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320 results on '"Narayana, Ponnada A."'

2. Dynamic Imaging of Blood Coagulation Within the Hematoma of Patients With Acute Hemorrhagic Stroke

Author

Haque, Muhammad E., Boren, Seth B., Mills, James, Schneider, Kerry G., Parekh, Maria, Fraser, Stuart M., Bach, Ivo, Hariharan, Praveen, Zelnick, Pamela J., Guerra Castanon, Felix S., Naveed, Asim, Tariq, Muhammad, Arevalo, Octavio D., Hasan, Khader M., Escobar, Miguel, Zhao, Xiurong, Sitton, Clark, Narayana, Ponnada A., Grotta, James C., Aronowski, Jaroslaw, and Savitz, Sean I.

Published
2024
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6. Automatic Active Lesion Tracking in Multiple Sclerosis Using Unsupervised Machine Learning.

Author

Uwaeze, Jason, Narayana, Ponnada A., Kamali, Arash, Braverman, Vladimir, Jacobs, Michael A., and Akhbardeh, Alireza

Subjects
*MULTIPLE sclerosis, *MACHINE learning, *MAGNETIC resonance imaging, *MEDICAL care costs, *CONTRAST media
Abstract

Background: Identifying active lesions in magnetic resonance imaging (MRI) is crucial for the diagnosis and treatment planning of multiple sclerosis (MS). Active lesions on MRI are identified following the administration of Gadolinium-based contrast agents (GBCAs). However, recent studies have reported that repeated administration of GBCA results in the accumulation of Gd in tissues. In addition, GBCA administration increases health care costs. Thus, reducing or eliminating GBCA administration for active lesion detection is important for improved patient safety and reduced healthcare costs. Current state-of-the-art methods for identifying active lesions in brain MRI without GBCA administration utilize data-intensive deep learning methods. Objective: To implement nonlinear dimensionality reduction (NLDR) methods, locally linear embedding (LLE) and isometric feature mapping (Isomap), which are less data-intensive, for automatically identifying active lesions on brain MRI in MS patients, without the administration of contrast agents. Materials and Methods: Fluid-attenuated inversion recovery (FLAIR), T2-weighted, proton density-weighted, and pre- and post-contrast T1-weighted images were included in the multiparametric MRI dataset used in this study. Subtracted pre- and post-contrast T1-weighted images were labeled by experts as active lesions (ground truth). Unsupervised methods, LLE and Isomap, were used to reconstruct multiparametric brain MR images into a single embedded image. Active lesions were identified on the embedded images and compared with ground truth lesions. The performance of NLDR methods was evaluated by calculating the Dice similarity (DS) index between the observed and identified active lesions in embedded images. Results: LLE and Isomap, were applied to 40 MS patients, achieving median DS scores of 0.74 ± 0.1 and 0.78 ± 0.09, respectively, outperforming current state-of-the-art methods. Conclusions: NLDR methods, Isomap and LLE, are viable options for the identification of active MS lesions on non-contrast images, and potentially could be used as a clinical decision tool. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Prospective in silico study of the feasibility and dosimetric advantages of MRI-guided dose adaptation for human papillomavirus positive oropharyngeal cancer patients compared with standard IMRT

Author

Mohamed, Abdallah S.R., Bahig, Houda, Aristophanous, Michalis, Blanchard, Pierre, Kamal, Mona, Ding, Yao, Cardenas, Carlos E., Brock, Kristy K., Lai, Stephen Y., Hutcheson, Katherine A., Phan, Jack, Wang, Jihong, Ibbott, Geoffrey, Gabr, Refaat E., Narayana, Ponnada A., Garden, Adam S., Rosenthal, David I., Gunn, G. Brandon, and Fuller, Clifton D.

Published
2018
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37. Functional MRI Correlates of Carbon Dioxide Chemosensing in Persons With Epilepsy.

Author

Hampson, Johnson P., Lacuey, Nuria, Rani, Sandhya M. R., Hampson, Jaison S., Simeone, Kristina A., Simeone, Timothy A., Narayana, Ponnada A., Lemieux, Louis, and Lhatoo, Samden D.

Subjects
FUNCTIONAL magnetic resonance imaging, PEOPLE with epilepsy, CARBON dioxide, FUNCTIONAL connectivity, SUDDEN death
Abstract

Objectives: Sudden unexpected death in epilepsy (SUDEP) is a catastrophic epilepsy outcome for which there are no reliable premortem imaging biomarkers of risk. Percival respiratory depression is seen in monitored SUDEP and near SUDEP cases, and abnormal chemosensing of raised blood carbon dioxide (CO2) is thought to contribute. Damage to brainstem respiratory control and chemosensing structures has been demonstrated in structural imaging and neuropathological studies of SUDEP We hypothesized that functional MRI (fMRI) correlates of abnormal chemosensing are detectable in brainstems of persons with epilepsy (PWE) and are different from healthy controls (HC). Methods: We analyzed fMRI BOLD activation and brain connectivity in 10 PWE and 10 age- and sex-matched HCs during precisely metered iso-oxic, hypercapnic breathing challenges. Segmented brainstem responses were of particular interest, along with characterization of functional connectivity metrics between these structures. Regional BOLD activations during hypercapnic challenges were convolved with hemodynamic responses, and the resulting activation maps were passed on to group-level analyses. For the functional connectivity analysis, significant clusters from BOLD results were used as seeds. Each individual seed time-series activation map was extracted for bivariate correlation coefficient analyses to study changes in brain connectivity between PWE and HCs. Results: (1) Greater brainstem BOLD activations in PWE were observed compared to HC during hypercapnic challenges in several structures with respiratory/chemosensing properties. Group comparison between PWE vs. HC showed significantly greater activation in the dorsal raphe among PWE (p < 0.05) compared to HCs. (2) PWE had significantly greater seed-seed connectivity and recruited more structures during hypercapnia compared to HC. Significance: The results of this study show that BOLD responses to hypercapnia in human brainstem are detectable and different in PWE compared to HC. Increased dorsal raphe BOLD activation in PWE and increased seed-seed connectivity between brainstem and adjacent subcortical areas may indicate abnormal chemosensing in these individuals. Imaging investigation of brainstem respiratory centers involved in respiratory regulation in PWE is an important step toward identifying suspected dysfunction of brainstem breathing control that culminates in SUDEP and deserve further study as potential imaging SUDEP biomarkers. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Diffusion tensor imaging in MDMA users and controls: association with decision making

Author

Moeller, F. Gerard, Steinberg, Joel L., Lane, Scott D., Buzby, Matthew, Swann, Alan C., Hasan, Khader M., Kramer, Larry A., and Narayana, Ponnada A.

Subjects
Ecstasy (Drug) -- Physiological aspects, Ecstasy (Drug) -- Research, Decision-making -- Physiological aspects, Decision-making -- Research, Impulse -- Physiological aspects, Impulse -- Research, Corpus callosum -- Medical examination, Corpus callosum -- Physiological aspects, Health, Psychology and mental health
Published
2007

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