Global brain-wide signals in functional magnetic resonance imaging (fMRI) are influenced by temporal variations in vigilance, peripheral physiological processes, head motion, and other potential neuronal and non-neuronal sources. These effects are challenging to disentangle as fluctuations in vigilance and peripheral physiology are difficult to detect with fMRI alone. In this study, we leveraged multimodal neuroimaging data (simultaneous fMRI, EEG, respiratory, and cardiac recordings) to investigate the ability of dimensionality reduction techniques to separate influences of vigilance, physiology, and other global effects in fMRI. Our study included resting-state fMRI from 30 subjects, parcellated into 317 brain regions. Two different methods, temporal independent component analysis (tICA) and a fully connected autoencoder, were used to project the atlas-based data into a lower dimensional latent space. The correlation of each latent component with the EEG alpha/theta power ratio (a marker of vigilance), physiological signals (respiratory volume and heart rate), and the global fMRI signal was computed. LASSO regression was additionally employed to reconstruct the alpha/theta ratio from the latent components. Our results showed that tICA, but not the autoencoder, was able to disentangle a vigilance-related component from other global effects. Both the vigilance and global components exhibited a moderate relationship with physiological activity. Therefore, tICA is useful for isolating vigilance-related influences in fMRI, which may aid in discovering novel clinical biomarkers linked to vigilance dysregulation as well as assist in explaining intersubject variability due to in-scanner state.
Sleep disturbances are commonly reported among patients with Alzheimer’s Disease (AD). Further, the disruption of subcortical areas such as the Basal Forebrain (BF) and its constituent Nucleus Basalis of Meynert (NBM), which play an important role in maintaining wakefulness or alertness (also known as vigilance), occurs early in AD. In this study, we delineate vigilance-linked fMRI patterns in an aging population and determine how these patterns relate to subcortical integrity and cognition. We used fMRI data from the Vanderbilt Memory and Aging Project dataset, consisting of 49 MCI patients and 75 healthy controls. Since external measures of vigilance are not present during fMRI, we used a data-driven technique for extracting vigilance information directly from fMRI data. With this approach, we derived subject-specific spatial maps reflecting a whole-brain activity pattern that is correlated with vigilance. We first assessed the relationships between cognitive measures (subject memory composite and executive function scores) and structural measures (BF and NBM volumes obtained from subject-specific segmentation methods) using Pearson correlations. BF and NBM volumes were found to be significantly correlated with memory composite in MCI subjects and with executive function in HCs. We then performed a mediation analysis to evaluate how NBM volume may mediate fMRI-derived vigilance effects on memory composite scores in MCI subjects. fMRI vigilance activity and memory composite were significantly associated in the hippocampus, posterior cingulate cortex, and anterior cingulate cortex, regions involved in the default-mode and salience networks. These results suggest that cognitive decline in AD may be linked with both subcortical structural changes and vigilance-related fMRI signals, opening new directions for potential functional biomarkers in pathological aging populations.
KEYWORDS: Distortion, Magnetic resonance imaging, Functional magnetic resonance imaging, Brain, Neuroimaging, Visualization, Signal attenuation, Image processing, Deep learning
Functional MRI (fMRI) suffers from susceptibility-induced geometric distortions. Current state-of-the-art distortion correction methods require reverse phase encoded images or additional field maps, but not all imaging protocols include these additional scans. We propose SynBOLD-DisCo to enable state-of-the-art distortion correction of single phase encoded fMRI using only an additional structural image. We use a 3D U-net to synthesize undistorted fMRI images from the structural image and use this undistorted synthetic image as an anatomical target for distortion correction with state-of-the-art methods. We demonstrate SynBOLD-DisCo produces results qualitatively and quantitatively equivalent to state-of-the-art correction methods without the need for additional calibration scans.
When negative tumor margins are achieved at the time of resection, breast conserving therapy (lumpectomy followed with radiation therapy) offers patients improved cosmetic outcomes and quality of life with equivalent survival outcomes to mastectomy. However, high reoperation rates ranging 10-59% continue to challenge adoption and suggest that improved intraoperative tumor localization is a pressing need. We propose to couple an optical tracker and stereo camera system for automated monitoring of surgical instruments and non-rigid breast surface deformations. A bracket was designed to rigidly pair an optical tracker with a stereo camera, optimizing overlap volume. Utilizing both devices allowed for precise instrument tracking of multiple objects with reliable, workflow friendly tracking of dynamic breast movements. Computer vision techniques were employed to automatically track fiducials, requiring one-time initialization with bounding boxes in stereo camera images. Point based rigid registration was performed between fiducial locations triangulated from stereo camera images and fiducial locations recorded with an optically tracked stylus. We measured fiducial registration error (FRE) and target registration error (TRE) with two different stereo camera devices using a phantom breast with five fiducials. Average FREs of 2.7 ± 0.4 mm and 2.4 ± 0.6 mm with each stereo-camera device demonstrate considerable promise for this approach in monitoring the surgical field. Automated tracking was shown to reduce error when compared to manually selected fiducial locations in stereo camera image-based localization. The proposed instrumentation framework demonstrated potential for the continuous measurement of surgical instruments in relation to the dynamic deformations of a breast during lumpectomy.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.