Methodist Hospital Neurological Institute

Houston, TX, United States

Methodist Hospital Neurological Institute

Houston, TX, United States
SEARCH FILTERS
Time filter
Source Type

Karmonik C.,Methodist Hospital Neurological Institute | Karmonik C.,Cornell University | Yen C.,Methodist Hospital Neurological Institute | Diaz O.,Methodist Hospital Neurological Institute | And 3 more authors.
Acta Neurochirurgica | Year: 2010

Purpose: To assess reliability of wall shear stress (WSS) calculations using computational fluid dynamics (CFD) dependent on inflow in internal carotid artery aneurysms (ICA). Materials and methods: Six unruptured ICA aneurysms were studied. 3D computational meshes were created from 3D digital subtraction angiographic images (Axiom Artis dBA, Siemens Medical Solutions). Transient CFD simulations (Fluent, ANSYS Inc.) were performed for two inflow conditions: (1) idealized averaged waveform from normal subjects (ID) and (2) patient-specific waveform (PS) measured with 2D phase contrast magnetic resonance imaging. Stability of calculation was assessed by comparing mean WSS (), temporal wall shear stress magnitude variation (ΔWSS), and oscillatory shear index (OSI, a measure of variation in the WSS direction) on the aneurysmal wall for both conditions. Results: For all cases, mean relative difference (PS-ID) of WSS () was -15% (range -32% to 11%). Mean ΔWSS difference was -29.3% ( -100% to 67%). Mean OSI difference was 7.5% (-12% to 40%). Large variations in histograms of these parameters were noted. Conclusion: For accurate calculations of WSS parameters, patient-specific information on physiological flow may be necessary. Results obtained with averaged or idealized flow waveforms may have to be interpreted with caution. © 2010 Springer-Verlag.


Karmonik C.,Methodist Hospital Neurological Institute | Brandt A.K.,Rice University | Fung S.H.,Rice University | Grossman R.G.,Methodist Hospital Neurological Institute | Frazier J.T.,Methodist Hospital
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2013

Benefits of listening to music with emotional attachment while recovering from a cerebral ischemic event have been reported. To develop a better understanding of the effects of music listening on the human brain, an algorithm for the graph-theoretical analysis of functional magnetic resonance imaging (fMRI) data was developed. From BOLD data of two paradigms (block-design, first piece: music without emotional attachment, additional visual guidance by a moving cursor in the score sheet; second piece: music with emotional attachment), network graphs were constructed with correlations between signal time courses as edge weights. Functional subunits in these graphs were identified with the MCODE clustering algorithm and mapped back into anatomical space using AFNI. Emotional centers including the right amygdala and bilateral insula were activated by the second piece (emotional attachment) but not by the first piece. Network clustering analysis revealed two separate networks of small-world property corresponding to task-oriented and resting state conditions, respectively. Functional subunits with highest interactions were bilateral precuneus for the first piece and left middle frontal gyrus and right amygdala, bilateral insula, left middle temporal gyrus for the second piece. Our results indicate that fMRI in connection with graph theoretical network analysis is capable of identifying and differentiating functional subunits in the human brain when listening to music with and without emotional attachment. © 2013 IEEE.


Christof K.,Methodist Hospital Neurological Institute | Christof K.,Methodist key Heart and Vascular Center | Christof K.,Cornell University | Bismuth J.,Methodist key Heart and Vascular Center | And 9 more authors.
Vascular and Endovascular Surgery | Year: 2011

Purpose: To demonstrate the capability of computational fluid dynamics (CFD) for quantifying hemodynamic forces pretreatment/posttreatment in type B aortic dissection (TB-AD). Methods: From CFD simulations initialized with dynamic magnetic resonance image data, wall shear stress (WSS) and dynamic pressure (dynP) changes post endovascular treatment were quantified. Results: After 1 year follow-up, thoracic aortic segment was completely remodeled, and persistent, nonthrombosed false lumen in the abdominal aorta was noted. Pretreatment, large WSS (>5 Pa) and dynP (>80 Pa) occurred at entrance tear and a stenotic region in the true lumen (TL). Posttreatment, WSS was lower than 3.3 Pa and dynP was lower than 55 Pa in TL, except at proximal end of the stent graft and at reentrance tear. Two focal locations of high dynP existed within the stent graft. Conclusions: Computational fluid dynamics may provide quantitative assessment of hemodynamic wall forces in TB-AD potentially of interest for follow-up examinations. © The Author(s) 2011.


O'Neill B.E.,Methodist Hospital Research Institute | Vo H.Q.,Methodist Hospital Research Institute | Shao H.,Methodist Hospital Research Institute | Shao H.,Anhui University of Science and Technology | And 4 more authors.
Journal of Magnetic Resonance Imaging | Year: 2013

Purpose To design an algorithm for optimizing pulsed high intensity focused ultrasound (p-HIFU) treatment parameters to maximize tissue transport while minimizing thermal necrosis based on MR image guidance. Materials and Methods P-HIFU power, duty cycle, and treatment duration were varied to generate different levels of thermal and mechanical deposition in rabbit muscle. Changes in T2-weighted and T1 contrast-enhanced (CE) signal were assessed immediately following treatment and at 24 h. Transport parameters were extracted by means of T1-weighted dynamic contrast-enhanced MRI (DCE-MRI) technique at 0 and 24-h time points. Results Successful p-HIFU treatment was indicated by focal hyperintensity on the T2-weighted image immediately post-treatment, suggesting increased fluid (edema), with little intensity change in CE image. After 24 h, the affected region expanded along the muscle fiber accompanied by clear hyperintensity in CE image (contrast uptake). Quantitative DCE-MRI analysis revealed statistically significant increases in both leakage rate and extracellular space, accompanied by a decrease in clearance rate. Conclusion Successful p-HIFU treatment was mainly correlated to tissue heating. Tissue transport properties following treatment success would result in improved contact between drug and targets in both time and space. MRI is the key to controlling treatment by means of thermometry and also monitoring efficacy by means of T2-weighted imaging. J. Magn. Reson. Imaging 2013;38:1094-1102. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.


Barber C.R.,Baylor College of Medicine | Chang J.,Baylor College of Medicine | Tham Y.L.,Baylor College of Medicine | Kalidas M.,Austin Diagnostic Clinic | And 3 more authors.
Journal of Cancer Education | Year: 2010

Cognitive appraisal affects adjustment to breast cancer. A self-forgiving attitude and spirituality may benefit breast cancer survivors who blame themselves for their cancer. One hundred and eight women with early breast cancers completed questionnaires assessing self-blame, self-forgiveness, spirituality, mood and quality of life (QoL) in an outpatient breast clinic. Women who blamed themselves reported more mood disturbance (p<0.01) and poorer QoL (p<0.01). Women who were more self-forgiving and more spiritual reported less mood disturbance and better QoL (p's<0.01). Interventions that reduce self-blame and facilitate self-forgiveness and spirituality could promote better adjustment to breast cancer. © 2010 Springer.


Calleo J.,Michael bakey Veterans Affairs Medical Center | Calleo J.,Baylor College of Medicine | Burrows C.,Parkinsons Disease Research Education and Clinical Center | Levin H.,Michael bakey Veterans Affairs Medical Center | And 7 more authors.
Parkinson's Disease | Year: 2012

Cognitive dysfunction in Parkinson's disease contributes to disability, caregiver strain, and diminished quality of life. Cognitive rehabilitation, a behavioral approach to improve cognitive skills, has potential as a treatment option to improve and maintain cognitive skills and increase quality of life for those with Parkinson's disease-related cognitive dysfunction. Four cognitive rehabilitation programs in individuals with PD are identified from the literature. Characteristics of the programs and outcomes are reviewed and critiqued. Current studies on cognitive rehabilitation in PD demonstrate feasibility and acceptability of a cognitive rehabilitation program for patients with PD, but are limited by their small sample size and data regarding generalization of effects over the long term. Because PD involves progressive heterogeneous physical, neurological, and affective difficulties, future cognitive rehabilitation programs should aim for flexibility and individualization, according to each patient's strengths and deficits. Copyright © 2012 Jessica Calleo et al.


Karmonik C.,Methodist Hospital Neurological Institute | Dulay M.,Methodist Hospital Neurological Institute | Verma A.,Methodist Hospital Neurological Institute | Grossman R.G.,Methodist Hospital Neurological Institute
Technology and Health Care | Year: 2010

Background and purpose: Various algorithms are available for the analysis of diffusion tensor (DTI) images. Many of these stand alone software packages require time-intensive user interactions not yet suited for routine clinical application Here, we demonstrate the use of the 'Analysis of Functional NeuroImages' (AFNI) software package, a standard for the analysis of functional magnetic resonance images (fMRI), to automatically align clinical DTI images onto the ICBM DTI81 atlas potentially enabling the combined presentation of fMRI and DTI results. Methods: Fractional anisotropy (FA) maps from seven patients diagnosed with video/EEG defined complex partial seizures were retrospectively analyzed. Affine transformations parameters for seven different cost functions provided by the 3dAllineate software tool were calculated. Alignment quality and variations of the transformation parameters were assessed. Results: Best alignment between the FA maps for each subject and the ICBM DTI81 atlas was achieved with cost functions utilizing the cost ratio (CR) (symmetrized* CR, symmetrized+ CR and unsymmetrized CR). Symmetrized* CR performed slightly better, in particular for lateral white matter structures. Relatively small variations in the transformation parameters emphasize the robustness of the transformations. Conclusions: Good alignment of FA maps to the ICBM DTI81 white matter atlas can be achieved using an automated affine transformation with software tools provided by AFNI potentially enabling the combined presentation of fMRI and DTI information. This procedure maybe readily be applied in clinical practice. ©2010 - IOS Press and the authors. All rights reserved.


Marshall D.F.,Baylor College of Medicine | Strutt A.M.,Baylor College of Medicine | Williams A.E.,Baylor College of Medicine | Simpson R.K.,Methodist Hospital Neurological Institute | And 3 more authors.
European Journal of Neurology | Year: 2012

Background and purpose: Despite common occurrences of verbal fluency declines following bilateral subthalamic nucleus deep brain stimulation (STN-DBS) for the treatment of Parkinson's disease (PD), alternating fluency measures using cued and uncued paradigms have not been evaluated. Methods: Twenty-three STN-DBS patients were compared with 20 non-surgical PD patients on a comprehensive neuropsychological assessment, including cued and uncued intradimensional (phonemic/phonemic and semantic/semantic) and extradimensional (phonemic/semantic) alternating fluency measures at baseline and 6-month follow-up. Results: STN-DBS patients demonstrated a greater decline on the cued phonemic/phonemic fluency and the uncued phonemic/semantic fluency tasks compared to the PD patients. For STN-DBS patients, verbal learning and information processing speed accounted for a significant proportion of the variance in declines in alternating phonemic/phonemic and phonemic/semantic fluency scores, respectively, whilst only naming was related to uncued phonemic/semantic performance for the PD patients. Both groups were aided by cueing for the extradimensional task at baseline and follow-up, and the PD patients were also aided by cueing for the phonemic/phonemic task on follow-up. Conclusions: These findings suggest that changes in alternating fluency are not related to disease progression alone as STN-DBS patients demonstrated greater declines over time than the PD patients, and this change was related to declines in information processing speed. © 2012 The Author(s) European Journal of Neurology © 2012 EFNS.


Karmonik C.,Methodist Hospital | Karmonik C.,Methodist Hospital Neurological Institute | Bismuth J.,Methodist Hospital | Shah D.J.,Methodist Hospital | And 3 more authors.
European Journal of Vascular and Endovascular Surgery | Year: 2011

Objectives: Outcome prediction in DeBakey Type III aortic dissections (ADs) remains challenging. Large variations in AD morphology, physiology and treatment exist. Here, we investigate if computational fluid dynamics (CFD) can provide an initial understanding of pressure changes in an AD computational model when covering entry and exit tears and removing the intra-arterial septum (IS). Design: A computational mesh was constructed from magnetic resonance images from one patient (one entrance and one exit tear) and CFD simulations performed (scenario #1). Additional meshes were derived by virtually (1) covering the exit tear (false lumen (FL) thrombus progression) (scenario #2), (2) covering the entrance tear (thoracic endovascular treatment, TEVAR) (scenario #3) and (3) completely removing the IS (fenestration) (scenario #4). Changes in flow patterns and pressures were quantified relative to the initial mesh. Results: Systolic pressures increased for #2 (300 Pa increase) with largest inter-luminal differences distally (2500 Pa). In #3, false lumen pressure decreased essentially to zero. In #4, systolic pressure in combined lumen reduced from 2400 to 800 Pa. Conclusions: CFD results from computational models of a DeBakey type III AD representing separate coverage of entrance and exit tears correlated with clinical experience. The reported results present a preliminary look at a complex clinical problem. © 2011 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.


Karmonik C.,Methodist Hospital Neurological Institute | Bismuth J.,Methodist Hospital Neurological Institute | Redel T.,Siemens AG | Anaya-Ayala J.E.,Methodist Hospital Neurological Institute | And 3 more authors.
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC'10 | Year: 2010

Stanford type B aortic dissections (TB-AD), which split the descending aorta in a true and false lumen, have better in-hospital survival than type A dissections affecting the ascending aorta. However, short-term and long-term prognosis for the individual patient remains challenging, with one in four patients not surviving after 3 years. Towards a better understanding of the influence of tear location on TB-AD hemodynamics, we performed computational fluid dynamics (CFD) with aortic geometry extracted from magnetic resonance angiographic (MRA) images and inflow conditions modeled using the aortic flow waveform measured with 2D phase contrast magnetic resonance imaging (2D pcMRI). Three configurations were investigated. Configuration 1 had both entrance and re-entrance tear (as imaged), in configuration 2 the re-entrance tear was virtually occluded to simulate disease progression (thrombus formation) and in configuration 3, the entrance tear was virtually occluded, simulating endovascular treatment (EVAR) i.e. placing a stentgraft to eliminate inflow into the false lumen. For incorporation of the simulation results into the clinical workflow, a Siemens Leonardo software plugin prototype was developed to visualize and quantify hemodynamic parameters as 4D (3D plus time) volumes. Pressure in the true lumen for all three configurations was similar and varied about 3.4 % (largest variation between configuration 1 and 3). Pressure in the false lumen increased by 7.4 % for configuration 2 compared to configuration 1 and dropped by 97 % for configuration 3 compared to configuration 1. Pressure difference curves (true lumen value subtracted from false lumen value) showed similar behavior for configuration 1 and 2 with largest differences occurring during systole. For configuration 3, largest decrease in pressure difference occurred during systole. Higher pressure in the false lumen compared to the true lumen was found at end systole, indicating reversal of sign of pressure difference in configuration 3 (virtually treated TB-AD by EVAR). Velocity patterns did not show pronounced differences between configuration 1 and 2 but revealed reduced flow in the false lumen for configuration 3. © 2010 IEEE.

Loading Methodist Hospital Neurological Institute collaborators
Loading Methodist Hospital Neurological Institute collaborators