Table . Conclusions: Traditional velocity measurements of maximum bulb-ICA PSV, mean MCA velocity and PI were not associated with cognitive performance in patients with advanced atherosclerotic disease, however maximum strain indices were associated with cognitive performance. Findings suggest that cognition may be associated with unstable plaque (plaques at greater risk for rupture) rather than blood flow.

Introduction: Grayscale (GS) texture features that examine homogeneity and echogenicity have been used to identify vulnerable plaques with in vivo ultrasound imaging have been shown to correlate with plaque tissue composition. However, the relationship of collagen fiber organization to GS texture features extracted from in vivo images is a novel idea to provide additional information about plaque structure. We hypothesize that collagen fiber alignment is clinically relevant to identify vulnerable plaques. The objective of this feasibility study was to use multiscale imaging (in vivo ultrasound and high resolution optical microscopy) to determine how GS texture features are related to plaque collagen structure. Methods: Participants (n=6) scheduled for clinically indicated carotid endarterectomy underwent in vivo carotid ultrasound imaging with texture feature extraction (spatial gray level dependence matrices method for calculating angular second moment [SGLDM-ASM] and grayscale median value [GSM]). Plaque specimens were sent to histopathology and stained with H&E. The collagen fibers in the fibrous cap of the plaque histopathology slides were imaged with liquid crystal based polarization microscopy and quantified using an established software tool (CurveAlign). Correlations between collagen alignment coefficient (range 0-1, 1 represents perfectly aligned fibers) and the texture feature SGLDM-ASM (a measure of homogeneity, higher values are more homogenous) and GSM (a measure of echogenicity higher values are more echogenic) were examined. Results: Participants were mean (SD) 72.5 (6.1) years of age, had 71.67 (8.16) percent stenosis. The mean SGLDM-ASM was 0.0017 (0.0023), the mean SD GSM was 73.13 (30.98). SGLDM-ASM was significantly correlated to collagen alignment (r=0.83; p=0.028). There was no significant correlation detected between GSM and collagen alignment (r=-0.43;p=0.38). Conclusion: Results of this study indicate the potential role for using high resolution optical microscopy with ultrasound to characterize collagen fiber alignment in plaques with measures of homogeneity. Future studies are needed to see how multiscale imaging can be used to inform in vivo imaging for identification of vulnerable plaque features.

Scientists have carried out experiments and theoretical modelling to investigate how bacteria are able to travel quickly through complex fluids.

Introduction: Microemboli, as detected by transcranial Doppler (TCD), are hypothesized to be associated with carotid plaque instability and symptomatic subject status associated with motor, sensory, visual and speech deficits of stroke and transient ischemic attack (TIA). However, the current clinical exam does not assess sequeli of small emboli and probable differences between symptomatic and asymptomatic plaques. The purpose of this study was to determine the relationship between symptomatic status, microemboli presence and histopathology findings. Methods: TCD examination was performed on 60 study subjects for an hour to assess the presence of microemboli, prior to undergoing clinically indicated carotid endarterectomy. Macroscopic scoring for cholesterol, thrombus, calcium and ulceration were performed with a dissecting microscope. Histopathological examination, with high power magnification on fixed plaque was scored for hemorrhage, hemosiderin, inflammation, percent cholesterol and calcium. Pearson’s chi-squared test was used to assess the frequency of microemboli between symptomatic and asymptomatic subjects. Logistic regression was used to analyze the relationship between operative and histopathology plaque findings and presence of microemboli. Results: The frequency of microemboli signals, as detected with TCD, was not significantly different between symptomatic and asymptomatic subject groups (p=0.88) nor was there any difference observed in the macroscopic or histopathology scoring of these plaques (p-values all > 0.05). The presence of microemboli was associated with an ulceration score (regardless of symptomatic or asymptomatic status, p=0.034), with a one level increase in ulceration rating associated with an odds ratio of 5.86 (95% [CI] 1.55, 4.34). Conclusion: These findings suggest that both symptomatic and asymptomatic subjects (with clinical indications for carotid endarterectomy) may have plaque with similar features of instability and ability to create emboli. Thus, identifying new ways to measure plaque instability may provide important information for optimizing treatment to prevent future stroke. It also suggests that present clinical exam does not detect the sequeli of small emboli.

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