Rectification of the EMG is an unnecessary and inappropriate step in the calculation of Corticomuscular coherence

Corticomuscular coherence (CMC) estimation is a frequency domain method used to detect a linear coupling between rhythmic activity recorded from sensorimotor cortex (EEG or MEG) and the electromyogram (EMG) of active muscles. In motor neuroscience, rectification of the surface EMG is a common pre-processing step prior to calculating CMC, intended to maximize information about action potential timing, whilst suppressing information relating to motor unit action potential (MUAP) shape. Rectification is believed to produce a general shift in the EMG spectrum towards lower frequencies, including those around the mean motor unit discharge rate. However, there are no published data to support the claim that EMG rectification enhances the detection of CMC. Furthermore, performing coherence analysis after the non-linear procedure of rectification, which results in a significant distortion of the EMG spectrum, is considered fundamentally flawed in engineering and digital signal processing. We calculated CMC between sensorimotor cortex EEG and EMG of two hand muscles during a key grip task in 14 healthy subjects. CMC calculated using unrectified and rectified EMG was compared. The use of rectified EMG did not enhance the detection of CMC, nor was there any evidence that MUAP shape information had an adverse effect on the CMC estimation. EMG rectification had inconsistent effects on the power and coherence spectra and obscured the detection of CMC in some cases. We also provide a comprehensive theoretical analysis, which, along with our empirical data, demonstrates that rectification is neither necessary nor appropriate in the calculation of CMC.     

Evaluation of 3D blood flow patterns and wall shear stress in the normal and dilated thoracic aorta using flow-sensitive 4D CMR

Background

The purpose of this study was to investigate 3D flow patterns and vessel wall parameters in patients with dilated ascending aorta, age-matched subjects, and healthy volunteers.

Methods

Thoracic time-resolved 3D phase contrast CMR with 3-directional velocity encoding was applied to 33 patients with dilated ascending aorta (diameter ≥40 mm, age=60±16 years), 15 age-matched normal controls (diameter ≤37 mm, age=68±7.5 years) and 15 young healthy volunteers (diameter ≤30 mm, age=23±2 years). 3D blood flow was visualized and flow patterns were graded regarding presence of supra-physiologic-helix and vortex flow using a semi-quantitative 3-point grading scale. Blood flow velocities, regional wall shear stress (WSS), and oscillatory shear index (OSI) were quantified.

Results

Incidence and strength of supra-physiologic-helix and vortex flow in the ascending aorta (AAo) was significantly higher in patients with dilated AAo (16/33 and 31/33, grade 0.9±1.0 and 1.5±0.6) than in controls (2/15 and 7/15, grade 0.2 ± 0.6 and 0.6 ± 0.7, P<.05) or healthy volunteers (1/15 and 0/15, grade 0.1 ± 0.3 P<.05). Greater strength of the ascending aortic helix and vortex flow were associated with significant differences in AAo diameters (P<.05). Peak systolic WSS in the ascending aorta and aortic arch was significantly lower in patients with dilated AAo (P<.0157-.0488). AAo diameter positively correlated to time to peak systolic velocities (r=0.30-0.53, P<.04), OSI (r=0.33-0.49, P<0.02) and inversely correlated to peak systolic WSS (r=0.32-0.40, P<.03). Peak systolic WSS was significantly lower in AAo aneurysms at the right and outer curvature within the AAo and proximal arch (P<.01-.05).

Conclusions

Increase in AAo diameter is significantly correlated with the presence and strength of supra-physiologic-helix and vortex formation in the AAo, as well with decrease in systolic WSS and increase in OSI.     

Adaptive Filter Based Two-Probe Noise Suppression System for Transient Evoked Otoacoustic Emission Detection

Transient otoacoustic emission (TEOAE) is a method widely used in clinical practice for assessment of hearing quality. The main problem in TEOAE detection is its much lower level than the level of environmental and biological noise. While the environmental noise level can be controlled, the biological noise can be only reduced by appropriate signal processing. This paper presents a new two-probe preprocessing TEOAE system for suppression of the biological noise by adaptive filtering. The system records biological noises in both ears and applies a specific adaptive filtering approach for suppression of biological noise in the ear canal with TEOAE. The adaptive filtering approach includes robust sign error LMS algorithm, stimuli response summation according to the derived non-linear response (DNLR) technique, subtraction of the estimated TEOAE signal and residual noise suppression. The proposed TEOAE detection system is tested by three quality measures: signal-to-noise ratio (S/N), reproducibility of TEOAE, and measurement time. The maximal TEOAE detection improvement is dependent on the coherence function between biological noise in left and right ears. The experimental results show maximal improvement of 7 dB in S/N, improvement in reproducibility near 40% and reduction in duration of TEOAE measurement of over 30%.     

Orthoptists' Management of Amblyopia—A Case-Based Survey

Purpose The aim of this study was to investigate the amblyopia treatment trends of Australian orthoptists and to identify variations or consistencies amongst treatment patterns. Methods A questionnaire was distributed to all orthoptists who attended an annual national scientific conference. This questionnaire consisted of four case vignettes of amblyopic patients. Each was presented with a series of multiple-choice questions that orthoptists were required to answer. Results The questionnaire was completed by 46 orthoptists. Large diversity between orthoptists in their treatment application was found. This related mostly to the intensity of occlusion treatment. Conclusion Treatment variability continues to exist between orthoptists. Further investigations evaluating the clinical decision making processes of clinicians in prescribing amblyopia treatment may help us to better understand the determinants that are considered when prescribing treatment. This would be useful in establishing best-practice guidelines.     

In Vivo Imaging and Computational Analysis of the Aortic Root. Application in Clinical Research and Design of Transcatheter Aortic Valve Systems

Valvular heart disease is a major cause of morbidity and mortality in developing and industrialized countries. For patients with advanced symptomatic disease, surgical open-heart valve replacement is an effective treatment, supported by long-term outcome data. More recently, less-invasive transcatheter approaches for valve replacement/implantation have been developed for patients that are not considered surgical candidates. An understanding of valvular and paravalvular anatomy and biomechanics is pivotal for the optimization of interventional valve procedures. Advanced imaging is increasingly used not only for clinical guidance but also for the design and further improvement of transcatheter valve systems. Computed tomography is particularly attractive because it acquires high-resolution volumetric data sets of the root including the leaflets and coronary artery ostia, with sufficient temporal resolution for multi-phasic analysis. These volumetric data sets allow subsequent 3-D and 4-D display, reconstruction in unlimited planes, and mathematical modeling. Computer modeling, specifically finite element analysis, of devices intended for implantation in the aortic root, allows for structural analysis of devices and modeling of the interaction between the device and cardiovascular anatomy. This paper will provide an overview of computer modeling of the aortic root and describe FEA approaches that could be applied to TAVI and have an impact on clinical practice and device design.     

Development and evaluation of the school cafeteria nutrition assessment measures

BACKGROUND: Foods provided in schools represent a substantial portion of US children's dietary intake; however, the school food environment has proven difficult to describe due to the lack of comprehensive, standardized, and validated measures. METHODS: As part of the Arkansas Act 1220 evaluation project, we developed the School Cafeteria Nutrition Assessment (SCNA) measures to assess food availability in public school cafeterias (n = 113). The SCNA provides a measure to evaluate monthly school lunch menus and to observe foods offered in school cafeterias during the lunch period. These measures provide information on the availability of fruit, vegetables, grains (whole or white), chips (reduced fat or regular), side dishes, main dishes, beverages, à la carte selections, and desserts, as well as information on healthier preparation of these items. Using independent raters, the inter‐rater reliability of the measure was determined among a subsample of these schools (n = 32). RESULTS: All food categories assessed, with the exception of the side dish and chip categories, had inter‐rater reliability rates of 0.79 or greater, regardless of school type. The SCNA scores encompassed the majority of the possible scores, indicating the ability for the measures to differentiate between school cafeterias in the availability of healthier options. CONCLUSION: These measures allow comprehensive, rapid measurement of school cafeteria food availability with high inter‐rater reliability for public health and school health professionals, communities, and school personnel. These measures have the potential to contribute to school health efforts to evaluate cafeteria offerings and/or the impact of policy changes regarding school foods.     

Assessment of HER2 gene status in breast carcinomas with polysomy of chromosome 17

BACKGROUND:

The current study was performed to determine the impact of polysomy 17 on the interpretation of HER2 testing of invasive breast carcinomas using fluorescent in situ hybridization methods. Current American Society of Clinical Oncology/College of American Pathologists guidelines define HER2‐positive tumors as those with >6 HER2 genes per nucleus or those with HER2/CEP17 (chromosome 17) ratio >2.2. These guidelines are potentially contradictory in tumors with polysomy of chromosome 17.

METHODS:

Seventy‐two breast carcinoma cases with reported polysomy of chromosome 17 (≥3 CEP17 signals on average) by fluorescent in situ hybridization were identified, and the corresponding HER2 immunohistochemistry was obtained. The HER2 status of the archived samples was reviewed, and the tumors were recategorized according to the 2007 American Society of Clinical Oncology/College of American Pathologists guidelines.

RESULTS:

The average CEP17 copy number for the group was 4.5 (range, 3.0‐10.4). Thirty‐three (45.8%) cases had >6 copies of HER2 per nucleus. Twenty‐one cases (29.2%) qualified as HER2 gene amplified using the HER2/CEP17 ratio (>2.2) guideline. All these cases had >6 HER2 signals, which represented 63.6% of all cases with >6 HER2 signals. HER2 protein expression showed significant positive correlations with both HER2 gene copy number and HER2/CEP17 ratio (P < .01, r_s = 0.56 and 0.64, respectively).

CONCLUSIONS:

Increased CEP17 signals detected in invasive breast carcinomas may lead to discordant interpretation of gene amplification in a significant proportion of the cases, depending on which criterion (ratio vs absolute number) is used for interpretation. However, increased gene dosage (>6 HER2 genes or HER2/CEP17 ratio >2.2), regardless of the evaluation method, is positively correlated with HER2 protein expression. Cancer 2011. © 2010 American Cancer Society.