scholarly journals The Hubble Law and Gravity as Manifestations of Linear Measurement Standards Variability

2015 ◽  
Author(s):  
Vitaly Groppen
Keyword(s):  
Linear Measurement ◽  
Measurement Standards

Kinematics in space with variable linear measurement standards

2010 ◽  
Author(s):  
Vitaly O. Groppen ◽  
Manuel de León ◽  
D. M. de Diego ◽  
R. M. Ros
Keyword(s):  
Linear Measurement ◽  
Measurement Standards

Investigation of the Accuracy of Reference Instruments for Measuring Vertical Angles by Reference Method of Their Calibration

2020 ◽  
pp. 3-14
Author(s):  
O. M. Samoylenko ◽  
O. V. Adamenko ◽  
B. P. Kukareka
Keyword(s):  
Horizontal Plane ◽  
Opposite Sign ◽  
Reference Method ◽  
Angle Measurement ◽  
Measurement Standard ◽  
Vertical Angle ◽  
Measurement Standards ◽  
Measurement Results ◽  
Electronic Measurement ◽  
Systematic Biases

Reference method for simultaneous calibration of the three and more measurement standards for vertical angle measurement is developed. This method can to use for obtaining the systematic biases of the vertical angles measurements for each of the measuring standards relative of the horizontal plain was averaged from measurement results in time their calibration or comparison. For realization of the reference method was developed the autocollimationel electronic measurement standard for the automatization measurement of the vertical angles SeaLineZero_Standard™ (SLZ_S™). Summary standard deviation (k=1) of the vertical angle measurement relative the horizontal plane, from the results of their calibration by reference method, is not more 0,07ʺ…0,15ʺ. This result was obtained without the use the systematic biases, for each measurement standards, as measurements corrections (with opposite sign). The measuring standards, that were developed and researched, are necessary for obtaining the systematic biases of the vertical angle measurement for total stations and theodolites, that have the normed standard error 0,5ʺ and 1ʺ, when these instruments are calibrating.

scholarly journals Bi-caudate ratio as a MRI marker of white matter atrophy in multiple sclerosis and ischemic leukocencephalopathy

2019 ◽  
Vol 50 (1) ◽  
Author(s):  
Dena Serag ◽  
Eman Ragab
Keyword(s):  
Multiple Sclerosis ◽  
White Matter ◽  
Surrogate Marker ◽  
Normal Subjects ◽  
Subjective Assessment ◽  
Linear Measurement ◽  
Control Group ◽  
Imaging Science ◽  
The Difference ◽  
Sensitivity Specificity

Abstract Background Brain atrophy measurement is now a cornerstone in basic neuro-imaging science. While assessment of white matter atrophy by visual inspection is subjective, volumetric approaches are time-consuming and not often feasible. Bi-caudate ratio represents a linear surrogate parameter of brain volume that can be derived from standard imaging sequences. This study highlights the value of the bi-caudate ratio (BCR) as a MRI marker of white matter atrophy in patients with multiple sclerosis and ischemic leukoencephalopathy and set a cut-off value to differentiate between patients with white matter atrophy and normal subjects. Results A total of 115 patients (54 males and 61 females) diagnosed with white matter leukoencephalopathy (MS in 51 patients and ischemic leukoencephalopathy in 64 patients) were included. Another group of 60 subjects with a normal white matter signal was recruited as a control group. BCR for the patient group ranged from 0.13 to 0.27 (mean (± SD) = 0.16 ± 0.02), while for the control group, it ranged from 0.05 mm to 0.13 (mean (± SD) = 0.09 ± 0.01). The difference between the two groups was statistically significant (P value < 0.001). A cut-off value of 0.13 was used to differentiate between the BCR in both patients and control groups with sensitivity, specificity, and accuracy of 99.2%, 100%, and 99%, respectively. The difference in BCR for patients diagnosed with MS and ischemic leukoencephalopathy was also statistically significant (P value < 0.001). Conclusion The bi-caudate ratio represents a linear measurement of subcortical atrophy that can be useful as a surrogate marker of global supra-tentorial white matter atrophy instead of the usually performed visual and therefore subjective assessment. It is an easily obtained measure that can be performed without complex time-consuming volumetric studies. Our findings also revealed that the BCR is higher in patients with ischemic leukoencephalopathy than in patients with MS.

scholarly journals Assessment of necessity of neuronavigation in localization of calvarial extra-axial lesions in the setting of limited resources

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hussein Soffar ◽  
Mohamed F. Alsawy
Keyword(s):  
Conventional Method ◽  
Linear Measurement ◽  
Limited Resources ◽  
Linear Measurements ◽  
Surgical Interventions ◽  
Localization Method ◽  
Mean Error ◽  
Significant Difference ◽  
The Mean ◽  
Mean Time

Abstract Background Neuronavigation is a very beneficial tool in modern neurosurgical practice. However, the neuronavigation is not available in most of the hospitals in our country raising the question about its importance in localizing the calvarial extra-axial lesions and to what extent it is safe to operate without it. Methods We studied twenty patients with calvarial extra-axial lesions who underwent surgical interventions. All lesions were preoperatively located with both neuronavigation and the usual linear measurements. Both methods were compared regarding the time consumed to localize the tumor and the accuracy of each method to anticipate the actual center of the tumor. Results The mean error of distance between the planned center of the tumor and the actual was 6.50 ± 1.762 mm in conventional method, whereas the error was 3.85 ± 1.309 mm in IGS method. Much more time was consumed during the neuronavigation method including booting, registration, and positioning. A statistically significant difference was found between the mean time passed in the conventional method and IGS method (2.05 ± 0.826, 24.90 ± 1.334, respectively), P-value < 0.001. Conclusion In the setting of limited resources, the linear measurement localization method seems to have an accepted accuracy in the localization of calvarial extra-axial lesions and it saves more time than neuronavigation method.

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