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Satish K Sharma - One of the best experts on this subject based on the ideXlab platform.
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spirograph planar monopole antenna spma providing unidirectional invariant radiation patterns by employing a broadband ground plane
IEEE Antennas and Wireless Propagation Letters, 2012Co-Authors: J T Rayno, Satish K SharmaAbstract:The spirograph planar monopole antenna (SPMA) is combined with the proposed broadband ground plane to achieve unidirectional radiation patterns with enhanced gain and minimal broadside gain variation. The broadband ground plane is a simple structure that consists of a resistive card and a copper sheet in a fixed position. The measured impedance bandwidth for the unidirectional SPMA, with VSWR <; 2 matching criterion, is 1.14-2.90 GHz (87.1% bandwidth). The antenna has a unidirectional radiation pattern that is mostly invariant over the entire frequency range, a single main lobe, and low cross polarization. The measured broadside gain varies from 2.59 to 6.85 dBi within the impedance bandwidth.
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compact spirograph planar monopole antenna covering c x band with invariant radiation pattern characteristics
IEEE Transactions on Antennas and Propagation, 2012Co-Authors: J T Rayno, Satish K SharmaAbstract:This communication presents a novel compact planar monopole antenna configuration: the spirograph planar monopole antenna (SPMA) covering C-/X-Band (4-12 GHz). The antenna has an invariant omnidirectional radiation pattern across the frequency band with no multi-lobe effect and low cross-polarization. The SPMA radiating element size is less than λ/2 at the highest frequency of operation such that it can be used as a beam scanning array element. For the SPMA, it was found that increasing the number of points in the antenna shape miniaturizes the radiating element and increases the impedance bandwidth. A prototype SPMA was fabricated and measured for impedance and radiation performance.
Fatta B Nahab - One of the best experts on this subject based on the ideXlab platform.
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progression of essential tremor over time using digital Spirography in patients on stable medication doses compared to untreated patients p6 067
Neurology, 2018Co-Authors: Katherine Longardner, Fatta B NahabAbstract:Objective: Longitudinal evaluation of essential tremor progression over time using digital Spirography to compare progression in treated vs. untreated patients Background: Essential tremor (ET) is the most common movement disorder in adults. Symptoms are disabling, impairing activities of daily living in up to 75% of affected people. Standardized hand-drawn writing samples may detect subtleties in tremor that are not visibly apparent to patients or physicians, allowing the opportunity for intervention before symptoms become clinically apparent. Digital Spirography has been shown to reliably measure tremor severity and response to therapy. We hypothesized that patients with ET who were treated with stable doses of medication would progress more slowly than patients who were untreated. Design/Methods: Twenty unique patients ( 12 receiving stable doses of medication, 8 untreated) diagnosed with ET using TRG criteria were followed for a mean duration of two years. We quantified kinetic tremor with a spiral drawing task using a digitizing tablet and a magnetic pen. A custom-designed algorithm was employed to calculate spiral amplitudes. We used the individual time points sampled throughout the spirogram to measure tremor frequency, amplitude, and variability. Two spiral traces were collected for each hand at each visit to minimize variability and any learning effects. Results: Over up to a two-year mean follow up, tremor improved in both groups (−1.2cm/year in treated group vs. −0.572cm/year in untreated group). Rate of improvement was greater in the group on stable therapy compared to group on no medications, though this was not statistically significant ( p= 0.58). Conclusions: We found no significant difference in progression of ET amplitude over time between those treated vs. untreated, with both groups showing improvements in tremor over a mean two-year follow up period. Factors to help explain this improvement include: improved coping skills through education and counseling and treatment of comorbid conditions including mood and sleep disorders. Disclosure: Dr. Longardner has nothing to disclose. Dr. Nahab has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Global Kinetics Corporation, Cala Health, and Merz.
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validation of digital spiral analysis as outcome parameter for clinical trials in essential tremor
Movement Disorders, 2011Co-Authors: Fatta B Nahab, Dietrich Haubenberger, Daniel Kalowitz, Camilo Toro, Loretta Wittevrongel, Dominic Ippolito, David A Luckenbaugh, Mark HallettAbstract:With a prevalence of up to 5%, essential tremor (ET) is one of the most common movement disorders in adulthood.1–3 Characteristic features include postural and kinetic tremor, affecting the hands in the majority of patients.4 Data suggest that up to 75% of ET patients experience impairment in their activities of daily living, such as eating, drinking, and handwriting.5 ET therapy is, therefore, geared toward reduction of tremor symptoms to reach an improvement in these functional domains. Current treatment recommendations also suggest future research on development and standardization of outcome measures assessing tremor and to determine the magnitude of treatment effect.6 In fact, it has been suggested that tremor-amplitude changes measured by tremor accelerometry, typically collected during an isometric posture position, often do not reflect task-related kinetic tremor intensities, such as tremor during writing, which have more impact on patients’ perception in their daily life and the disability caused by tremor. Although the objective nature of quantifying postural tremor reflects the main advantage of accelerometry, ratings of Archimedes spirals help to document kinetic tremor during a task more reflective of activities of daily living. Drawing of spirals has been an integral part of the routine examination of tremor patients and was integrated into clinical rating scales.7,8 Visual rating of spirals was proposed by Bain et al.9 This scale has been widely used as a screening instrument and outcome measure in clinical trials of ET.10–13 Collecting spirals using a digitizing tablet offers the advantage not only to graphically store the image of a spiral, but also allows a time-series generation of data points for further quantification through numerical methods, such as spectral analysis of derived velocity or acceleration that describe features of tremor power (i.e., severity) and frequency.14,15 Similar objective methods of spirographic tremor assessment have been validated in parkinsonian tremor16 and have been used to document tremor in patients with Niemann-Pick disease type C and ET.17,18 A semidigitized method of measuring tremor amplitudes from scanned spirals originally drawn on paper was suggested to correlate well with spiral ratings.19 To our knowledge, no study has formally investigated the validity of Spirography time-series analysis to document tremor intensities in a prospective treatment design. Here, we present a digitizing-tablet–based method for quantifying ET spirals and report data on validity, reliability, and sensitivity to reflect tremor-intensity changes before and after a standardized treatment intervention.
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abstract 12 computerized essential tremor Spirography development of a rater independent outcome measure for clinical trials
Neurotherapeutics, 2010Co-Authors: Dietrich Haubenberger, Fatta B Nahab, Daniel Kalowitz, Camilo Toro, Daniel Ippolito, Loretta Wittevrongel, Mark HallettAbstract:Action tremor represents the cardinal symptom of essential tremor (ET) impairing patients' activities of daily living such as handwriting. Although visually rated Archimedes spirals are used to document tremor intensities, computerized methods of spiral analysis have been presented to quantify ET tremor. Here, we describe a method to objectively quantify tremor using digitizing tablet–based Spirography and compare the measures with standardized visual rating after treatment intervention. Nine ET patients underwent a standardized ethanol challenge. Spirals were drawn at six time-points (baseline, 15, 30, 45, 60, and 75 min post-ethanol) using a digitizing tablet. Two methods for data-selection were applied (T: fixed number of time-points of the time-series, S: fixed space by capturing 3.75 spiral turns). After numerical differentiation of the time series, velocity spectra were calculated. Velocity at the spectral peak frequency was used as measure of tremor amplitude. As reference method, visual ratings (VR) were obtained from seven raters using a standard rating scale. Per method, values were normalized to baseline. Larger amplitude changes between time-points were considered as higher sensitivity in demonstrating changes after treatment intervention. Repeated measures ANOVA was used to calculate differences between methods, with Bonferroni correction for post hoc comparisons. For each method, repeated measures ANOVA showed a significant time effect, demonstrating a reduction in tremor amplitudes after ethanol intake (VR: p = 0.001; T: p = 0.008; S: p = 0.003). After normalizing to baseline, the method effect across time-points was significant ( p = 0.001), as well as factor time ( p = 0.002). Method S exhibited larger changes from baseline across time-points ( p = 0.041), whereas method T showed no significant differences compared with VR. Ethanol significantly reduced tremor amplitudes across all methods. Computerized method T equally documented change across time-points as VR; method S, however, showed a significantly higher sensitivity to change, compared with the reference method. In conclusion, the proposed methods of spiral analysis are either equally sensitive (method T) or more sensitive (method S) to treatment-induced changes of tremor intensity and therefore might be useful as outcome measures in clinical trials in ET.
Mark Hallett - One of the best experts on this subject based on the ideXlab platform.
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validation of digital spiral analysis as outcome parameter for clinical trials in essential tremor
Movement Disorders, 2011Co-Authors: Fatta B Nahab, Dietrich Haubenberger, Daniel Kalowitz, Camilo Toro, Loretta Wittevrongel, Dominic Ippolito, David A Luckenbaugh, Mark HallettAbstract:With a prevalence of up to 5%, essential tremor (ET) is one of the most common movement disorders in adulthood.1–3 Characteristic features include postural and kinetic tremor, affecting the hands in the majority of patients.4 Data suggest that up to 75% of ET patients experience impairment in their activities of daily living, such as eating, drinking, and handwriting.5 ET therapy is, therefore, geared toward reduction of tremor symptoms to reach an improvement in these functional domains. Current treatment recommendations also suggest future research on development and standardization of outcome measures assessing tremor and to determine the magnitude of treatment effect.6 In fact, it has been suggested that tremor-amplitude changes measured by tremor accelerometry, typically collected during an isometric posture position, often do not reflect task-related kinetic tremor intensities, such as tremor during writing, which have more impact on patients’ perception in their daily life and the disability caused by tremor. Although the objective nature of quantifying postural tremor reflects the main advantage of accelerometry, ratings of Archimedes spirals help to document kinetic tremor during a task more reflective of activities of daily living. Drawing of spirals has been an integral part of the routine examination of tremor patients and was integrated into clinical rating scales.7,8 Visual rating of spirals was proposed by Bain et al.9 This scale has been widely used as a screening instrument and outcome measure in clinical trials of ET.10–13 Collecting spirals using a digitizing tablet offers the advantage not only to graphically store the image of a spiral, but also allows a time-series generation of data points for further quantification through numerical methods, such as spectral analysis of derived velocity or acceleration that describe features of tremor power (i.e., severity) and frequency.14,15 Similar objective methods of spirographic tremor assessment have been validated in parkinsonian tremor16 and have been used to document tremor in patients with Niemann-Pick disease type C and ET.17,18 A semidigitized method of measuring tremor amplitudes from scanned spirals originally drawn on paper was suggested to correlate well with spiral ratings.19 To our knowledge, no study has formally investigated the validity of Spirography time-series analysis to document tremor intensities in a prospective treatment design. Here, we present a digitizing-tablet–based method for quantifying ET spirals and report data on validity, reliability, and sensitivity to reflect tremor-intensity changes before and after a standardized treatment intervention.
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abstract 12 computerized essential tremor Spirography development of a rater independent outcome measure for clinical trials
Neurotherapeutics, 2010Co-Authors: Dietrich Haubenberger, Fatta B Nahab, Daniel Kalowitz, Camilo Toro, Daniel Ippolito, Loretta Wittevrongel, Mark HallettAbstract:Action tremor represents the cardinal symptom of essential tremor (ET) impairing patients' activities of daily living such as handwriting. Although visually rated Archimedes spirals are used to document tremor intensities, computerized methods of spiral analysis have been presented to quantify ET tremor. Here, we describe a method to objectively quantify tremor using digitizing tablet–based Spirography and compare the measures with standardized visual rating after treatment intervention. Nine ET patients underwent a standardized ethanol challenge. Spirals were drawn at six time-points (baseline, 15, 30, 45, 60, and 75 min post-ethanol) using a digitizing tablet. Two methods for data-selection were applied (T: fixed number of time-points of the time-series, S: fixed space by capturing 3.75 spiral turns). After numerical differentiation of the time series, velocity spectra were calculated. Velocity at the spectral peak frequency was used as measure of tremor amplitude. As reference method, visual ratings (VR) were obtained from seven raters using a standard rating scale. Per method, values were normalized to baseline. Larger amplitude changes between time-points were considered as higher sensitivity in demonstrating changes after treatment intervention. Repeated measures ANOVA was used to calculate differences between methods, with Bonferroni correction for post hoc comparisons. For each method, repeated measures ANOVA showed a significant time effect, demonstrating a reduction in tremor amplitudes after ethanol intake (VR: p = 0.001; T: p = 0.008; S: p = 0.003). After normalizing to baseline, the method effect across time-points was significant ( p = 0.001), as well as factor time ( p = 0.002). Method S exhibited larger changes from baseline across time-points ( p = 0.041), whereas method T showed no significant differences compared with VR. Ethanol significantly reduced tremor amplitudes across all methods. Computerized method T equally documented change across time-points as VR; method S, however, showed a significantly higher sensitivity to change, compared with the reference method. In conclusion, the proposed methods of spiral analysis are either equally sensitive (method T) or more sensitive (method S) to treatment-induced changes of tremor intensity and therefore might be useful as outcome measures in clinical trials in ET.
Xuguang Liu - One of the best experts on this subject based on the ideXlab platform.
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Digitised Spirography as an evaluation tool for intention tremor in multiple sclerosis.
Journal of neuroscience methods, 2006Co-Authors: Peter Feys, Werner Helsen, Stephan Ilsbroukx, Ann Prinsmel, Shouyan Wang, Xuguang LiuAbstract:This study investigated validity and reliability of digitised circle and square spiral drawing for quantifying intention tremor severity and related disability in patients with multiple sclerosis (MS). The tremor amplitude was measured as the standard deviation of the drawing velocity of the arm in the radial and tangential direction for circle spiral drawing, and in the horizontal and vertical direction for square spiral drawing. Results were compared with those of MS patients without tremor and healthy controls, and correlated with clinical assessments of tremor severity and arm functionality including Fahn's tremor rating scale, Test d'Evaluation des Membres superieurs des Personnes Agees (TEMPA) and the nine-hole-peg test to examine validity. Comparison of patient's performance between four repeated trials examined short-term test-retest reliability. All digitised Spirography variables discriminated between the MS-tremor and both MS-no-tremor and healthy control groups. Validity was also shown by high spearman correlation coefficients between Spirography variables and clinical ratings. Tremor appeared to be most profound in the radial and vertical direction during circle and square spiral drawing, respectively. The consistency and high correlations between four repeated executions indicated short-term test-retest reliability. We conclude that the digitised Spirography provide a useful instrumentation for quantifying MS intention tremor.
Peter G Bain - One of the best experts on this subject based on the ideXlab platform.
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pomd13 distinguishing tremor dominant parkinson s disease from tremulous subjects without evidence of dopaminergic deficit by Spirography an fp cit validated study
Journal of Neurology Neurosurgery and Psychiatry, 2010Co-Authors: Peter G Bain, M Knobel, Vamsi Gontu, N P S BajaAbstract:Five to fifteen per cent of de novo patients recruited for recent clinical trials of anti-parkinsonian drugs had no evidence of nigrostriatal dopamine denervation on functional imaging. These diagnostically challenging subjects without evidence of dopaminergic deficit (SWEDDs) had tremulous syndromes other than Parkinson9s disease (PD). Our objective was to analyse the accuracy of Spirography in distinguishing cases of tremor dominant PD from tremulous SWEDDs cases. Analyses were carried out by observers blinded to the clinical data and supplied with just spiral drawings, from which tremor severity, 3-turn spiral diameter and spiral density were measured. A spiral coefficient, averaged for the spirals drawn by each hand, was derived from these three indices. A cut off of
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stereotactic lesional surgery for the treatment of tremor in multiple sclerosis a prospective case controlled study
Brain, 2001Co-Authors: S H Alusi, Tipu Z Aziz, S Glickman, Marjan Jahanshahi, J F Stein, Peter G BainAbstract:The effect of stereotactic lesional surgery for the treatment of tremor in multiple sclerosis was examined in a prospective case-controlled study. Surgery was not undertaken in 33 patients (72% of 46 cases referred for stereotactic surgery), two of whom died within 4 months of referral. Twenty-four multiple sclerosis patients were included in the study; 13 underwent surgery and were matched against 11 controls on the basis of age, sex, expanded disability system scores (EDSS) and disease duration. Assessments were carried out at baseline/preoperatively, and then 3 and 12 months later; these included accelerometric and clinical ratings of tremor, Spirography, handwriting, a finger-tapping test, nine-hole peg test, tremor-related disability, general neurological examination, Barthel Activities of Daily Living (ADL) Index of general disability, EDSS, a 0-4 ataxia scale, Mini-Mental State (MMS) examination, speech and swallowing assessments and grip strength. Postoperative MRI scans demonstrated that tremor could be attenuated by lesions centred on the thalamus in seven cases, on the zona incerta in five cases and in the subthalamic nucleus in one case. Two patients developed hemiparesis and in two cases epilepsy recurred. Two surgical patients and one control patient died between the 3 and 6 months assessments. Both groups had a significant deterioration in EDSS but not Barthel ADL Index scores at 1 year, but the difference between the groups was not significant. Similarly, no differences between the groups' rates of deterioration of speech or swallowing or MMS were found. Significant improvements in contralateral upper limb postural (P2) and kinetic tremors, spiral scores and head tremor were detected at 3 and 12 months after surgery (but not handwriting or nine-hole peg test performance). Tremor-related disability and finger-tapping speed were also significantly better 12 months after surgery, the latter having significantly worsened for the control group. A 3 Hz 'filter' for postural (P2) upper limb tremor was detected by accelerometry/spectral analysis above which tremor was always abolished and at or below which some residual tremor invariably remained. Criteria for selecting multiple sclerosis patients for this form of surgery are discussed.